drivers/block/loop.c

/* [<][>][^][v][top][bottom][index][help] */
This source file includes following definitions.
transfer_xor
xor_init
get_size
get_loop_size
__loop_update_dio
figure_loop_size
lo_do_transfer
lo_write_bvec
lo_write_simple
lo_write_transfer
lo_read_simple
lo_read_transfer
lo_fallocate
lo_req_flush
lo_complete_rq
lo_rw_aio_do_completion
lo_rw_aio_complete
lo_rw_aio
do_req_filebacked
loop_update_dio
loop_reread_partitions
is_loop_device
loop_validate_file
loop_change_fd
loop_attr_show
loop_attr_backing_file_show
loop_attr_offset_show
loop_attr_sizelimit_show
loop_attr_autoclear_show
loop_attr_partscan_show
loop_attr_dio_show
loop_sysfs_init
loop_sysfs_exit
loop_config_discard
loop_unprepare_queue
loop_kthread_worker_fn
loop_prepare_queue
loop_update_rotational
loop_set_fd
loop_release_xfer
loop_init_xfer
__loop_clr_fd
loop_clr_fd
loop_set_status
loop_get_status
loop_info64_from_old
loop_info64_to_old
loop_set_status_old
loop_set_status64
loop_get_status_old
loop_get_status64
loop_set_capacity
loop_set_dio
loop_set_block_size
lo_simple_ioctl
lo_ioctl
loop_info64_from_compat
loop_info64_to_compat
loop_set_status_compat
loop_get_status_compat
lo_compat_ioctl
lo_open
lo_release
loop_register_transfer
unregister_transfer_cb
loop_unregister_transfer
loop_queue_rq
loop_handle_cmd
loop_queue_work
loop_init_request
loop_add
loop_remove
find_free_cb
loop_lookup
loop_probe
loop_control_ioctl
loop_init
loop_exit_cb
loop_exit
max_loop_setup
   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. Bolsø, <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 <linux/ioprio.h>
  80 #include <linux/blk-cgroup.h>
  81 
  82 #include "loop.h"
  83 
  84 #include <linux/uaccess.h>
  85 
  86 static DEFINE_IDR(loop_index_idr);
  87 static DEFINE_MUTEX(loop_ctl_mutex);
  88 
  89 static int max_part;
  90 static int part_shift;
  91 
  92 static int transfer_xor(struct loop_device *lo, int cmd,
  93                         struct page *raw_page, unsigned raw_off,
  94                         struct page *loop_page, unsigned loop_off,
  95                         int size, sector_t real_block)
  96 {
  97         char *raw_buf = kmap_atomic(raw_page) + raw_off;
  98         char *loop_buf = kmap_atomic(loop_page) + loop_off;
  99         char *in, *out, *key;
 100         int i, keysize;
 101 
 102         if (cmd == READ) {
 103                 in = raw_buf;
 104                 out = loop_buf;
 105         } else {
 106                 in = loop_buf;
 107                 out = raw_buf;
 108         }
 109 
 110         key = lo->lo_encrypt_key;
 111         keysize = lo->lo_encrypt_key_size;
 112         for (i = 0; i < size; i++)
 113                 *out++ = *in++ ^ key[(i & 511) % keysize];
 114 
 115         kunmap_atomic(loop_buf);
 116         kunmap_atomic(raw_buf);
 117         cond_resched();
 118         return 0;
 119 }
 120 
 121 static int xor_init(struct loop_device *lo, const struct loop_info64 *info)
 122 {
 123         if (unlikely(info->lo_encrypt_key_size <= 0))
 124                 return -EINVAL;
 125         return 0;
 126 }
 127 
 128 static struct loop_func_table none_funcs = {
 129         .number = LO_CRYPT_NONE,
 130 }; 
 131 
 132 static struct loop_func_table xor_funcs = {
 133         .number = LO_CRYPT_XOR,
 134         .transfer = transfer_xor,
 135         .init = xor_init
 136 }; 
 137 
 138 /* xfer_funcs[0] is special - its release function is never called */
 139 static struct loop_func_table *xfer_funcs[MAX_LO_CRYPT] = {
 140         &none_funcs,
 141         &xor_funcs
 142 };
 143 
 144 static loff_t get_size(loff_t offset, loff_t sizelimit, struct file *file)
 145 {
 146         loff_t loopsize;
 147 
 148         /* Compute loopsize in bytes */
 149         loopsize = i_size_read(file->f_mapping->host);
 150         if (offset > 0)
 151                 loopsize -= offset;
 152         /* offset is beyond i_size, weird but possible */
 153         if (loopsize < 0)
 154                 return 0;
 155 
 156         if (sizelimit > 0 && sizelimit < loopsize)
 157                 loopsize = sizelimit;
 158         /*
 159          * Unfortunately, if we want to do I/O on the device,
 160          * the number of 512-byte sectors has to fit into a sector_t.
