linux/drivers/block/loop.c
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   1/*
   2 *  linux/drivers/block/loop.c
   3 *
   4 *  Written by Theodore Ts'o, 3/29/93
   5 *
   6 * Copyright 1993 by Theodore Ts'o.  Redistribution of this file is
   7 * permitted under the GNU General Public License.
   8 *
   9 * DES encryption plus some minor changes by Werner Almesberger, 30-MAY-1993
  10 * more DES encryption plus IDEA encryption by Nicholas J. Leon, June 20, 1996
  11 *
  12 * Modularized and updated for 1.1.16 kernel - Mitch Dsouza 28th May 1994
  13 * Adapted for 1.3.59 kernel - Andries Brouwer, 1 Feb 1996
  14 *
  15 * Fixed do_loop_request() re-entrancy - Vincent.Renardias@waw.com Mar 20, 1997
  16 *
  17 * Added devfs support - Richard Gooch <rgooch@atnf.csiro.au> 16-Jan-1998
  18 *
  19 * Handle sparse backing files correctly - Kenn Humborg, Jun 28, 1998
  20 *
  21 * Loadable modules and other fixes by AK, 1998
  22 *
  23 * Make real block number available to downstream transfer functions, enables
  24 * CBC (and relatives) mode encryption requiring unique IVs per data block.
  25 * Reed H. Petty, rhp@draper.net
  26 *
  27 * Maximum number of loop devices now dynamic via max_loop module parameter.
  28 * Russell Kroll <rkroll@exploits.org> 19990701
  29 *
  30 * Maximum number of loop devices when compiled-in now selectable by passing
  31 * max_loop=<1-255> to the kernel on boot.
  32 * Erik I. Bols\xC3\xB8, <eriki@himolde.no>, Oct 31, 1999
  33 *
  34 * Completely rewrite request handling to be make_request_fn style and
  35 * non blocking, pushing work to a helper thread. Lots of fixes from
  36 * Al Viro too.
  37 * Jens Axboe <axboe@suse.de>, Nov 2000
  38 *
  39 * Support up to 256 loop devices
  40 * Heinz Mauelshagen <mge@sistina.com>, Feb 2002
  41 *
  42 * Support for falling back on the write file operation when the address space
  43 * operations write_begin is not available on the backing filesystem.
  44 * Anton Altaparmakov, 16 Feb 2005
  45 *
  46 * Still To Fix:
  47 * - Advisory locking is ignored here.
  48 * - Should use an own CAP_* category instead of CAP_SYS_ADMIN
  49 *
  50 */
  51
  52#include <linux/module.h>
  53#include <linux/moduleparam.h>
  54#include <linux/sched.h>
  55#include <linux/fs.h>
  56#include <linux/file.h>
  57#include <linux/stat.h>
  58#include <linux/errno.h>
  59#include <linux/major.h>
  60#include <linux/wait.h>
  61#include <linux/blkdev.h>
  62#include <linux/blkpg.h>
  63#include <linux/init.h>
  64#include <linux/swap.h>
  65#include <linux/slab.h>
  66#include <linux/compat.h>
  67#include <linux/suspend.h>
  68#include <linux/freezer.h>
  69#include <linux/mutex.h>
  70#include <linux/writeback.h>
  71#include <linux/completion.h>
  72#include <linux/highmem.h>
  73#include <linux/kthread.h>
  74#include <linux/splice.h>
  75#include <linux/sysfs.h>
  76#include <linux/miscdevice.h>
  77#include <linux/falloc.h>
  78#include <linux/uio.h>
  79#include "loop.h"
  80
  81#include <asm/uaccess.h>
  82
  83static DEFINE_IDR(loop_index_idr);
  84static DEFINE_MUTEX(loop_index_mutex);
  85
  86static int max_part;
  87static int part_shift;
  88
  89static int transfer_xor(struct loop_device *lo, int cmd,
  90                        struct page *raw_page, unsigned raw_off,
  91                        struct page *loop_page, unsigned loop_off,
  92                        int size, sector_t real_block)
  93{
  94        char *raw_buf = kmap_atomic(raw_page) + raw_off;
  95        char *loop_buf = kmap_atomic(loop_page) + loop_off;
  96        char *in, *out, *key;
  97        int i, keysize;
  98
  99        if (cmd == READ) {
 100                in = raw_buf;
 101                out = loop_buf;
 102        } else {
 103                in = loop_buf;
 104                out = raw_buf;
 105        }
 106
 107        key = lo->lo_encrypt_key;
 108        keysize = lo->lo_encrypt_key_size;
 109        for (i = 0; i < size; i++)
 110                *out++ = *in++ ^ key[(i & 511) % keysize];
 111
 112        kunmap_atomic(loop_buf);
 113        kunmap_atomic(raw_buf);
 114        cond_resched();
 115        return 0;
 116}
 117
 118static int xor_init(struct loop_device *lo, const struct loop_info64 *info)
 119{
 120        if (unlikely(info->lo_encrypt_key_size <= 0))
 121                return -EINVAL;
 122        return 0;
 123}
 124
 125static struct loop_func_table none_funcs = {
 126        .number = LO_CRYPT_NONE,
 127}; 
 128
 129static struct loop_func_table xor_funcs = {
 130        .number = LO_CRYPT_XOR,
 131        .transfer = transfer_xor,
 132        .init = xor_init
 133}; 
 134
 135/* xfer_funcs[0] is special - its release function is never called */
 136static struct loop_func_table *xfer_funcs[MAX_LO_CRYPT] = {
 137        &none_funcs,
 138        &xor_funcs
 139};
 140
 141static loff_t get_size(loff_t offset, loff_t sizelimit, struct file *file)
 142{
 143        loff_t loopsize;
 144
 145        /* Compute loopsize in bytes */
 146        loopsize = i_size_read(file->f_mapping->host);
 147        if (offset > 0)
 148                loopsize -= offset;
 149        /* offset is beyond i_size, weird but possible */
 150        if (loopsize < 0)
 151                return 0;
 152
 153        if (sizelimit > 0 && sizelimit < loopsize)
 154                loopsize = sizelimit;
 155        /*
 156         * Unfortunately, if we want to do I/O on the device,
 157         * the number of 512-byte sectors has to fit into a sector_t.
 158         */
 159        return loopsize >> 9;
 160}
 161
 162static loff_t get_loop_size(struct loop_device *lo, struct file *file)
 163{
 164        return get_size(lo->lo_offset, lo->lo_sizelimit, file);
 165}
 166
 167static void __loop_update_dio(struct loop_device *lo, bool dio)
 168{
 169        struct file *file = lo->lo_backing_file;
 170        struct address_space *mapping = file->f_mapping;
 171        struct inode *inode = mapping->host;
 172        unsigned short sb_bsize = 0;
 173        unsigned dio_align = 0;
 174        bool use_dio;
 175
 176        if (inode->i_sb->s_bdev) {
 177                sb_bsize = bdev_logical_block_size(inode->i_sb->s_bdev);
 178                dio_align = sb_bsize - 1;
 179        }
 180
 181        /*
 182         * We support direct I/O only if lo_offset is aligned with the
 183         * logical I/O size of backing device, and the logical block
 184         * size of loop is bigger than the backing device's and the loop
 185         * needn't transform transfer.
 186         *
 187         * TODO: the above condition may be loosed in the future, and
 188         * direct I/O may be switched runtime at that time because most
 189         * of requests in sane appplications should be PAGE_SIZE algined
 190         */
 191        if (dio) {
 192                if (queue_logical_block_size(lo->lo_queue) >= sb_bsize &&
 193                                !(lo->lo_offset & dio_align) &&
 194                                mapping->a_ops->direct_IO &&
 195                                !lo->transfer)
 196                        use_dio = true;
 197                else
 198                        use_dio = false;
 199        } else {
 200                use_dio = false;
 201        }
 202
 203        if (lo->use_dio == use_dio)
 204                return;
 205
 206        /* flush dirty pages before changing direct IO */
 207        vfs_fsync(file, 0);
 208
 209        /*
 210         * The flag of LO_FLAGS_DIRECT_IO is handled similarly with
 211         * LO_FLAGS_READ_ONLY, both are set from kernel, and losetup
 212         * will get updated by ioctl(LOOP_GET_STATUS)
 213         */
 214        blk_mq_freeze_queue(lo->lo_queue);
 215        lo->use_dio = use_dio;
 216        if (use_dio)
 217                lo->lo_flags |= LO_FLAGS_DIRECT_IO;
 218        else
 219                lo->lo_flags &= ~LO_FLAGS_DIRECT_IO;
 220        blk_mq_unfreeze_queue(lo->lo_queue);
 221}
 222
 223static int
 224figure_loop_size(struct loop_device *lo, loff_t offset, loff_t sizelimit)
 225{
 226        loff_t size = get_size(offset, sizelimit, lo->lo_backing_file);
 227        sector_t x = (sector_t)size;
 228        struct block_device *bdev = lo->lo_device;
 229
 230        if (unlikely((loff_t)x != size))
 231                return -EFBIG;
 232        if (lo->lo_offset != offset)
 233                lo->lo_offset = offset;
 234        if (lo->lo_sizelimit != sizelimit)
 235                lo->lo_sizelimit = sizelimit;
 236        set_capacity(lo->lo_disk, x);
 237        bd_set_size(bdev, (loff_t)get_capacity(bdev->bd_disk) << 9);
 238        /* let user-space know about the new size */
 239        kobject_uevent(&disk_to_dev(bdev->bd_disk)->kobj, KOBJ_CHANGE);
 240        return 0;
 241}
 242
 243static inline int
 244lo_do_transfer(struct loop_device *lo, int cmd,
 245               struct page *rpage, unsigned roffs,
 246               struct page *lpage, unsigned loffs,
 247               int size, sector_t rblock)
 248{
 249        int ret;
 250
 251        ret = lo->transfer(lo, cmd, rpage, roffs, lpage, loffs, size, rblock);
 252        if (likely(!ret))
 253                return 0;
 254
 255        printk_ratelimited(KERN_ERR
 256                "loop: Transfer error at byte offset %llu, length %i.\n",
 257                (unsigned long long)rblock << 9, size);
 258        return ret;
 259}
 260
 261static int lo_write_bvec(struct file *file, struct bio_vec *bvec, loff_t *ppos)
 262{
 263        struct iov_iter i;
 264        ssize_t bw;
 265
 266        iov_iter_bvec(&i, ITER_BVEC, bvec, 1, bvec->bv_len);
 267
 268        file_start_write(file);
 269        bw = vfs_iter_write(file, &i, ppos);
 270        file_end_write(file);
 271
 272        if (likely(bw ==  bvec->bv_len))
 273                return 0;
 274
 275        printk_ratelimited(KERN_ERR
 276                "loop: Write error at byte offset %llu, length %i.\n",
 277                (unsigned long long)*ppos, bvec->bv_len);
 278        if (bw >= 0)
 279                bw = -EIO;
 280        return bw;
 281}
 282
 283static int lo_write_simple(struct loop_device *lo, struct request *rq,
 284                loff_t pos)
 285{
 286        struct bio_vec bvec;
 287        struct req_iterator iter;
 288        int ret = 0;
 289
 290        rq_for_each_segment(bvec, rq, iter) {
 291                ret = lo_write_bvec(lo->lo_backing_file, &bvec, &pos);
 292                if (ret < 0)
 293                        break;
 294                cond_resched();
 295        }
 296
 297        return ret;
 298}
 299
 300/*
 301 * This is the slow, transforming version that needs to double buffer the
 302 * data as it cannot do the transformations in place without having direct
 303 * access to the destination pages of the backing file.
