linux/fs/xfs/xfs_buf.c
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   1/*
   2 * Copyright (c) 2000-2006 Silicon Graphics, Inc.
   3 * All Rights Reserved.
   4 *
   5 * This program is free software; you can redistribute it and/or
   6 * modify it under the terms of the GNU General Public License as
   7 * published by the Free Software Foundation.
   8 *
   9 * This program is distributed in the hope that it would be useful,
  10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12 * GNU General Public License for more details.
  13 *
  14 * You should have received a copy of the GNU General Public License
  15 * along with this program; if not, write the Free Software Foundation,
  16 * Inc.,  51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
  17 */
  18#include "xfs.h"
  19#include <linux/stddef.h>
  20#include <linux/errno.h>
  21#include <linux/gfp.h>
  22#include <linux/pagemap.h>
  23#include <linux/init.h>
  24#include <linux/vmalloc.h>
  25#include <linux/bio.h>
  26#include <linux/sysctl.h>
  27#include <linux/proc_fs.h>
  28#include <linux/workqueue.h>
  29#include <linux/percpu.h>
  30#include <linux/blkdev.h>
  31#include <linux/hash.h>
  32#include <linux/kthread.h>
  33#include <linux/migrate.h>
  34#include <linux/backing-dev.h>
  35#include <linux/freezer.h>
  36
  37#include "xfs_sb.h"
  38#include "xfs_log.h"
  39#include "xfs_ag.h"
  40#include "xfs_mount.h"
  41#include "xfs_trace.h"
  42
  43static kmem_zone_t *xfs_buf_zone;
  44
  45static struct workqueue_struct *xfslogd_workqueue;
  46
  47#ifdef XFS_BUF_LOCK_TRACKING
  48# define XB_SET_OWNER(bp)       ((bp)->b_last_holder = current->pid)
  49# define XB_CLEAR_OWNER(bp)     ((bp)->b_last_holder = -1)
  50# define XB_GET_OWNER(bp)       ((bp)->b_last_holder)
  51#else
  52# define XB_SET_OWNER(bp)       do { } while (0)
  53# define XB_CLEAR_OWNER(bp)     do { } while (0)
  54# define XB_GET_OWNER(bp)       do { } while (0)
  55#endif
  56
  57#define xb_to_gfp(flags) \
  58        ((((flags) & XBF_READ_AHEAD) ? __GFP_NORETRY : GFP_NOFS) | __GFP_NOWARN)
  59
  60
  61static inline int
  62xfs_buf_is_vmapped(
  63        struct xfs_buf  *bp)
  64{
  65        /*
  66         * Return true if the buffer is vmapped.
  67         *
  68         * b_addr is null if the buffer is not mapped, but the code is clever
  69         * enough to know it doesn't have to map a single page, so the check has
  70         * to be both for b_addr and bp->b_page_count > 1.
  71         */
  72        return bp->b_addr && bp->b_page_count > 1;
  73}
  74
  75static inline int
  76xfs_buf_vmap_len(
  77        struct xfs_buf  *bp)
  78{
  79        return (bp->b_page_count * PAGE_SIZE) - bp->b_offset;
  80}
  81
  82/*
  83 * xfs_buf_lru_add - add a buffer to the LRU.
  84 *
  85 * The LRU takes a new reference to the buffer so that it will only be freed
  86 * once the shrinker takes the buffer off the LRU.
  87 */
  88STATIC void
  89xfs_buf_lru_add(
  90        struct xfs_buf  *bp)
  91{
  92        struct xfs_buftarg *btp = bp->b_target;
  93
  94        spin_lock(&btp->bt_lru_lock);
  95        if (list_empty(&bp->b_lru)) {
  96                atomic_inc(&bp->b_hold);
  97                list_add_tail(&bp->b_lru, &btp->bt_lru);
  98                btp->bt_lru_nr++;
  99                bp->b_lru_flags &= ~_XBF_LRU_DISPOSE;
 100        }
 101        spin_unlock(&btp->bt_lru_lock);
 102}
 103
 104/*
 105 * xfs_buf_lru_del - remove a buffer from the LRU
 106 *
 107 * The unlocked check is safe here because it only occurs when there are not
 108 * b_lru_ref counts left on the inode under the pag->pag_buf_lock. it is there
 109 * to optimise the shrinker removing the buffer from the LRU and calling
 110 * xfs_buf_free(). i.e. it removes an unnecessary round trip on the
 111 * bt_lru_lock.
 112 */
 113STATIC void
 114xfs_buf_lru_del(
 115        struct xfs_buf  *bp)
 116{
 117        struct xfs_buftarg *btp = bp->b_target;
 118
 119        if (list_empty(&bp->b_lru))
 120                return;
 121
 122        spin_lock(&btp->bt_lru_lock);
 123        if (!list_empty(&bp->b_lru)) {
 124                list_del_init(&bp->b_lru);
 125                btp->bt_lru_nr--;
 126        }
 127        spin_unlock(&btp->bt_lru_lock);
 128}
 129
 130/*
 131 * When we mark a buffer stale, we remove the buffer from the LRU and clear the
 132 * b_lru_ref count so that the buffer is freed immediately when the buffer
 133 * reference count falls to zero. If the buffer is already on the LRU, we need
 134 * to remove the reference that LRU holds on the buffer.
 135 *
 136 * This prevents build-up of stale buffers on the LRU.
 137 */
 138void
 139xfs_buf_stale(
 140        struct xfs_buf  *bp)
 141{
 142        ASSERT(xfs_buf_islocked(bp));
 143
 144        bp->b_flags |= XBF_STALE;
 145
 146        /*
 147         * Clear the delwri status so that a delwri queue walker will not
 148         * flush this buffer to disk now that it is stale. The delwri queue has
 149         * a reference to the buffer, so this is safe to do.
 150         */
 151        bp->b_flags &= ~_XBF_DELWRI_Q;
 152
 153        atomic_set(&(bp)->b_lru_ref, 0);
 154        if (!list_empty(&bp->b_lru)) {
 155                struct xfs_buftarg *btp = bp->b_target;
 156
 157                spin_lock(&btp->bt_lru_lock);
 158                if (!list_empty(&bp->b_lru) &&
 159                    !(bp->b_lru_flags & _XBF_LRU_DISPOSE)) {
 160                        list_del_init(&bp->b_lru);
 161                        btp->bt_lru_nr--;
 162                        atomic_dec(&bp->b_hold);
 163                }
 164                spin_unlock(&btp->bt_lru_lock);
 165        }
 166        ASSERT(atomic_read(&bp->b_hold) >= 1);
 167}
 168
 169static int
 170xfs_buf_get_maps(
 171        struct xfs_buf          *bp,
 172        int                     map_count)
 173{
 174        ASSERT(bp->b_maps == NULL);
 175        bp->b_map_count = map_count;
 176
 177        if (map_count == 1) {
 178                bp->b_maps = &bp->__b_map;
 179                return 0;
 180        }
 181
 182        bp->b_maps = kmem_zalloc(map_count * sizeof(struct xfs_buf_map),
 183                                KM_NOFS);
 184        if (!bp->b_maps)
 185                return ENOMEM;
 186        return 0;
 187}
 188
 189/*
 190 *      Frees b_pages if it was allocated.
 191 */
 192static void
 193xfs_buf_free_maps(
 194        struct xfs_buf  *bp)
 195{
 196        if (bp->b_maps != &bp->__b_map) {
 197                kmem_free(bp->b_maps);
 198                bp->b_maps = NULL;
 199        }
 200}
 201
 202struct xfs_buf *
 203_xfs_buf_alloc(
 204        struct xfs_buftarg      *target,
 205        struct xfs_buf_map      *map,
 206        int                     nmaps,
 207        xfs_buf_flags_t         flags)
 208{
 209        struct xfs_buf          *bp;
 210        int                     error;
 211        int                     i;
 212
 213        bp = kmem_zone_zalloc(xfs_buf_zone, KM_NOFS);
 214        if (unlikely(!bp))
 215                return NULL;
 216
 217        /*
 218         * We don't want certain flags to appear in b_flags unless they are
 219         * specifically set by later operations on the buffer.
