linux/drivers/block/xen-blkfront.c
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   1/*
   2 * blkfront.c
   3 *
   4 * XenLinux virtual block device driver.
   5 *
   6 * Copyright (c) 2003-2004, Keir Fraser & Steve Hand
   7 * Modifications by Mark A. Williamson are (c) Intel Research Cambridge
   8 * Copyright (c) 2004, Christian Limpach
   9 * Copyright (c) 2004, Andrew Warfield
  10 * Copyright (c) 2005, Christopher Clark
  11 * Copyright (c) 2005, XenSource Ltd
  12 *
  13 * This program is free software; you can redistribute it and/or
  14 * modify it under the terms of the GNU General Public License version 2
  15 * as published by the Free Software Foundation; or, when distributed
  16 * separately from the Linux kernel or incorporated into other
  17 * software packages, subject to the following license:
  18 *
  19 * Permission is hereby granted, free of charge, to any person obtaining a copy
  20 * of this source file (the "Software"), to deal in the Software without
  21 * restriction, including without limitation the rights to use, copy, modify,
  22 * merge, publish, distribute, sublicense, and/or sell copies of the Software,
  23 * and to permit persons to whom the Software is furnished to do so, subject to
  24 * the following conditions:
  25 *
  26 * The above copyright notice and this permission notice shall be included in
  27 * all copies or substantial portions of the Software.
  28 *
  29 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  30 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  31 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  32 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  33 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
  34 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
  35 * IN THE SOFTWARE.
  36 */
  37
  38#include <linux/interrupt.h>
  39#include <linux/blkdev.h>
  40#include <linux/blk-mq.h>
  41#include <linux/hdreg.h>
  42#include <linux/cdrom.h>
  43#include <linux/module.h>
  44#include <linux/slab.h>
  45#include <linux/mutex.h>
  46#include <linux/scatterlist.h>
  47#include <linux/bitmap.h>
  48#include <linux/list.h>
  49#include <linux/workqueue.h>
  50#include <linux/sched/mm.h>
  51
  52#include <xen/xen.h>
  53#include <xen/xenbus.h>
  54#include <xen/grant_table.h>
  55#include <xen/events.h>
  56#include <xen/page.h>
  57#include <xen/platform_pci.h>
  58
  59#include <xen/interface/grant_table.h>
  60#include <xen/interface/io/blkif.h>
  61#include <xen/interface/io/protocols.h>
  62
  63#include <asm/xen/hypervisor.h>
  64
  65/*
  66 * The minimal size of segment supported by the block framework is PAGE_SIZE.
  67 * When Linux is using a different page size than Xen, it may not be possible
  68 * to put all the data in a single segment.
  69 * This can happen when the backend doesn't support indirect descriptor and
  70 * therefore the maximum amount of data that a request can carry is
  71 * BLKIF_MAX_SEGMENTS_PER_REQUEST * XEN_PAGE_SIZE = 44KB
  72 *
  73 * Note that we only support one extra request. So the Linux page size
  74 * should be <= ( 2 * BLKIF_MAX_SEGMENTS_PER_REQUEST * XEN_PAGE_SIZE) =
  75 * 88KB.
  76 */
  77#define HAS_EXTRA_REQ (BLKIF_MAX_SEGMENTS_PER_REQUEST < XEN_PFN_PER_PAGE)
  78
  79enum blkif_state {
  80        BLKIF_STATE_DISCONNECTED,
  81        BLKIF_STATE_CONNECTED,
  82        BLKIF_STATE_SUSPENDED,
  83};
  84
  85struct grant {
  86        grant_ref_t gref;
  87        struct page *page;
  88        struct list_head node;
  89};
  90
  91enum blk_req_status {
  92        REQ_WAITING,
  93        REQ_DONE,
  94        REQ_ERROR,
  95        REQ_EOPNOTSUPP,
  96};
  97
  98struct blk_shadow {
  99        struct blkif_request req;
 100        struct request *request;
 101        struct grant **grants_used;
 102        struct grant **indirect_grants;
 103        struct scatterlist *sg;
 104        unsigned int num_sg;
 105        enum blk_req_status status;
 106
 107        #define NO_ASSOCIATED_ID ~0UL
 108        /*
 109         * Id of the sibling if we ever need 2 requests when handling a
 110         * block I/O request
 111         */
 112        unsigned long associated_id;
 113};
 114
 115struct blkif_req {
 116        blk_status_t    error;
 117};
 118
 119static inline struct blkif_req *blkif_req(struct request *rq)
 120{
 121        return blk_mq_rq_to_pdu(rq);
 122}
 123
 124static DEFINE_MUTEX(blkfront_mutex);
 125static const struct block_device_operations xlvbd_block_fops;
 126static struct delayed_work blkfront_work;
 127static LIST_HEAD(info_list);
 128
 129/*
 130 * Maximum number of segments in indirect requests, the actual value used by
 131 * the frontend driver is the minimum of this value and the value provided
 132 * by the backend driver.
 133 */
 134
 135static unsigned int xen_blkif_max_segments = 32;
 136module_param_named(max_indirect_segments, xen_blkif_max_segments, uint, 0444);
 137MODULE_PARM_DESC(max_indirect_segments,
 138                 "Maximum amount of segments in indirect requests (default is 32)");
 139
 140static unsigned int xen_blkif_max_queues = 4;
 141module_param_named(max_queues, xen_blkif_max_queues, uint, 0444);
 142MODULE_PARM_DESC(max_queues, "Maximum number of hardware queues/rings used per virtual disk");
 143
 144/*
 145 * Maximum order of pages to be used for the shared ring between front and
 146 * backend, 4KB page granularity is used.
 147 */
 148static unsigned int xen_blkif_max_ring_order;
 149module_param_named(max_ring_page_order, xen_blkif_max_ring_order, int, 0444);
 150MODULE_PARM_DESC(max_ring_page_order, "Maximum order of pages to be used for the shared ring");
 151
 152#define BLK_RING_SIZE(info)     \
 153        __CONST_RING_SIZE(blkif, XEN_PAGE_SIZE * (info)->nr_ring_pages)
 154
 155/*
 156 * ring-ref%u i=(-1UL) would take 11 characters + 'ring-ref' is 8, so 19
 157 * characters are enough. Define to 20 to keep consistent with backend.
 158 */
 159#define RINGREF_NAME_LEN (20)
 160/*
 161 * queue-%u would take 7 + 10(UINT_MAX) = 17 characters.
 162 */
 163#define QUEUE_NAME_LEN (17)
 164
 165/*
 166 *  Per-ring info.
 167 *  Every blkfront device can associate with one or more blkfront_ring_info,
 168 *  depending on how many hardware queues/rings to be used.
 169 */
 170struct blkfront_ring_info {
 171        /* Lock to protect data in every ring buffer. */
 172        spinlock_t ring_lock;
 173        struct blkif_front_ring ring;
 174        unsigned int ring_ref[XENBUS_MAX_RING_GRANTS];
 175        unsigned int evtchn, irq;
 176        struct work_struct work;
 177        struct gnttab_free_callback callback;
 178        struct list_head indirect_pages;
 179        struct list_head grants;
 180        unsigned int persistent_gnts_c;
 181        unsigned long shadow_free;
 182        struct blkfront_info *dev_info;
 183        struct blk_shadow shadow[];
 184};
 185
 186/*
 187 * We have one of these per vbd, whether ide, scsi or 'other'.  They
 188 * hang in private_data off the gendisk structure. We may end up
 189 * putting all kinds of interesting stuff here :-)
 190 */
 191struct blkfront_info
 192{
 193        struct mutex mutex;
 194        struct xenbus_device *xbdev;
 195        struct gendisk *gd;
 196        u16 sector_size;
 197        unsigned int physical_sector_size;
 198        int vdevice;
 199        blkif_vdev_t handle;
 200        enum blkif_state connected;
 201        /* Number of pages per ring buffer. */
 202        unsigned int nr_ring_pages;
 203        struct request_queue *rq;
 204        unsigned int feature_flush:1;
 205        unsigned int feature_fua:1;
 206        unsigned int feature_discard:1;
 207        unsigned int feature_secdiscard:1;
 208        unsigned int feature_persistent:1;
 209        unsigned int discard_granularity;
 210        unsigned int discard_alignment;
 211        /* Number of 4KB segments handled */
 212        unsigned int max_indirect_segments;
 213        int is_ready;
 214        struct blk_mq_tag_set tag_set;
 215        struct blkfront_ring_info *rinfo;
 216        unsigned int nr_rings;
 217        unsigned int rinfo_size;
 218        /* Save uncomplete reqs and bios for migration. */
 219        struct list_head requests;
 220        struct bio_list bio_list;
 221        struct list_head info_list;
 222};
 223
 224static unsigned int nr_minors;
 225static unsigned long *minors;
 226static DEFINE_SPINLOCK(minor_lock);
 227
 228#define GRANT_INVALID_REF       0
 229
 230#define PARTS_PER_DISK          16
 231#define PARTS_PER_EXT_DISK      256
 232
 233#define BLKIF_MAJOR(dev) ((dev)>>8)
 234#define BLKIF_MINOR(dev) ((dev) & 0xff)
 235
 236#define EXT_SHIFT 28
 237#define EXTENDED (1<<EXT_SHIFT)
 238#define VDEV_IS_EXTENDED(dev) ((dev)&(EXTENDED))
 239#define BLKIF_MINOR_EXT(dev) ((dev)&(~EXTENDED))
 240#define EMULATED_HD_DISK_MINOR_OFFSET (0)
 241#define EMULATED_HD_DISK_NAME_OFFSET (EMULATED_HD_DISK_MINOR_OFFSET / 256)
 242#define EMULATED_SD_DISK_MINOR_OFFSET (0)
 243#define EMULATED_SD_DISK_NAME_OFFSET (EMULATED_SD_DISK_MINOR_OFFSET / 256)
 244
 245#define DEV_NAME        "xvd"   /* name in /dev */
 246
 247/*
 248 * Grants are always the same size as a Xen page (i.e 4KB).
 249 * A physical segment is always the same size as a Linux page.