 304 */
 305static int lo_write_transfer(struct loop_device *lo, struct request *rq,
 306                loff_t pos)
 307{
 308        struct bio_vec bvec, b;
 309        struct req_iterator iter;
 310        struct page *page;
 311        int ret = 0;
 312
 313        page = alloc_page(GFP_NOIO);
 314        if (unlikely(!page))
 315                return -ENOMEM;
 316
 317        rq_for_each_segment(bvec, rq, iter) {
 318                ret = lo_do_transfer(lo, WRITE, page, 0, bvec.bv_page,
 319                        bvec.bv_offset, bvec.bv_len, pos >> 9);
 320                if (unlikely(ret))
 321                        break;
 322
 323                b.bv_page = page;
 324                b.bv_offset = 0;
 325                b.bv_len = bvec.bv_len;
 326                ret = lo_write_bvec(lo->lo_backing_file, &b, &pos);
 327                if (ret < 0)
 328                        break;
 329        }
 330
 331        __free_page(page);
 332        return ret;
 333}
 334
 335static int lo_read_simple(struct loop_device *lo, struct request *rq,
 336                loff_t pos)
 337{
 338        struct bio_vec bvec;
 339        struct req_iterator iter;
 340        struct iov_iter i;
 341        ssize_t len;
 342
 343        rq_for_each_segment(bvec, rq, iter) {
 344                iov_iter_bvec(&i, ITER_BVEC, &bvec, 1, bvec.bv_len);
 345                len = vfs_iter_read(lo->lo_backing_file, &i, &pos);
 346                if (len < 0)
 347                        return len;
 348
 349                flush_dcache_page(bvec.bv_page);
 350
 351                if (len != bvec.bv_len) {
 352                        struct bio *bio;
 353
 354                        __rq_for_each_bio(bio, rq)
 355                                zero_fill_bio(bio);
 356                        break;
 357                }
 358                cond_resched();
 359        }
 360
 361        return 0;
 362}
 363
 364static int lo_read_transfer(struct loop_device *lo, struct request *rq,
 365                loff_t pos)
 366{
 367        struct bio_vec bvec, b;
 368        struct req_iterator iter;
 369        struct iov_iter i;
 370        struct page *page;
 371        ssize_t len;
 372        int ret = 0;
 373
 374        page = alloc_page(GFP_NOIO);
 375        if (unlikely(!page))
 376                return -ENOMEM;
 377
 378        rq_for_each_segment(bvec, rq, iter) {
 379                loff_t offset = pos;
 380
 381                b.bv_page = page;
 382                b.bv_offset = 0;
 383                b.bv_len = bvec.bv_len;
 384
 385                iov_iter_bvec(&i, ITER_BVEC, &b, 1, b.bv_len);
 386                len = vfs_iter_read(lo->lo_backing_file, &i, &pos);
 387                if (len < 0) {
 388                        ret = len;
 389                        goto out_free_page;
 390                }
 391
 392                ret = lo_do_transfer(lo, READ, page, 0, bvec.bv_page,
 393                        bvec.bv_offset, len, offset >> 9);
 394                if (ret)
 395                        goto out_free_page;
 396
 397                flush_dcache_page(bvec.bv_page);
 398
 399                if (len != bvec.bv_len) {
 400                        struct bio *bio;
 401
 402                        __rq_for_each_bio(bio, rq)
 403                                zero_fill_bio(bio);
 404                        break;
 405                }
 406        }
 407
 408        ret = 0;
 409out_free_page:
 410        __free_page(page);
 411        return ret;
 412}
 413
 414static int lo_discard(struct loop_device *lo, struct request *rq, loff_t pos)
 415{
 416        /*
 417         * We use punch hole to reclaim the free space used by the
 418         * image a.k.a. discard. However we do not support discard if
 419         * encryption is enabled, because it may give an attacker
 420         * useful information.
 421         */
 422        struct file *file = lo->lo_backing_file;
 423        int mode = FALLOC_FL_PUNCH_HOLE | FALLOC_FL_KEEP_SIZE;
 424        int ret;
 425
 426        if ((!file->f_op->fallocate) || lo->lo_encrypt_key_size) {
 427                ret = -EOPNOTSUPP;
 428                goto out;
 429        }
 430
 431        ret = file->f_op->fallocate(file, mode, pos, blk_rq_bytes(rq));
 432        if (unlikely(ret && ret != -EINVAL && ret != -EOPNOTSUPP))
 433                ret = -EIO;
 434 out:
 435        return ret;
 436}
 437
 438static int lo_req_flush(struct loop_device *lo, struct request *rq)
 439{
 440        struct file *file = lo->lo_backing_file;
 441        int ret = vfs_fsync(file, 0);
 442        if (unlikely(ret && ret != -EINVAL))
 443                ret = -EIO;
 444
 445        return ret;
 446}
 447
 448static inline void handle_partial_read(struct loop_cmd *cmd, long bytes)
 449{
 450        if (bytes < 0 || (cmd->rq->cmd_flags & REQ_WRITE))
 451                return;
 452
 453        if (unlikely(bytes < blk_rq_bytes(cmd->rq))) {
 454                struct bio *bio = cmd->rq->bio;
 455
 456                bio_advance(bio, bytes);
 457                zero_fill_bio(bio);
 458        }
 459}
 460
 461static void lo_rw_aio_complete(struct kiocb *iocb, long ret, long ret2)
 462{
 463        struct loop_cmd *cmd = container_of(iocb, struct loop_cmd, iocb);
 464        struct request *rq = cmd->rq;
 465
 466        handle_partial_read(cmd, ret);
 467
 468        if (ret > 0)
 469                ret = 0;
 470        else if (ret < 0)
 471                ret = -EIO;
 472
 473        blk_mq_complete_request(rq, ret);
 474}
 475
 476static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd,
 477                     loff_t pos, bool rw)
 478{
 479        struct iov_iter iter;
 480        struct bio_vec *bvec;
 481        struct bio *bio = cmd->rq->bio;
 482        struct file *file = lo->lo_backing_file;
 483        int ret;
 484
 485        /* nomerge for loop request queue */
 486        WARN_ON(cmd->rq->bio != cmd->rq->biotail);
 487
 488        bvec = __bvec_iter_bvec(bio->bi_io_vec, bio->bi_iter);
 489        iov_iter_bvec(&iter, ITER_BVEC | rw, bvec,
 490                      bio_segments(bio), blk_rq_bytes(cmd->rq));
 491        /*
 492         * This bio may be started from the middle of the 'bvec'
 493         * because of bio splitting, so offset from the bvec must
 494         * be passed to iov iterator
 495         */
 496        iter.iov_offset = bio->bi_iter.bi_bvec_done;
 497
 498        cmd->iocb.ki_pos = pos;
 499        cmd->iocb.ki_filp = file;
 500        cmd->iocb.ki_complete = lo_rw_aio_complete;
 501        cmd->iocb.ki_flags = IOCB_DIRECT;
 502
 503        if (rw == WRITE)
 504                ret = file->f_op->write_iter(&cmd->iocb, &iter);
 505        else
 506                ret = file->f_op->read_iter(&cmd->iocb, &iter);
 507
 508        if (ret != -EIOCBQUEUED)
 509                cmd->iocb.ki_complete(&cmd->iocb, ret, 0);
 510        return 0;
 511}
 512
 513
 514static inline int lo_rw_simple(struct loop_device *lo,
 515                struct request *rq, loff_t pos, bool rw)
 516{
 517        struct loop_cmd *cmd = blk_mq_rq_to_pdu(rq);
 518
 519        if (cmd->use_aio)
 520                return lo_rw_aio(lo, cmd, pos, rw);
 521
 522        /*
 523         * lo_write_simple and lo_read_simple should have been covered
 524         * by io submit style function like lo_rw_aio(), one blocker
 525         * is that lo_read_simple() need to call flush_dcache_page after
 526         * the page is written from kernel, and it isn't easy to handle
 527         * this in io submit style function which submits all segments
 528         * of the req at one time. And direct read IO doesn't need to
 529         * run flush_dcache_page().