 220         */
 221        flags &= ~(XBF_UNMAPPED | XBF_TRYLOCK | XBF_ASYNC | XBF_READ_AHEAD);
 222
 223        atomic_set(&bp->b_hold, 1);
 224        atomic_set(&bp->b_lru_ref, 1);
 225        init_completion(&bp->b_iowait);
 226        INIT_LIST_HEAD(&bp->b_lru);
 227        INIT_LIST_HEAD(&bp->b_list);
 228        RB_CLEAR_NODE(&bp->b_rbnode);
 229        sema_init(&bp->b_sema, 0); /* held, no waiters */
 230        XB_SET_OWNER(bp);
 231        bp->b_target = target;
 232        bp->b_flags = flags;
 233
 234        /*
 235         * Set length and io_length to the same value initially.
 236         * I/O routines should use io_length, which will be the same in
 237         * most cases but may be reset (e.g. XFS recovery).
 238         */
 239        error = xfs_buf_get_maps(bp, nmaps);
 240        if (error)  {
 241                kmem_zone_free(xfs_buf_zone, bp);
 242                return NULL;
 243        }
 244
 245        bp->b_bn = map[0].bm_bn;
 246        bp->b_length = 0;
 247        for (i = 0; i < nmaps; i++) {
 248                bp->b_maps[i].bm_bn = map[i].bm_bn;
 249                bp->b_maps[i].bm_len = map[i].bm_len;
 250                bp->b_length += map[i].bm_len;
 251        }
 252        bp->b_io_length = bp->b_length;
 253
 254        atomic_set(&bp->b_pin_count, 0);
 255        init_waitqueue_head(&bp->b_waiters);
 256
 257        XFS_STATS_INC(xb_create);
 258        trace_xfs_buf_init(bp, _RET_IP_);
 259
 260        return bp;
 261}
 262
 263/*
 264 *      Allocate a page array capable of holding a specified number
 265 *      of pages, and point the page buf at it.
 266 */
 267STATIC int
 268_xfs_buf_get_pages(
 269        xfs_buf_t               *bp,
 270        int                     page_count,
 271        xfs_buf_flags_t         flags)
 272{
 273        /* Make sure that we have a page list */
 274        if (bp->b_pages == NULL) {
 275                bp->b_page_count = page_count;
 276                if (page_count <= XB_PAGES) {
 277                        bp->b_pages = bp->b_page_array;
 278                } else {
 279                        bp->b_pages = kmem_alloc(sizeof(struct page *) *
 280                                                 page_count, KM_NOFS);
 281                        if (bp->b_pages == NULL)
 282                                return -ENOMEM;
 283                }
 284                memset(bp->b_pages, 0, sizeof(struct page *) * page_count);
 285        }
 286        return 0;
 287}
 288
 289/*
 290 *      Frees b_pages if it was allocated.
 291 */
 292STATIC void
 293_xfs_buf_free_pages(
 294        xfs_buf_t       *bp)
 295{
 296        if (bp->b_pages != bp->b_page_array) {
 297                kmem_free(bp->b_pages);
 298                bp->b_pages = NULL;
 299        }
 300}
 301
 302/*
 303 *      Releases the specified buffer.
 304 *
 305 *      The modification state of any associated pages is left unchanged.
 306 *      The buffer most not be on any hash - use xfs_buf_rele instead for
 307 *      hashed and refcounted buffers
 308 */
 309void
 310xfs_buf_free(
 311        xfs_buf_t               *bp)
 312{
 313        trace_xfs_buf_free(bp, _RET_IP_);
 314
 315        ASSERT(list_empty(&bp->b_lru));
 316
 317        if (bp->b_flags & _XBF_PAGES) {
 318                uint            i;
 319
 320                if (xfs_buf_is_vmapped(bp))
 321                        vm_unmap_ram(bp->b_addr - bp->b_offset,
 322                                        bp->b_page_count);
 323
 324                for (i = 0; i < bp->b_page_count; i++) {
 325                        struct page     *page = bp->b_pages[i];
 326
 327                        __free_page(page);
 328                }
 329        } else if (bp->b_flags & _XBF_KMEM)
 330                kmem_free(bp->b_addr);
 331        _xfs_buf_free_pages(bp);
 332        xfs_buf_free_maps(bp);
 333        kmem_zone_free(xfs_buf_zone, bp);
 334}
 335
 336/*
 337 * Allocates all the pages for buffer in question and builds it's page list.
 338 */
 339STATIC int
 340xfs_buf_allocate_memory(
 341        xfs_buf_t               *bp,
 342        uint                    flags)
 343{
 344        size_t                  size;
 345        size_t                  nbytes, offset;
 346        gfp_t                   gfp_mask = xb_to_gfp(flags);
 347        unsigned short          page_count, i;
 348        xfs_off_t               start, end;
 349        int                     error;
 350
 351        /*
 352         * for buffers that are contained within a single page, just allocate
 353         * the memory from the heap - there's no need for the complexity of
 354         * page arrays to keep allocation down to order 0.
 355         */
 356        size = BBTOB(bp->b_length);
 357        if (size < PAGE_SIZE) {
 358                bp->b_addr = kmem_alloc(size, KM_NOFS);
 359                if (!bp->b_addr) {
 360                        /* low memory - use alloc_page loop instead */
 361                        goto use_alloc_page;
 362                }
 363
 364                if (((unsigned long)(bp->b_addr + size - 1) & PAGE_MASK) !=
 365                    ((unsigned long)bp->b_addr & PAGE_MASK)) {
 366                        /* b_addr spans two pages - use alloc_page instead */
 367                        kmem_free(bp->b_addr);
 368                        bp->b_addr = NULL;
 369                        goto use_alloc_page;
 370                }
 371                bp->b_offset = offset_in_page(bp->b_addr);
 372                bp->b_pages = bp->b_page_array;
 373                bp->b_pages[0] = virt_to_page(bp->b_addr);
 374                bp->b_page_count = 1;
 375                bp->b_flags |= _XBF_KMEM;
 376                return 0;
 377        }
 378
 379use_alloc_page:
 380        start = BBTOB(bp->b_maps[0].bm_bn) >> PAGE_SHIFT;
 381        end = (BBTOB(bp->b_maps[0].bm_bn + bp->b_length) + PAGE_SIZE - 1)
 382                                                                >> PAGE_SHIFT;
 383        page_count = end - start;
 384        error = _xfs_buf_get_pages(bp, page_count, flags);
 385        if (unlikely(error))
 386                return error;
 387
 388        offset = bp->b_offset;
 389        bp->b_flags |= _XBF_PAGES;
 390
 391        for (i = 0; i < bp->b_page_count; i++) {
 392                struct page     *page;
 393                uint            retries = 0;
 394retry:
 395                page = alloc_page(gfp_mask);
 396                if (unlikely(page == NULL)) {
 397                        if (flags & XBF_READ_AHEAD) {
 398                                bp->b_page_count = i;
 399                                error = ENOMEM;
 400                                goto out_free_pages;
 401                        }
 402
 403                        /*
 404                         * This could deadlock.
 405                         *
 406                         * But until all the XFS lowlevel code is revamped to
 407                         * handle buffer allocation failures we can't do much.
 408                         */
 409                        if (!(++retries % 100))
 410                                xfs_err(NULL,
 411                "possible memory allocation deadlock in %s (mode:0x%x)",
 412                                        __func__, gfp_mask);
 413
 414                        XFS_STATS_INC(xb_page_retries);
 415                        congestion_wait(BLK_RW_ASYNC, HZ/50);
 416                        goto retry;
 417                }
 418
 419                XFS_STATS_INC(xb_page_found);
 420
 421                nbytes = min_t(size_t, size, PAGE_SIZE - offset);
 422                size -= nbytes;
 423                bp->b_pages[i] = page;
 424                offset = 0;
 425        }
 426        return 0;
 427
 428out_free_pages:
 429        for (i = 0; i < bp->b_page_count; i++)
 430                __free_page(bp->b_pages[i]);
 431        return error;
 432}
 433
 434/*
 435 *      Map buffer into kernel address-space if necessary.
 436 */
 437STATIC int
 438_xfs_buf_map_pages(
 439        xfs_buf_t               *bp,
 440        uint                    flags)
 441{
 442        ASSERT(bp->b_flags & _XBF_PAGES);
 443        if (bp->b_page_count == 1) {
 444                /* A single page buffer is always mappable */
 445                bp->b_addr = page_address(bp->b_pages[0]) + bp->b_offset;
 446        } else if (flags & XBF_UNMAPPED) {
 447                bp->b_addr = NULL;
 448        } else {
 449                int retried = 0;
 450
 451                do {
 452                        bp->b_addr = vm_map_ram(bp->b_pages, bp->b_page_count,
 453                                                -1, PAGE_KERNEL);
 454                        if (bp->b_addr)
 455                                break;
 456                        vm_unmap_aliases();
 457                } while (retried++ <= 1);
 458
 459                if (!bp->b_addr)
 460                        return -ENOMEM;
 461                bp->b_addr += bp->b_offset;
 462        }
 463
 464        return 0;
 465}
 466
 467/*
 468 *      Finding and Reading Buffers
 469 */
 470
 471/*
 472 *      Look up, and creates if absent, a lockable buffer for
 473 *      a given range of an inode.  The buffer is returned
 474 *      locked. No I/O is implied by this call.