 161          */
 162         return loopsize >> 9;
 163 }
 164 
 165 static loff_t get_loop_size(struct loop_device *lo, struct file *file)
 166 {
 167         return get_size(lo->lo_offset, lo->lo_sizelimit, file);
 168 }
 169 
 170 static void __loop_update_dio(struct loop_device *lo, bool dio)
 171 {
 172         struct file *file = lo->lo_backing_file;
 173         struct address_space *mapping = file->f_mapping;
 174         struct inode *inode = mapping->host;
 175         unsigned short sb_bsize = 0;
 176         unsigned dio_align = 0;
 177         bool use_dio;
 178 
 179         if (inode->i_sb->s_bdev) {
 180                 sb_bsize = bdev_logical_block_size(inode->i_sb->s_bdev);
 181                 dio_align = sb_bsize - 1;
 182         }
 183 
 184         /*
 185          * We support direct I/O only if lo_offset is aligned with the
 186          * logical I/O size of backing device, and the logical block
 187          * size of loop is bigger than the backing device's and the loop
 188          * needn't transform transfer.
 189          *
 190          * TODO: the above condition may be loosed in the future, and
 191          * direct I/O may be switched runtime at that time because most
 192          * of requests in sane applications should be PAGE_SIZE aligned
 193          */
 194         if (dio) {
 195                 if (queue_logical_block_size(lo->lo_queue) >= sb_bsize &&
 196                                 !(lo->lo_offset & dio_align) &&
 197                                 mapping->a_ops->direct_IO &&
 198                                 !lo->transfer)
 199                         use_dio = true;
 200                 else
 201                         use_dio = false;
 202         } else {
 203                 use_dio = false;
 204         }
 205 
 206         if (lo->use_dio == use_dio)
 207                 return;
 208 
 209         /* flush dirty pages before changing direct IO */
 210         vfs_fsync(file, 0);
 211 
 212         /*
 213          * The flag of LO_FLAGS_DIRECT_IO is handled similarly with
 214          * LO_FLAGS_READ_ONLY, both are set from kernel, and losetup
 215          * will get updated by ioctl(LOOP_GET_STATUS)
 216          */
 217         blk_mq_freeze_queue(lo->lo_queue);
 218         lo->use_dio = use_dio;
 219         if (use_dio) {
 220                 blk_queue_flag_clear(QUEUE_FLAG_NOMERGES, lo->lo_queue);
 221                 lo->lo_flags |= LO_FLAGS_DIRECT_IO;
 222         } else {
 223                 blk_queue_flag_set(QUEUE_FLAG_NOMERGES, lo->lo_queue);
 224                 lo->lo_flags &= ~LO_FLAGS_DIRECT_IO;
 225         }
 226         blk_mq_unfreeze_queue(lo->lo_queue);
 227 }
 228 
 229 static int
 230 figure_loop_size(struct loop_device *lo, loff_t offset, loff_t sizelimit)
 231 {
 232         loff_t size = get_size(offset, sizelimit, lo->lo_backing_file);
 233         sector_t x = (sector_t)size;
 234         struct block_device *bdev = lo->lo_device;
 235 
 236         if (unlikely((loff_t)x != size))
 237                 return -EFBIG;
 238         if (lo->lo_offset != offset)
 239                 lo->lo_offset = offset;
 240         if (lo->lo_sizelimit != sizelimit)
 241                 lo->lo_sizelimit = sizelimit;
 242         set_capacity(lo->lo_disk, x);
 243         bd_set_size(bdev, (loff_t)get_capacity(bdev->bd_disk) << 9);
 244         /* let user-space know about the new size */
 245         kobject_uevent(&disk_to_dev(bdev->bd_disk)->kobj, KOBJ_CHANGE);
 246         return 0;
 247 }
 248 
 249 static inline int
 250 lo_do_transfer(struct loop_device *lo, int cmd,
 251                struct page *rpage, unsigned roffs,
 252                struct page *lpage, unsigned loffs,