 530         */
 531        if (rw == WRITE)
 532                return lo_write_simple(lo, rq, pos);
 533        else
 534                return lo_read_simple(lo, rq, pos);
 535}
 536
 537static int do_req_filebacked(struct loop_device *lo, struct request *rq)
 538{
 539        loff_t pos;
 540        int ret;
 541
 542        pos = ((loff_t) blk_rq_pos(rq) << 9) + lo->lo_offset;
 543
 544        if (rq->cmd_flags & REQ_WRITE) {
 545                if (rq->cmd_flags & REQ_FLUSH)
 546                        ret = lo_req_flush(lo, rq);
 547                else if (rq->cmd_flags & REQ_DISCARD)
 548                        ret = lo_discard(lo, rq, pos);
 549                else if (lo->transfer)
 550                        ret = lo_write_transfer(lo, rq, pos);
 551                else
 552                        ret = lo_rw_simple(lo, rq, pos, WRITE);
 553
 554        } else {
 555                if (lo->transfer)
 556                        ret = lo_read_transfer(lo, rq, pos);
 557                else
 558                        ret = lo_rw_simple(lo, rq, pos, READ);
 559        }
 560
 561        return ret;
 562}
 563
 564struct switch_request {
 565        struct file *file;
 566        struct completion wait;
 567};
 568
 569static inline void loop_update_dio(struct loop_device *lo)
 570{
 571        __loop_update_dio(lo, io_is_direct(lo->lo_backing_file) |
 572                        lo->use_dio);
 573}
 574
 575/*
 576 * Do the actual switch; called from the BIO completion routine
 577 */
 578static void do_loop_switch(struct loop_device *lo, struct switch_request *p)
 579{
 580        struct file *file = p->file;
 581        struct file *old_file = lo->lo_backing_file;
 582        struct address_space *mapping;
 583
 584        /* if no new file, only flush of queued bios requested */
 585        if (!file)
 586                return;
 587
 588        mapping = file->f_mapping;
 589        mapping_set_gfp_mask(old_file->f_mapping, lo->old_gfp_mask);
 590        lo->lo_backing_file = file;
 591        lo->lo_blocksize = S_ISBLK(mapping->host->i_mode) ?
 592                mapping->host->i_bdev->bd_block_size : PAGE_SIZE;
 593        lo->old_gfp_mask = mapping_gfp_mask(mapping);
 594        mapping_set_gfp_mask(mapping, lo->old_gfp_mask & ~(__GFP_IO|__GFP_FS));
 595        loop_update_dio(lo);
 596}
 597
 598/*
 599 * loop_switch performs the hard work of switching a backing store.
 600 * First it needs to flush existing IO, it does this by sending a magic
 601 * BIO down the pipe. The completion of this BIO does the actual switch.
 602 */
 603static int loop_switch(struct loop_device *lo, struct file *file)
 604{
 605        struct switch_request w;
 606
 607        w.file = file;
 608
 609        /* freeze queue and wait for completion of scheduled requests */
 610        blk_mq_freeze_queue(lo->lo_queue);
 611
 612        /* do the switch action */
 613        do_loop_switch(lo, &w);
 614
 615        /* unfreeze */
 616        blk_mq_unfreeze_queue(lo->lo_queue);
 617
 618        return 0;
 619}
 620
 621/*
 622 * Helper to flush the IOs in loop, but keeping loop thread running
 623 */
 624static int loop_flush(struct loop_device *lo)
 625{
 626        return loop_switch(lo, NULL);
 627}
 628
 629static void loop_reread_partitions(struct loop_device *lo,
 630                                   struct block_device *bdev)
 631{
 632        int rc;
 633
 634        /*
 635         * bd_mutex has been held already in release path, so don't
 636         * acquire it if this function is called in such case.
 637         *
 638         * If the reread partition isn't from release path, lo_refcnt
 639         * must be at least one and it can only become zero when the
 640         * current holder is released.
 641         */
 642        if (!atomic_read(&lo->lo_refcnt))
 643                rc = __blkdev_reread_part(bdev);
 644        else
 645                rc = blkdev_reread_part(bdev);
 646        if (rc)
 647                pr_warn("%s: partition scan of loop%d (%s) failed (rc=%d)\n",
 648                        __func__, lo->lo_number, lo->lo_file_name, rc);
 649}
 650
 651/*
 652 * loop_change_fd switched the backing store of a loopback device to
 653 * a new file. This is useful for operating system installers to free up
 654 * the original file and in High Availability environments to switch to
 655 * an alternative location for the content in case of server meltdown.
 656 * This can only work if the loop device is used read-only, and if the
 657 * new backing store is the same size and type as the old backing store.
 658 */
 659static int loop_change_fd(struct loop_device *lo, struct block_device *bdev,
 660                          unsigned int arg)
 661{
 662        struct file     *file, *old_file;
 663        struct inode    *inode;
 664        int             error;
 665
 666        error = -ENXIO;
 667        if (lo->lo_state != Lo_bound)
 668                goto out;
 669
 670        /* the loop device has to be read-only */
 671        error = -EINVAL;
 672        if (!(lo->lo_flags & LO_FLAGS_READ_ONLY))
 673                goto out;
 674
 675        error = -EBADF;
 676        file = fget(arg);
 677        if (!file)
 678                goto out;
 679
 680        inode = file->f_mapping->host;
 681        old_file = lo->lo_backing_file;
 682
 683        error = -EINVAL;
 684
 685        if (!S_ISREG(inode->i_mode) && !S_ISBLK(inode->i_mode))
 686                goto out_putf;
 687
 688        /* size of the new backing store needs to be the same */
 689        if (get_loop_size(lo, file) != get_loop_size(lo, old_file))
 690                goto out_putf;
 691
 692        /* and ... switch */
 693        error = loop_switch(lo, file);
 694        if (error)
 695                goto out_putf;
 696
 697        fput(old_file);
 698        if (lo->lo_flags & LO_FLAGS_PARTSCAN)
 699                loop_reread_partitions(lo, bdev);
 700        return 0;
 701
 702 out_putf:
 703        fput(file);
 704 out:
 705        return error;
 706}
 707
 708static inline int is_loop_device(struct file *file)
 709{
 710        struct inode *i = file->f_mapping->host;
 711
 712        return i && S_ISBLK(i->i_mode) && MAJOR(i->i_rdev) == LOOP_MAJOR;
 713}
 714
 715/* loop sysfs attributes */
 716
 717static ssize_t loop_attr_show(struct device *dev, char *page,
 718                              ssize_t (*callback)(struct loop_device *, char *))
 719{
 720        struct gendisk *disk = dev_to_disk(dev);
 721        struct loop_device *lo = disk->private_data;
 722
 723        return callback(lo, page);
 724}
 725
 726#define LOOP_ATTR_RO(_name)                                             \
 727static ssize_t loop_attr_##_name##_show(struct loop_device *, char *);  \
 728static ssize_t loop_attr_do_show_##_name(struct device *d,              \
 729                                struct device_attribute *attr, char *b) \
 730{                                                                       \
 731        return loop_attr_show(d, b, loop_attr_##_name##_show);          \
 732}                                                                       \
 733static struct device_attribute loop_attr_##_name =                      \
 734        __ATTR(_name, S_IRUGO, loop_attr_do_show_##_name, NULL);
 735
 736static ssize_t loop_attr_backing_file_show(struct loop_device *lo, char *buf)
 737{
 738        ssize_t ret;
 739        char *p = NULL;
 740
 741        spin_lock_irq(&lo->lo_lock);
 742        if (lo->lo_backing_file)
 743                p = file_path(lo->lo_backing_file, buf, PAGE_SIZE - 1);
 744        spin_unlock_irq(&lo->lo_lock);
 745
 746        if (IS_ERR_OR_NULL(p))
 747                ret = PTR_ERR(p);
 748        else {
 749                ret = strlen(p);
 750                memmove(buf, p, ret);
 751                buf[ret++] = '\n';
 752                buf[ret] = 0;
 753        }
 754
 755        return ret;
 756}
 757
 758static ssize_t loop_attr_offset_show(struct loop_device *lo, char *buf)
 759{
 760        return sprintf(buf, "%llu\n", (unsigned long long)lo->lo_offset);
 761}
 762
 763static ssize_t loop_attr_sizelimit_show(struct loop_device *lo, char *buf)
 764{
 765        return sprintf(buf, "%llu\n", (unsigned long long)lo->lo_sizelimit);
 766}
 767
 768static ssize_t loop_attr_autoclear_show(struct loop_device *lo, char *buf)
 769{
 770        int autoclear = (lo->lo_flags & LO_FLAGS_AUTOCLEAR);
 771
 772        return sprintf(buf, "%s\n", autoclear ? "1" : "0");
 773}
 774
 775static ssize_t loop_attr_partscan_show(struct loop_device *lo, char *buf)
 776{
 777        int partscan = (lo->lo_flags & LO_FLAGS_PARTSCAN);
 778
 779        return sprintf(buf, "%s\n", partscan ? "1" : "0");
 780}
 781
 782static ssize_t loop_attr_dio_show(struct loop_device *lo, char *buf)
 783{
 784        int dio = (lo->lo_flags & LO_FLAGS_DIRECT_IO);
 785
 786        return sprintf(buf, "%s\n", dio ? "1" : "0");
 787}
 788
 789LOOP_ATTR_RO(backing_file);
 790LOOP_ATTR_RO(offset);
 791LOOP_ATTR_RO(sizelimit);
 792LOOP_ATTR_RO(autoclear);
 793LOOP_ATTR_RO(partscan);
 794LOOP_ATTR_RO(dio);
 795
 796static struct attribute *loop_attrs[] = {
 797        &loop_attr_backing_file.attr,
 798        &loop_attr_offset.attr,
 799        &loop_attr_sizelimit.attr,
 800        &loop_attr_autoclear.attr,
 801        &loop_attr_partscan.attr,
 802        &loop_attr_dio.attr,
 803        NULL,
 804};
 805
 806static struct attribute_group loop_attribute_group = {
 807        .name = "loop",
 808        .attrs= loop_attrs,
 809};
 810
 811static int loop_sysfs_init(struct loop_device *lo)
 812{
 813        return sysfs_create_group(&disk_to_dev(lo->lo_disk)->kobj,
 814                                  &loop_attribute_group);
 815}
 816
 817static void loop_sysfs_exit(struct loop_device *lo)
 818{
 819        sysfs_remove_group(&disk_to_dev(lo->lo_disk)->kobj,
 820                           &loop_attribute_group);
 821}
 822
 823static void loop_config_discard(struct loop_device *lo)
 824{
 825        struct file *file = lo->lo_backing_file;
 826        struct inode *inode = file->f_mapping->host;
 827        struct request_queue *q = lo->lo_queue;
 828
 829        /*
 830         * We use punch hole to reclaim the free space used by the
 831         * image a.k.a. discard. However we do not support discard if
 832         * encryption is enabled, because it may give an attacker
 833         * useful information.