 475 */
 476xfs_buf_t *
 477_xfs_buf_find(
 478        struct xfs_buftarg      *btp,
 479        struct xfs_buf_map      *map,
 480        int                     nmaps,
 481        xfs_buf_flags_t         flags,
 482        xfs_buf_t               *new_bp)
 483{
 484        size_t                  numbytes;
 485        struct xfs_perag        *pag;
 486        struct rb_node          **rbp;
 487        struct rb_node          *parent;
 488        xfs_buf_t               *bp;
 489        xfs_daddr_t             blkno = map[0].bm_bn;
 490        xfs_daddr_t             eofs;
 491        int                     numblks = 0;
 492        int                     i;
 493
 494        for (i = 0; i < nmaps; i++)
 495                numblks += map[i].bm_len;
 496        numbytes = BBTOB(numblks);
 497
 498        /* Check for IOs smaller than the sector size / not sector aligned */
 499        ASSERT(!(numbytes < (1 << btp->bt_sshift)));
 500        ASSERT(!(BBTOB(blkno) & (xfs_off_t)btp->bt_smask));
 501
 502        /*
 503         * Corrupted block numbers can get through to here, unfortunately, so we
 504         * have to check that the buffer falls within the filesystem bounds.
 505         */
 506        eofs = XFS_FSB_TO_BB(btp->bt_mount, btp->bt_mount->m_sb.sb_dblocks);
 507        if (blkno >= eofs) {
 508                /*
 509                 * XXX (dgc): we should really be returning EFSCORRUPTED here,
 510                 * but none of the higher level infrastructure supports
 511                 * returning a specific error on buffer lookup failures.
 512                 */
 513                xfs_alert(btp->bt_mount,
 514                          "%s: Block out of range: block 0x%llx, EOFS 0x%llx ",
 515                          __func__, blkno, eofs);
 516                return NULL;
 517        }
 518
 519        /* get tree root */
 520        pag = xfs_perag_get(btp->bt_mount,
 521                                xfs_daddr_to_agno(btp->bt_mount, blkno));
 522
 523        /* walk tree */
 524        spin_lock(&pag->pag_buf_lock);
 525        rbp = &pag->pag_buf_tree.rb_node;
 526        parent = NULL;
 527        bp = NULL;
 528        while (*rbp) {
 529                parent = *rbp;
 530                bp = rb_entry(parent, struct xfs_buf, b_rbnode);
 531
 532                if (blkno < bp->b_bn)
 533                        rbp = &(*rbp)->rb_left;
 534                else if (blkno > bp->b_bn)
 535                        rbp = &(*rbp)->rb_right;
 536                else {
 537                        /*
 538                         * found a block number match. If the range doesn't
 539                         * match, the only way this is allowed is if the buffer
 540                         * in the cache is stale and the transaction that made
 541                         * it stale has not yet committed. i.e. we are
 542                         * reallocating a busy extent. Skip this buffer and
 543                         * continue searching to the right for an exact match.
 544                         */
 545                        if (bp->b_length != numblks) {
 546                                ASSERT(bp->b_flags & XBF_STALE);
 547                                rbp = &(*rbp)->rb_right;
 548                                continue;
 549                        }
 550                        atomic_inc(&bp->b_hold);
 551                        goto found;
 552                }
 553        }
 554
 555        /* No match found */
 556        if (new_bp) {
 557                rb_link_node(&new_bp->b_rbnode, parent, rbp);
 558                rb_insert_color(&new_bp->b_rbnode, &pag->pag_buf_tree);
 559                /* the buffer keeps the perag reference until it is freed */
 560                new_bp->b_pag = pag;
 561                spin_unlock(&pag->pag_buf_lock);
 562        } else {
 563                XFS_STATS_INC(xb_miss_locked);
 564                spin_unlock(&pag->pag_buf_lock);
 565                xfs_perag_put(pag);
 566        }
 567        return new_bp;
 568
 569found:
 570        spin_unlock(&pag->pag_buf_lock);
 571        xfs_perag_put(pag);
 572
 573        if (!xfs_buf_trylock(bp)) {
 574                if (flags & XBF_TRYLOCK) {
 575                        xfs_buf_rele(bp);
 576                        XFS_STATS_INC(xb_busy_locked);
 577                        return NULL;
 578                }
 579                xfs_buf_lock(bp);
 580                XFS_STATS_INC(xb_get_locked_waited);
 581        }
 582
 583        /*
 584         * if the buffer is stale, clear all the external state associated with
 585         * it. We need to keep flags such as how we allocated the buffer memory
 586         * intact here.
 587         */
 588        if (bp->b_flags & XBF_STALE) {
 589                ASSERT((bp->b_flags & _XBF_DELWRI_Q) == 0);
 590                ASSERT(bp->b_iodone == NULL);
 591                bp->b_flags &= _XBF_KMEM | _XBF_PAGES;
 592                bp->b_ops = NULL;
 593        }
 594
 595        trace_xfs_buf_find(bp, flags, _RET_IP_);
 596        XFS_STATS_INC(xb_get_locked);
 597        return bp;
 598}
 599
 600/*
 601 * Assembles a buffer covering the specified range. The code is optimised for
 602 * cache hits, as metadata intensive workloads will see 3 orders of magnitude
 603 * more hits than misses.
 604 */
 605struct xfs_buf *
 606xfs_buf_get_map(
 607        struct xfs_buftarg      *target,
 608        struct xfs_buf_map      *map,
 609        int                     nmaps,
 610        xfs_buf_flags_t         flags)
 611{
 612        struct xfs_buf          *bp;
 613        struct xfs_buf          *new_bp;
 614        int                     error = 0;
 615
 616        bp = _xfs_buf_find(target, map, nmaps, flags, NULL);
 617        if (likely(bp))
 618                goto found;
 619
 620        new_bp = _xfs_buf_alloc(target, map, nmaps, flags);
 621        if (unlikely(!new_bp))
 622                return NULL;
 623
 624        error = xfs_buf_allocate_memory(new_bp, flags);
 625        if (error) {
 626                xfs_buf_free(new_bp);
 627                return NULL;
 628        }
 629
 630        bp = _xfs_buf_find(target, map, nmaps, flags, new_bp);
 631        if (!bp) {
 632                xfs_buf_free(new_bp);
 633                return NULL;
 634        }
 635
 636        if (bp != new_bp)
 637                xfs_buf_free(new_bp);
 638
 639found:
 640        if (!bp->b_addr) {
 641                error = _xfs_buf_map_pages(bp, flags);
 642                if (unlikely(error)) {
 643                        xfs_warn(target->bt_mount,
 644                                "%s: failed to map pages\n", __func__);
 645                        xfs_buf_relse(bp);
 646                        return NULL;
 647                }
 648        }
 649
 650        XFS_STATS_INC(xb_get);
 651        trace_xfs_buf_get(bp, flags, _RET_IP_);
 652        return bp;
 653}
 654
 655STATIC int
 656_xfs_buf_read(
 657        xfs_buf_t               *bp,
 658        xfs_buf_flags_t         flags)
 659{
 660        ASSERT(!(flags & XBF_WRITE));
 661        ASSERT(bp->b_maps[0].bm_bn != XFS_BUF_DADDR_NULL);
 662
 663        bp->b_flags &= ~(XBF_WRITE | XBF_ASYNC | XBF_READ_AHEAD);
 664        bp->b_flags |= flags & (XBF_READ | XBF_ASYNC | XBF_READ_AHEAD);
 665
 666        xfs_buf_iorequest(bp);
 667        if (flags & XBF_ASYNC)
 668                return 0;
 669        return xfs_buf_iowait(bp);
 670}
 671
 672xfs_buf_t *
 673xfs_buf_read_map(
 674        struct xfs_buftarg      *target,
 675        struct xfs_buf_map      *map,
 676        int                     nmaps,
 677        xfs_buf_flags_t         flags,
 678        const struct xfs_buf_ops *ops)
 679{
 680        struct xfs_buf          *bp;
 681
 682        flags |= XBF_READ;
 683
 684        bp = xfs_buf_get_map(target, map, nmaps, flags);
 685        if (bp) {
 686                trace_xfs_buf_read(bp, flags, _RET_IP_);
 687
 688                if (!XFS_BUF_ISDONE(bp)) {
 689                        XFS_STATS_INC(xb_get_read);
 690                        bp->b_ops = ops;
 691                        _xfs_buf_read(bp, flags);
 692                } else if (flags & XBF_ASYNC) {
 693                        /*
 694                         * Read ahead call which is already satisfied,
 695                         * drop the buffer
 696                         */
 697                        xfs_buf_relse(bp);
 698                        return NULL;
 699                } else {
 700                        /* We do not want read in the flags */
 701                        bp->b_flags &= ~XBF_READ;
 702                }
 703        }
 704
 705        return bp;
 706}
 707
 708/*
 709 *      If we are not low on memory then do the readahead in a deadlock
 710 *      safe manner.