 253                int size, sector_t rblock)
 254 {
 255         int ret;
 256 
 257         ret = lo->transfer(lo, cmd, rpage, roffs, lpage, loffs, size, rblock);
 258         if (likely(!ret))
 259                 return 0;
 260 
 261         printk_ratelimited(KERN_ERR
 262                 "loop: Transfer error at byte offset %llu, length %i.\n",
 263                 (unsigned long long)rblock << 9, size);
 264         return ret;
 265 }
 266 
 267 static int lo_write_bvec(struct file *file, struct bio_vec *bvec, loff_t *ppos)
 268 {
 269         struct iov_iter i;
 270         ssize_t bw;
 271 
 272         iov_iter_bvec(&i, WRITE, bvec, 1, bvec->bv_len);
 273 
 274         file_start_write(file);
 275         bw = vfs_iter_write(file, &i, ppos, 0);
 276         file_end_write(file);
 277 
 278         if (likely(bw ==  bvec->bv_len))
 279                 return 0;
 280 
 281         printk_ratelimited(KERN_ERR
 282                 "loop: Write error at byte offset %llu, length %i.\n",
 283                 (unsigned long long)*ppos, bvec->bv_len);
 284         if (bw >= 0)
 285                 bw = -EIO;
 286         return bw;
 287 }
 288 
 289 static int lo_write_simple(struct loop_device *lo, struct request *rq,
 290                 loff_t pos)
 291 {
 292         struct bio_vec bvec;
 293         struct req_iterator iter;
 294         int ret = 0;
 295 
 296         rq_for_each_segment(bvec, rq, iter) {
 297                 ret = lo_write_bvec(lo->lo_backing_file, &bvec, &pos);
 298                 if (ret < 0)
 299                         break;
 300                 cond_resched();
 301         }
 302 
 303         return ret;
 304 }
 305 
 306 /*
 307  * This is the slow, transforming version that needs to double buffer the
 308  * data as it cannot do the transformations in place without having direct
 309  * access to the destination pages of the backing file.
 310  */
 311 static int lo_write_transfer(struct loop_device *lo, struct request *rq,
 312                 loff_t pos)
 313 {
 314         struct bio_vec bvec, b;
 315         struct req_iterator iter;
 316         struct page *page;
 317         int ret = 0;
 318 
 319         page = alloc_page(GFP_NOIO);
 320         if (unlikely(!page))
 321                 return -ENOMEM;
 322 
 323         rq_for_each_segment(bvec, rq, iter) {
 324                 ret = lo_do_transfer(lo, WRITE, page, 0, bvec.bv_page,
 325                         bvec.bv_offset, bvec.bv_len, pos >> 9);
 326                 if (unlikely(ret))
 327                         break;
 328 
 329                 b.bv_page = page;
 330                 b.bv_offset = 0;
 331                 b.bv_len = bvec.bv_len;
 332                 ret = lo_write_bvec(lo->lo_backing_file, &b, &pos);
 333                 if (ret < 0)
 334                         break;
 335         }
 336 
 337         __free_page(page);
 338         return ret;
 339 }
 340 
 341 static int lo_read_simple(struct loop_device *lo, struct request *rq,
 342                 loff_t pos)
 343 {
 344         struct bio_vec bvec;
 345         struct req_iterator iter;
 346         struct iov_iter i;
 347         ssize_t len;
 348 
 349         rq_for_each_segment(bvec, rq, iter) {
 350                 iov_iter_bvec(&i, READ, &bvec, 1, bvec.bv_len);
 351                 len = vfs_iter_read(lo->lo_backing_file, &i, &pos, 0);
 352                 if (len < 0)
 353                         return len;
 354 
 355                 flush_dcache_page(bvec.bv_page);
 356 
 357                 if (len != bvec.bv_len) {
 358                         struct bio *bio;
 359 
 360                         __rq_for_each_bio(bio, rq)