 834         */
 835        if ((!file->f_op->fallocate) ||
 836            lo->lo_encrypt_key_size) {
 837                q->limits.discard_granularity = 0;
 838                q->limits.discard_alignment = 0;
 839                blk_queue_max_discard_sectors(q, 0);
 840                q->limits.discard_zeroes_data = 0;
 841                queue_flag_clear_unlocked(QUEUE_FLAG_DISCARD, q);
 842                return;
 843        }
 844
 845        q->limits.discard_granularity = inode->i_sb->s_blocksize;
 846        q->limits.discard_alignment = 0;
 847        blk_queue_max_discard_sectors(q, UINT_MAX >> 9);
 848        q->limits.discard_zeroes_data = 1;
 849        queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, q);
 850}
 851
 852static void loop_unprepare_queue(struct loop_device *lo)
 853{
 854        flush_kthread_worker(&lo->worker);
 855        kthread_stop(lo->worker_task);
 856}
 857
 858static int loop_prepare_queue(struct loop_device *lo)
 859{
 860        init_kthread_worker(&lo->worker);
 861        lo->worker_task = kthread_run(kthread_worker_fn,
 862                        &lo->worker, "loop%d", lo->lo_number);
 863        if (IS_ERR(lo->worker_task))
 864                return -ENOMEM;
 865        set_user_nice(lo->worker_task, MIN_NICE);
 866        return 0;
 867}
 868
 869static int loop_set_fd(struct loop_device *lo, fmode_t mode,
 870                       struct block_device *bdev, unsigned int arg)
 871{
 872        struct file     *file, *f;
 873        struct inode    *inode;
 874        struct address_space *mapping;
 875        unsigned lo_blocksize;
 876        int             lo_flags = 0;
 877        int             error;
 878        loff_t          size;
 879
 880        /* This is safe, since we have a reference from open(). */
 881        __module_get(THIS_MODULE);
 882
 883        error = -EBADF;
 884        file = fget(arg);
 885        if (!file)
 886                goto out;
 887
 888        error = -EBUSY;
 889        if (lo->lo_state != Lo_unbound)
 890                goto out_putf;
 891
 892        /* Avoid recursion */
 893        f = file;
 894        while (is_loop_device(f)) {
 895                struct loop_device *l;
 896
 897                if (f->f_mapping->host->i_bdev == bdev)
 898                        goto out_putf;
 899
 900                l = f->f_mapping->host->i_bdev->bd_disk->private_data;
 901                if (l->lo_state == Lo_unbound) {
 902                        error = -EINVAL;
 903                        goto out_putf;
 904                }
 905                f = l->lo_backing_file;
 906        }
 907
 908        mapping = file->f_mapping;
 909        inode = mapping->host;
 910
 911        error = -EINVAL;
 912        if (!S_ISREG(inode->i_mode) && !S_ISBLK(inode->i_mode))
 913                goto out_putf;
 914
 915        if (!(file->f_mode & FMODE_WRITE) || !(mode & FMODE_WRITE) ||
 916            !file->f_op->write_iter)
 917                lo_flags |= LO_FLAGS_READ_ONLY;
 918
 919        lo_blocksize = S_ISBLK(inode->i_mode) ?
 920                inode->i_bdev->bd_block_size : PAGE_SIZE;
 921
 922        error = -EFBIG;
 923        size = get_loop_size(lo, file);
 924        if ((loff_t)(sector_t)size != size)
 925                goto out_putf;
 926        error = loop_prepare_queue(lo);
 927        if (error)
 928                goto out_putf;
 929
 930        error = 0;
 931
 932        set_device_ro(bdev, (lo_flags & LO_FLAGS_READ_ONLY) != 0);
 933
 934        lo->use_dio = false;
 935        lo->lo_blocksize = lo_blocksize;
 936        lo->lo_device = bdev;
 937        lo->lo_flags = lo_flags;
 938        lo->lo_backing_file = file;
 939        lo->transfer = NULL;
 940        lo->ioctl = NULL;
 941        lo->lo_sizelimit = 0;
 942        lo->old_gfp_mask = mapping_gfp_mask(mapping);
 943        mapping_set_gfp_mask(mapping, lo->old_gfp_mask & ~(__GFP_IO|__GFP_FS));
 944
 945        if (!(lo_flags & LO_FLAGS_READ_ONLY) && file->f_op->fsync)
 946                blk_queue_flush(lo->lo_queue, REQ_FLUSH);
 947
 948        loop_update_dio(lo);
 949        set_capacity(lo->lo_disk, size);
 950        bd_set_size(bdev, size << 9);
 951        loop_sysfs_init(lo);
 952        /* let user-space know about the new size */
 953        kobject_uevent(&disk_to_dev(bdev->bd_disk)->kobj, KOBJ_CHANGE);
 954
 955        set_blocksize(bdev, lo_blocksize);
 956
 957        lo->lo_state = Lo_bound;
 958        if (part_shift)
 959                lo->lo_flags |= LO_FLAGS_PARTSCAN;
 960        if (lo->lo_flags & LO_FLAGS_PARTSCAN)
 961                loop_reread_partitions(lo, bdev);
 962
 963        /* Grab the block_device to prevent its destruction after we
 964         * put /dev/loopXX inode. Later in loop_clr_fd() we bdput(bdev).
 965         */
 966        bdgrab(bdev);
 967        return 0;
 968
 969 out_putf:
 970        fput(file);
 971 out:
 972        /* This is safe: open() is still holding a reference. */
 973        module_put(THIS_MODULE);
 974        return error;
 975}
 976
 977static int
 978loop_release_xfer(struct loop_device *lo)
 979{
 980        int err = 0;
 981        struct loop_func_table *xfer = lo->lo_encryption;
 982
 983        if (xfer) {
 984                if (xfer->release)
 985                        err = xfer->release(lo);
 986                lo->transfer = NULL;
 987                lo->lo_encryption = NULL;
 988                module_put(xfer->owner);
 989        }
 990        return err;
 991}
 992
 993static int
 994loop_init_xfer(struct loop_device *lo, struct loop_func_table *xfer,
 995               const struct loop_info64 *i)
 996{
 997        int err = 0;
 998
 999        if (xfer) {
1000                struct module *owner = xfer->owner;
1001
1002                if (!try_module_get(owner))
1003                        return -EINVAL;
1004                if (xfer->init)
1005                        err = xfer->init(lo, i);
1006                if (err)
1007                        module_put(owner);
1008                else
1009                        lo->lo_encryption = xfer;
1010        }
1011        return err;
1012}
1013
1014static int loop_clr_fd(struct loop_device *lo)
1015{
1016        struct file *filp = lo->lo_backing_file;
1017        gfp_t gfp = lo->old_gfp_mask;
1018        struct block_device *bdev = lo->lo_device;
1019
1020        if (lo->lo_state != Lo_bound)
1021                return -ENXIO;
1022
1023        /*
1024         * If we've explicitly asked to tear down the loop device,
1025         * and it has an elevated reference count, set it for auto-teardown when
1026         * the last reference goes away. This stops $!~#$@ udev from
1027         * preventing teardown because it decided that it needs to run blkid on
1028         * the loopback device whenever they appear. xfstests is notorious for
1029         * failing tests because blkid via udev races with a losetup
1030         * <dev>/do something like mkfs/losetup -d <dev> causing the losetup -d
1031         * command to fail with EBUSY.