 711 */
 712void
 713xfs_buf_readahead_map(
 714        struct xfs_buftarg      *target,
 715        struct xfs_buf_map      *map,
 716        int                     nmaps,
 717        const struct xfs_buf_ops *ops)
 718{
 719        if (bdi_read_congested(target->bt_bdi))
 720                return;
 721
 722        xfs_buf_read_map(target, map, nmaps,
 723                     XBF_TRYLOCK|XBF_ASYNC|XBF_READ_AHEAD, ops);
 724}
 725
 726/*
 727 * Read an uncached buffer from disk. Allocates and returns a locked
 728 * buffer containing the disk contents or nothing.
 729 */
 730struct xfs_buf *
 731xfs_buf_read_uncached(
 732        struct xfs_buftarg      *target,
 733        xfs_daddr_t             daddr,
 734        size_t                  numblks,
 735        int                     flags,
 736        const struct xfs_buf_ops *ops)
 737{
 738        struct xfs_buf          *bp;
 739
 740        bp = xfs_buf_get_uncached(target, numblks, flags);
 741        if (!bp)
 742                return NULL;
 743
 744        /* set up the buffer for a read IO */
 745        ASSERT(bp->b_map_count == 1);
 746        bp->b_bn = daddr;
 747        bp->b_maps[0].bm_bn = daddr;
 748        bp->b_flags |= XBF_READ;
 749        bp->b_ops = ops;
 750
 751        xfsbdstrat(target->bt_mount, bp);
 752        xfs_buf_iowait(bp);
 753        return bp;
 754}
 755
 756/*
 757 * Return a buffer allocated as an empty buffer and associated to external
 758 * memory via xfs_buf_associate_memory() back to it's empty state.
 759 */
 760void
 761xfs_buf_set_empty(
 762        struct xfs_buf          *bp,
 763        size_t                  numblks)
 764{
 765        if (bp->b_pages)
 766                _xfs_buf_free_pages(bp);
 767
 768        bp->b_pages = NULL;
 769        bp->b_page_count = 0;
 770        bp->b_addr = NULL;
 771        bp->b_length = numblks;
 772        bp->b_io_length = numblks;
 773
 774        ASSERT(bp->b_map_count == 1);
 775        bp->b_bn = XFS_BUF_DADDR_NULL;
 776        bp->b_maps[0].bm_bn = XFS_BUF_DADDR_NULL;
 777        bp->b_maps[0].bm_len = bp->b_length;
 778}
 779
 780static inline struct page *
 781mem_to_page(
 782        void                    *addr)
 783{
 784        if ((!is_vmalloc_addr(addr))) {
 785                return virt_to_page(addr);
 786        } else {
 787                return vmalloc_to_page(addr);
 788        }
 789}
 790
 791int
 792xfs_buf_associate_memory(
 793        xfs_buf_t               *bp,
 794        void                    *mem,
 795        size_t                  len)
 796{
 797        int                     rval;
 798        int                     i = 0;
 799        unsigned long           pageaddr;
 800        unsigned long           offset;
 801        size_t                  buflen;
 802        int                     page_count;
 803
 804        pageaddr = (unsigned long)mem & PAGE_MASK;
 805        offset = (unsigned long)mem - pageaddr;
 806        buflen = PAGE_ALIGN(len + offset);
 807        page_count = buflen >> PAGE_SHIFT;
 808
 809        /* Free any previous set of page pointers */
 810        if (bp->b_pages)
 811                _xfs_buf_free_pages(bp);
 812
 813        bp->b_pages = NULL;
 814        bp->b_addr = mem;
 815
 816        rval = _xfs_buf_get_pages(bp, page_count, 0);
 817        if (rval)
 818                return rval;
 819
 820        bp->b_offset = offset;
 821
 822        for (i = 0; i < bp->b_page_count; i++) {
 823                bp->b_pages[i] = mem_to_page((void *)pageaddr);
 824                pageaddr += PAGE_SIZE;
 825        }
 826
 827        bp->b_io_length = BTOBB(len);
 828        bp->b_length = BTOBB(buflen);
 829
 830        return 0;
 831}
 832
 833xfs_buf_t *
 834xfs_buf_get_uncached(
 835        struct xfs_buftarg      *target,
 836        size_t                  numblks,
 837        int                     flags)
 838{
 839        unsigned long           page_count;
 840        int                     error, i;
 841        struct xfs_buf          *bp;
 842        DEFINE_SINGLE_BUF_MAP(map, XFS_BUF_DADDR_NULL, numblks);
 843
 844        bp = _xfs_buf_alloc(target, &map, 1, 0);
 845        if (unlikely(bp == NULL))
 846                goto fail;
 847
 848        page_count = PAGE_ALIGN(numblks << BBSHIFT) >> PAGE_SHIFT;
 849        error = _xfs_buf_get_pages(bp, page_count, 0);
 850        if (error)
 851                goto fail_free_buf;
 852
 853        for (i = 0; i < page_count; i++) {
 854                bp->b_pages[i] = alloc_page(xb_to_gfp(flags));
 855                if (!bp->b_pages[i])
 856                        goto fail_free_mem;
 857        }
 858        bp->b_flags |= _XBF_PAGES;
 859
 860        error = _xfs_buf_map_pages(bp, 0);
 861        if (unlikely(error)) {
 862                xfs_warn(target->bt_mount,
 863                        "%s: failed to map pages\n", __func__);
 864                goto fail_free_mem;
 865        }
 866
 867        trace_xfs_buf_get_uncached(bp, _RET_IP_);
 868        return bp;
 869
 870 fail_free_mem:
 871        while (--i >= 0)
 872                __free_page(bp->b_pages[i]);
 873        _xfs_buf_free_pages(bp);
 874 fail_free_buf:
 875        xfs_buf_free_maps(bp);
 876        kmem_zone_free(xfs_buf_zone, bp);
 877 fail:
 878        return NULL;
 879}
 880
 881/*
 882 *      Increment reference count on buffer, to hold the buffer concurrently
 883 *      with another thread which may release (free) the buffer asynchronously.
 884 *      Must hold the buffer already to call this function.
 885 */
 886void
 887xfs_buf_hold(
 888        xfs_buf_t               *bp)
 889{
 890        trace_xfs_buf_hold(bp, _RET_IP_);
 891        atomic_inc(&bp->b_hold);
 892}
 893
 894/*
 895 *      Releases a hold on the specified buffer.  If the
 896 *      the hold count is 1, calls xfs_buf_free.
 897 */
 898void
 899xfs_buf_rele(
 900        xfs_buf_t               *bp)
 901{
 902        struct xfs_perag        *pag = bp->b_pag;
 903
 904        trace_xfs_buf_rele(bp, _RET_IP_);
 905
 906        if (!pag) {
 907                ASSERT(list_empty(&bp->b_lru));
 908                ASSERT(RB_EMPTY_NODE(&bp->b_rbnode));
 909                if (atomic_dec_and_test(&bp->b_hold))
 910                        xfs_buf_free(bp);
 911                return;
 912        }
 913
 914        ASSERT(!RB_EMPTY_NODE(&bp->b_rbnode));
 915
 916        ASSERT(atomic_read(&bp->b_hold) > 0);
 917        if (atomic_dec_and_lock(&bp->b_hold, &pag->pag_buf_lock)) {
 918                if (!(bp->b_flags & XBF_STALE) &&
 919                           atomic_read(&bp->b_lru_ref)) {
 920                        xfs_buf_lru_add(bp);
 921                        spin_unlock(&pag->pag_buf_lock);
 922                } else {
 923                        xfs_buf_lru_del(bp);
 924                        ASSERT(!(bp->b_flags & _XBF_DELWRI_Q));
 925                        rb_erase(&bp->b_rbnode, &pag->pag_buf_tree);
 926                        spin_unlock(&pag->pag_buf_lock);
 927                        xfs_perag_put(pag);
 928                        xfs_buf_free(bp);
 929                }
 930        }
 931}
 932
 933
 934/*
 935 *      Lock a buffer object, if it is not already locked.