 361                                 zero_fill_bio(bio);
 362                         break;
 363                 }
 364                 cond_resched();
 365         }
 366 
 367         return 0;
 368 }
 369 
 370 static int lo_read_transfer(struct loop_device *lo, struct request *rq,
 371                 loff_t pos)
 372 {
 373         struct bio_vec bvec, b;
 374         struct req_iterator iter;
 375         struct iov_iter i;
 376         struct page *page;
 377         ssize_t len;
 378         int ret = 0;
 379 
 380         page = alloc_page(GFP_NOIO);
 381         if (unlikely(!page))
 382                 return -ENOMEM;
 383 
 384         rq_for_each_segment(bvec, rq, iter) {
 385                 loff_t offset = pos;
 386 
 387                 b.bv_page = page;
 388                 b.bv_offset = 0;
 389                 b.bv_len = bvec.bv_len;
 390 
 391                 iov_iter_bvec(&i, READ, &b, 1, b.bv_len);
 392                 len = vfs_iter_read(lo->lo_backing_file, &i, &pos, 0);
 393                 if (len < 0) {
 394                         ret = len;
 395                         goto out_free_page;
 396                 }
 397 
 398                 ret = lo_do_transfer(lo, READ, page, 0, bvec.bv_page,
 399                         bvec.bv_offset, len, offset >> 9);
 400                 if (ret)
 401                         goto out_free_page;
 402 
 403                 flush_dcache_page(bvec.bv_page);
 404 
 405                 if (len != bvec.bv_len) {
 406                         struct bio *bio;
 407 
 408                         __rq_for_each_bio(bio, rq)
 409                                 zero_fill_bio(bio);
 410                         break;
 411                 }
 412         }
 413 
 414         ret = 0;
 415 out_free_page:
 416         __free_page(page);
 417         return ret;
 418 }
 419 
 420 static int lo_fallocate(struct loop_device *lo, struct request *rq, loff_t pos,
 421                         int mode)
 422 {
 423         /*
 424          * We use fallocate to manipulate the space mappings used by the image
 425          * a.k.a. discard/zerorange. However we do not support this if
 426          * encryption is enabled, because it may give an attacker useful
 427          * information.
 428          */
 429         struct file *file = lo->lo_backing_file;
 430         struct request_queue *q = lo->lo_queue;
 431         int ret;
 432 
 433         mode |= FALLOC_FL_KEEP_SIZE;
 434 
 435         if (!blk_queue_discard(q)) {
 436                 ret = -EOPNOTSUPP;
 437                 goto out;
 438         }
 439 
 440         ret = file->f_op->fallocate(file, mode, pos, blk_rq_bytes(rq));
 441         if (unlikely(ret && ret != -EINVAL && ret != -EOPNOTSUPP))
 442                 ret = -EIO;
 443  out:
 444         return ret;
 445 }
 446 
 447 static int lo_req_flush(struct loop_device *lo, struct request *rq)
 448 {
 449         struct file *file = lo->lo_backing_file;
 450         int ret = vfs_fsync(file, 0);
 451         if (unlikely(ret && ret != -EINVAL))
 452                 ret = -EIO;
 453 
 454         return ret;
 455 }
 456 
 457 static void lo_complete_rq(struct request *rq)
 458 {
 459         struct loop_cmd *cmd = blk_mq_rq_to_pdu(rq);
 460         blk_status_t ret = BLK_STS_OK;
 461 
 462         if (!cmd->use_aio || cmd->ret < 0 || cmd->ret == blk_rq_bytes(rq) ||
 463             req_op(rq) != REQ_OP_READ) {
 464                 if (cmd->ret < 0)
 465                         ret = BLK_STS_IOERR;
 466                 goto end_io;
 467         }
 468 
 469         /*
 470          * Short READ - if we got some data, advance our request and
 471          * retry it. If we got no data, end the rest with EIO.