1032         */
1033        if (atomic_read(&lo->lo_refcnt) > 1) {
1034                lo->lo_flags |= LO_FLAGS_AUTOCLEAR;
1035                mutex_unlock(&lo->lo_ctl_mutex);
1036                return 0;
1037        }
1038
1039        if (filp == NULL)
1040                return -EINVAL;
1041
1042        /* freeze request queue during the transition */
1043        blk_mq_freeze_queue(lo->lo_queue);
1044
1045        spin_lock_irq(&lo->lo_lock);
1046        lo->lo_state = Lo_rundown;
1047        lo->lo_backing_file = NULL;
1048        spin_unlock_irq(&lo->lo_lock);
1049
1050        loop_release_xfer(lo);
1051        lo->transfer = NULL;
1052        lo->ioctl = NULL;
1053        lo->lo_device = NULL;
1054        lo->lo_encryption = NULL;
1055        lo->lo_offset = 0;
1056        lo->lo_sizelimit = 0;
1057        lo->lo_encrypt_key_size = 0;
1058        memset(lo->lo_encrypt_key, 0, LO_KEY_SIZE);
1059        memset(lo->lo_crypt_name, 0, LO_NAME_SIZE);
1060        memset(lo->lo_file_name, 0, LO_NAME_SIZE);
1061        if (bdev) {
1062                bdput(bdev);
1063                invalidate_bdev(bdev);
1064        }
1065        set_capacity(lo->lo_disk, 0);
1066        loop_sysfs_exit(lo);
1067        if (bdev) {
1068                bd_set_size(bdev, 0);
1069                /* let user-space know about this change */
1070                kobject_uevent(&disk_to_dev(bdev->bd_disk)->kobj, KOBJ_CHANGE);
1071        }
1072        mapping_set_gfp_mask(filp->f_mapping, gfp);
1073        lo->lo_state = Lo_unbound;
1074        /* This is safe: open() is still holding a reference. */
1075        module_put(THIS_MODULE);
1076        blk_mq_unfreeze_queue(lo->lo_queue);
1077
1078        if (lo->lo_flags & LO_FLAGS_PARTSCAN && bdev)
1079                loop_reread_partitions(lo, bdev);
1080        lo->lo_flags = 0;
1081        if (!part_shift)
1082                lo->lo_disk->flags |= GENHD_FL_NO_PART_SCAN;
1083        loop_unprepare_queue(lo);
1084        mutex_unlock(&lo->lo_ctl_mutex);
1085        /*
1086         * Need not hold lo_ctl_mutex to fput backing file.
1087         * Calling fput holding lo_ctl_mutex triggers a circular
1088         * lock dependency possibility warning as fput can take
1089         * bd_mutex which is usually taken before lo_ctl_mutex.
1090         */
1091        fput(filp);
1092        return 0;
1093}
1094
1095static int
1096loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
1097{
1098        int err;
1099        struct loop_func_table *xfer;
1100        kuid_t uid = current_uid();
1101
1102        if (lo->lo_encrypt_key_size &&
1103            !uid_eq(lo->lo_key_owner, uid) &&
1104            !capable(CAP_SYS_ADMIN))
1105                return -EPERM;
1106        if (lo->lo_state != Lo_bound)
1107                return -ENXIO;
1108        if ((unsigned int) info->lo_encrypt_key_size > LO_KEY_SIZE)
1109                return -EINVAL;
1110
1111        err = loop_release_xfer(lo);
1112        if (err)
1113                return err;
1114
1115        if (info->lo_encrypt_type) {
1116                unsigned int type = info->lo_encrypt_type;
1117
1118                if (type >= MAX_LO_CRYPT)
1119                        return -EINVAL;
1120                xfer = xfer_funcs[type];
1121                if (xfer == NULL)
1122                        return -EINVAL;
1123        } else
1124                xfer = NULL;
1125
1126        err = loop_init_xfer(lo, xfer, info);
1127        if (err)
1128                return err;
1129
1130        if (lo->lo_offset != info->lo_offset ||
1131            lo->lo_sizelimit != info->lo_sizelimit)
1132                if (figure_loop_size(lo, info->lo_offset, info->lo_sizelimit))
1133                        return -EFBIG;
1134
1135        loop_config_discard(lo);
1136
1137        memcpy(lo->lo_file_name, info->lo_file_name, LO_NAME_SIZE);
1138        memcpy(lo->lo_crypt_name, info->lo_crypt_name, LO_NAME_SIZE);
1139        lo->lo_file_name[LO_NAME_SIZE-1] = 0;
1140        lo->lo_crypt_name[LO_NAME_SIZE-1] = 0;
1141
1142        if (!xfer)
1143                xfer = &none_funcs;
1144        lo->transfer = xfer->transfer;
1145        lo->ioctl = xfer->ioctl;
1146
1147        if ((lo->lo_flags & LO_FLAGS_AUTOCLEAR) !=
1148             (info->lo_flags & LO_FLAGS_AUTOCLEAR))
1149                lo->lo_flags ^= LO_FLAGS_AUTOCLEAR;
1150
1151        if ((info->lo_flags & LO_FLAGS_PARTSCAN) &&
1152             !(lo->lo_flags & LO_FLAGS_PARTSCAN)) {
1153                lo->lo_flags |= LO_FLAGS_PARTSCAN;
1154                lo->lo_disk->flags &= ~GENHD_FL_NO_PART_SCAN;
1155                loop_reread_partitions(lo, lo->lo_device);
1156        }
1157
1158        lo->lo_encrypt_key_size = info->lo_encrypt_key_size;
1159        lo->lo_init[0] = info->lo_init[0];
1160        lo->lo_init[1] = info->lo_init[1];
1161        if (info->lo_encrypt_key_size) {
1162                memcpy(lo->lo_encrypt_key, info->lo_encrypt_key,
1163                       info->lo_encrypt_key_size);
1164                lo->lo_key_owner = uid;
1165        }
1166
1167        /* update dio if lo_offset or transfer is changed */
1168        __loop_update_dio(lo, lo->use_dio);
1169
1170        return 0;
1171}
1172
1173static int
1174loop_get_status(struct loop_device *lo, struct loop_info64 *info)
1175{
1176        struct file *file = lo->lo_backing_file;
1177        struct kstat stat;
1178        int error;
1179
1180        if (lo->lo_state != Lo_bound)
1181                return -ENXIO;
1182        error = vfs_getattr(&file->f_path, &stat);
1183        if (error)
1184                return error;
1185        memset(info, 0, sizeof(*info));
1186        info->lo_number = lo->lo_number;
1187        info->lo_device = huge_encode_dev(stat.dev);
1188        info->lo_inode = stat.ino;
1189        info->lo_rdevice = huge_encode_dev(lo->lo_device ? stat.rdev : stat.dev);
1190        info->lo_offset = lo->lo_offset;
1191        info->lo_sizelimit = lo->lo_sizelimit;
1192        info->lo_flags = lo->lo_flags;
1193        memcpy(info->lo_file_name, lo->lo_file_name, LO_NAME_SIZE);
1194        memcpy(info->lo_crypt_name, lo->lo_crypt_name, LO_NAME_SIZE);
1195        info->lo_encrypt_type =
1196                lo->lo_encryption ? lo->lo_encryption->number : 0;
1197        if (lo->lo_encrypt_key_size && capable(CAP_SYS_ADMIN)) {
1198                info->lo_encrypt_key_size = lo->lo_encrypt_key_size;
1199                memcpy(info->lo_encrypt_key, lo->lo_encrypt_key,
1200                       lo->lo_encrypt_key_size);
1201        }
1202        return 0;
1203}
1204
1205static void
1206loop_info64_from_old(const struct loop_info *info, struct loop_info64 *info64)
1207{
1208        memset(info64, 0, sizeof(*info64));
1209        info64->lo_number = info->lo_number;
1210        info64->lo_device = info->lo_device;
1211        info64->lo_inode = info->lo_inode;
1212        info64->lo_rdevice = info->lo_rdevice;
1213        info64->lo_offset = info->lo_offset;
1214        info64->lo_sizelimit = 0;
1215        info64->lo_encrypt_type = info->lo_encrypt_type;
1216        info64->lo_encrypt_key_size = info->lo_encrypt_key_size;
1217        info64->lo_flags = info->lo_flags;
1218        info64->lo_init[0] = info->lo_init[0];
1219        info64->lo_init[1] = info->lo_init[1];
1220        if (info->lo_encrypt_type == LO_CRYPT_CRYPTOAPI)
1221                memcpy(info64->lo_crypt_name, info->lo_name, LO_NAME_SIZE);
1222        else
1223                memcpy(info64->lo_file_name, info->lo_name, LO_NAME_SIZE);
1224        memcpy(info64->lo_encrypt_key, info->lo_encrypt_key, LO_KEY_SIZE);
1225}
1226
1227static int
1228loop_info64_to_old(const struct loop_info64 *info64, struct loop_info *info)
1229{
1230        memset(info, 0, sizeof(*info));
1231        info->lo_number = info64->lo_number;
1232        info->lo_device = info64->lo_device;
1233        info->lo_inode = info64->lo_inode;
1234        info->lo_rdevice = info64->lo_rdevice;
1235        info->lo_offset = info64->lo_offset;
1236        info->lo_encrypt_type = info64->lo_encrypt_type;
1237        info->lo_encrypt_key_size = info64->lo_encrypt_key_size;
1238        info->lo_flags = info64->lo_flags;
1239        info->lo_init[0] = info64->lo_init[0];
1240        info->lo_init[1] = info64->lo_init[1];
1241        if (info->lo_encrypt_type == LO_CRYPT_CRYPTOAPI)
1242                memcpy(info->lo_name, info64->lo_crypt_name, LO_NAME_SIZE);
1243        else
1244                memcpy(info->lo_name, info64->lo_file_name, LO_NAME_SIZE);
1245        memcpy(info->lo_encrypt_key, info64->lo_encrypt_key, LO_KEY_SIZE);
1246
1247        /* error in case values were truncated */
1248        if (info->lo_device != info64->lo_device ||
1249            info->lo_rdevice != info64->lo_rdevice ||
1250            info->lo_inode != info64->lo_inode ||
1251            info->lo_offset != info64->lo_offset)
1252                return -EOVERFLOW;
1253
1254        return 0;
1255}
1256
1257static int
1258loop_set_status_old(struct loop_device *lo, const struct loop_info __user *arg)
1259{
1260        struct loop_info info;
1261        struct loop_info64 info64;
1262
1263        if (copy_from_user(&info, arg, sizeof (struct loop_info)))
1264                return -EFAULT;
1265        loop_info64_from_old(&info, &info64);
1266        return loop_set_status(lo, &info64);
1267}
1268
1269static int
1270loop_set_status64(struct loop_device *lo, const struct loop_info64 __user *arg)
1271{
1272        struct loop_info64 info64;
1273
1274        if (copy_from_user(&info64, arg, sizeof (struct loop_info64)))
1275                return -EFAULT;
1276        return loop_set_status(lo, &info64);
1277}
1278
1279static int
1280loop_get_status_old(struct loop_device *lo, struct loop_info __user *arg) {
1281        struct loop_info info;
1282        struct loop_info64 info64;
1283        int err = 0;
1284
1285        if (!arg)
1286                err = -EINVAL;
1287        if (!err)
1288                err = loop_get_status(lo, &info64);
1289        if (!err)
1290                err = loop_info64_to_old(&info64, &info);
1291        if (!err && copy_to_user(arg, &info, sizeof(info)))
1292                err = -EFAULT;
1293
1294        return err;
1295}
1296
1297static int
1298loop_get_status64(struct loop_device *lo, struct loop_info64 __user *arg) {
1299        struct loop_info64 info64;