 936 *
 937 *      If we come across a stale, pinned, locked buffer, we know that we are
 938 *      being asked to lock a buffer that has been reallocated. Because it is
 939 *      pinned, we know that the log has not been pushed to disk and hence it
 940 *      will still be locked.  Rather than continuing to have trylock attempts
 941 *      fail until someone else pushes the log, push it ourselves before
 942 *      returning.  This means that the xfsaild will not get stuck trying
 943 *      to push on stale inode buffers.
 944 */
 945int
 946xfs_buf_trylock(
 947        struct xfs_buf          *bp)
 948{
 949        int                     locked;
 950
 951        locked = down_trylock(&bp->b_sema) == 0;
 952        if (locked)
 953                XB_SET_OWNER(bp);
 954        else if (atomic_read(&bp->b_pin_count) && (bp->b_flags & XBF_STALE))
 955                xfs_log_force(bp->b_target->bt_mount, 0);
 956
 957        trace_xfs_buf_trylock(bp, _RET_IP_);
 958        return locked;
 959}
 960
 961/*
 962 *      Lock a buffer object.
 963 *
 964 *      If we come across a stale, pinned, locked buffer, we know that we
 965 *      are being asked to lock a buffer that has been reallocated. Because
 966 *      it is pinned, we know that the log has not been pushed to disk and
 967 *      hence it will still be locked. Rather than sleeping until someone
 968 *      else pushes the log, push it ourselves before trying to get the lock.
 969 */
 970void
 971xfs_buf_lock(
 972        struct xfs_buf          *bp)
 973{
 974        trace_xfs_buf_lock(bp, _RET_IP_);
 975
 976        if (atomic_read(&bp->b_pin_count) && (bp->b_flags & XBF_STALE))
 977                xfs_log_force(bp->b_target->bt_mount, 0);
 978        down(&bp->b_sema);
 979        XB_SET_OWNER(bp);
 980
 981        trace_xfs_buf_lock_done(bp, _RET_IP_);
 982}
 983
 984void
 985xfs_buf_unlock(
 986        struct xfs_buf          *bp)
 987{
 988        XB_CLEAR_OWNER(bp);
 989        up(&bp->b_sema);
 990
 991        trace_xfs_buf_unlock(bp, _RET_IP_);
 992}
 993
 994STATIC void
 995xfs_buf_wait_unpin(
 996        xfs_buf_t               *bp)
 997{
 998        DECLARE_WAITQUEUE       (wait, current);
 999
1000        if (atomic_read(&bp->b_pin_count) == 0)
1001                return;
1002
1003        add_wait_queue(&bp->b_waiters, &wait);
1004        for (;;) {
1005                set_current_state(TASK_UNINTERRUPTIBLE);
1006                if (atomic_read(&bp->b_pin_count) == 0)
1007                        break;
1008                io_schedule();
1009        }
1010        remove_wait_queue(&bp->b_waiters, &wait);
1011        set_current_state(TASK_RUNNING);
1012}
1013
1014/*
1015 *      Buffer Utility Routines
1016 */
1017
1018STATIC void
1019xfs_buf_iodone_work(
1020        struct work_struct      *work)
1021{
1022        struct xfs_buf          *bp =
1023                container_of(work, xfs_buf_t, b_iodone_work);
1024        bool                    read = !!(bp->b_flags & XBF_READ);
1025
1026        bp->b_flags &= ~(XBF_READ | XBF_WRITE | XBF_READ_AHEAD);
1027        if (read && bp->b_ops)
1028                bp->b_ops->verify_read(bp);
1029
1030        if (bp->b_iodone)
1031                (*(bp->b_iodone))(bp);
1032        else if (bp->b_flags & XBF_ASYNC)
1033                xfs_buf_relse(bp);
1034        else {
1035                ASSERT(read && bp->b_ops);
1036                complete(&bp->b_iowait);
1037        }
1038}
1039
1040void
1041xfs_buf_ioend(
1042        struct xfs_buf  *bp,
1043        int             schedule)
1044{
1045        bool            read = !!(bp->b_flags & XBF_READ);
1046
1047        trace_xfs_buf_iodone(bp, _RET_IP_);
1048
1049        if (bp->b_error == 0)
1050                bp->b_flags |= XBF_DONE;
1051
1052        if (bp->b_iodone || (read && bp->b_ops) || (bp->b_flags & XBF_ASYNC)) {
1053                if (schedule) {
1054                        INIT_WORK(&bp->b_iodone_work, xfs_buf_iodone_work);
1055                        queue_work(xfslogd_workqueue, &bp->b_iodone_work);
1056                } else {
1057                        xfs_buf_iodone_work(&bp->b_iodone_work);
1058                }
1059        } else {
1060                bp->b_flags &= ~(XBF_READ | XBF_WRITE | XBF_READ_AHEAD);
1061                complete(&bp->b_iowait);
1062        }
1063}
1064
1065void
1066xfs_buf_ioerror(
1067        xfs_buf_t               *bp,
1068        int                     error)
1069{
1070        ASSERT(error >= 0 && error <= 0xffff);
1071        bp->b_error = (unsigned short)error;
1072        trace_xfs_buf_ioerror(bp, error, _RET_IP_);
1073}
1074
1075void
1076xfs_buf_ioerror_alert(
1077        struct xfs_buf          *bp,
1078        const char              *func)
1079{
1080        xfs_alert(bp->b_target->bt_mount,
1081"metadata I/O error: block 0x%llx (\"%s\") error %d numblks %d",
1082                (__uint64_t)XFS_BUF_ADDR(bp), func, bp->b_error, bp->b_length);
1083}
1084
1085/*
1086 * Called when we want to stop a buffer from getting written or read.
1087 * We attach the EIO error, muck with its flags, and call xfs_buf_ioend
1088 * so that the proper iodone callbacks get called.
1089 */
1090STATIC int
1091xfs_bioerror(
1092        xfs_buf_t *bp)
1093{
1094#ifdef XFSERRORDEBUG
1095        ASSERT(XFS_BUF_ISREAD(bp) || bp->b_iodone);
1096#endif
1097
1098        /*
1099         * No need to wait until the buffer is unpinned, we aren't flushing it.
1100         */
1101        xfs_buf_ioerror(bp, EIO);
1102
1103        /*
1104         * We're calling xfs_buf_ioend, so delete XBF_DONE flag.
1105         */
1106        XFS_BUF_UNREAD(bp);
1107        XFS_BUF_UNDONE(bp);
1108        xfs_buf_stale(bp);
1109
1110        xfs_buf_ioend(bp, 0);
1111
1112        return EIO;
1113}
1114
1115/*
1116 * Same as xfs_bioerror, except that we are releasing the buffer
1117 * here ourselves, and avoiding the xfs_buf_ioend call.
1118 * This is meant for userdata errors; metadata bufs come with
1119 * iodone functions attached, so that we can track down errors.
1120 */
1121STATIC int
1122xfs_bioerror_relse(
1123        struct xfs_buf  *bp)
1124{
1125        int64_t         fl = bp->b_flags;
1126        /*
1127         * No need to wait until the buffer is unpinned.
1128         * We aren't flushing it.
1129         *
1130         * chunkhold expects B_DONE to be set, whether
1131         * we actually finish the I/O or not. We don't want to
1132         * change that interface.
1133         */
1134        XFS_BUF_UNREAD(bp);
1135        XFS_BUF_DONE(bp);
1136        xfs_buf_stale(bp);
1137        bp->b_iodone = NULL;
1138        if (!(fl & XBF_ASYNC)) {
1139                /*
1140                 * Mark b_error and B_ERROR _both_.
1141                 * Lot's of chunkcache code assumes that.
1142                 * There's no reason to mark error for
1143                 * ASYNC buffers.