 250 * Number of grants per physical segment
 251 */
 252#define GRANTS_PER_PSEG (PAGE_SIZE / XEN_PAGE_SIZE)
 253
 254#define GRANTS_PER_INDIRECT_FRAME \
 255        (XEN_PAGE_SIZE / sizeof(struct blkif_request_segment))
 256
 257#define INDIRECT_GREFS(_grants)         \
 258        DIV_ROUND_UP(_grants, GRANTS_PER_INDIRECT_FRAME)
 259
 260static int blkfront_setup_indirect(struct blkfront_ring_info *rinfo);
 261static void blkfront_gather_backend_features(struct blkfront_info *info);
 262static int negotiate_mq(struct blkfront_info *info);
 263
 264#define for_each_rinfo(info, ptr, idx)                          \
 265        for ((ptr) = (info)->rinfo, (idx) = 0;                  \
 266             (idx) < (info)->nr_rings;                          \
 267             (idx)++, (ptr) = (void *)(ptr) + (info)->rinfo_size)
 268
 269static inline struct blkfront_ring_info *
 270get_rinfo(const struct blkfront_info *info, unsigned int i)
 271{
 272        BUG_ON(i >= info->nr_rings);
 273        return (void *)info->rinfo + i * info->rinfo_size;
 274}
 275
 276static int get_id_from_freelist(struct blkfront_ring_info *rinfo)
 277{
 278        unsigned long free = rinfo->shadow_free;
 279
 280        BUG_ON(free >= BLK_RING_SIZE(rinfo->dev_info));
 281        rinfo->shadow_free = rinfo->shadow[free].req.u.rw.id;
 282        rinfo->shadow[free].req.u.rw.id = 0x0fffffee; /* debug */
 283        return free;
 284}
 285
 286static int add_id_to_freelist(struct blkfront_ring_info *rinfo,
 287                              unsigned long id)
 288{
 289        if (rinfo->shadow[id].req.u.rw.id != id)
 290                return -EINVAL;
 291        if (rinfo->shadow[id].request == NULL)
 292                return -EINVAL;
 293        rinfo->shadow[id].req.u.rw.id  = rinfo->shadow_free;
 294        rinfo->shadow[id].request = NULL;
 295        rinfo->shadow_free = id;
 296        return 0;
 297}
 298
 299static int fill_grant_buffer(struct blkfront_ring_info *rinfo, int num)
 300{
 301        struct blkfront_info *info = rinfo->dev_info;
 302        struct page *granted_page;
 303        struct grant *gnt_list_entry, *n;
 304        int i = 0;
 305
 306        while (i < num) {
 307                gnt_list_entry = kzalloc(sizeof(struct grant), GFP_NOIO);
 308                if (!gnt_list_entry)
 309                        goto out_of_memory;
 310
 311                if (info->feature_persistent) {
 312                        granted_page = alloc_page(GFP_NOIO);
 313                        if (!granted_page) {
 314                                kfree(gnt_list_entry);
 315                                goto out_of_memory;
 316                        }
 317                        gnt_list_entry->page = granted_page;
 318                }
 319
 320                gnt_list_entry->gref = GRANT_INVALID_REF;
 321                list_add(&gnt_list_entry->node, &rinfo->grants);
 322                i++;
 323        }
 324
 325        return 0;
 326
 327out_of_memory:
 328        list_for_each_entry_safe(gnt_list_entry, n,
 329                                 &rinfo->grants, node) {
 330                list_del(&gnt_list_entry->node);
 331                if (info->feature_persistent)
 332                        __free_page(gnt_list_entry->page);
 333                kfree(gnt_list_entry);
 334                i--;
 335        }
 336        BUG_ON(i != 0);
 337        return -ENOMEM;
 338}
 339
 340static struct grant *get_free_grant(struct blkfront_ring_info *rinfo)
 341{
 342        struct grant *gnt_list_entry;
 343
 344        BUG_ON(list_empty(&rinfo->grants));
 345        gnt_list_entry = list_first_entry(&rinfo->grants, struct grant,
 346                                          node);
 347        list_del(&gnt_list_entry->node);
 348
 349        if (gnt_list_entry->gref != GRANT_INVALID_REF)
 350                rinfo->persistent_gnts_c--;
 351
 352        return gnt_list_entry;
 353}
 354
 355static inline void grant_foreign_access(const struct grant *gnt_list_entry,
 356                                        const struct blkfront_info *info)
 357{
 358        gnttab_page_grant_foreign_access_ref_one(gnt_list_entry->gref,
 359                                                 info->xbdev->otherend_id,
 360                                                 gnt_list_entry->page,
 361                                                 0);
 362}
 363
 364static struct grant *get_grant(grant_ref_t *gref_head,
 365                               unsigned long gfn,
 366                               struct blkfront_ring_info *rinfo)
 367{
 368        struct grant *gnt_list_entry = get_free_grant(rinfo);
 369        struct blkfront_info *info = rinfo->dev_info;
 370
 371        if (gnt_list_entry->gref != GRANT_INVALID_REF)
 372                return gnt_list_entry;
 373
 374        /* Assign a gref to this page */
 375        gnt_list_entry->gref = gnttab_claim_grant_reference(gref_head);
 376        BUG_ON(gnt_list_entry->gref == -ENOSPC);
 377        if (info->feature_persistent)
 378                grant_foreign_access(gnt_list_entry, info);
 379        else {
 380                /* Grant access to the GFN passed by the caller */
 381                gnttab_grant_foreign_access_ref(gnt_list_entry->gref,
 382                                                info->xbdev->otherend_id,
 383                                                gfn, 0);
 384        }
 385
 386        return gnt_list_entry;
 387}
 388
 389static struct grant *get_indirect_grant(grant_ref_t *gref_head,
 390                                        struct blkfront_ring_info *rinfo)
 391{
 392        struct grant *gnt_list_entry = get_free_grant(rinfo);
 393        struct blkfront_info *info = rinfo->dev_info;
 394
 395        if (gnt_list_entry->gref != GRANT_INVALID_REF)
 396                return gnt_list_entry;
 397
 398        /* Assign a gref to this page */
 399        gnt_list_entry->gref = gnttab_claim_grant_reference(gref_head);
 400        BUG_ON(gnt_list_entry->gref == -ENOSPC);
 401        if (!info->feature_persistent) {
 402                struct page *indirect_page;
 403
 404                /* Fetch a pre-allocated page to use for indirect grefs */
 405                BUG_ON(list_empty(&rinfo->indirect_pages));
 406                indirect_page = list_first_entry(&rinfo->indirect_pages,
 407                                                 struct page, lru);
 408                list_del(&indirect_page->lru);
 409                gnt_list_entry->page = indirect_page;
 410        }
 411        grant_foreign_access(gnt_list_entry, info);
 412
 413        return gnt_list_entry;
 414}
 415
 416static const char *op_name(int op)
 417{
 418        static const char *const names[] = {
 419                [BLKIF_OP_READ] = "read",
 420                [BLKIF_OP_WRITE] = "write",
 421                [BLKIF_OP_WRITE_BARRIER] = "barrier",
 422                [BLKIF_OP_FLUSH_DISKCACHE] = "flush",
 423                [BLKIF_OP_DISCARD] = "discard" };
 424
 425        if (op < 0 || op >= ARRAY_SIZE(names))
 426                return "unknown";
 427
 428        if (!names[op])
 429                return "reserved";
 430
 431        return names[op];
 432}
 433static int xlbd_reserve_minors(unsigned int minor, unsigned int nr)
 434{
 435        unsigned int end = minor + nr;
 436        int rc;
 437
 438        if (end > nr_minors) {
 439                unsigned long *bitmap, *old;
 440
 441                bitmap = kcalloc(BITS_TO_LONGS(end), sizeof(*bitmap),
 442                                 GFP_KERNEL);
 443                if (bitmap == NULL)
 444                        return -ENOMEM;
 445
 446                spin_lock(&minor_lock);
 447                if (end > nr_minors) {
 448                        old = minors;
 449                        memcpy(bitmap, minors,
 450                               BITS_TO_LONGS(nr_minors) * sizeof(*bitmap));
 451                        minors = bitmap;
 452                        nr_minors = BITS_TO_LONGS(end) * BITS_PER_LONG;
 453                } else
 454                        old = bitmap;
 455                spin_unlock(&minor_lock);
 456                kfree(old);
 457        }
 458
 459        spin_lock(&minor_lock);
 460        if (find_next_bit(minors, end, minor) >= end) {
 461                bitmap_set(minors, minor, nr);
 462                rc = 0;
 463        } else
 464                rc = -EBUSY;
 465        spin_unlock(&minor_lock);
 466
 467        return rc;
 468}
 469
 470static void xlbd_release_minors(unsigned int minor, unsigned int nr)
 471{
 472        unsigned int end = minor + nr;
 473
 474        BUG_ON(end > nr_minors);
 475        spin_lock(&minor_lock);
 476        bitmap_clear(minors,  minor, nr);
 477        spin_unlock(&minor_lock);
 478}
 479
 480static void blkif_restart_queue_callback(void *arg)
 481{
 482        struct blkfront_ring_info *rinfo = (struct blkfront_ring_info *)arg;
 483        schedule_work(&rinfo->work);
 484}
 485
 486static int blkif_getgeo(struct block_device *bd, struct hd_geometry *hg)
 487{
 488        /* We don't have real geometry info, but let's at least return
 489           values consistent with the size of the device */
 490        sector_t nsect = get_capacity(bd->bd_disk);
 491        sector_t cylinders = nsect;
 492
 493        hg->heads = 0xff;
 494        hg->sectors = 0x3f;
 495        sector_div(cylinders, hg->heads * hg->sectors);
 496        hg->cylinders = cylinders;
 497        if ((sector_t)(hg->cylinders + 1) * hg->heads * hg->sectors < nsect)
 498                hg->cylinders = 0xffff;
 499        return 0;
 500}
 501
 502static int blkif_ioctl(struct block_device *bdev, fmode_t mode,
 503                       unsigned command, unsigned long argument)
 504{
 505        struct blkfront_info *info = bdev->bd_disk->private_data;
 506        int i;
 507
 508        dev_dbg(&info->xbdev->dev, "command: 0x%x, argument: 0x%lx\n",
 509                command, (long)argument);
 510
 511        switch (command) {
 512        case CDROMMULTISESSION:
 513                dev_dbg(&info->xbdev->dev, "FIXME: support multisession CDs later\n");
 514                for (i = 0; i < sizeof(struct cdrom_multisession); i++)
 515                        if (put_user(0, (char __user *)(argument + i)))
 516                                return -EFAULT;
 517                return 0;
 518
 519        case CDROM_GET_CAPABILITY: {
 520                struct gendisk *gd = info->gd;
 521                if (gd->flags & GENHD_FL_CD)
 522                        return 0;
 523                return -EINVAL;
 524        }
 525
 526        default:
 527                /*printk(KERN_ALERT "ioctl %08x not supported by Xen blkdev\n",
 528                  command);*/
 529                return -EINVAL; /* same return as native Linux */
 530        }
 531
 532        return 0;
 533}
 534
 535static unsigned long blkif_ring_get_request(struct blkfront_ring_info *rinfo,
 536                                            struct request *req,
 537                                            struct blkif_request **ring_req)
 538{
 539        unsigned long id;
 540
 541        *ring_req = RING_GET_REQUEST(&rinfo->ring, rinfo->ring.req_prod_pvt);
 542        rinfo->ring.req_prod_pvt++;
 543
 544        id = get_id_from_freelist(rinfo);
 545        rinfo->shadow[id].request = req;
 546        rinfo->shadow[id].status = REQ_WAITING;
 547        rinfo->shadow[id].associated_id = NO_ASSOCIATED_ID;
 548
 549        (*ring_req)->u.rw.id = id;
 550
 551        return id;
 552}
 553
 554static int blkif_queue_discard_req(struct request *req, struct blkfront_ring_info *rinfo)
 555{
 556        struct blkfront_info *info = rinfo->dev_info;
 557        struct blkif_request *ring_req;
 558        unsigned long id;
 559
 560        /* Fill out a communications ring structure. */
 561        id = blkif_ring_get_request(rinfo, req, &ring_req);
 562
 563        ring_req->operation = BLKIF_OP_DISCARD;
 564        ring_req->u.discard.nr_sectors = blk_rq_sectors(req);
 565        ring_req->u.discard.id = id;
 566        ring_req->u.discard.sector_number = (blkif_sector_t)blk_rq_pos(req);
 567        if (req_op(req) == REQ_OP_SECURE_ERASE && info->feature_secdiscard)
 568                ring_req->u.discard.flag = BLKIF_DISCARD_SECURE;
 569        else
 570                ring_req->u.discard.flag = 0;
 571
 572        /* Keep a private copy so we can reissue requests when recovering. */
 573        rinfo->shadow[id].req = *ring_req;
 574
 575        return 0;
 576}
 577
 578struct setup_rw_req {
 579        unsigned int grant_idx;
 580        struct blkif_request_segment *segments;
 581        struct blkfront_ring_info *rinfo;
 582        struct blkif_request *ring_req;
 583        grant_ref_t gref_head;
 584        unsigned int id;
 585        /* Only used when persistent grant is used and it's a read request */
 586        bool need_copy;
 587        unsigned int bvec_off;
 588        char *bvec_data;
 589
 590        bool require_extra_req;
 591        struct blkif_request *extra_ring_req;
 592};
 593
 594static void blkif_setup_rw_req_grant(unsigned long gfn, unsigned int offset,
 595                                     unsigned int len, void *data)
 596{
 597        struct setup_rw_req *setup = data;
 598        int n, ref;
 599        struct grant *gnt_list_entry;
 600        unsigned int fsect, lsect;
 601        /* Convenient aliases */
 602        unsigned int grant_idx = setup->grant_idx;
 603        struct blkif_request *ring_req = setup->ring_req;
 604        struct blkfront_ring_info *rinfo = setup->rinfo;
 605        /*
 606         * We always use the shadow of the first request to store the list
 607         * of grant associated to the block I/O request. This made the
 608         * completion more easy to handle even if the block I/O request is
 609         * split.
 610         */
 611        struct blk_shadow *shadow = &rinfo->shadow[setup->id];
 612
 613        if (unlikely(setup->require_extra_req &&
 614                     grant_idx >= BLKIF_MAX_SEGMENTS_PER_REQUEST)) {
 615                /*
 616                 * We are using the second request, setup grant_idx
 617                 * to be the index of the segment array.
 618                 */
 619                grant_idx -= BLKIF_MAX_SEGMENTS_PER_REQUEST;
 620                ring_req = setup->extra_ring_req;
 621        }
 622
 623        if ((ring_req->operation == BLKIF_OP_INDIRECT) &&
 624            (grant_idx % GRANTS_PER_INDIRECT_FRAME == 0)) {
 625                if (setup->segments)
 626                        kunmap_atomic(setup->segments);
 627
 628                n = grant_idx / GRANTS_PER_INDIRECT_FRAME;
 629                gnt_list_entry = get_indirect_grant(&setup->gref_head, rinfo);
 630                shadow->indirect_grants[n] = gnt_list_entry;
 631                setup->segments = kmap_atomic(gnt_list_entry->page);
 632                ring_req->u.indirect.indirect_grefs[n] = gnt_list_entry->gref;
 633        }
 634
 635        gnt_list_entry = get_grant(&setup->gref_head, gfn, rinfo);
 636        ref = gnt_list_entry->gref;
 637        /*
 638         * All the grants are stored in the shadow of the first
 639         * request. Therefore we have to use the global index.
 640         */
 641        shadow->grants_used[setup->grant_idx] = gnt_list_entry;
 642
 643        if (setup->need_copy) {
 644                void *shared_data;
 645
 646                shared_data = kmap_atomic(gnt_list_entry->page);
 647                /*
 648                 * this does not wipe data stored outside the
 649                 * range sg->offset..sg->offset+sg->length.
 650                 * Therefore, blkback *could* see data from
 651                 * previous requests. This is OK as long as
 652                 * persistent grants are shared with just one
 653                 * domain. It may need refactoring if this
 654                 * changes
 655                 */
 656                memcpy(shared_data + offset,
 657                       setup->bvec_data + setup->bvec_off,
 658                       len);
 659
 660                kunmap_atomic(shared_data);
 661                setup->bvec_off += len;
 662        }
 663
 664        fsect = offset >> 9;
 665        lsect = fsect + (len >> 9) - 1;
 666        if (ring_req->operation != BLKIF_OP_INDIRECT) {
 667                ring_req->u.rw.seg[grant_idx] =
 668                        (struct blkif_request_segment) {
 669                                .gref       = ref,
 670                                .first_sect = fsect,
 671                                .last_sect  = lsect };
 672        } else {
 673                setup->segments[grant_idx % GRANTS_PER_INDIRECT_FRAME] =
 674                        (struct blkif_request_segment) {
 675                                .gref       = ref,
 676                                .first_sect = fsect,
 677                                .last_sect  = lsect };
 678        }
 679
 680        (setup->grant_idx)++;
 681}
 682
 683static void blkif_setup_extra_req(struct blkif_request *first,
 684                                  struct blkif_request *second)
 685{
 686        uint16_t nr_segments = first->u.rw.nr_segments;
 687
 688        /*
 689         * The second request is only present when the first request uses
 690         * all its segments. It's always the continuity of the first one.