1300        int err = 0;
1301
1302        if (!arg)
1303                err = -EINVAL;
1304        if (!err)
1305                err = loop_get_status(lo, &info64);
1306        if (!err && copy_to_user(arg, &info64, sizeof(info64)))
1307                err = -EFAULT;
1308
1309        return err;
1310}
1311
1312static int loop_set_capacity(struct loop_device *lo, struct block_device *bdev)
1313{
1314        if (unlikely(lo->lo_state != Lo_bound))
1315                return -ENXIO;
1316
1317        return figure_loop_size(lo, lo->lo_offset, lo->lo_sizelimit);
1318}
1319
1320static int loop_set_dio(struct loop_device *lo, unsigned long arg)
1321{
1322        int error = -ENXIO;
1323        if (lo->lo_state != Lo_bound)
1324                goto out;
1325
1326        __loop_update_dio(lo, !!arg);
1327        if (lo->use_dio == !!arg)
1328                return 0;
1329        error = -EINVAL;
1330 out:
1331        return error;
1332}
1333
1334static int lo_ioctl(struct block_device *bdev, fmode_t mode,
1335        unsigned int cmd, unsigned long arg)
1336{
1337        struct loop_device *lo = bdev->bd_disk->private_data;
1338        int err;
1339
1340        mutex_lock_nested(&lo->lo_ctl_mutex, 1);
1341        switch (cmd) {
1342        case LOOP_SET_FD:
1343                err = loop_set_fd(lo, mode, bdev, arg);
1344                break;
1345        case LOOP_CHANGE_FD:
1346                err = loop_change_fd(lo, bdev, arg);
1347                break;
1348        case LOOP_CLR_FD:
1349                /* loop_clr_fd would have unlocked lo_ctl_mutex on success */
1350                err = loop_clr_fd(lo);
1351                if (!err)
1352                        goto out_unlocked;
1353                break;
1354        case LOOP_SET_STATUS:
1355                err = -EPERM;
1356                if ((mode & FMODE_WRITE) || capable(CAP_SYS_ADMIN))
1357                        err = loop_set_status_old(lo,
1358                                        (struct loop_info __user *)arg);
1359                break;
1360        case LOOP_GET_STATUS:
1361                err = loop_get_status_old(lo, (struct loop_info __user *) arg);
1362                break;
1363        case LOOP_SET_STATUS64:
1364                err = -EPERM;
1365                if ((mode & FMODE_WRITE) || capable(CAP_SYS_ADMIN))
1366                        err = loop_set_status64(lo,
1367                                        (struct loop_info64 __user *) arg);
1368                break;
1369        case LOOP_GET_STATUS64:
1370                err = loop_get_status64(lo, (struct loop_info64 __user *) arg);
1371                break;
1372        case LOOP_SET_CAPACITY:
1373                err = -EPERM;
1374                if ((mode & FMODE_WRITE) || capable(CAP_SYS_ADMIN))
1375                        err = loop_set_capacity(lo, bdev);
1376                break;
1377        case LOOP_SET_DIRECT_IO:
1378                err = -EPERM;
1379                if ((mode & FMODE_WRITE) || capable(CAP_SYS_ADMIN))
1380                        err = loop_set_dio(lo, arg);
1381                break;
1382        default:
1383                err = lo->ioctl ? lo->ioctl(lo, cmd, arg) : -EINVAL;
1384        }
1385        mutex_unlock(&lo->lo_ctl_mutex);
1386
1387out_unlocked:
1388        return err;
1389}
1390
1391#ifdef CONFIG_COMPAT
1392struct compat_loop_info {
1393        compat_int_t    lo_number;      /* ioctl r/o */
1394        compat_dev_t    lo_device;      /* ioctl r/o */
1395        compat_ulong_t  lo_inode;       /* ioctl r/o */
1396        compat_dev_t    lo_rdevice;     /* ioctl r/o */
1397        compat_int_t    lo_offset;
1398        compat_int_t    lo_encrypt_type;
1399        compat_int_t    lo_encrypt_key_size;    /* ioctl w/o */
1400        compat_int_t    lo_flags;       /* ioctl r/o */
1401        char            lo_name[LO_NAME_SIZE];
1402        unsigned char   lo_encrypt_key[LO_KEY_SIZE]; /* ioctl w/o */
1403        compat_ulong_t  lo_init[2];
1404        char            reserved[4];
1405};
1406
1407/*
1408 * Transfer 32-bit compatibility structure in userspace to 64-bit loop info
1409 * - noinlined to reduce stack space usage in main part of driver
1410 */
1411static noinline int
1412loop_info64_from_compat(const struct compat_loop_info __user *arg,
1413                        struct loop_info64 *info64)
1414{
1415        struct compat_loop_info info;
1416
1417        if (copy_from_user(&info, arg, sizeof(info)))
1418                return -EFAULT;
1419
1420        memset(info64, 0, sizeof(*info64));
1421        info64->lo_number = info.lo_number;
1422        info64->lo_device = info.lo_device;
1423        info64->lo_inode = info.lo_inode;
1424        info64->lo_rdevice = info.lo_rdevice;
1425        info64->lo_offset = info.lo_offset;
1426        info64->lo_sizelimit = 0;
1427        info64->lo_encrypt_type = info.lo_encrypt_type;
1428        info64->lo_encrypt_key_size = info.lo_encrypt_key_size;
1429        info64->lo_flags = info.lo_flags;
1430        info64->lo_init[0] = info.lo_init[0];
1431        info64->lo_init[1] = info.lo_init[1];
1432        if (info.lo_encrypt_type == LO_CRYPT_CRYPTOAPI)
1433                memcpy(info64->lo_crypt_name, info.lo_name, LO_NAME_SIZE);
1434        else
1435                memcpy(info64->lo_file_name, info.lo_name, LO_NAME_SIZE);
1436        memcpy(info64->lo_encrypt_key, info.lo_encrypt_key, LO_KEY_SIZE);
1437        return 0;
1438}
1439
1440/*
1441 * Transfer 64-bit loop info to 32-bit compatibility structure in userspace
1442 * - noinlined to reduce stack space usage in main part of driver
1443 */
1444static noinline int
1445loop_info64_to_compat(const struct loop_info64 *info64,
1446                      struct compat_loop_info __user *arg)
1447{
1448        struct compat_loop_info info;
1449
1450        memset(&info, 0, sizeof(info));
1451        info.lo_number = info64->lo_number;
1452        info.lo_device = info64->lo_device;
1453        info.lo_inode = info64->lo_inode;
1454        info.lo_rdevice = info64->lo_rdevice;
1455        info.lo_offset = info64->lo_offset;
1456        info.lo_encrypt_type = info64->lo_encrypt_type;
1457        info.lo_encrypt_key_size = info64->lo_encrypt_key_size;
1458        info.lo_flags = info64->lo_flags;
1459        info.lo_init[0] = info64->lo_init[0];
1460        info.lo_init[1] = info64->lo_init[1];
1461        if (info.lo_encrypt_type == LO_CRYPT_CRYPTOAPI)
1462                memcpy(info.lo_name, info64->lo_crypt_name, LO_NAME_SIZE);
1463        else
1464                memcpy(info.lo_name, info64->lo_file_name, LO_NAME_SIZE);
1465        memcpy(info.lo_encrypt_key, info64->lo_encrypt_key, LO_KEY_SIZE);
1466
1467        /* error in case values were truncated */
1468        if (info.lo_device != info64->lo_device ||
1469            info.lo_rdevice != info64->lo_rdevice ||
1470            info.lo_inode != info64->lo_inode ||
1471            info.lo_offset != info64->lo_offset ||
1472            info.lo_init[0] != info64->lo_init[0] ||
1473            info.lo_init[1] != info64->lo_init[1])
1474                return -EOVERFLOW;
1475
1476        if (copy_to_user(arg, &info, sizeof(info)))
1477                return -EFAULT;
1478        return 0;
1479}
1480
1481static int
1482loop_set_status_compat(struct loop_device *lo,
1483                       const struct compat_loop_info __user *arg)
1484{
1485        struct loop_info64 info64;
1486        int ret;
1487
1488        ret = loop_info64_from_compat(arg, &info64);
1489        if (ret < 0)
1490                return ret;
1491        return loop_set_status(lo, &info64);
1492}
1493
1494static int
1495loop_get_status_compat(struct loop_device *lo,
1496                       struct compat_loop_info __user *arg)
1497{
1498        struct loop_info64 info64;
1499        int err = 0;
1500
1501        if (!arg)
1502                err = -EINVAL;
1503        if (!err)
1504                err = loop_get_status(lo, &info64);
1505        if (!err)
1506                err = loop_info64_to_compat(&info64, arg);
1507        return err;
1508}
1509
1510static int lo_compat_ioctl(struct block_device *bdev, fmode_t mode,
1511                           unsigned int cmd, unsigned long arg)
1512{
1513        struct loop_device *lo = bdev->bd_disk->private_data;
1514        int err;
1515
1516        switch(cmd) {
1517        case LOOP_SET_STATUS:
1518                mutex_lock(&lo->lo_ctl_mutex);
1519                err = loop_set_status_compat(
1520                        lo, (const struct compat_loop_info __user *) arg);
1521                mutex_unlock(&lo->lo_ctl_mutex);
1522                break;
1523        case LOOP_GET_STATUS:
1524                mutex_lock(&lo->lo_ctl_mutex);
1525                err = loop_get_status_compat(
1526                        lo, (struct compat_loop_info __user *) arg);
1527                mutex_unlock(&lo->lo_ctl_mutex);
1528                break;
1529        case LOOP_SET_CAPACITY:
1530        case LOOP_CLR_FD:
1531        case LOOP_GET_STATUS64:
1532        case LOOP_SET_STATUS64:
1533                arg = (unsigned long) compat_ptr(arg);
1534        case LOOP_SET_FD:
1535        case LOOP_CHANGE_FD:
1536                err = lo_ioctl(bdev, mode, cmd, arg);
1537                break;
1538        default:
1539                err = -ENOIOCTLCMD;
1540                break;
1541        }
1542        return err;
1543}
1544#endif
1545
1546static int lo_open(struct block_device *bdev, fmode_t mode)
1547{
1548        struct loop_device *lo;
1549        int err = 0;
1550
1551        mutex_lock(&loop_index_mutex);
1552        lo = bdev->bd_disk->private_data;
1553        if (!lo) {
1554                err = -ENXIO;
1555                goto out;
1556        }
1557
1558        atomic_inc(&lo->lo_refcnt);
1559out:
1560        mutex_unlock(&loop_index_mutex);
1561        return err;
1562}
1563
1564static void lo_release(struct gendisk *disk, fmode_t mode)
1565{
1566        struct loop_device *lo = disk->private_data;
1567        int err;
1568
1569        if (atomic_dec_return(&lo->lo_refcnt))
1570                return;
1571
1572        mutex_lock(&lo->lo_ctl_mutex);
1573        if (lo->lo_flags & LO_FLAGS_AUTOCLEAR) {
1574                /*
1575                 * In autoclear mode, stop the loop thread
1576                 * and remove configuration after last close.