1144                 */
1145                xfs_buf_ioerror(bp, EIO);
1146                complete(&bp->b_iowait);
1147        } else {
1148                xfs_buf_relse(bp);
1149        }
1150
1151        return EIO;
1152}
1153
1154STATIC int
1155xfs_bdstrat_cb(
1156        struct xfs_buf  *bp)
1157{
1158        if (XFS_FORCED_SHUTDOWN(bp->b_target->bt_mount)) {
1159                trace_xfs_bdstrat_shut(bp, _RET_IP_);
1160                /*
1161                 * Metadata write that didn't get logged but
1162                 * written delayed anyway. These aren't associated
1163                 * with a transaction, and can be ignored.
1164                 */
1165                if (!bp->b_iodone && !XFS_BUF_ISREAD(bp))
1166                        return xfs_bioerror_relse(bp);
1167                else
1168                        return xfs_bioerror(bp);
1169        }
1170
1171        xfs_buf_iorequest(bp);
1172        return 0;
1173}
1174
1175int
1176xfs_bwrite(
1177        struct xfs_buf          *bp)
1178{
1179        int                     error;
1180
1181        ASSERT(xfs_buf_islocked(bp));
1182
1183        bp->b_flags |= XBF_WRITE;
1184        bp->b_flags &= ~(XBF_ASYNC | XBF_READ | _XBF_DELWRI_Q);
1185
1186        xfs_bdstrat_cb(bp);
1187
1188        error = xfs_buf_iowait(bp);
1189        if (error) {
1190                xfs_force_shutdown(bp->b_target->bt_mount,
1191                                   SHUTDOWN_META_IO_ERROR);
1192        }
1193        return error;
1194}
1195
1196/*
1197 * Wrapper around bdstrat so that we can stop data from going to disk in case
1198 * we are shutting down the filesystem.  Typically user data goes thru this
1199 * path; one of the exceptions is the superblock.
1200 */
1201void
1202xfsbdstrat(
1203        struct xfs_mount        *mp,
1204        struct xfs_buf          *bp)
1205{
1206        if (XFS_FORCED_SHUTDOWN(mp)) {
1207                trace_xfs_bdstrat_shut(bp, _RET_IP_);
1208                xfs_bioerror_relse(bp);
1209                return;
1210        }
1211
1212        xfs_buf_iorequest(bp);
1213}
1214
1215STATIC void
1216_xfs_buf_ioend(
1217        xfs_buf_t               *bp,
1218        int                     schedule)
1219{
1220        if (atomic_dec_and_test(&bp->b_io_remaining) == 1)
1221                xfs_buf_ioend(bp, schedule);
1222}
1223
1224STATIC void
1225xfs_buf_bio_end_io(
1226        struct bio              *bio,
1227        int                     error)
1228{
1229        xfs_buf_t               *bp = (xfs_buf_t *)bio->bi_private;
1230
1231        /*
1232         * don't overwrite existing errors - otherwise we can lose errors on
1233         * buffers that require multiple bios to complete.
1234         */
1235        if (!bp->b_error)
1236                xfs_buf_ioerror(bp, -error);
1237
1238        if (!bp->b_error && xfs_buf_is_vmapped(bp) && (bp->b_flags & XBF_READ))
1239                invalidate_kernel_vmap_range(bp->b_addr, xfs_buf_vmap_len(bp));
1240
1241        _xfs_buf_ioend(bp, 1);
1242        bio_put(bio);
1243}
1244
1245static void
1246xfs_buf_ioapply_map(
1247        struct xfs_buf  *bp,
1248        int             map,
1249        int             *buf_offset,
1250        int             *count,
1251        int             rw)
1252{
1253        int             page_index;
1254        int             total_nr_pages = bp->b_page_count;
1255        int             nr_pages;
1256        struct bio      *bio;
1257        sector_t        sector =  bp->b_maps[map].bm_bn;
1258        int             size;
1259        int             offset;
1260
1261        total_nr_pages = bp->b_page_count;
1262
1263        /* skip the pages in the buffer before the start offset */
1264        page_index = 0;
1265        offset = *buf_offset;
1266        while (offset >= PAGE_SIZE) {
1267                page_index++;
1268                offset -= PAGE_SIZE;
1269        }
1270
1271        /*
1272         * Limit the IO size to the length of the current vector, and update the
1273         * remaining IO count for the next time around.
1274         */
1275        size = min_t(int, BBTOB(bp->b_maps[map].bm_len), *count);
1276        *count -= size;
1277        *buf_offset += size;
1278
1279next_chunk:
1280        atomic_inc(&bp->b_io_remaining);
1281        nr_pages = BIO_MAX_SECTORS >> (PAGE_SHIFT - BBSHIFT);
1282        if (nr_pages > total_nr_pages)
1283                nr_pages = total_nr_pages;
1284
1285        bio = bio_alloc(GFP_NOIO, nr_pages);
1286        bio->bi_bdev = bp->b_target->bt_bdev;
1287        bio->bi_sector = sector;
1288        bio->bi_end_io = xfs_buf_bio_end_io;
1289        bio->bi_private = bp;
1290
1291
1292        for (; size && nr_pages; nr_pages--, page_index++) {
1293                int     rbytes, nbytes = PAGE_SIZE - offset;
1294
1295                if (nbytes > size)
1296                        nbytes = size;
1297
1298                rbytes = bio_add_page(bio, bp->b_pages[page_index], nbytes,
1299                                      offset);
1300                if (rbytes < nbytes)
1301                        break;
1302
1303                offset = 0;
1304                sector += BTOBB(nbytes);
1305                size -= nbytes;
1306                total_nr_pages--;
1307        }
1308
1309        if (likely(bio->bi_size)) {
1310                if (xfs_buf_is_vmapped(bp)) {
1311                        flush_kernel_vmap_range(bp->b_addr,
1312                                                xfs_buf_vmap_len(bp));
1313                }
1314                submit_bio(rw, bio);
1315                if (size)
1316                        goto next_chunk;
1317        } else {
1318                /*
1319                 * This is guaranteed not to be the last io reference count
1320                 * because the caller (xfs_buf_iorequest) holds a count itself.
1321                 */
1322                atomic_dec(&bp->b_io_remaining);
1323                xfs_buf_ioerror(bp, EIO);
1324                bio_put(bio);
1325        }
1326
1327}
1328
1329STATIC void
1330_xfs_buf_ioapply(
1331        struct xfs_buf  *bp)
1332{
1333        struct blk_plug plug;
1334        int             rw;
1335        int             offset;
1336        int             size;
1337        int             i;
1338
1339        if (bp->b_flags & XBF_WRITE) {
1340                if (bp->b_flags & XBF_SYNCIO)
1341                        rw = WRITE_SYNC;
1342                else
1343                        rw = WRITE;
1344                if (bp->b_flags & XBF_FUA)
1345                        rw |= REQ_FUA;
1346                if (bp->b_flags & XBF_FLUSH)
1347                        rw |= REQ_FLUSH;
1348
1349                /*
1350                 * Run the write verifier callback function if it exists. If
1351                 * this function fails it will mark the buffer with an error and
1352                 * the IO should not be dispatched.
1353                 */
1354                if (bp->b_ops) {
1355                        bp->b_ops->verify_write(bp);
1356                        if (bp->b_error) {
1357                                xfs_force_shutdown(bp->b_target->bt_mount,
1358                                                   SHUTDOWN_CORRUPT_INCORE);
1359                                return;
1360                        }
1361                }
1362        } else if (bp->b_flags & XBF_READ_AHEAD) {
1363                rw = READA;
1364        } else {
1365                rw = READ;
1366        }
1367
1368        /* we only use the buffer cache for meta-data */
1369        rw |= REQ_META;
1370
1371        /*
1372         * Walk all the vectors issuing IO on them. Set up the initial offset
1373         * into the buffer and the desired IO size before we start -
1374         * _xfs_buf_ioapply_vec() will modify them appropriately for each
1375         * subsequent call.
1376         */
1377        offset = bp->b_offset;
1378        size = BBTOB(bp->b_io_length);
1379        blk_start_plug(&plug);
1380        for (i = 0; i < bp->b_map_count; i++) {
1381                xfs_buf_ioapply_map(bp, i, &offset, &size, rw);
1382                if (bp->b_error)
1383                        break;
1384                if (size <= 0)
1385                        break;  /* all done */
1386        }
1387        blk_finish_plug(&plug);
1388}
1389
1390void
1391xfs_buf_iorequest(
1392        xfs_buf_t               *bp)
1393{
1394        trace_xfs_buf_iorequest(bp, _RET_IP_);
1395
1396        ASSERT(!(bp->b_flags & _XBF_DELWRI_Q));
1397
1398        if (bp->b_flags & XBF_WRITE)
1399                xfs_buf_wait_unpin(bp);
1400        xfs_buf_hold(bp);
1401
1402        /* Set the count to 1 initially, this will stop an I/O
1403         * completion callout which happens before we have started
1404         * all the I/O from calling xfs_buf_ioend too early.