 472          */
 473         if (cmd->ret) {
 474                 blk_update_request(rq, BLK_STS_OK, cmd->ret);
 475                 cmd->ret = 0;
 476                 blk_mq_requeue_request(rq, true);
 477         } else {
 478                 if (cmd->use_aio) {
 479                         struct bio *bio = rq->bio;
 480 
 481                         while (bio) {
 482                                 zero_fill_bio(bio);
 483                                 bio = bio->bi_next;
 484                         }
 485                 }
 486                 ret = BLK_STS_IOERR;
 487 end_io:
 488                 blk_mq_end_request(rq, ret);
 489         }
 490 }
 491 
 492 static void lo_rw_aio_do_completion(struct loop_cmd *cmd)
 493 {
 494         struct request *rq = blk_mq_rq_from_pdu(cmd);
 495 
 496         if (!atomic_dec_and_test(&cmd->ref))
 497                 return;
 498         kfree(cmd->bvec);
 499         cmd->bvec = NULL;
 500         blk_mq_complete_request(rq);
 501 }
 502 
 503 static void lo_rw_aio_complete(struct kiocb *iocb, long ret, long ret2)
 504 {
 505         struct loop_cmd *cmd = container_of(iocb, struct loop_cmd, iocb);
 506 
 507         if (cmd->css)
 508                 css_put(cmd->css);
 509         cmd->ret = ret;
 510         lo_rw_aio_do_completion(cmd);
 511 }
 512 
 513 static int lo_rw_aio(struct loop_device *lo, struct loop_cmd *cmd,
 514                      loff_t pos, bool rw)
 515 {
 516         struct iov_iter iter;
 517         struct req_iterator rq_iter;
 518         struct bio_vec *bvec;
 519         struct request *rq = blk_mq_rq_from_pdu(cmd);
 520         struct bio *bio = rq->bio;
 521         struct file *file = lo->lo_backing_file;
 522         struct bio_vec tmp;
 523         unsigned int offset;
 524         int nr_bvec = 0;
 525         int ret;
 526 
 527         rq_for_each_bvec(tmp, rq, rq_iter)
 528                 nr_bvec++;
 529 
 530         if (rq->bio != rq->biotail) {
 531 
 532                 bvec = kmalloc_array(nr_bvec, sizeof(struct bio_vec),
 533                                      GFP_NOIO);
 534                 if (!bvec)
 535                         return -EIO;
 536                 cmd->bvec = bvec;
 537 
 538                 /*
 539                  * The bios of the request may be started from the middle of
 540                  * the 'bvec' because of bio splitting, so we can't directly
 541                  * copy bio->bi_iov_vec to new bvec. The rq_for_each_bvec
 542                  * API will take care of all details for us.
 543                  */
 544                 rq_for_each_bvec(tmp, rq, rq_iter) {
 545                         *bvec = tmp;
 546                         bvec++;
 547                 }
 548                 bvec = cmd->bvec;
 549                 offset = 0;
 550         } else {
 551                 /*
 552                  * Same here, this bio may be started from the middle of the
 553                  * 'bvec' because of bio splitting, so offset from the bvec
 554                  * must be passed to iov iterator
 555                  */
 556                 offset = bio->bi_iter.bi_bvec_done;
 557                 bvec = __bvec_iter_bvec(bio->bi_io_vec, bio->bi_iter);
 558         }
 559         atomic_set(&cmd->ref, 2);
 560 
 561         iov_iter_bvec(&iter, rw, bvec, nr_bvec, blk_rq_bytes(rq));
 562         iter.iov_offset = offset;
 563 
 564         cmd->iocb.ki_pos = pos;
 565         cmd->iocb.ki_filp = file;
 566         cmd->iocb.ki_complete = lo_rw_aio_complete;
 567         cmd->iocb.ki_flags = IOCB_DIRECT;
 568         cmd->iocb.ki_ioprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_NONE, 0);
 569         if (cmd->css)
 570                 kthread_associate_blkcg(cmd->css);
 571 
 572         if (rw == WRITE)
 573                 ret = call_write_iter(file, &cmd->iocb, &iter);
 574         else
 575                 ret = call_read_iter(file, &cmd->iocb, &iter);
 576 
 577         lo_rw_aio_do_completion(cmd);
 578         kthread_associate_blkcg(NULL);
 579 
 580         if (ret != -EIOCBQUEUED)
 581                 cmd->iocb.ki_complete(&cmd->iocb, ret, 0);
 582         return 0;
 583 }
 584 
 585 static int do_req_filebacked(struct loop_device *lo, struct request *rq)
 586 {
 587         struct loop_cmd *cmd = blk_mq_rq_to_pdu(rq);
 588         loff_t pos = ((loff_t) blk_rq_pos(rq) << 9) + lo->lo_offset;
 589 
 590         /*
 591          * lo_write_simple and lo_read_simple should have been covered
 592          * by io submit style function like lo_rw_aio(), one blocker
 593          * is that lo_read_simple() need to call flush_dcache_page after
 594          * the page is written from kernel, and it isn't easy to handle
 595          * this in io submit style function which submits all segments
 596          * of the req at one time. And direct read IO doesn't need to
 597          * run flush_dcache_page().