 691         */
 692        first->u.rw.nr_segments = BLKIF_MAX_SEGMENTS_PER_REQUEST;
 693
 694        second->u.rw.nr_segments = nr_segments - BLKIF_MAX_SEGMENTS_PER_REQUEST;
 695        second->u.rw.sector_number = first->u.rw.sector_number +
 696                (BLKIF_MAX_SEGMENTS_PER_REQUEST * XEN_PAGE_SIZE) / 512;
 697
 698        second->u.rw.handle = first->u.rw.handle;
 699        second->operation = first->operation;
 700}
 701
 702static int blkif_queue_rw_req(struct request *req, struct blkfront_ring_info *rinfo)
 703{
 704        struct blkfront_info *info = rinfo->dev_info;
 705        struct blkif_request *ring_req, *extra_ring_req = NULL;
 706        unsigned long id, extra_id = NO_ASSOCIATED_ID;
 707        bool require_extra_req = false;
 708        int i;
 709        struct setup_rw_req setup = {
 710                .grant_idx = 0,
 711                .segments = NULL,
 712                .rinfo = rinfo,
 713                .need_copy = rq_data_dir(req) && info->feature_persistent,
 714        };
 715
 716        /*
 717         * Used to store if we are able to queue the request by just using
 718         * existing persistent grants, or if we have to get new grants,
 719         * as there are not sufficiently many free.
 720         */
 721        bool new_persistent_gnts = false;
 722        struct scatterlist *sg;
 723        int num_sg, max_grefs, num_grant;
 724
 725        max_grefs = req->nr_phys_segments * GRANTS_PER_PSEG;
 726        if (max_grefs > BLKIF_MAX_SEGMENTS_PER_REQUEST)
 727                /*
 728                 * If we are using indirect segments we need to account
 729                 * for the indirect grefs used in the request.
 730                 */
 731                max_grefs += INDIRECT_GREFS(max_grefs);
 732
 733        /* Check if we have enough persistent grants to allocate a requests */
 734        if (rinfo->persistent_gnts_c < max_grefs) {
 735                new_persistent_gnts = true;
 736
 737                if (gnttab_alloc_grant_references(
 738                    max_grefs - rinfo->persistent_gnts_c,
 739                    &setup.gref_head) < 0) {
 740                        gnttab_request_free_callback(
 741                                &rinfo->callback,
 742                                blkif_restart_queue_callback,
 743                                rinfo,
 744                                max_grefs - rinfo->persistent_gnts_c);
 745                        return 1;
 746                }
 747        }
 748
 749        /* Fill out a communications ring structure. */
 750        id = blkif_ring_get_request(rinfo, req, &ring_req);
 751
 752        num_sg = blk_rq_map_sg(req->q, req, rinfo->shadow[id].sg);
 753        num_grant = 0;
 754        /* Calculate the number of grant used */
 755        for_each_sg(rinfo->shadow[id].sg, sg, num_sg, i)
 756               num_grant += gnttab_count_grant(sg->offset, sg->length);
 757
 758        require_extra_req = info->max_indirect_segments == 0 &&
 759                num_grant > BLKIF_MAX_SEGMENTS_PER_REQUEST;
 760        BUG_ON(!HAS_EXTRA_REQ && require_extra_req);
 761
 762        rinfo->shadow[id].num_sg = num_sg;
 763        if (num_grant > BLKIF_MAX_SEGMENTS_PER_REQUEST &&
 764            likely(!require_extra_req)) {
 765                /*
 766                 * The indirect operation can only be a BLKIF_OP_READ or
 767                 * BLKIF_OP_WRITE
 768                 */
 769                BUG_ON(req_op(req) == REQ_OP_FLUSH || req->cmd_flags & REQ_FUA);
 770                ring_req->operation = BLKIF_OP_INDIRECT;
 771                ring_req->u.indirect.indirect_op = rq_data_dir(req) ?
 772                        BLKIF_OP_WRITE : BLKIF_OP_READ;
 773                ring_req->u.indirect.sector_number = (blkif_sector_t)blk_rq_pos(req);
 774                ring_req->u.indirect.handle = info->handle;
 775                ring_req->u.indirect.nr_segments = num_grant;
 776        } else {
 777                ring_req->u.rw.sector_number = (blkif_sector_t)blk_rq_pos(req);
 778                ring_req->u.rw.handle = info->handle;
 779                ring_req->operation = rq_data_dir(req) ?
 780                        BLKIF_OP_WRITE : BLKIF_OP_READ;
 781                if (req_op(req) == REQ_OP_FLUSH || req->cmd_flags & REQ_FUA) {
 782                        /*
 783                         * Ideally we can do an unordered flush-to-disk.
 784                         * In case the backend onlysupports barriers, use that.
 785                         * A barrier request a superset of FUA, so we can
 786                         * implement it the same way.  (It's also a FLUSH+FUA,
 787                         * since it is guaranteed ordered WRT previous writes.)
 788                         */
 789                        if (info->feature_flush && info->feature_fua)
 790                                ring_req->operation =
 791                                        BLKIF_OP_WRITE_BARRIER;
 792                        else if (info->feature_flush)
 793                                ring_req->operation =
 794                                        BLKIF_OP_FLUSH_DISKCACHE;
 795                        else
 796                                ring_req->operation = 0;
 797                }
 798                ring_req->u.rw.nr_segments = num_grant;
 799                if (unlikely(require_extra_req)) {
 800                        extra_id = blkif_ring_get_request(rinfo, req,
 801                                                          &extra_ring_req);
 802                        /*
 803                         * Only the first request contains the scatter-gather
 804                         * list.
 805                         */
 806                        rinfo->shadow[extra_id].num_sg = 0;
 807
 808                        blkif_setup_extra_req(ring_req, extra_ring_req);
 809
 810                        /* Link the 2 requests together */
 811                        rinfo->shadow[extra_id].associated_id = id;
 812                        rinfo->shadow[id].associated_id = extra_id;
 813                }
 814        }
 815
 816        setup.ring_req = ring_req;
 817        setup.id = id;
 818
 819        setup.require_extra_req = require_extra_req;
 820        if (unlikely(require_extra_req))
 821                setup.extra_ring_req = extra_ring_req;
 822
 823        for_each_sg(rinfo->shadow[id].sg, sg, num_sg, i) {
 824                BUG_ON(sg->offset + sg->length > PAGE_SIZE);
 825
 826                if (setup.need_copy) {
 827                        setup.bvec_off = sg->offset;
 828                        setup.bvec_data = kmap_atomic(sg_page(sg));
 829                }
 830
 831                gnttab_foreach_grant_in_range(sg_page(sg),
 832                                              sg->offset,
 833                                              sg->length,
 834                                              blkif_setup_rw_req_grant,
 835                                              &setup);
 836
 837                if (setup.need_copy)
 838                        kunmap_atomic(setup.bvec_data);
 839        }
 840        if (setup.segments)
 841                kunmap_atomic(setup.segments);
 842
 843        /* Keep a private copy so we can reissue requests when recovering. */
 844        rinfo->shadow[id].req = *ring_req;
 845        if (unlikely(require_extra_req))
 846                rinfo->shadow[extra_id].req = *extra_ring_req;
 847
 848        if (new_persistent_gnts)
 849                gnttab_free_grant_references(setup.gref_head);
 850
 851        return 0;
 852}
 853
 854/*
 855 * Generate a Xen blkfront IO request from a blk layer request.  Reads
 856 * and writes are handled as expected.
 857 *
 858 * @req: a request struct
 859 */
 860static int blkif_queue_request(struct request *req, struct blkfront_ring_info *rinfo)
 861{
 862        if (unlikely(rinfo->dev_info->connected != BLKIF_STATE_CONNECTED))
 863                return 1;
 864
 865        if (unlikely(req_op(req) == REQ_OP_DISCARD ||
 866                     req_op(req) == REQ_OP_SECURE_ERASE))
 867                return blkif_queue_discard_req(req, rinfo);
 868        else
 869                return blkif_queue_rw_req(req, rinfo);
 870}
 871
 872static inline void flush_requests(struct blkfront_ring_info *rinfo)
 873{
 874        int notify;
 875
 876        RING_PUSH_REQUESTS_AND_CHECK_NOTIFY(&rinfo->ring, notify);
 877
 878        if (notify)
 879                notify_remote_via_irq(rinfo->irq);
 880}
 881
 882static inline bool blkif_request_flush_invalid(struct request *req,
 883                                               struct blkfront_info *info)
 884{
 885        return (blk_rq_is_passthrough(req) ||
 886                ((req_op(req) == REQ_OP_FLUSH) &&
 887                 !info->feature_flush) ||
 888                ((req->cmd_flags & REQ_FUA) &&
 889                 !info->feature_fua));
 890}
 891
 892static blk_status_t blkif_queue_rq(struct blk_mq_hw_ctx *hctx,
 893                          const struct blk_mq_queue_data *qd)
 894{
 895        unsigned long flags;
 896        int qid = hctx->queue_num;
 897        struct blkfront_info *info = hctx->queue->queuedata;
 898        struct blkfront_ring_info *rinfo = NULL;
 899
 900        rinfo = get_rinfo(info, qid);
 901        blk_mq_start_request(qd->rq);
 902        spin_lock_irqsave(&rinfo->ring_lock, flags);
 903        if (RING_FULL(&rinfo->ring))
 904                goto out_busy;
 905
 906        if (blkif_request_flush_invalid(qd->rq, rinfo->dev_info))
 907                goto out_err;
 908
 909        if (blkif_queue_request(qd->rq, rinfo))
 910                goto out_busy;
 911
 912        flush_requests(rinfo);
 913        spin_unlock_irqrestore(&rinfo->ring_lock, flags);
 914        return BLK_STS_OK;
 915
 916out_err:
 917        spin_unlock_irqrestore(&rinfo->ring_lock, flags);
 918        return BLK_STS_IOERR;
 919
 920out_busy:
 921        blk_mq_stop_hw_queue(hctx);
 922        spin_unlock_irqrestore(&rinfo->ring_lock, flags);
 923        return BLK_STS_DEV_RESOURCE;
 924}
 925
 926static void blkif_complete_rq(struct request *rq)
 927{
 928        blk_mq_end_request(rq, blkif_req(rq)->error);
 929}
 930
 931static const struct blk_mq_ops blkfront_mq_ops = {
 932        .queue_rq = blkif_queue_rq,
 933        .complete = blkif_complete_rq,
 934};
 935
 936static void blkif_set_queue_limits(struct blkfront_info *info)
 937{
 938        struct request_queue *rq = info->rq;
 939        struct gendisk *gd = info->gd;
 940        unsigned int segments = info->max_indirect_segments ? :
 941                                BLKIF_MAX_SEGMENTS_PER_REQUEST;
 942
 943        blk_queue_flag_set(QUEUE_FLAG_VIRT, rq);
 944
 945        if (info->feature_discard) {
 946                blk_queue_flag_set(QUEUE_FLAG_DISCARD, rq);
 947                blk_queue_max_discard_sectors(rq, get_capacity(gd));
 948                rq->limits.discard_granularity = info->discard_granularity ?:
 949                                                 info->physical_sector_size;
 950                rq->limits.discard_alignment = info->discard_alignment;
 951                if (info->feature_secdiscard)
 952                        blk_queue_flag_set(QUEUE_FLAG_SECERASE, rq);
 953        }
 954
 955        /* Hard sector size and max sectors impersonate the equiv. hardware. */
 956        blk_queue_logical_block_size(rq, info->sector_size);
 957        blk_queue_physical_block_size(rq, info->physical_sector_size);
 958        blk_queue_max_hw_sectors(rq, (segments * XEN_PAGE_SIZE) / 512);
 959
 960        /* Each segment in a request is up to an aligned page in size. */
 961        blk_queue_segment_boundary(rq, PAGE_SIZE - 1);
 962        blk_queue_max_segment_size(rq, PAGE_SIZE);
 963
 964        /* Ensure a merged request will fit in a single I/O ring slot. */
 965        blk_queue_max_segments(rq, segments / GRANTS_PER_PSEG);
 966
 967        /* Make sure buffer addresses are sector-aligned. */
 968        blk_queue_dma_alignment(rq, 511);
 969}
 970
 971static int xlvbd_init_blk_queue(struct gendisk *gd, u16 sector_size,
 972                                unsigned int physical_sector_size)
 973{
 974        struct request_queue *rq;
 975        struct blkfront_info *info = gd->private_data;
 976
 977        memset(&info->tag_set, 0, sizeof(info->tag_set));
 978        info->tag_set.ops = &blkfront_mq_ops;
 979        info->tag_set.nr_hw_queues = info->nr_rings;
 980        if (HAS_EXTRA_REQ && info->max_indirect_segments == 0) {
 981                /*
 982                 * When indirect descriptior is not supported, the I/O request
 983                 * will be split between multiple request in the ring.
 984                 * To avoid problems when sending the request, divide by
 985                 * 2 the depth of the queue.