1405         */
1406        atomic_set(&bp->b_io_remaining, 1);
1407        _xfs_buf_ioapply(bp);
1408        _xfs_buf_ioend(bp, 1);
1409
1410        xfs_buf_rele(bp);
1411}
1412
1413/*
1414 * Waits for I/O to complete on the buffer supplied.  It returns immediately if
1415 * no I/O is pending or there is already a pending error on the buffer.  It
1416 * returns the I/O error code, if any, or 0 if there was no error.
1417 */
1418int
1419xfs_buf_iowait(
1420        xfs_buf_t               *bp)
1421{
1422        trace_xfs_buf_iowait(bp, _RET_IP_);
1423
1424        if (!bp->b_error)
1425                wait_for_completion(&bp->b_iowait);
1426
1427        trace_xfs_buf_iowait_done(bp, _RET_IP_);
1428        return bp->b_error;
1429}
1430
1431xfs_caddr_t
1432xfs_buf_offset(
1433        xfs_buf_t               *bp,
1434        size_t                  offset)
1435{
1436        struct page             *page;
1437
1438        if (bp->b_addr)
1439                return bp->b_addr + offset;
1440
1441        offset += bp->b_offset;
1442        page = bp->b_pages[offset >> PAGE_SHIFT];
1443        return (xfs_caddr_t)page_address(page) + (offset & (PAGE_SIZE-1));
1444}
1445
1446/*
1447 *      Move data into or out of a buffer.
1448 */
1449void
1450xfs_buf_iomove(
1451        xfs_buf_t               *bp,    /* buffer to process            */
1452        size_t                  boff,   /* starting buffer offset       */
1453        size_t                  bsize,  /* length to copy               */
1454        void                    *data,  /* data address                 */
1455        xfs_buf_rw_t            mode)   /* read/write/zero flag         */
1456{
1457        size_t                  bend;
1458
1459        bend = boff + bsize;
1460        while (boff < bend) {
1461                struct page     *page;
1462                int             page_index, page_offset, csize;
1463
1464                page_index = (boff + bp->b_offset) >> PAGE_SHIFT;
1465                page_offset = (boff + bp->b_offset) & ~PAGE_MASK;
1466                page = bp->b_pages[page_index];
1467                csize = min_t(size_t, PAGE_SIZE - page_offset,
1468                                      BBTOB(bp->b_io_length) - boff);
1469
1470                ASSERT((csize + page_offset) <= PAGE_SIZE);
1471
1472                switch (mode) {
1473                case XBRW_ZERO:
1474                        memset(page_address(page) + page_offset, 0, csize);
1475                        break;
1476                case XBRW_READ:
1477                        memcpy(data, page_address(page) + page_offset, csize);
1478                        break;
1479                case XBRW_WRITE:
1480                        memcpy(page_address(page) + page_offset, data, csize);
1481                }
1482
1483                boff += csize;
1484                data += csize;
1485        }
1486}
1487
1488/*
1489 *      Handling of buffer targets (buftargs).
1490 */
1491
1492/*
1493 * Wait for any bufs with callbacks that have been submitted but have not yet
1494 * returned. These buffers will have an elevated hold count, so wait on those
1495 * while freeing all the buffers only held by the LRU.
1496 */
1497void
1498xfs_wait_buftarg(
1499        struct xfs_buftarg      *btp)
1500{
1501        struct xfs_buf          *bp;
1502
1503restart:
1504        spin_lock(&btp->bt_lru_lock);
1505        while (!list_empty(&btp->bt_lru)) {
1506                bp = list_first_entry(&btp->bt_lru, struct xfs_buf, b_lru);
1507                if (atomic_read(&bp->b_hold) > 1) {
1508                        trace_xfs_buf_wait_buftarg(bp, _RET_IP_);
1509                        list_move_tail(&bp->b_lru, &btp->bt_lru);
1510                        spin_unlock(&btp->bt_lru_lock);
1511                        delay(100);
1512                        goto restart;
1513                }
1514                /*
1515                 * clear the LRU reference count so the buffer doesn't get
1516                 * ignored in xfs_buf_rele().
1517                 */
1518                atomic_set(&bp->b_lru_ref, 0);
1519                spin_unlock(&btp->bt_lru_lock);
1520                xfs_buf_rele(bp);
1521                spin_lock(&btp->bt_lru_lock);
1522        }
1523        spin_unlock(&btp->bt_lru_lock);
1524}
1525
1526int
1527xfs_buftarg_shrink(
1528        struct shrinker         *shrink,
1529        struct shrink_control   *sc)
1530{
1531        struct xfs_buftarg      *btp = container_of(shrink,
1532                                        struct xfs_buftarg, bt_shrinker);
1533        struct xfs_buf          *bp;
1534        int nr_to_scan = sc->nr_to_scan;
1535        LIST_HEAD(dispose);
1536
1537        if (!nr_to_scan)
1538                return btp->bt_lru_nr;
1539
1540        spin_lock(&btp->bt_lru_lock);
1541        while (!list_empty(&btp->bt_lru)) {
1542                if (nr_to_scan-- <= 0)
1543                        break;
1544
1545                bp = list_first_entry(&btp->bt_lru, struct xfs_buf, b_lru);
1546
1547                /*
1548                 * Decrement the b_lru_ref count unless the value is already
1549                 * zero. If the value is already zero, we need to reclaim the
1550                 * buffer, otherwise it gets another trip through the LRU.
1551                 */
1552                if (!atomic_add_unless(&bp->b_lru_ref, -1, 0)) {
1553                        list_move_tail(&bp->b_lru, &btp->bt_lru);
1554                        continue;
1555                }
1556
1557                /*
1558                 * remove the buffer from the LRU now to avoid needing another
1559                 * lock round trip inside xfs_buf_rele().
1560                 */
1561                list_move(&bp->b_lru, &dispose);
1562                btp->bt_lru_nr--;
1563                bp->b_lru_flags |= _XBF_LRU_DISPOSE;
1564        }
1565        spin_unlock(&btp->bt_lru_lock);
1566
1567        while (!list_empty(&dispose)) {
1568                bp = list_first_entry(&dispose, struct xfs_buf, b_lru);
1569                list_del_init(&bp->b_lru);
1570                xfs_buf_rele(bp);
1571        }
1572
1573        return btp->bt_lru_nr;
1574}
1575
1576void
1577xfs_free_buftarg(
1578        struct xfs_mount        *mp,
1579        struct xfs_buftarg      *btp)
1580{
1581        unregister_shrinker(&btp->bt_shrinker);
1582
1583        if (mp->m_flags & XFS_MOUNT_BARRIER)
1584                xfs_blkdev_issue_flush(btp);
1585
1586        kmem_free(btp);
1587}
1588
1589STATIC int
1590xfs_setsize_buftarg_flags(
1591        xfs_buftarg_t           *btp,
1592        unsigned int            blocksize,
1593        unsigned int            sectorsize,
1594        int                     verbose)
1595{
1596        btp->bt_bsize = blocksize;
1597        btp->bt_sshift = ffs(sectorsize) - 1;
1598        btp->bt_smask = sectorsize - 1;
1599
1600        if (set_blocksize(btp->bt_bdev, sectorsize)) {
1601                char name[BDEVNAME_SIZE];
1602
1603                bdevname(btp->bt_bdev, name);
1604
1605                xfs_warn(btp->bt_mount,
1606                        "Cannot set_blocksize to %u on device %s\n",
1607                        sectorsize, name);
1608                return EINVAL;
1609        }
1610
1611        return 0;
1612}
1613
1614/*
1615 *      When allocating the initial buffer target we have not yet
1616 *      read in the superblock, so don't know what sized sectors
1617 *      are being used is at this early stage.  Play safe.