 598          */
 599         switch (req_op(rq)) {
 600         case REQ_OP_FLUSH:
 601                 return lo_req_flush(lo, rq);
 602         case REQ_OP_WRITE_ZEROES:
 603                 /*
 604                  * If the caller doesn't want deallocation, call zeroout to
 605                  * write zeroes the range.  Otherwise, punch them out.
 606                  */
 607                 return lo_fallocate(lo, rq, pos,
 608                         (rq->cmd_flags & REQ_NOUNMAP) ?
 609                                 FALLOC_FL_ZERO_RANGE :
 610                                 FALLOC_FL_PUNCH_HOLE);
 611         case REQ_OP_DISCARD:
 612                 return lo_fallocate(lo, rq, pos, FALLOC_FL_PUNCH_HOLE);
 613         case REQ_OP_WRITE:
 614                 if (lo->transfer)
 615                         return lo_write_transfer(lo, rq, pos);
 616                 else if (cmd->use_aio)
 617                         return lo_rw_aio(lo, cmd, pos, WRITE);
 618                 else
 619                         return lo_write_simple(lo, rq, pos);
 620         case REQ_OP_READ:
 621                 if (lo->transfer)
 622                         return lo_read_transfer(lo, rq, pos);
 623                 else if (cmd->use_aio)
 624                         return lo_rw_aio(lo, cmd, pos, READ);
 625                 else
 626                         return lo_read_simple(lo, rq, pos);
 627         default:
 628                 WARN_ON_ONCE(1);
 629                 return -EIO;
 630         }
 631 }
 632 
 633 static inline void loop_update_dio(struct loop_device *lo)
 634 {
 635         __loop_update_dio(lo, io_is_direct(lo->lo_backing_file) |
 636                         lo->use_dio);
 637 }
 638 
 639 static void loop_reread_partitions(struct loop_device *lo,
 640                                    struct block_device *bdev)
 641 {
 642         int rc;
 643 
 644         rc = blkdev_reread_part(bdev);
 645         if (rc)
 646                 pr_warn("%s: partition scan of loop%d (%s) failed (rc=%d)\n",
 647                         __func__, lo->lo_number, lo->lo_file_name, rc);
 648 }
 649 
 650 static inline int is_loop_device(struct file *file)
 651 {
 652         struct inode *i = file->f_mapping->host;
 653 
 654         return i && S_ISBLK(i->i_mode) && MAJOR(i->i_rdev) == LOOP_MAJOR;
 655 }
 656 
 657 static int loop_validate_file(struct file *file, struct block_device *bdev)
 658 {
 659         struct inode    *inode = file->f_mapping->host;
 660         struct file     *f = file;
 661 
 662         /* Avoid recursion */
 663         while (is_loop_device(f)) {
 664                 struct loop_device *l;
 665 
 666                 if (f->f_mapping->host->i_bdev == bdev)
 667                         return -EBADF;
 668 
 669                 l = f->f_mapping->host->i_bdev->bd_disk->private_data;
 670                 if (l->lo_state != Lo_bound) {
 671                         return -EINVAL;
 672                 }
 673                 f = l->lo_backing_file;
 674         }
 675         if (!S_ISREG(inode->i_mode) && !S_ISBLK(inode->i_mode))
 676                 return -EINVAL;
 677         return 0;
 678 }
 679 
 680 /*
 681  * loop_change_fd switched the backing store of a loopback device to
 682  * a new file. This is useful for operating system installers to free up
 683  * the original file and in High Availability environments to switch to
 684  * an alternative location for the content in case of server meltdown.