1577                 */
1578                err = loop_clr_fd(lo);
1579                if (!err)
1580                        return;
1581        } else {
1582                /*
1583                 * Otherwise keep thread (if running) and config,
1584                 * but flush possible ongoing bios in thread.
1585                 */
1586                loop_flush(lo);
1587        }
1588
1589        mutex_unlock(&lo->lo_ctl_mutex);
1590}
1591
1592static const struct block_device_operations lo_fops = {
1593        .owner =        THIS_MODULE,
1594        .open =         lo_open,
1595        .release =      lo_release,
1596        .ioctl =        lo_ioctl,
1597#ifdef CONFIG_COMPAT
1598        .compat_ioctl = lo_compat_ioctl,
1599#endif
1600};
1601
1602/*
1603 * And now the modules code and kernel interface.
1604 */
1605static int max_loop;
1606module_param(max_loop, int, S_IRUGO);
1607MODULE_PARM_DESC(max_loop, "Maximum number of loop devices");
1608module_param(max_part, int, S_IRUGO);
1609MODULE_PARM_DESC(max_part, "Maximum number of partitions per loop device");
1610MODULE_LICENSE("GPL");
1611MODULE_ALIAS_BLOCKDEV_MAJOR(LOOP_MAJOR);
1612
1613int loop_register_transfer(struct loop_func_table *funcs)
1614{
1615        unsigned int n = funcs->number;
1616
1617        if (n >= MAX_LO_CRYPT || xfer_funcs[n])
1618                return -EINVAL;
1619        xfer_funcs[n] = funcs;
1620        return 0;
1621}
1622
1623static int unregister_transfer_cb(int id, void *ptr, void *data)
1624{
1625        struct loop_device *lo = ptr;
1626        struct loop_func_table *xfer = data;
1627
1628        mutex_lock(&lo->lo_ctl_mutex);
1629        if (lo->lo_encryption == xfer)
1630                loop_release_xfer(lo);
1631        mutex_unlock(&lo->lo_ctl_mutex);
1632        return 0;
1633}
1634
1635int loop_unregister_transfer(int number)
1636{
1637        unsigned int n = number;
1638        struct loop_func_table *xfer;
1639
1640        if (n == 0 || n >= MAX_LO_CRYPT || (xfer = xfer_funcs[n]) == NULL)
1641                return -EINVAL;
1642
1643        xfer_funcs[n] = NULL;
1644        idr_for_each(&loop_index_idr, &unregister_transfer_cb, xfer);
1645        return 0;
1646}
1647
1648EXPORT_SYMBOL(loop_register_transfer);
1649EXPORT_SYMBOL(loop_unregister_transfer);
1650
1651static int loop_queue_rq(struct blk_mq_hw_ctx *hctx,
1652                const struct blk_mq_queue_data *bd)
1653{
1654        struct loop_cmd *cmd = blk_mq_rq_to_pdu(bd->rq);
1655        struct loop_device *lo = cmd->rq->q->queuedata;
1656
1657        blk_mq_start_request(bd->rq);
1658
1659        if (lo->lo_state != Lo_bound)
1660                return -EIO;
1661
1662        if (lo->use_dio && !(cmd->rq->cmd_flags & (REQ_FLUSH |
1663                                        REQ_DISCARD)))
1664                cmd->use_aio = true;
1665        else
1666                cmd->use_aio = false;
1667
1668        queue_kthread_work(&lo->worker, &cmd->work);
1669
1670        return BLK_MQ_RQ_QUEUE_OK;
1671}
1672
1673static void loop_handle_cmd(struct loop_cmd *cmd)
1674{
1675        const bool write = cmd->rq->cmd_flags & REQ_WRITE;
1676        struct loop_device *lo = cmd->rq->q->queuedata;
1677        int ret = 0;
1678
1679        if (write && (lo->lo_flags & LO_FLAGS_READ_ONLY)) {
1680                ret = -EIO;
1681                goto failed;
1682        }
1683
1684        ret = do_req_filebacked(lo, cmd->rq);
1685 failed:
1686        /* complete non-aio request */
1687        if (!cmd->use_aio || ret)
1688                blk_mq_complete_request(cmd->rq, ret ? -EIO : 0);
1689}
1690
1691static void loop_queue_work(struct kthread_work *work)
1692{
1693        struct loop_cmd *cmd =
1694                container_of(work, struct loop_cmd, work);
1695
1696        loop_handle_cmd(cmd);
1697}
1698
1699static int loop_init_request(void *data, struct request *rq,
1700                unsigned int hctx_idx, unsigned int request_idx,
1701                unsigned int numa_node)
1702{
1703        struct loop_cmd *cmd = blk_mq_rq_to_pdu(rq);
1704
1705        cmd->rq = rq;
1706        init_kthread_work(&cmd->work, loop_queue_work);
1707
1708        return 0;
1709}
1710
1711static struct blk_mq_ops loop_mq_ops = {
1712        .queue_rq       = loop_queue_rq,
1713        .map_queue      = blk_mq_map_queue,
1714        .init_request   = loop_init_request,
1715};
1716
1717static int loop_add(struct loop_device **l, int i)
1718{
1719        struct loop_device *lo;
1720        struct gendisk *disk;
1721        int err;
1722
1723        err = -ENOMEM;
1724        lo = kzalloc(sizeof(*lo), GFP_KERNEL);
1725        if (!lo)
1726                goto out;
1727
1728        lo->lo_state = Lo_unbound;
1729
1730        /* allocate id, if @id >= 0, we're requesting that specific id */
1731        if (i >= 0) {
1732                err = idr_alloc(&loop_index_idr, lo, i, i + 1, GFP_KERNEL);
1733                if (err == -ENOSPC)
1734                        err = -EEXIST;
1735        } else {
1736                err = idr_alloc(&loop_index_idr, lo, 0, 0, GFP_KERNEL);
1737        }
1738        if (err < 0)
1739                goto out_free_dev;
1740        i = err;
1741
1742        err = -ENOMEM;
1743        lo->tag_set.ops = &loop_mq_ops;
1744        lo->tag_set.nr_hw_queues = 1;
1745        lo->tag_set.queue_depth = 128;
1746        lo->tag_set.numa_node = NUMA_NO_NODE;
1747        lo->tag_set.cmd_size = sizeof(struct loop_cmd);
1748        lo->tag_set.flags = BLK_MQ_F_SHOULD_MERGE | BLK_MQ_F_SG_MERGE;
1749        lo->tag_set.driver_data = lo;
1750
1751        err = blk_mq_alloc_tag_set(&lo->tag_set);
1752        if (err)
1753                goto out_free_idr;
1754
1755        lo->lo_queue = blk_mq_init_queue(&lo->tag_set);
1756        if (IS_ERR_OR_NULL(lo->lo_queue)) {
1757                err = PTR_ERR(lo->lo_queue);
1758                goto out_cleanup_tags;
1759        }
1760        lo->lo_queue->queuedata = lo;
1761
1762        /*
1763         * It doesn't make sense to enable merge because the I/O
1764         * submitted to backing file is handled page by page.
1765         */
1766        queue_flag_set_unlocked(QUEUE_FLAG_NOMERGES, lo->lo_queue);
1767
1768        disk = lo->lo_disk = alloc_disk(1 << part_shift);
1769        if (!disk)
1770                goto out_free_queue;
1771
1772        /*
1773         * Disable partition scanning by default. The in-kernel partition
1774         * scanning can be requested individually per-device during its
1775         * setup. Userspace can always add and remove partitions from all
1776         * devices. The needed partition minors are allocated from the
1777         * extended minor space, the main loop device numbers will continue
1778         * to match the loop minors, regardless of the number of partitions
1779         * used.