 986                 */
 987                info->tag_set.queue_depth =  BLK_RING_SIZE(info) / 2;
 988        } else
 989                info->tag_set.queue_depth = BLK_RING_SIZE(info);
 990        info->tag_set.numa_node = NUMA_NO_NODE;
 991        info->tag_set.flags = BLK_MQ_F_SHOULD_MERGE;
 992        info->tag_set.cmd_size = sizeof(struct blkif_req);
 993        info->tag_set.driver_data = info;
 994
 995        if (blk_mq_alloc_tag_set(&info->tag_set))
 996                return -EINVAL;
 997        rq = blk_mq_init_queue(&info->tag_set);
 998        if (IS_ERR(rq)) {
 999                blk_mq_free_tag_set(&info->tag_set);
1000                return PTR_ERR(rq);
1001        }
1002
1003        rq->queuedata = info;
1004        info->rq = gd->queue = rq;
1005        info->gd = gd;
1006        info->sector_size = sector_size;
1007        info->physical_sector_size = physical_sector_size;
1008        blkif_set_queue_limits(info);
1009
1010        return 0;
1011}
1012
1013static const char *flush_info(struct blkfront_info *info)
1014{
1015        if (info->feature_flush && info->feature_fua)
1016                return "barrier: enabled;";
1017        else if (info->feature_flush)
1018                return "flush diskcache: enabled;";
1019        else
1020                return "barrier or flush: disabled;";
1021}
1022
1023static void xlvbd_flush(struct blkfront_info *info)
1024{
1025        blk_queue_write_cache(info->rq, info->feature_flush ? true : false,
1026                              info->feature_fua ? true : false);
1027        pr_info("blkfront: %s: %s %s %s %s %s\n",
1028                info->gd->disk_name, flush_info(info),
1029                "persistent grants:", info->feature_persistent ?
1030                "enabled;" : "disabled;", "indirect descriptors:",
1031                info->max_indirect_segments ? "enabled;" : "disabled;");
1032}
1033
1034static int xen_translate_vdev(int vdevice, int *minor, unsigned int *offset)
1035{
1036        int major;
1037        major = BLKIF_MAJOR(vdevice);
1038        *minor = BLKIF_MINOR(vdevice);
1039        switch (major) {
1040                case XEN_IDE0_MAJOR:
1041                        *offset = (*minor / 64) + EMULATED_HD_DISK_NAME_OFFSET;
1042                        *minor = ((*minor / 64) * PARTS_PER_DISK) +
1043                                EMULATED_HD_DISK_MINOR_OFFSET;
1044                        break;
1045                case XEN_IDE1_MAJOR:
1046                        *offset = (*minor / 64) + 2 + EMULATED_HD_DISK_NAME_OFFSET;
1047                        *minor = (((*minor / 64) + 2) * PARTS_PER_DISK) +
1048                                EMULATED_HD_DISK_MINOR_OFFSET;
1049                        break;
1050                case XEN_SCSI_DISK0_MAJOR:
1051                        *offset = (*minor / PARTS_PER_DISK) + EMULATED_SD_DISK_NAME_OFFSET;
1052                        *minor = *minor + EMULATED_SD_DISK_MINOR_OFFSET;
1053                        break;
1054                case XEN_SCSI_DISK1_MAJOR:
1055                case XEN_SCSI_DISK2_MAJOR:
1056                case XEN_SCSI_DISK3_MAJOR:
1057                case XEN_SCSI_DISK4_MAJOR:
1058                case XEN_SCSI_DISK5_MAJOR:
1059                case XEN_SCSI_DISK6_MAJOR:
1060                case XEN_SCSI_DISK7_MAJOR:
1061                        *offset = (*minor / PARTS_PER_DISK) + 
1062                                ((major - XEN_SCSI_DISK1_MAJOR + 1) * 16) +
1063                                EMULATED_SD_DISK_NAME_OFFSET;
1064                        *minor = *minor +
1065                                ((major - XEN_SCSI_DISK1_MAJOR + 1) * 16 * PARTS_PER_DISK) +
1066                                EMULATED_SD_DISK_MINOR_OFFSET;
1067                        break;
1068                case XEN_SCSI_DISK8_MAJOR:
1069                case XEN_SCSI_DISK9_MAJOR:
1070                case XEN_SCSI_DISK10_MAJOR:
1071                case XEN_SCSI_DISK11_MAJOR:
1072                case XEN_SCSI_DISK12_MAJOR:
1073                case XEN_SCSI_DISK13_MAJOR:
1074                case XEN_SCSI_DISK14_MAJOR:
1075                case XEN_SCSI_DISK15_MAJOR:
1076                        *offset = (*minor / PARTS_PER_DISK) + 
1077                                ((major - XEN_SCSI_DISK8_MAJOR + 8) * 16) +
1078                                EMULATED_SD_DISK_NAME_OFFSET;
1079                        *minor = *minor +
1080                                ((major - XEN_SCSI_DISK8_MAJOR + 8) * 16 * PARTS_PER_DISK) +
1081                                EMULATED_SD_DISK_MINOR_OFFSET;
1082                        break;
1083                case XENVBD_MAJOR:
1084                        *offset = *minor / PARTS_PER_DISK;
1085                        break;
1086                default:
1087                        printk(KERN_WARNING "blkfront: your disk configuration is "
1088                                        "incorrect, please use an xvd device instead\n");
1089                        return -ENODEV;
1090        }
1091        return 0;
1092}
1093
1094static char *encode_disk_name(char *ptr, unsigned int n)
1095{
1096        if (n >= 26)
1097                ptr = encode_disk_name(ptr, n / 26 - 1);
1098        *ptr = 'a' + n % 26;
1099        return ptr + 1;
1100}
1101
1102static int xlvbd_alloc_gendisk(blkif_sector_t capacity,
1103                               struct blkfront_info *info,
1104                               u16 vdisk_info, u16 sector_size,
1105                               unsigned int physical_sector_size)
1106{
1107        struct gendisk *gd;
1108        int nr_minors = 1;
1109        int err;
1110        unsigned int offset;
1111        int minor;
1112        int nr_parts;
1113        char *ptr;
1114
1115        BUG_ON(info->gd != NULL);
1116        BUG_ON(info->rq != NULL);
1117
1118        if ((info->vdevice>>EXT_SHIFT) > 1) {
1119                /* this is above the extended range; something is wrong */
1120                printk(KERN_WARNING "blkfront: vdevice 0x%x is above the extended range; ignoring\n", info->vdevice);
1121                return -ENODEV;
1122        }
1123
1124        if (!VDEV_IS_EXTENDED(info->vdevice)) {
1125                err = xen_translate_vdev(info->vdevice, &minor, &offset);
1126                if (err)
1127                        return err;
1128                nr_parts = PARTS_PER_DISK;
1129        } else {
1130                minor = BLKIF_MINOR_EXT(info->vdevice);
1131                nr_parts = PARTS_PER_EXT_DISK;
1132                offset = minor / nr_parts;
1133                if (xen_hvm_domain() && offset < EMULATED_HD_DISK_NAME_OFFSET + 4)
1134                        printk(KERN_WARNING "blkfront: vdevice 0x%x might conflict with "
1135                                        "emulated IDE disks,\n\t choose an xvd device name"
1136                                        "from xvde on\n", info->vdevice);
1137        }
1138        if (minor >> MINORBITS) {
1139                pr_warn("blkfront: %#x's minor (%#x) out of range; ignoring\n",
1140                        info->vdevice, minor);
1141                return -ENODEV;
1142        }
1143
1144        if ((minor % nr_parts) == 0)
1145                nr_minors = nr_parts;
1146
1147        err = xlbd_reserve_minors(minor, nr_minors);
1148        if (err)
1149                goto out;
1150        err = -ENODEV;
1151
1152        gd = alloc_disk(nr_minors);
1153        if (gd == NULL)
1154                goto release;
1155
1156        strcpy(gd->disk_name, DEV_NAME);
1157        ptr = encode_disk_name(gd->disk_name + sizeof(DEV_NAME) - 1, offset);
1158        BUG_ON(ptr >= gd->disk_name + DISK_NAME_LEN);
1159        if (nr_minors > 1)
1160                *ptr = 0;
1161        else
1162                snprintf(ptr, gd->disk_name + DISK_NAME_LEN - ptr,
1163                         "%d", minor & (nr_parts - 1));
1164
1165        gd->major = XENVBD_MAJOR;
1166        gd->first_minor = minor;
1167        gd->fops = &xlvbd_block_fops;
1168        gd->private_data = info;
1169        set_capacity(gd, capacity);
1170
1171        if (xlvbd_init_blk_queue(gd, sector_size, physical_sector_size)) {
1172                del_gendisk(gd);
1173                goto release;
1174        }
1175
1176        xlvbd_flush(info);
1177
1178        if (vdisk_info & VDISK_READONLY)
1179                set_disk_ro(gd, 1);
1180
1181        if (vdisk_info & VDISK_REMOVABLE)
1182                gd->flags |= GENHD_FL_REMOVABLE;
1183
1184        if (vdisk_info & VDISK_CDROM)
1185                gd->flags |= GENHD_FL_CD;
1186
1187        return 0;
1188
1189 release:
1190        xlbd_release_minors(minor, nr_minors);
1191 out:
1192        return err;
1193}
1194
1195static void xlvbd_release_gendisk(struct blkfront_info *info)
1196{
1197        unsigned int minor, nr_minors, i;
1198        struct blkfront_ring_info *rinfo;
1199
1200        if (info->rq == NULL)
1201                return;
1202
1203        /* No more blkif_request(). */
1204        blk_mq_stop_hw_queues(info->rq);
1205
1206        for_each_rinfo(info, rinfo, i) {
1207                /* No more gnttab callback work. */
1208                gnttab_cancel_free_callback(&rinfo->callback);
1209
1210                /* Flush gnttab callback work. Must be done with no locks held. */
1211                flush_work(&rinfo->work);
1212        }
1213
1214        del_gendisk(info->gd);
1215
1216        minor = info->gd->first_minor;
1217        nr_minors = info->gd->minors;
1218        xlbd_release_minors(minor, nr_minors);
1219
1220        blk_cleanup_queue(info->rq);
1221        blk_mq_free_tag_set(&info->tag_set);
1222        info->rq = NULL;
1223
1224        put_disk(info->gd);
1225        info->gd = NULL;
1226}
1227
1228/* Already hold rinfo->ring_lock. */
1229static inline void kick_pending_request_queues_locked(struct blkfront_ring_info *rinfo)
1230{
1231        if (!RING_FULL(&rinfo->ring))
1232                blk_mq_start_stopped_hw_queues(rinfo->dev_info->rq, true);
1233}
1234
1235static void kick_pending_request_queues(struct blkfront_ring_info *rinfo)
1236{
1237        unsigned long flags;
1238
1239        spin_lock_irqsave(&rinfo->ring_lock, flags);
1240        kick_pending_request_queues_locked(rinfo);
1241        spin_unlock_irqrestore(&rinfo->ring_lock, flags);
1242}
1243
1244static void blkif_restart_queue(struct work_struct *work)
1245{
1246        struct blkfront_ring_info *rinfo = container_of(work, struct blkfront_ring_info, work);
1247
1248        if (rinfo->dev_info->connected == BLKIF_STATE_CONNECTED)
1249                kick_pending_request_queues(rinfo);
1250}
1251
1252static void blkif_free_ring(struct blkfront_ring_info *rinfo)
1253{
1254        struct grant *persistent_gnt, *n;
1255        struct blkfront_info *info = rinfo->dev_info;
1256        int i, j, segs;
1257
1258        /*
1259         * Remove indirect pages, this only happens when using indirect
1260         * descriptors but not persistent grants
1261         */
1262        if (!list_empty(&rinfo->indirect_pages)) {
1263                struct page *indirect_page, *n;
1264
1265                BUG_ON(info->feature_persistent);
1266                list_for_each_entry_safe(indirect_page, n, &rinfo->indirect_pages, lru) {
1267                        list_del(&indirect_page->lru);
1268                        __free_page(indirect_page);
1269                }
1270        }
1271
1272        /* Remove all persistent grants. */
1273        if (!list_empty(&rinfo->grants)) {
1274                list_for_each_entry_safe(persistent_gnt, n,
1275                                         &rinfo->grants, node) {
1276                        list_del(&persistent_gnt->node);
1277                        if (persistent_gnt->gref != GRANT_INVALID_REF) {
1278                                gnttab_end_foreign_access(persistent_gnt->gref,
1279                                                          0, 0UL);
1280                                rinfo->persistent_gnts_c--;
1281                        }
1282                        if (info->feature_persistent)
1283                                __free_page(persistent_gnt->page);
1284                        kfree(persistent_gnt);
1285                }
1286        }
1287        BUG_ON(rinfo->persistent_gnts_c != 0);
1288
1289        for (i = 0; i < BLK_RING_SIZE(info); i++) {
1290                /*
1291                 * Clear persistent grants present in requests already
1292                 * on the shared ring
1293                 */
1294                if (!rinfo->shadow[i].request)
1295                        goto free_shadow;
1296
1297                segs = rinfo->shadow[i].req.operation == BLKIF_OP_INDIRECT ?