1618 */
1619STATIC int
1620xfs_setsize_buftarg_early(
1621        xfs_buftarg_t           *btp,
1622        struct block_device     *bdev)
1623{
1624        return xfs_setsize_buftarg_flags(btp,
1625                        PAGE_SIZE, bdev_logical_block_size(bdev), 0);
1626}
1627
1628int
1629xfs_setsize_buftarg(
1630        xfs_buftarg_t           *btp,
1631        unsigned int            blocksize,
1632        unsigned int            sectorsize)
1633{
1634        return xfs_setsize_buftarg_flags(btp, blocksize, sectorsize, 1);
1635}
1636
1637xfs_buftarg_t *
1638xfs_alloc_buftarg(
1639        struct xfs_mount        *mp,
1640        struct block_device     *bdev,
1641        int                     external,
1642        const char              *fsname)
1643{
1644        xfs_buftarg_t           *btp;
1645
1646        btp = kmem_zalloc(sizeof(*btp), KM_SLEEP);
1647
1648        btp->bt_mount = mp;
1649        btp->bt_dev =  bdev->bd_dev;
1650        btp->bt_bdev = bdev;
1651        btp->bt_bdi = blk_get_backing_dev_info(bdev);
1652        if (!btp->bt_bdi)
1653                goto error;
1654
1655        INIT_LIST_HEAD(&btp->bt_lru);
1656        spin_lock_init(&btp->bt_lru_lock);
1657        if (xfs_setsize_buftarg_early(btp, bdev))
1658                goto error;
1659        btp->bt_shrinker.shrink = xfs_buftarg_shrink;
1660        btp->bt_shrinker.seeks = DEFAULT_SEEKS;
1661        register_shrinker(&btp->bt_shrinker);
1662        return btp;
1663
1664error:
1665        kmem_free(btp);
1666        return NULL;
1667}
1668
1669/*
1670 * Add a buffer to the delayed write list.
1671 *
1672 * This queues a buffer for writeout if it hasn't already been.  Note that
1673 * neither this routine nor the buffer list submission functions perform
1674 * any internal synchronization.  It is expected that the lists are thread-local
1675 * to the callers.
1676 *
1677 * Returns true if we queued up the buffer, or false if it already had
1678 * been on the buffer list.
1679 */
1680bool
1681xfs_buf_delwri_queue(
1682        struct xfs_buf          *bp,
1683        struct list_head        *list)
1684{
1685        ASSERT(xfs_buf_islocked(bp));
1686        ASSERT(!(bp->b_flags & XBF_READ));
1687
1688        /*
1689         * If the buffer is already marked delwri it already is queued up
1690         * by someone else for imediate writeout.  Just ignore it in that
1691         * case.
1692         */
1693        if (bp->b_flags & _XBF_DELWRI_Q) {
1694                trace_xfs_buf_delwri_queued(bp, _RET_IP_);
1695                return false;
1696        }
1697
1698        trace_xfs_buf_delwri_queue(bp, _RET_IP_);
1699
1700        /*
1701         * If a buffer gets written out synchronously or marked stale while it
1702         * is on a delwri list we lazily remove it. To do this, the other party
1703         * clears the  _XBF_DELWRI_Q flag but otherwise leaves the buffer alone.
1704         * It remains referenced and on the list.  In a rare corner case it
1705         * might get readded to a delwri list after the synchronous writeout, in
1706         * which case we need just need to re-add the flag here.
1707         */
1708        bp->b_flags |= _XBF_DELWRI_Q;
1709        if (list_empty(&bp->b_list)) {
1710                atomic_inc(&bp->b_hold);
1711                list_add_tail(&bp->b_list, list);
1712        }
1713
1714        return true;
1715}
1716
1717/*
1718 * Compare function is more complex than it needs to be because
1719 * the return value is only 32 bits and we are doing comparisons
1720 * on 64 bit values
1721 */
1722static int
1723xfs_buf_cmp(
1724        void            *priv,
1725        struct list_head *a,
1726        struct list_head *b)
1727{
1728        struct xfs_buf  *ap = container_of(a, struct xfs_buf, b_list);
1729        struct xfs_buf  *bp = container_of(b, struct xfs_buf, b_list);
1730        xfs_daddr_t             diff;
1731
1732        diff = ap->b_maps[0].bm_bn - bp->b_maps[0].bm_bn;
1733        if (diff < 0)
1734                return -1;
1735        if (diff > 0)
1736                return 1;
1737        return 0;
1738}
1739
1740static int
1741__xfs_buf_delwri_submit(
1742        struct list_head        *buffer_list,
1743        struct list_head        *io_list,
1744        bool                    wait)
1745{
1746        struct blk_plug         plug;
1747        struct xfs_buf          *bp, *n;
1748        int                     pinned = 0;
1749
1750        list_for_each_entry_safe(bp, n, buffer_list, b_list) {
1751                if (!wait) {
1752                        if (xfs_buf_ispinned(bp)) {
1753                                pinned++;
1754                                continue;
1755                        }
1756                        if (!xfs_buf_trylock(bp))
1757                                continue;
1758                } else {
1759                        xfs_buf_lock(bp);
1760                }
1761
1762                /*
1763                 * Someone else might have written the buffer synchronously or
1764                 * marked it stale in the meantime.  In that case only the
1765                 * _XBF_DELWRI_Q flag got cleared, and we have to drop the
1766                 * reference and remove it from the list here.
1767                 */
1768                if (!(bp->b_flags & _XBF_DELWRI_Q)) {
1769                        list_del_init(&bp->b_list);
1770                        xfs_buf_relse(bp);
1771                        continue;
1772                }
1773
1774                list_move_tail(&bp->b_list, io_list);
1775                trace_xfs_buf_delwri_split(bp, _RET_IP_);
1776        }
1777
1778        list_sort(NULL, io_list, xfs_buf_cmp);
1779
1780        blk_start_plug(&plug);
1781        list_for_each_entry_safe(bp, n, io_list, b_list) {
1782                bp->b_flags &= ~(_XBF_DELWRI_Q | XBF_ASYNC);
1783                bp->b_flags |= XBF_WRITE;
1784
1785                if (!wait) {
1786                        bp->b_flags |= XBF_ASYNC;
1787                        list_del_init(&bp->b_list);
1788                }
1789                xfs_bdstrat_cb(bp);
1790        }
1791        blk_finish_plug(&plug);
1792
1793        return pinned;
1794}
1795
1796/*
1797 * Write out a buffer list asynchronously.
1798 *
1799 * This will take the @buffer_list, write all non-locked and non-pinned buffers
1800 * out and not wait for I/O completion on any of the buffers.  This interface
1801 * is only safely useable for callers that can track I/O completion by higher
1802 * level means, e.g. AIL pushing as the @buffer_list is consumed in this
1803 * function.
1804 */
1805int
1806xfs_buf_delwri_submit_nowait(
1807        struct list_head        *buffer_list)
1808{
1809        LIST_HEAD               (io_list);
1810        return __xfs_buf_delwri_submit(buffer_list, &io_list, false);
1811}
1812
1813/*
1814 * Write out a buffer list synchronously.
1815 *
1816 * This will take the @buffer_list, write all buffers out and wait for I/O
1817 * completion on all of the buffers. @buffer_list is consumed by the function,
1818 * so callers must have some other way of tracking buffers if they require such
1819 * functionality.
1820 */
1821int
1822xfs_buf_delwri_submit(
1823        struct list_head        *buffer_list)
1824{
1825        LIST_HEAD               (io_list);
1826        int                     error = 0, error2;
1827        struct xfs_buf          *bp;
1828
1829        __xfs_buf_delwri_submit(buffer_list, &io_list, true);
1830
1831        /* Wait for IO to complete. */
1832        while (!list_empty(&io_list)) {
1833                bp = list_first_entry(&io_list, struct xfs_buf, b_list);
1834
1835                list_del_init(&bp->b_list);
1836                error2 = xfs_buf_iowait(bp);
1837                xfs_buf_relse(bp);
1838                if (!error)
1839                        error = error2;
1840        }
1841
1842        return error;
1843}
1844
1845int __init
1846xfs_buf_init(void)
1847{
1848        xfs_buf_zone = kmem_zone_init_flags(sizeof(xfs_buf_t), "xfs_buf",
1849                                                KM_ZONE_HWALIGN, NULL);
1850        if (!xfs_buf_zone)
1851                goto out;
1852
1853        xfslogd_workqueue = alloc_workqueue("xfslogd",
1854                                        WQ_MEM_RECLAIM | WQ_HIGHPRI, 1);
1855        if (!xfslogd_workqueue)
1856                goto out_free_buf_zone;
1857
1858        return 0;
1859
1860 out_free_buf_zone:
1861        kmem_zone_destroy(xfs_buf_zone);
1862 out:
1863        return -ENOMEM;
1864}
1865
1866void
1867xfs_buf_terminate(void)
1868{
1869        destroy_workqueue(xfslogd_workqueue);
1870        kmem_zone_destroy(xfs_buf_zone);
1871}
1872
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