1780         *
1781         * If max_part is given, partition scanning is globally enabled for
1782         * all loop devices. The minors for the main loop devices will be
1783         * multiples of max_part.
1784         *
1785         * Note: Global-for-all-devices, set-only-at-init, read-only module
1786         * parameteters like 'max_loop' and 'max_part' make things needlessly
1787         * complicated, are too static, inflexible and may surprise
1788         * userspace tools. Parameters like this in general should be avoided.
1789         */
1790        if (!part_shift)
1791                disk->flags |= GENHD_FL_NO_PART_SCAN;
1792        disk->flags |= GENHD_FL_EXT_DEVT;
1793        mutex_init(&lo->lo_ctl_mutex);
1794        atomic_set(&lo->lo_refcnt, 0);
1795        lo->lo_number           = i;
1796        spin_lock_init(&lo->lo_lock);
1797        disk->major             = LOOP_MAJOR;
1798        disk->first_minor       = i << part_shift;
1799        disk->fops              = &lo_fops;
1800        disk->private_data      = lo;
1801        disk->queue             = lo->lo_queue;
1802        sprintf(disk->disk_name, "loop%d", i);
1803        add_disk(disk);
1804        *l = lo;
1805        return lo->lo_number;
1806
1807out_free_queue:
1808        blk_cleanup_queue(lo->lo_queue);
1809out_cleanup_tags:
1810        blk_mq_free_tag_set(&lo->tag_set);
1811out_free_idr:
1812        idr_remove(&loop_index_idr, i);
1813out_free_dev:
1814        kfree(lo);
1815out:
1816        return err;
1817}
1818
1819static void loop_remove(struct loop_device *lo)
1820{
1821        blk_cleanup_queue(lo->lo_queue);
1822        del_gendisk(lo->lo_disk);
1823        blk_mq_free_tag_set(&lo->tag_set);
1824        put_disk(lo->lo_disk);
1825        kfree(lo);
1826}
1827
1828static int find_free_cb(int id, void *ptr, void *data)
1829{
1830        struct loop_device *lo = ptr;
1831        struct loop_device **l = data;
1832
1833        if (lo->lo_state == Lo_unbound) {
1834                *l = lo;
1835                return 1;
1836        }
1837        return 0;
1838}
1839
1840static int loop_lookup(struct loop_device **l, int i)
1841{
1842        struct loop_device *lo;
1843        int ret = -ENODEV;
1844
1845        if (i < 0) {
1846                int err;
1847
1848                err = idr_for_each(&loop_index_idr, &find_free_cb, &lo);
1849                if (err == 1) {
1850                        *l = lo;
1851                        ret = lo->lo_number;
1852                }
1853                goto out;
1854        }
1855
1856        /* lookup and return a specific i */
1857        lo = idr_find(&loop_index_idr, i);
1858        if (lo) {
1859                *l = lo;
1860                ret = lo->lo_number;
1861        }
1862out:
1863        return ret;
1864}
1865
1866static struct kobject *loop_probe(dev_t dev, int *part, void *data)
1867{
1868        struct loop_device *lo;
1869        struct kobject *kobj;
1870        int err;
1871
1872        mutex_lock(&loop_index_mutex);
1873        err = loop_lookup(&lo, MINOR(dev) >> part_shift);
1874        if (err < 0)
1875                err = loop_add(&lo, MINOR(dev) >> part_shift);
1876        if (err < 0)
1877                kobj = NULL;
1878        else
1879                kobj = get_disk(lo->lo_disk);
1880        mutex_unlock(&loop_index_mutex);
1881
1882        *part = 0;
1883        return kobj;
1884}
1885
1886static long loop_control_ioctl(struct file *file, unsigned int cmd,
1887                               unsigned long parm)
1888{
1889        struct loop_device *lo;
1890        int ret = -ENOSYS;
1891
1892        mutex_lock(&loop_index_mutex);
1893        switch (cmd) {
1894        case LOOP_CTL_ADD:
1895                ret = loop_lookup(&lo, parm);
1896                if (ret >= 0) {
1897                        ret = -EEXIST;
1898                        break;
1899                }
1900                ret = loop_add(&lo, parm);
1901                break;
1902        case LOOP_CTL_REMOVE:
1903                ret = loop_lookup(&lo, parm);
1904                if (ret < 0)
1905                        break;
1906                mutex_lock(&lo->lo_ctl_mutex);
1907                if (lo->lo_state != Lo_unbound) {
1908                        ret = -EBUSY;
1909                        mutex_unlock(&lo->lo_ctl_mutex);
1910                        break;
1911                }
1912                if (atomic_read(&lo->lo_refcnt) > 0) {
1913                        ret = -EBUSY;
1914                        mutex_unlock(&lo->lo_ctl_mutex);
1915                        break;
1916                }
1917                lo->lo_disk->private_data = NULL;
1918                mutex_unlock(&lo->lo_ctl_mutex);
1919                idr_remove(&loop_index_idr, lo->lo_number);
1920                loop_remove(lo);
1921                break;
1922        case LOOP_CTL_GET_FREE:
1923                ret = loop_lookup(&lo, -1);
1924                if (ret >= 0)
1925                        break;
1926                ret = loop_add(&lo, -1);
1927        }
1928        mutex_unlock(&loop_index_mutex);
1929
1930        return ret;
1931}
1932
1933static const struct file_operations loop_ctl_fops = {
1934        .open           = nonseekable_open,
1935        .unlocked_ioctl = loop_control_ioctl,
1936        .compat_ioctl   = loop_control_ioctl,
1937        .owner          = THIS_MODULE,
1938        .llseek         = noop_llseek,
1939};
1940
1941static struct miscdevice loop_misc = {
1942        .minor          = LOOP_CTRL_MINOR,
1943        .name           = "loop-control",
1944        .fops           = &loop_ctl_fops,
1945};
1946
1947MODULE_ALIAS_MISCDEV(LOOP_CTRL_MINOR);
1948MODULE_ALIAS("devname:loop-control");
1949
1950static int __init loop_init(void)
1951{
1952        int i, nr;
1953        unsigned long range;
1954        struct loop_device *lo;
1955        int err;
1956
1957        err = misc_register(&loop_misc);
1958        if (err < 0)
1959                return err;
1960
1961        part_shift = 0;
1962        if (max_part > 0) {
1963                part_shift = fls(max_part);
1964
1965                /*
1966                 * Adjust max_part according to part_shift as it is exported
1967                 * to user space so that user can decide correct minor number
1968                 * if [s]he want to create more devices.
1969                 *
1970                 * Note that -1 is required because partition 0 is reserved
1971                 * for the whole disk.
1972                 */
1973                max_part = (1UL << part_shift) - 1;
1974        }
1975
1976        if ((1UL << part_shift) > DISK_MAX_PARTS) {
1977                err = -EINVAL;
1978                goto misc_out;
1979        }
1980
1981        if (max_loop > 1UL << (MINORBITS - part_shift)) {
1982                err = -EINVAL;
1983                goto misc_out;
1984        }
1985
1986        /*
1987         * If max_loop is specified, create that many devices upfront.
1988         * This also becomes a hard limit. If max_loop is not specified,
1989         * create CONFIG_BLK_DEV_LOOP_MIN_COUNT loop devices at module
1990         * init time. Loop devices can be requested on-demand with the
1991         * /dev/loop-control interface, or be instantiated by accessing
1992         * a 'dead' device node.
1993         */
1994        if (max_loop) {
1995                nr = max_loop;
1996                range = max_loop << part_shift;
1997        } else {
1998                nr = CONFIG_BLK_DEV_LOOP_MIN_COUNT;
1999                range = 1UL << MINORBITS;
2000        }
2001
2002        if (register_blkdev(LOOP_MAJOR, "loop")) {
2003                err = -EIO;
2004                goto misc_out;
2005        }
2006
2007        blk_register_region(MKDEV(LOOP_MAJOR, 0), range,
2008                                  THIS_MODULE, loop_probe, NULL, NULL);
2009
2010        /* pre-create number of devices given by config or max_loop */
2011        mutex_lock(&loop_index_mutex);
2012        for (i = 0; i < nr; i++)
2013                loop_add(&lo, i);
2014        mutex_unlock(&loop_index_mutex);
2015
2016        printk(KERN_INFO "loop: module loaded\n");
2017        return 0;
2018
2019misc_out:
2020        misc_deregister(&loop_misc);
2021        return err;
2022}
2023
2024static int loop_exit_cb(int id, void *ptr, void *data)
2025{
2026        struct loop_device *lo = ptr;
2027
2028        loop_remove(lo);
2029        return 0;
2030}
2031
2032static void __exit loop_exit(void)
2033{
2034        unsigned long range;
2035
2036        range = max_loop ? max_loop << part_shift : 1UL << MINORBITS;
2037
2038        idr_for_each(&loop_index_idr, &loop_exit_cb, NULL);
2039        idr_destroy(&loop_index_idr);
2040
2041        blk_unregister_region(MKDEV(LOOP_MAJOR, 0), range);
2042        unregister_blkdev(LOOP_MAJOR, "loop");
2043
2044        misc_deregister(&loop_misc);
2045}
2046
2047module_init(loop_init);
2048module_exit(loop_exit);
2049
2050#ifndef MODULE
2051static int __init max_loop_setup(char *str)
2052{
2053        max_loop = simple_strtol(str, NULL, 0);
2054        return 1;
2055}
2056
2057__setup("max_loop=", max_loop_setup);
2058#endif
2059
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