1298                       rinfo->shadow[i].req.u.indirect.nr_segments :
1299                       rinfo->shadow[i].req.u.rw.nr_segments;
1300                for (j = 0; j < segs; j++) {
1301                        persistent_gnt = rinfo->shadow[i].grants_used[j];
1302                        gnttab_end_foreign_access(persistent_gnt->gref, 0, 0UL);
1303                        if (info->feature_persistent)
1304                                __free_page(persistent_gnt->page);
1305                        kfree(persistent_gnt);
1306                }
1307
1308                if (rinfo->shadow[i].req.operation != BLKIF_OP_INDIRECT)
1309                        /*
1310                         * If this is not an indirect operation don't try to
1311                         * free indirect segments
1312                         */
1313                        goto free_shadow;
1314
1315                for (j = 0; j < INDIRECT_GREFS(segs); j++) {
1316                        persistent_gnt = rinfo->shadow[i].indirect_grants[j];
1317                        gnttab_end_foreign_access(persistent_gnt->gref, 0, 0UL);
1318                        __free_page(persistent_gnt->page);
1319                        kfree(persistent_gnt);
1320                }
1321
1322free_shadow:
1323                kvfree(rinfo->shadow[i].grants_used);
1324                rinfo->shadow[i].grants_used = NULL;
1325                kvfree(rinfo->shadow[i].indirect_grants);
1326                rinfo->shadow[i].indirect_grants = NULL;
1327                kvfree(rinfo->shadow[i].sg);
1328                rinfo->shadow[i].sg = NULL;
1329        }
1330
1331        /* No more gnttab callback work. */
1332        gnttab_cancel_free_callback(&rinfo->callback);
1333
1334        /* Flush gnttab callback work. Must be done with no locks held. */
1335        flush_work(&rinfo->work);
1336
1337        /* Free resources associated with old device channel. */
1338        for (i = 0; i < info->nr_ring_pages; i++) {
1339                if (rinfo->ring_ref[i] != GRANT_INVALID_REF) {
1340                        gnttab_end_foreign_access(rinfo->ring_ref[i], 0, 0);
1341                        rinfo->ring_ref[i] = GRANT_INVALID_REF;
1342                }
1343        }
1344        free_pages((unsigned long)rinfo->ring.sring, get_order(info->nr_ring_pages * XEN_PAGE_SIZE));
1345        rinfo->ring.sring = NULL;
1346
1347        if (rinfo->irq)
1348                unbind_from_irqhandler(rinfo->irq, rinfo);
1349        rinfo->evtchn = rinfo->irq = 0;
1350}
1351
1352static void blkif_free(struct blkfront_info *info, int suspend)
1353{
1354        unsigned int i;
1355        struct blkfront_ring_info *rinfo;
1356
1357        /* Prevent new requests being issued until we fix things up. */
1358        info->connected = suspend ?
1359                BLKIF_STATE_SUSPENDED : BLKIF_STATE_DISCONNECTED;
1360        /* No more blkif_request(). */
1361        if (info->rq)
1362                blk_mq_stop_hw_queues(info->rq);
1363
1364        for_each_rinfo(info, rinfo, i)
1365                blkif_free_ring(rinfo);
1366
1367        kvfree(info->rinfo);
1368        info->rinfo = NULL;
1369        info->nr_rings = 0;
1370}
1371
1372struct copy_from_grant {
1373        const struct blk_shadow *s;
1374        unsigned int grant_idx;
1375        unsigned int bvec_offset;
1376        char *bvec_data;
1377};
1378
1379static void blkif_copy_from_grant(unsigned long gfn, unsigned int offset,
1380                                  unsigned int len, void *data)
1381{
1382        struct copy_from_grant *info = data;
1383        char *shared_data;
1384        /* Convenient aliases */
1385        const struct blk_shadow *s = info->s;
1386
1387        shared_data = kmap_atomic(s->grants_used[info->grant_idx]->page);
1388
1389        memcpy(info->bvec_data + info->bvec_offset,
1390               shared_data + offset, len);
1391
1392        info->bvec_offset += len;
1393        info->grant_idx++;
1394
1395        kunmap_atomic(shared_data);
1396}
1397
1398static enum blk_req_status blkif_rsp_to_req_status(int rsp)
1399{
1400        switch (rsp)
1401        {
1402        case BLKIF_RSP_OKAY:
1403                return REQ_DONE;
1404        case BLKIF_RSP_EOPNOTSUPP:
1405                return REQ_EOPNOTSUPP;
1406        case BLKIF_RSP_ERROR:
1407        default:
1408                return REQ_ERROR;
1409        }
1410}
1411
1412/*
1413 * Get the final status of the block request based on two ring response
1414 */
1415static int blkif_get_final_status(enum blk_req_status s1,
1416                                  enum blk_req_status s2)
1417{
1418        BUG_ON(s1 == REQ_WAITING);
1419        BUG_ON(s2 == REQ_WAITING);
1420
1421        if (s1 == REQ_ERROR || s2 == REQ_ERROR)
1422                return BLKIF_RSP_ERROR;
1423        else if (s1 == REQ_EOPNOTSUPP || s2 == REQ_EOPNOTSUPP)
1424                return BLKIF_RSP_EOPNOTSUPP;
1425        return BLKIF_RSP_OKAY;
1426}
1427
1428static bool blkif_completion(unsigned long *id,
1429                             struct blkfront_ring_info *rinfo,
1430                             struct blkif_response *bret)
1431{
1432        int i = 0;
1433        struct scatterlist *sg;
1434        int num_sg, num_grant;
1435        struct blkfront_info *info = rinfo->dev_info;
1436        struct blk_shadow *s = &rinfo->shadow[*id];
1437        struct copy_from_grant data = {
1438                .grant_idx = 0,
1439        };
1440
1441        num_grant = s->req.operation == BLKIF_OP_INDIRECT ?
1442                s->req.u.indirect.nr_segments : s->req.u.rw.nr_segments;
1443
1444        /* The I/O request may be split in two. */
1445        if (unlikely(s->associated_id != NO_ASSOCIATED_ID)) {
1446                struct blk_shadow *s2 = &rinfo->shadow[s->associated_id];
1447
1448                /* Keep the status of the current response in shadow. */
1449                s->status = blkif_rsp_to_req_status(bret->status);
1450
1451                /* Wait the second response if not yet here. */
1452                if (s2->status == REQ_WAITING)
1453                        return false;
1454
1455                bret->status = blkif_get_final_status(s->status,
1456                                                      s2->status);
1457
1458                /*
1459                 * All the grants is stored in the first shadow in order
1460                 * to make the completion code simpler.
1461                 */
1462                num_grant += s2->req.u.rw.nr_segments;
1463
1464                /*
1465                 * The two responses may not come in order. Only the
1466                 * first request will store the scatter-gather list.
1467                 */
1468                if (s2->num_sg != 0) {
1469                        /* Update "id" with the ID of the first response. */
1470                        *id = s->associated_id;
1471                        s = s2;
1472                }
1473
1474                /*
1475                 * We don't need anymore the second request, so recycling
1476                 * it now.
1477                 */
1478                if (add_id_to_freelist(rinfo, s->associated_id))
1479                        WARN(1, "%s: can't recycle the second part (id = %ld) of the request\n",
1480                             info->gd->disk_name, s->associated_id);
1481        }
1482
1483        data.s = s;
1484        num_sg = s->num_sg;
1485
1486        if (bret->operation == BLKIF_OP_READ && info->feature_persistent) {
1487                for_each_sg(s->sg, sg, num_sg, i) {
1488                        BUG_ON(sg->offset + sg->length > PAGE_SIZE);
1489
1490                        data.bvec_offset = sg->offset;
1491                        data.bvec_data = kmap_atomic(sg_page(sg));
1492
1493                        gnttab_foreach_grant_in_range(sg_page(sg),
1494                                                      sg->offset,
1495                                                      sg->length,
1496                                                      blkif_copy_from_grant,
1497                                                      &data);
1498
1499                        kunmap_atomic(data.bvec_data);
1500                }
1501        }
1502        /* Add the persistent grant into the list of free grants */
1503        for (i = 0; i < num_grant; i++) {
1504                if (gnttab_query_foreign_access(s->grants_used[i]->gref)) {
1505                        /*
1506                         * If the grant is still mapped by the backend (the
1507                         * backend has chosen to make this grant persistent)
1508                         * we add it at the head of the list, so it will be
1509                         * reused first.
1510                         */
1511                        if (!info->feature_persistent)
1512                                pr_alert_ratelimited("backed has not unmapped grant: %u\n",
1513                                                     s->grants_used[i]->gref);
1514                        list_add(&s->grants_used[i]->node, &rinfo->grants);
1515                        rinfo->persistent_gnts_c++;
1516                } else {
1517                        /*
1518                         * If the grant is not mapped by the backend we end the
1519                         * foreign access and add it to the tail of the list,
1520                         * so it will not be picked again unless we run out of
1521                         * persistent grants.
1522                         */
1523                        gnttab_end_foreign_access(s->grants_used[i]->gref, 0, 0UL);
1524                        s->grants_used[i]->gref = GRANT_INVALID_REF;
1525                        list_add_tail(&s->grants_used[i]->node, &rinfo->grants);
1526                }
1527        }
1528        if (s->req.operation == BLKIF_OP_INDIRECT) {
1529                for (i = 0; i < INDIRECT_GREFS(num_grant); i++) {
1530                        if (gnttab_query_foreign_access(s->indirect_grants[i]->gref)) {
1531                                if (!info->feature_persistent)
1532                                        pr_alert_ratelimited("backed has not unmapped grant: %u\n",
1533                                                             s->indirect_grants[i]->gref);
1534                                list_add(&s->indirect_grants[i]->node, &rinfo->grants);
1535                                rinfo->persistent_gnts_c++;
1536                        } else {
1537                                struct page *indirect_page;
1538
1539                                gnttab_end_foreign_access(s->indirect_grants[i]->gref, 0, 0UL);
1540                                /*
1541                                 * Add the used indirect page back to the list of
1542                                 * available pages for indirect grefs.
1543                                 */
1544                                if (!info->feature_persistent) {
1545                                        indirect_page = s->indirect_grants[i]->page;
1546                                        list_add(&indirect_page->lru, &rinfo->indirect_pages);
1547                                }
1548                                s->indirect_grants[i]->gref = GRANT_INVALID_REF;
1549                                list_add_tail(&s->indirect_grants[i]->node, &rinfo->grants);
1550                        }
1551                }
1552        }
1553
1554        return true;
1555}
1556
1557static irqreturn_t blkif_interrupt(int irq, void *dev_id)
1558{
1559        struct request *req;
1560        struct blkif_response *bret;
1561        RING_IDX i, rp;
1562        unsigned long flags;
1563        struct blkfront_ring_info *rinfo = (struct blkfront_ring_info *)dev_id;
1564        struct blkfront_info *info = rinfo->dev_info;
1565
1566        if (unlikely(info->connected != BLKIF_STATE_CONNECTED))
1567                return IRQ_HANDLED;
1568
1569        spin_lock_irqsave(&rinfo->ring_lock, flags);
1570 again:
1571        rp = rinfo->ring.sring->rsp_prod;
1572        rmb(); /* Ensure we see queued responses up to 'rp'. */
1573
1574        for (i = rinfo->ring.rsp_cons; i != rp; i++) {
1575                unsigned long id;
1576
1577                bret = RING_GET_RESPONSE(&rinfo->ring, i);
1578                id   = bret->id;
1579                /*
1580                 * The backend has messed up and given us an id that we would
1581                 * never have given to it (we stamp it up to BLK_RING_SIZE -
1582                 * look in get_id_from_freelist.
1583                 */
1584                if (id >= BLK_RING_SIZE(info)) {
1585                        WARN(1, "%s: response to %s has incorrect id (%ld)\n",
1586                             info->gd->disk_name, op_name(bret->operation), id);
1587                        /* We can't safely get the 'struct request' as
1588                         * the id is busted. */
1589                        continue;
1590                }
1591                req  = rinfo->shadow[id].request;
1592
1593                if (bret->operation != BLKIF_OP_DISCARD) {
1594                        /*
1595                         * We may need to wait for an extra response if the
1596                         * I/O request is split in 2
1597                         */
1598                        if (!blkif_completion(&id, rinfo, bret))
1599                                continue;
1600                }
1601
1602                if (add_id_to_freelist(rinfo, id)) {
1603                        WARN(1, "%s: response to %s (id %ld) couldn't be recycled!\n",
1604                             info->gd->disk_name, op_name(bret->operation), id);
1605                        continue;
1606                }
1607
1608                if (bret->status == BLKIF_RSP_OKAY)
1609                        blkif_req(req)->error = BLK_STS_OK;
1610                else
1611                        blkif_req(req)->error = BLK_STS_IOERR;
1612
1613                switch (bret->operation) {
1614                case BLKIF_OP_DISCARD:
1615                        if (unlikely(bret->status == BLKIF_RSP_EOPNOTSUPP)) {
1616                                struct request_queue *rq = info->rq;
1617                                printk(KERN_WARNING "blkfront: %s: %s op failed\n",
1618                                           info->gd->disk_name, op_name(bret->operation));
1619                                blkif_req(req)->error = BLK_STS_NOTSUPP;
1620                                info->feature_discard = 0;
1621                                info->feature_secdiscard = 0;
1622                                blk_queue_flag_clear(QUEUE_FLAG_DISCARD, rq);
1623                                blk_queue_flag_clear(QUEUE_FLAG_SECERASE, rq);
1624                        }
1625                        break;
1626                case BLKIF_OP_FLUSH_DISKCACHE:
1627                case BLKIF_OP_WRITE_BARRIER:
1628                        if (unlikely(bret->status == BLKIF_RSP_EOPNOTSUPP)) {
1629                                printk(KERN_WARNING "blkfront: %s: %s op failed\n",
1630                                       info->gd->disk_name, op_name(bret->operation));
1631                                blkif_req(req)->error = BLK_STS_NOTSUPP;
1632                        }
1633                        if (unlikely(bret->status == BLKIF_RSP_ERROR &&
1634                                     rinfo->shadow[id].req.u.rw.nr_segments == 0)) {
1635                                printk(KERN_WARNING "blkfront: %s: empty %s op failed\n",
1636                                       info->gd->disk_name, op_name(bret->operation));
1637                                blkif_req(req)->error = BLK_STS_NOTSUPP;
1638                        }
1639                        if (unlikely(blkif_req(req)->error)) {
1640                                if (blkif_req(req)->error == BLK_STS_NOTSUPP)
1641                                        blkif_req(req)->error = BLK_STS_OK;
1642                                info->feature_fua = 0;
1643                                info->feature_flush = 0;
1644                                xlvbd_flush(info);
1645                        }
1646                        fallthrough;
1647                case BLKIF_OP_READ:
1648                case BLKIF_OP_WRITE:
1649                        if (unlikely(bret->status != BLKIF_RSP_OKAY))
1650                                dev_dbg(&info->xbdev->dev, "Bad return from blkdev data "
1651                                        "request: %x\n", bret->status);
1652
1653                        break;
1654                default:
1655                        BUG();
1656                }
1657
1658                if (likely(!blk_should_fake_timeout(req->q)))
1659                        blk_mq_complete_request(req);
1660        }
1661
1662        rinfo->ring.rsp_cons = i;
1663
1664        if (i != rinfo->ring.req_prod_pvt) {
1665                int more_to_do;
1666                RING_FINAL_CHECK_FOR_RESPONSES(&rinfo->ring, more_to_do);
1667                if (more_to_do)
1668                        goto again;
1669        } else
1670                rinfo->ring.sring->rsp_event = i + 1;
1671
1672        kick_pending_request_queues_locked(rinfo);
1673
1674        spin_unlock_irqrestore(&rinfo->ring_lock, flags);
1675
1676        return IRQ_HANDLED;
1677}
1678
1679
1680static int setup_blkring(struct xenbus_device *dev,
1681                         struct blkfront_ring_info *rinfo)
1682{
1683        struct blkif_sring *sring;
1684        int err, i;
1685        struct blkfront_info *info = rinfo->dev_info;
1686        unsigned long ring_size = info->nr_ring_pages * XEN_PAGE_SIZE;
1687        grant_ref_t gref[XENBUS_MAX_RING_GRANTS];
1688
1689        for (i = 0; i < info->nr_ring_pages; i++)
1690                rinfo->ring_ref[i] = GRANT_INVALID_REF;
1691
1692        sring = (struct blkif_sring *)__get_free_pages(GFP_NOIO | __GFP_HIGH,
1693                                                       get_order(ring_size));
1694        if (!sring) {
1695                xenbus_dev_fatal(dev, -ENOMEM, "allocating shared ring");
1696                return -ENOMEM;
1697        }
1698        SHARED_RING_INIT(sring);
1699        FRONT_RING_INIT(&rinfo->ring, sring, ring_size);
1700
1701        err = xenbus_grant_ring(dev, rinfo->ring.sring, info->nr_ring_pages, gref);
1702        if (err < 0) {
1703                free_pages((unsigned long)sring, get_order(ring_size));
1704                rinfo->ring.sring = NULL;
1705                goto fail;
1706        }
1707        for (i = 0; i < info->nr_ring_pages; i++)
1708                rinfo->ring_ref[i] = gref[i];
1709
1710        err = xenbus_alloc_evtchn(dev, &rinfo->evtchn);
1711        if (err)
1712                goto fail;
1713
1714        err = bind_evtchn_to_irqhandler(rinfo->evtchn, blkif_interrupt, 0,
1715                                        "blkif", rinfo);
1716        if (err <= 0) {
1717                xenbus_dev_fatal(dev, err,
1718                                 "bind_evtchn_to_irqhandler failed");
1719                goto fail;
1720        }
1721        rinfo->irq = err;
1722
1723        return 0;
1724fail:
1725        blkif_free(info, 0);
1726        return err;
1727}
1728
1729/*
1730 * Write out per-ring/queue nodes including ring-ref and event-channel, and each
1731 * ring buffer may have multi pages depending on ->nr_ring_pages.
1732 */
1733static int write_per_ring_nodes(struct xenbus_transaction xbt,
1734                                struct blkfront_ring_info *rinfo, const char *dir)
1735{
1736        int err;
1737        unsigned int i;
1738        const char *message = NULL;
1739        struct blkfront_info *info = rinfo->dev_info;
1740
1741        if (info->nr_ring_pages == 1) {
1742                err = xenbus_printf(xbt, dir, "ring-ref", "%u", rinfo->ring_ref[0]);
1743                if (err) {
1744                        message = "writing ring-ref";
1745                        goto abort_transaction;
1746                }
1747        } else {
1748                for (i = 0; i < info->nr_ring_pages; i++) {
1749                        char ring_ref_name[RINGREF_NAME_LEN];
1750
1751                        snprintf(ring_ref_name, RINGREF_NAME_LEN, "ring-ref%u", i);
1752                        err = xenbus_printf(xbt, dir, ring_ref_name,
1753                                            "%u", rinfo->ring_ref[i]);
1754                        if (err) {
1755                                message = "writing ring-ref";
1756                                goto abort_transaction;
1757                        }
1758                }
1759        }
1760
1761        err = xenbus_printf(xbt, dir, "event-channel", "%u", rinfo->evtchn);
1762        if (err) {
1763                message = "writing event-channel";
1764                goto abort_transaction;
1765        }
1766
1767        return 0;
1768
1769abort_transaction:
1770        xenbus_transaction_end(xbt, 1);
1771        if (message)
1772                xenbus_dev_fatal(info->xbdev, err, "%s", message);
1773
1774        return err;
1775}
1776
1777static void free_info(struct blkfront_info *info)
1778{
1779        list_del(&info->info_list);
1780        kfree(info);
1781}
1782
1783/* Common code used when first setting up, and when resuming. */
1784static int talk_to_blkback(struct xenbus_device *dev,
1785                           struct blkfront_info *info)
1786{
1787        const char *message = NULL;
1788        struct xenbus_transaction xbt;
1789        int err;
1790        unsigned int i, max_page_order;
1791        unsigned int ring_page_order;
1792        struct blkfront_ring_info *rinfo;
1793
1794        if (!info)
1795                return -ENODEV;
1796
1797        max_page_order = xenbus_read_unsigned(info->xbdev->otherend,
1798                                              "max-ring-page-order", 0);
1799        ring_page_order = min(xen_blkif_max_ring_order, max_page_order);
1800        info->nr_ring_pages = 1 << ring_page_order;
1801
1802        err = negotiate_mq(info);
1803        if (err)
1804                goto destroy_blkring;
1805
1806        for_each_rinfo(info, rinfo, i) {
1807                /* Create shared ring, alloc event channel. */
1808                err = setup_blkring(dev, rinfo);
1809                if (err)
1810                        goto destroy_blkring;
1811        }
1812
1813again:
1814        err = xenbus_transaction_start(&xbt);
1815        if (err) {
1816                xenbus_dev_fatal(dev, err, "starting transaction");
1817                goto destroy_blkring;
1818        }
1819
1820        if (info->nr_ring_pages > 1) {
1821                err = xenbus_printf(xbt, dev->nodename, "ring-page-order", "%u",
1822                                    ring_page_order);
1823                if (err) {
1824                        message = "writing ring-page-order";
1825                        goto abort_transaction;
1826                }
1827        }
1828
1829        /* We already got the number of queues/rings in _probe */
1830        if (info->nr_rings == 1) {
1831                err = write_per_ring_nodes(xbt, info->rinfo, dev->nodename);
1832                if (err)
1833                        goto destroy_blkring;
1834        } else {
1835                char *path;
1836                size_t pathsize;
1837
1838                err = xenbus_printf(xbt, dev->nodename, "multi-queue-num-queues", "%u",
1839                                    info->nr_rings);
1840                if (err) {
1841                        message = "writing multi-queue-num-queues";
1842                        goto abort_transaction;
1843                }
1844
1845                pathsize = strlen(dev->nodename) + QUEUE_NAME_LEN;
1846                path = kmalloc(pathsize, GFP_KERNEL);
1847                if (!path) {
1848                        err = -ENOMEM;
1849                        message = "ENOMEM while writing ring references";
1850                        goto abort_transaction;
1851                }
1852
1853                for_each_rinfo(info, rinfo, i) {
1854                        memset(path, 0, pathsize);
1855                        snprintf(path, pathsize, "%s/queue-%u", dev->nodename, i);
1856                        err = write_per_ring_nodes(xbt, rinfo, path);
1857                        if (err) {
1858                                kfree(path);
1859                                goto destroy_blkring;
1860                        }
1861                }
1862                kfree(path);
1863        }
1864        err = xenbus_printf(xbt, dev->nodename, "protocol", "%s",
1865                            XEN_IO_PROTO_ABI_NATIVE);
1866        if (err) {
1867                message = "writing protocol";
1868                goto abort_transaction;
1869        }
1870        err = xenbus_printf(xbt, dev->nodename, "feature-persistent", "%u",
1871                        info->feature_persistent);
1872        if (err)
1873                dev_warn(&dev->dev,
1874                         "writing persistent grants feature to xenbus");
1875
1876        err = xenbus_transaction_end(xbt, 0);
1877        if (err) {
1878                if (err == -EAGAIN)
1879                        goto again;
1880                xenbus_dev_fatal(dev, err, "completing transaction");
1881                goto destroy_blkring;
1882        }
1883
1884        for_each_rinfo(info, rinfo, i) {
1885                unsigned int j;
1886
1887                for (j = 0; j < BLK_RING_SIZE(info); j++)
1888                        rinfo->shadow[j].req.u.rw.id = j + 1;
1889                rinfo->shadow[BLK_RING_SIZE(info)-1].req.u.rw.id = 0x0fffffff;
1890        }
1891        xenbus_switch_state(dev, XenbusStateInitialised);
1892
1893        return 0;
1894
1895 abort_transaction:
1896        xenbus_transaction_end(xbt, 1);
1897        if (message)
1898                xenbus_dev_fatal(dev, err, "%s", message);
1899 destroy_blkring:
1900        blkif_free(info, 0);
1901
1902        mutex_lock(&blkfront_mutex);
1903        free_info(info);
1904        mutex_unlock(&blkfront_mutex);
1905
1906        dev_set_drvdata(&dev->dev, NULL);
1907
1908        return err;
1909}
1910
1911static int negotiate_mq(struct blkfront_info *info)
1912{
1913        unsigned int backend_max_queues;
1914        unsigned int i;
1915        struct blkfront_ring_info *rinfo;
1916
1917        BUG_ON(info->nr_rings);
1918
1919        /* Check if backend supports multiple queues. */
1920        backend_max_queues = xenbus_read_unsigned(info->xbdev->otherend,
1921                                                  "multi-queue-max-queues", 1);
1922        info->nr_rings = min(backend_max_queues, xen_blkif_max_queues);
1923        /* We need at least one ring. */
1924        if (!info->nr_rings)
1925                info->nr_rings = 1;
1926
1927        info->rinfo_size = struct_size(info->rinfo, shadow,
1928                                       BLK_RING_SIZE(info));
1929        info->rinfo = kvcalloc(info->nr_rings, info->rinfo_size, GFP_KERNEL);
1930        if (!info->rinfo) {
1931                xenbus_dev_fatal(info->xbdev, -ENOMEM, "allocating ring_info structure");
1932                info->nr_rings = 0;
1933                return -ENOMEM;
1934        }
1935
1936        for_each_rinfo(info, rinfo, i) {
1937                INIT_LIST_HEAD(&rinfo->indirect_pages);
1938                INIT_LIST_HEAD(&rinfo->grants);
1939                rinfo->dev_info = info;
1940                INIT_WORK(&rinfo->work, blkif_restart_queue);
1941                spin_lock_init(&rinfo->ring_lock);
1942        }
1943        return 0;
1944}
1945
1946/* Enable the persistent grants feature. */
1947static bool feature_persistent = true;
1948module_param(feature_persistent, bool, 0644);
1949MODULE_PARM_DESC(feature_persistent,
1950                "Enables the persistent grants feature");
1951
1952/*
1953 * Entry point to this code when a new device is created.  Allocate the basic
1954 * structures and the ring buffer for communication with the backend, and
1955 * inform the backend of the appropriate details for those.  Switch to
1956 * Initialised state.
1957 */
1958static int blkfront_probe(struct xenbus_device *dev,
1959                          const struct xenbus_device_id *id)
1960{
1961        int err, vdevice;
1962        struct blkfront_info *info;
1963
1964        /* FIXME: Use dynamic device id if this is not set. */
1965        err = xenbus_scanf(XBT_NIL, dev->nodename,
1966                           "virtual-device", "%i", &vdevice);
1967        if (err != 1) {
1968                /* go looking in the extended area instead */
1969                err = xenbus_scanf(XBT_NIL, dev->nodename, "virtual-device-ext",
1970                                   "%i", &vdevice);
1971                if (err != 1) {
1972                        xenbus_dev_fatal(dev, err, "reading virtual-device");
1973                        return err;
1974                }
1975        }
1976
1977        if (xen_hvm_domain()) {
1978                char *type;
1979                int len;
1980                /* no unplug has been done: do not hook devices != xen vbds */
1981                if (xen_has_pv_and_legacy_disk_devices()) {
1982                        int major;
1983
1984                        if (!VDEV_IS_EXTENDED(vdevice))
1985                                major = BLKIF_MAJOR(vdevice);
1986                        else
1987                                major = XENVBD_MAJOR;
1988
1989                        if (major != XENVBD_MAJOR) {
1990                                printk(KERN_INFO
1991                                                "%s: HVM does not support vbd %d as xen block device\n",
1992                                                __func__, vdevice);
1993                                return -ENODEV;
1994                        }
1995                }
1996                /* do not create a PV cdrom device if we are an HVM guest */
1997                type = xenbus_read(XBT_NIL, dev->nodename, "device-type", &len);
1998                if (IS_ERR(type))
1999                        return -ENODEV;
2000                if (strncmp(type, "cdrom", 5) == 0) {
2001                        kfree(type);
2002                        return -ENODEV;
2003                }
2004                kfree(type);
2005        }
2006        info = kzalloc(sizeof(*info), GFP_KERNEL);
2007        if (!info) {
2008                xenbus_dev_fatal(dev, -ENOMEM, "allocating info structure");
2009                return -ENOMEM;
2010        }
2011
2012        info->xbdev = dev;
2013
2014        mutex_init(&info->mutex);
2015        info->vdevice = vdevice;
2016        info->connected = BLKIF_STATE_DISCONNECTED;
2017
2018        info->feature_persistent = feature_persistent;
2019
2020        /* Front end dir is a number, which is used as the id. */
2021        info->handle = simple_strtoul(strrchr(dev->nodename, '/')+1, NULL, 0);
2022        dev_set_drvdata(&dev->dev, info);
2023
2024        mutex_lock(&blkfront_mutex);
2025        list_add(&info->info_list, &info_list);
2026        mutex_unlock(&blkfront_mutex);
2027
2028        return 0;
2029}
2030
2031static int blkif_recover(struct blkfront_info *info)
2032{
2033        unsigned int r_index;
2034        struct request *req, *n;
2035        int rc;
2036        struct bio *bio;
2037        unsigned int segs;
2038        struct blkfront_ring_info *rinfo;
2039
2040        blkfront_gather_backend_features(info);
2041        /* Reset limits changed by blk_mq_update_nr_hw_queues(). */
2042        blkif_set_queue_limits(info);
2043        segs = info->max_indirect_segments ? : BLKIF_MAX_SEGMENTS_PER_REQUEST;
2044        blk_queue_max_segments(info->rq, segs / GRANTS_PER_PSEG);
2045
2046        for_each_rinfo(info, rinfo, r_index) {
2047                rc = blkfront_setup_indirect(rinfo);
2048                if (rc)
2049                        return rc;
2050        }
2051        xenbus_switch_state(info->xbdev, XenbusStateConnected);
2052
2053        /* Now safe for us to use the shared ring */
2054        info->connected = BLKIF_STATE_CONNECTED;
2055
2056        for_each_rinfo(info, rinfo, r_index) {
2057                /* Kick any other new requests queued since we resumed */
2058                kick_pending_request_queues(rinfo);
2059        }
2060
2061        list_for_each_entry_safe(req, n, &info->requests, queuelist) {
2062                /* Requeue pending requests (flush or discard) */
2063                list_del_init(&req->queuelist);
2064                BUG_ON(req->nr_phys_segments > segs);
2065                blk_mq_requeue_request(req, false);
2066        }
2067        blk_mq_start_stopped_hw_queues(info->rq, true);
2068        blk_mq_kick_requeue_list(info->rq);
2069
2070        while ((bio = bio_list_pop(&info->bio_list)) != NULL) {
2071                /* Traverse the list of pending bios and re-queue them */
2072                submit_bio(bio);
2073        }
2074
2075        return 0;
2076}
2077
2078/*
2079 * We are reconnecting to the backend, due to a suspend/resume, or a backend
2080 * driver restart.  We tear down our blkif structure and recreate it, but
2081 * leave the device-layer structures intact so that this is transparent to the
2082 * rest of the kernel.
2083 */
2084static int blkfront_resume(struct xenbus_device *dev)
2085{
2086        struct blkfront_info *info = dev_get_drvdata(&dev->dev);
2087        int err = 0;
2088        unsigned int i, j;
2089        struct blkfront_ring_info *rinfo;
2090
2091        dev_dbg(&dev->dev, "blkfront_resume: %s\n", dev->nodename);
2092
2093        bio_list_init(&info->bio_list);
2094        INIT_LIST_HEAD(&info->requests);
2095        for_each_rinfo(info, rinfo, i) {
2096                struct bio_list merge_bio;
2097                struct blk_shadow *shadow = rinfo->shadow;
2098
2099                for (j = 0; j < BLK_RING_SIZE(info); j++) {
2100                        /* Not in use? */
2101                        if (!shadow[j].request)
2102                                continue;
2103
2104                        /*
2105                         * Get the bios in the request so we can re-queue them.
2106                         */
2107                        if (req_op(shadow[j].request) == REQ_OP_FLUSH ||
2108                            req_op(shadow[j].request) == REQ_OP_DISCARD ||
2109                            req_op(shadow[j].request) == REQ_OP_SECURE_ERASE ||
2110                            shadow[j].request->cmd_flags & REQ_FUA) {
2111                                /*
2112                                 * Flush operations don't contain bios, so
2113                                 * we need to requeue the whole request
2114                                 *
2115                                 * XXX: but this doesn't make any sense for a
2116                                 * write with the FUA flag set..
2117                                 */
2118                                list_add(&shadow[j].request->queuelist, &info->requests);
2119                                continue;
2120                        }
2121                        merge_bio.head = shadow[j].request->bio;
2122                        merge_bio.tail = shadow[j].request->biotail;
2123                        bio_list_merge(&info->bio_list, &merge_bio);
2124                        shadow[j].request->bio = NULL;
2125                        blk_mq_end_request(shadow[j].request, BLK_STS_OK);
2126                }
2127        }
2128
2129        blkif_free(info, info->connected == BLKIF_STATE_CONNECTED);
2130
2131        err = talk_to_blkback(dev, info);
2132        if (!err)
2133                blk_mq_update_nr_hw_queues(&info->tag_set, info->nr_rings);
2134
2135        /*
2136         * We have to wait for the backend to switch to
2137         * connected state, since we want to read which
2138         * features it supports.
2139         */
2140
2141        return err;
2142}
2143
2144static void blkfront_closing(struct blkfront_info *info)
2145{
2146        struct xenbus_device *xbdev = info->xbdev;
2147        struct block_device *bdev = NULL;
2148
2149        mutex_lock(&info->mutex);
2150
2151        if (xbdev->state == XenbusStateClosing) {
2152                mutex_unlock(&info->mutex);
2153                return;
2154        }
2155
2156        if (info->gd)
2157                bdev = bdgrab(info->gd->part0);
2158
2159        mutex_unlock(&info->mutex);
2160
2161        if (!bdev) {
2162                xenbus_frontend_closed(xbdev);
2163                return;
2164        }
2165
2166        mutex_lock(&bdev->bd_mutex);
2167
2168        if (bdev->bd_openers) {
2169                xenbus_dev_error(xbdev, -EBUSY,
2170                                 "Device in use; refusing to close");
2171                xenbus_switch_state(xbdev, XenbusStateClosing);
2172        } else {
2173                xlvbd_release_gendisk(info);
2174                xenbus_frontend_closed(xbdev);
2175        }
2176
2177        mutex_unlock(&bdev->bd_mutex);
2178        bdput(bdev);
2179}
2180
2181static void blkfront_setup_discard(struct blkfront_info *info)
2182{
2183        info->feature_discard = 1;
2184        info->discard_granularity = xenbus_read_unsigned(info->xbdev->otherend,
2185                                                         "discard-granularity",
2186                                                         0);
2187        info->discard_alignment = xenbus_read_unsigned(info->xbdev->otherend,
2188                                                       "discard-alignment", 0);
2189        info->feature_secdiscard =
2190                !!xenbus_read_unsigned(info->xbdev->otherend, "discard-secure",
2191                                       0);
2192}
2193
2194static int blkfront_setup_indirect(struct blkfront_ring_info *rinfo)
2195{
2196        unsigned int psegs, grants, memflags;
2197        int err, i;
2198        struct blkfront_info *info = rinfo->dev_info;
2199
2200        memflags = memalloc_noio_save();
2201
2202        if (info->max_indirect_segments == 0) {
2203                if (!HAS_EXTRA_REQ)
2204                        grants = BLKIF_MAX_SEGMENTS_PER_REQUEST;
2205                else {
2206                        /*
2207                         * When an extra req is required, the maximum
2208                         * grants supported is related to the size of the
2209                         * Linux block segment.
2210                         */
2211                        grants = GRANTS_PER_PSEG;
2212                }
2213        }
2214        else
2215                grants = info->max_indirect_segments;
2216        psegs = DIV_ROUND_UP(grants, GRANTS_PER_PSEG);
2217
2218        err = fill_grant_buffer(rinfo,
2219                                (grants + INDIRECT_GREFS(grants)) * BLK_RING_SIZE(info));
2220        if (err)
2221                goto out_of_memory;
2222
2223        if (!info->feature_persistent && info->max_indirect_segments) {
2224                /*
2225                 * We are using indirect descriptors but not persistent
2226                 * grants, we need to allocate a set of pages that can be
2227                 * used for mapping indirect grefs
2228                 */
2229                int num = INDIRECT_GREFS(grants) * BLK_RING_SIZE(info);
2230
2231                BUG_ON(!list_empty(&rinfo->indirect_pages));
2232                for (i = 0; i < num; i++) {
2233                        struct page *indirect_page = alloc_page(GFP_KERNEL);
2234                        if (!indirect_page)
2235                                goto out_of_memory;
2236                        list_add(&indirect_page->lru, &rinfo->indirect_pages);
2237                }
2238        }
2239
2240        for (i = 0; i < BLK_RING_SIZE(info); i++) {
2241                rinfo->shadow[i].grants_used =
2242                        kvcalloc(grants,
2243                                 sizeof(rinfo->shadow[i].grants_used[0]),
2244                                 GFP_KERNEL);
2245                rinfo->shadow[i].sg = kvcalloc(psegs,
2246                                               sizeof(rinfo->shadow[i].sg[0]),
2247                                               GFP_KERNEL);
2248                if (info->max_indirect_segments)
2249                        rinfo->shadow[i].indirect_grants =
2250                                kvcalloc(INDIRECT_GREFS(grants),
2251                                         sizeof(rinfo->shadow[i].indirect_grants[0]),
2252                                         GFP_KERNEL);
2253                if ((rinfo->shadow[i].grants_used == NULL) ||
2254                        (rinfo->shadow[i].sg == NULL) ||
2255                     (info->max_indirect_segments &&
2256                     (rinfo->shadow[i].indirect_grants == NULL)))
2257                        goto out_of_memory;
2258                sg_init_table(rinfo->shadow[i].sg, psegs);
2259        }
2260
2261        memalloc_noio_restore(memflags);
2262
2263        return 0;
2264
2265out_of_memory:
2266        for (i = 0; i < BLK_RING_SIZE(info); i++) {
2267                kvfree(rinfo->shadow[i].grants_used);
2268                rinfo->shadow[i].grants_used = NULL;
2269                kvfree(rinfo->shadow[i].sg);
2270                rinfo->shadow[i].sg = NULL;
2271                kvfree(rinfo->shadow[i].indirect_grants);
2272                rinfo->shadow[i].indirect_grants = NULL;
2273        }
2274        if (!list_empty(&rinfo->indirect_pages)) {
2275                struct page *indirect_page, *n;
2276                list_for_each_entry_safe(indirect_page, n, &rinfo->indirect_pages, lru) {
2277                        list_del(&indirect_page->lru);
2278                        __free_page(indirect_page);
2279                }
2280        }
2281
2282        memalloc_noio_restore(memflags);
2283
2284        return -ENOMEM;
2285}
2286
2287/*
2288 * Gather all backend feature-*
2289 */
2290static void blkfront_gather_backend_features(struct blkfront_info *info)
2291{
2292        unsigned int indirect_segments;
2293
2294        info->feature_flush = 0;
2295        info->feature_fua = 0;
2296
2297        /*
2298         * If there's no "feature-barrier" defined, then it means
2299         * we're dealing with a very old backend which writes
2300         * synchronously; nothing to do.
2301         *
2302         * If there are barriers, then we use flush.
2303         */
2304        if (xenbus_read_unsigned(info->xbdev->otherend, "feature-barrier", 0)) {
2305                info->feature_flush = 1;
2306                info->feature_fua = 1;
2307        }
2308
2309        /*
2310         * And if there is "feature-flush-cache" use that above
2311         * barriers.
2312         */
2313        if (xenbus_read_unsigned(info->xbdev->otherend, "feature-flush-cache",
2314                                 0)) {
2315                info->feature_flush = 1;
2316                info->feature_fua = 0;
2317        }
2318
2319        if (xenbus_read_unsigned(info->xbdev->otherend, "feature-discard", 0))
2320                blkfront_setup_discard(info);
2321
2322        if (info->feature_persistent)
2323                info->feature_persistent =
2324                        !!xenbus_read_unsigned(info->xbdev->otherend,
2325                                               "feature-persistent", 0);
2326
2327        indirect_segments = xenbus_read_unsigned(info->xbdev->otherend,
2328                                        "feature-max-indirect-segments", 0);
2329        if (indirect_segments > xen_blkif_max_segments)
2330                indirect_segments = xen_blkif_max_segments;
2331        if (indirect_segments <= BLKIF_MAX_SEGMENTS_PER_REQUEST)
2332                indirect_segments = 0;
2333        info->max_indirect_segments = indirect_segments;
2334
2335        if (info->feature_persistent) {
2336                mutex_lock(&blkfront_mutex);
2337                schedule_delayed_work(&blkfront_work, HZ * 10);
2338                mutex_unlock(&blkfront_mutex);
2339        }
2340}
2341
2342/*
2343 * Invoked when the backend is finally 'ready' (and has told produced
2344 * the details about the physical device - #sectors, size, etc).
2345 */
2346static void blkfront_connect(struct blkfront_info *info)
2347{
2348        unsigned long long sectors;
2349        unsigned long sector_size;
2350        unsigned int physical_sector_size;
2351        unsigned int binfo;
2352        int err, i;
2353        struct blkfront_ring_info *rinfo;
2354
2355        switch (info->connected) {
2356        case BLKIF_STATE_CONNECTED:
2357                /*
2358                 * Potentially, the back-end may be signalling
2359                 * a capacity change; update the capacity.
2360                 */
2361                err = xenbus_scanf(XBT_NIL, info->xbdev->otherend,
2362                                   "sectors", "%Lu", &sectors);
2363                if (XENBUS_EXIST_ERR(err))
2364                        return;
2365                printk(KERN_INFO "Setting capacity to %Lu\n",
2366                       sectors);
2367                set_capacity_and_notify(info->gd, sectors);
2368
2369                return;
2370        case BLKIF_STATE_SUSPENDED:
2371                /*
2372                 * If we are recovering from suspension, we need to wait
2373                 * for the backend to announce it's features before
2374                 * reconnecting, at least we need to know if the backend
2375                 * supports indirect descriptors, and how many.
2376                 */
2377                blkif_recover(info);
2378                return;
2379
2380        default:
2381                break;
2382        }
2383
2384        dev_dbg(&info->xbdev->dev, "%s:%s.\n",
2385                __func__, info->xbdev->otherend);
2386
2387        err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
2388                            "sectors", "%llu", &sectors,
2389                            "info", "%u", &binfo,
2390                            "sector-size", "%lu", &sector_size,
2391                            NULL);
2392        if (err) {
2393                xenbus_dev_fatal(info->xbdev, err,
2394                                 "reading backend fields at %s",
2395                                 info->xbdev->otherend);
2396                return;
2397        }
2398
2399        /*
2400         * physical-sector-size is a newer field, so old backends may not
2401         * provide this. Assume physical sector size to be the same as
2402         * sector_size in that case.
2403         */
2404        physical_sector_size = xenbus_read_unsigned(info->xbdev->otherend,
2405                                                    "physical-sector-size",
2406                                                    sector_size);
2407        blkfront_gather_backend_features(info);
2408        for_each_rinfo(info, rinfo, i) {
2409                err = blkfront_setup_indirect(rinfo);
2410                if (err) {
2411                        xenbus_dev_fatal(info->xbdev, err, "setup_indirect at %s",
2412                                         info->xbdev->otherend);
2413                        blkif_free(info, 0);
2414                        break;
2415                }
2416        }
2417
2418        err = xlvbd_alloc_gendisk(sectors, info, binfo, sector_size,
2419                                  physical_sector_size);
2420        if (err) {
2421                xenbus_dev_fatal(info->xbdev, err, "xlvbd_add at %s",
2422                                 info->xbdev->otherend);
2423                goto fail;
2424        }
2425
2426        xenbus_switch_state(info->xbdev, XenbusStateConnected);
2427
2428        /* Kick pending requests. */
2429        info->connected = BLKIF_STATE_CONNECTED;
2430        for_each_rinfo(info, rinfo, i)
2431                kick_pending_request_queues(rinfo);
2432
2433        device_add_disk(&info->xbdev->dev, info->gd, NULL);
2434
2435        info->is_ready = 1;
2436        return;
2437
2438fail:
2439        blkif_free(info, 0);
2440        return;
2441}
2442
2443/*
2444 * Callback received when the backend's state changes.
2445 */
2446static void blkback_changed(struct xenbus_device *dev,
2447                            enum xenbus_state backend_state)
2448{
2449        struct blkfront_info *info = dev_get_drvdata(&dev->dev);
2450
2451        dev_dbg(&dev->dev, "blkfront:blkback_changed to state %d.\n", backend_state);
2452
2453        switch (backend_state) {
2454        case XenbusStateInitWait:
2455                if (dev->state != XenbusStateInitialising)
2456                        break;
2457                if (talk_to_blkback(dev, info))
2458                        break;
2459                break;
2460        case XenbusStateInitialising:
2461        case XenbusStateInitialised:
2462        case XenbusStateReconfiguring:
2463        case XenbusStateReconfigured:
2464        case XenbusStateUnknown:
2465                break;
2466
2467        case XenbusStateConnected:
2468                /*
2469                 * talk_to_blkback sets state to XenbusStateInitialised
2470                 * and blkfront_connect sets it to XenbusStateConnected
2471                 * (if connection went OK).
2472                 *
2473                 * If the backend (or toolstack) decides to poke at backend
2474                 * state (and re-trigger the watch by setting the state repeatedly
2475                 * to XenbusStateConnected (4)) we need to deal with this.
2476                 * This is allowed as this is used to communicate to the guest
2477                 * that the size of disk has changed!
2478                 */
2479                if ((dev->state != XenbusStateInitialised) &&
2480                    (dev->state != XenbusStateConnected)) {
2481                        if (talk_to_blkback(dev, info))
2482                                break;
2483                }
2484
2485                blkfront_connect(info);
2486                break;
2487
2488        case XenbusStateClosed:
2489                if (dev->state == XenbusStateClosed)
2490                        break;
2491                fallthrough;
2492        case XenbusStateClosing:
2493                if (info)
2494                        blkfront_closing(info);
2495                break;
2496        }
2497}
2498
2499static int blkfront_remove(struct xenbus_device *xbdev)
2500{
2501        struct blkfront_info *info = dev_get_drvdata(&xbdev->dev);
2502        struct block_device *bdev = NULL;
2503        struct gendisk *disk;
2504
2505        dev_dbg(&xbdev->dev, "%s removed", xbdev->nodename);
2506
2507        if (!info)
2508                return 0;
2509
2510        blkif_free(info, 0);
2511
2512        mutex_lock(&info->mutex);
2513
2514        disk = info->gd;
2515        if (disk)
2516                bdev = bdgrab(disk->part0);
2517
2518        info->xbdev = NULL;
2519        mutex_unlock(&info->mutex);
2520
2521        if (!bdev) {
2522                mutex_lock(&blkfront_mutex);
2523                free_info(info);
2524                mutex_unlock(&blkfront_mutex);
2525                return 0;
2526        }
2527
2528        /*
2529         * The xbdev was removed before we reached the Closed
2530         * state. See if it's safe to remove the disk. If the bdev
2531         * isn't closed yet, we let release take care of it.
2532         */
2533
2534        mutex_lock(&bdev->bd_mutex);
2535        info = disk->private_data;
2536
2537        dev_warn(disk_to_dev(disk),
2538                 "%s was hot-unplugged, %d stale handles\n",
2539                 xbdev->nodename, bdev->bd_openers);
2540
2541        if (info && !bdev->bd_openers) {
2542                xlvbd_release_gendisk(info);
2543                disk->private_data = NULL;
2544                mutex_lock(&blkfront_mutex);
2545                free_info(info);
2546                mutex_unlock(&blkfront_mutex);
2547        }
2548
2549        mutex_unlock(&bdev->bd_mutex);
2550        bdput(bdev);
2551
2552        return 0;
2553}
2554
2555static int blkfront_is_ready(struct xenbus_device *dev)
2556{
2557        struct blkfront_info *info = dev_get_drvdata(&dev->dev);
2558
2559        return info->is_ready && info->xbdev;
2560}
2561
2562static int blkif_open(struct block_device *bdev, fmode_t mode)
2563{
2564        struct gendisk *disk = bdev->bd_disk;
2565        struct blkfront_info *info;
2566        int err = 0;
2567
2568        mutex_lock(&blkfront_mutex);
2569
2570        info = disk->private_data;
2571        if (!info) {
2572                /* xbdev gone */
2573                err = -ERESTARTSYS;
2574                goto out;
2575        }
2576
2577        mutex_lock(&info->mutex);
2578
2579        if (!info->gd)
2580                /* xbdev is closed */
2581                err = -ERESTARTSYS;
2582
2583        mutex_unlock(&info->mutex);
2584
2585out:
2586        mutex_unlock(&blkfront_mutex);
2587        return err;
2588}
2589
2590static void blkif_release(struct gendisk *disk, fmode_t mode)
2591{
2592        struct blkfront_info *info = disk->private_data;
2593        struct xenbus_device *xbdev;
2594
2595        mutex_lock(&blkfront_mutex);
2596        if (disk->part0->bd_openers)
2597                goto out_mutex;
2598
2599        /*
2600         * Check if we have been instructed to close. We will have
2601         * deferred this request, because the bdev was still open.
2602         */
2603
2604        mutex_lock(&info->mutex);
2605        xbdev = info->xbdev;
2606
2607        if (xbdev && xbdev->state == XenbusStateClosing) {
2608                /* pending switch to state closed */
2609                dev_info(disk_to_dev(disk), "releasing disk\n");
2610                xlvbd_release_gendisk(info);
2611                xenbus_frontend_closed(info->xbdev);
2612        }
2613
2614        mutex_unlock(&info->mutex);
2615
2616        if (!xbdev) {
2617                /* sudden device removal */
2618                dev_info(disk_to_dev(disk), "releasing disk\n");
2619                xlvbd_release_gendisk(info);
2620                disk->private_data = NULL;
2621                free_info(info);
2622        }
2623
2624out_mutex:
2625        mutex_unlock(&blkfront_mutex);
2626}
2627
2628static const struct block_device_operations xlvbd_block_fops =
2629{
2630        .owner = THIS_MODULE,
2631        .open = blkif_open,
2632        .release = blkif_release,
2633        .getgeo = blkif_getgeo,
2634        .ioctl = blkif_ioctl,
2635        .compat_ioctl = blkdev_compat_ptr_ioctl,
2636};
2637
2638
2639static const struct xenbus_device_id blkfront_ids[] = {
2640        { "vbd" },
2641        { "" }
2642};
2643
2644static struct xenbus_driver blkfront_driver = {
2645        .ids  = blkfront_ids,
2646        .probe = blkfront_probe,
2647        .remove = blkfront_remove,
2648        .resume = blkfront_resume,
2649        .otherend_changed = blkback_changed,
2650        .is_ready = blkfront_is_ready,
2651};
2652
2653static void purge_persistent_grants(struct blkfront_info *info)
2654{
2655        unsigned int i;
2656        unsigned long flags;
2657        struct blkfront_ring_info *rinfo;
2658
2659        for_each_rinfo(info, rinfo, i) {
2660                struct grant *gnt_list_entry, *tmp;
2661
2662                spin_lock_irqsave(&rinfo->ring_lock, flags);
2663
2664                if (rinfo->persistent_gnts_c == 0) {
2665                        spin_unlock_irqrestore(&rinfo->ring_lock, flags);
2666                        continue;
2667                }
2668
2669                list_for_each_entry_safe(gnt_list_entry, tmp, &rinfo->grants,
2670                                         node) {
2671                        if (gnt_list_entry->gref == GRANT_INVALID_REF ||
2672                            gnttab_query_foreign_access(gnt_list_entry->gref))
2673                                continue;
2674
2675                        list_del(&gnt_list_entry->node);
2676                        gnttab_end_foreign_access(gnt_list_entry->gref, 0, 0UL);
2677                        rinfo->persistent_gnts_c--;
2678                        gnt_list_entry->gref = GRANT_INVALID_REF;
2679                        list_add_tail(&gnt_list_entry->node, &rinfo->grants);
2680                }
2681
2682                spin_unlock_irqrestore(&rinfo->ring_lock, flags);
2683        }
2684}
2685
2686static void blkfront_delay_work(struct work_struct *work)
2687{
2688        struct blkfront_info *info;
2689        bool need_schedule_work = false;
2690
2691        mutex_lock(&blkfront_mutex);
2692
2693        list_for_each_entry(info, &info_list, info_list) {
2694                if (info->feature_persistent) {
2695                        need_schedule_work = true;
2696                        mutex_lock(&info->mutex);
2697                        purge_persistent_grants(info);
2698                        mutex_unlock(&info->mutex);
2699                }
2700        }
2701
2702        if (need_schedule_work)
2703                schedule_delayed_work(&blkfront_work, HZ * 10);
2704
2705        mutex_unlock(&blkfront_mutex);
2706}
2707
2708static int __init xlblk_init(void)
2709{
2710        int ret;
2711        int nr_cpus = num_online_cpus();
2712
2713        if (!xen_domain())
2714                return -ENODEV;
2715
2716        if (!xen_has_pv_disk_devices())
2717                return -ENODEV;
2718
2719        if (register_blkdev(XENVBD_MAJOR, DEV_NAME)) {
2720                pr_warn("xen_blk: can't get major %d with name %s\n",
2721                        XENVBD_MAJOR, DEV_NAME);
2722                return -ENODEV;
2723        }
2724
2725        if (xen_blkif_max_segments < BLKIF_MAX_SEGMENTS_PER_REQUEST)
2726                xen_blkif_max_segments = BLKIF_MAX_SEGMENTS_PER_REQUEST;
2727
2728        if (xen_blkif_max_ring_order > XENBUS_MAX_RING_GRANT_ORDER) {
2729                pr_info("Invalid max_ring_order (%d), will use default max: %d.\n",
2730                        xen_blkif_max_ring_order, XENBUS_MAX_RING_GRANT_ORDER);
2731                xen_blkif_max_ring_order = XENBUS_MAX_RING_GRANT_ORDER;
2732        }
2733
2734        if (xen_blkif_max_queues > nr_cpus) {
2735                pr_info("Invalid max_queues (%d), will use default max: %d.\n",
2736                        xen_blkif_max_queues, nr_cpus);
2737                xen_blkif_max_queues = nr_cpus;
2738        }
2739
2740        INIT_DELAYED_WORK(&blkfront_work, blkfront_delay_work);
2741
2742        ret = xenbus_register_frontend(&blkfront_driver);
2743        if (ret) {
2744                unregister_blkdev(XENVBD_MAJOR, DEV_NAME);
2745                return ret;
2746        }
2747
2748        return 0;
2749}
2750module_init(xlblk_init);
2751
2752
2753static void __exit xlblk_exit(void)
2754{
2755        cancel_delayed_work_sync(&blkfront_work);
2756
2757        xenbus_unregister_driver(&blkfront_driver);
2758        unregister_blkdev(XENVBD_MAJOR, DEV_NAME);
2759        kfree(minors);
2760}
2761module_exit(xlblk_exit);
2762
2763MODULE_DESCRIPTION("Xen virtual block device frontend");
2764MODULE_LICENSE("GPL");
2765MODULE_ALIAS_BLOCKDEV_MAJOR(XENVBD_MAJOR);
2766MODULE_ALIAS("xen:vbd");
2767MODULE_ALIAS("xenblk");
2768