 685  * This can only work if the loop device is used read-only, and if the
 686  * new backing store is the same size and type as the old backing store.
 687  */
 688 static int loop_change_fd(struct loop_device *lo, struct block_device *bdev,
 689                           unsigned int arg)
 690 {
 691         struct file     *file = NULL, *old_file;
 692         int             error;
 693         bool            partscan;
 694 
 695         error = mutex_lock_killable(&loop_ctl_mutex);
 696         if (error)
 697                 return error;
 698         error = -ENXIO;
 699         if (lo->lo_state != Lo_bound)
 700                 goto out_err;
 701 
 702         /* the loop device has to be read-only */
 703         error = -EINVAL;
 704         if (!(lo->lo_flags & LO_FLAGS_READ_ONLY))
 705                 goto out_err;
 706 
 707         error = -EBADF;
 708         file = fget(arg);
 709         if (!file)
 710                 goto out_err;
 711 
 712         error = loop_validate_file(file, bdev);
 713         if (error)
 714                 goto out_err;
 715 
 716         old_file = lo->lo_backing_file;
 717 
 718         error = -EINVAL;
 719 
 720         /* size of the new backing store needs to be the same */
 721         if (get_loop_size(lo, file) != get_loop_size(lo, old_file))
 722                 goto out_err;
 723 
 724         /* and ... switch */
 725         blk_mq_freeze_queue(lo->lo_queue);
 726         mapping_set_gfp_mask(old_file->f_mapping, lo->old_gfp_mask);
 727         lo->lo_backing_file = file;
 728         lo->old_gfp_mask = mapping_gfp_mask(file->f_mapping);
 729         mapping_set_gfp_mask(file->f_mapping,
 730                              lo->old_gfp_mask & ~(__GFP_IO|__GFP_FS));
 731         loop_update_dio(lo);
 732         blk_mq_unfreeze_queue(lo->lo_queue);
 733         partscan = lo->lo_flags & LO_FLAGS_PARTSCAN;
 734         mutex_unlock(&loop_ctl_mutex);
 735         /*
 736          * We must drop file reference outside of loop_ctl_mutex as dropping
 737          * the file ref can take bd_mutex which creates circular locking
 738          * dependency.
 739          */
 740         fput(old_file);
 741         if (partscan)
 742                 loop_reread_partitions(lo, bdev);
 743         return 0;
 744 
 745 out_err:
 746         mutex_unlock(&loop_ctl_mutex);
 747         if (file)
 748                 fput(file);
 749         return error;
 750 }
 751 
 752 /* loop sysfs attributes */
 753 
 754 static ssize_t loop_attr_show(struct device *dev, char *page,
 755                               ssize_t (*callback)(struct loop_device *, char *))
 756 {
 757         struct gendisk *disk = dev_to_disk(dev);
 758         struct loop_device *lo = disk->private_data;
 759 
 760         return callback(lo, page);
 761 }
 762 
 763 #define LOOP_ATTR_RO(_name)                                             \
 764 static ssize_t loop_attr_##_name##_show(struct loop_device *, char *);  \
 765 static ssize_t loop_attr_do_show_##_name(struct device *d,              \
 766                                 struct device_attribute *attr, char *b) \
 767 {                                                                       \
 768         return loop_attr_show(d, b, loop_attr_##_name##_show);          \
 769 }                                                                       \
 770 static struct device_attribute loop_attr_##_name =                      \
 771         __ATTR(_name, 0444, loop_attr_do_show_##_name, NULL);
 772 
 773 static ssize_t loop_attr_backing_file_show(struct loop_device *lo, char *buf)
 774 {
 775         ssize_t ret;
 776         char *p = NULL;
 777 
 778         spin_lock_irq(&lo->lo_lock);
 779         if (lo->lo_backing_file)
 780                 p = file_path(lo->lo_backing_file, buf, PAGE_SIZE - 1);
 781         spin_unlock_irq(&lo->lo_lock);
 782 
 783         if (IS_ERR_OR_NULL(p))
 784                 ret = PTR_ERR(p);
 785         else {
 786                 ret = strlen(p);
 787                 memmove(buf, p, ret);
 788                 buf[ret++] = '\n';
 789                 buf[ret] = 0;
 790         }
 791 
 792         return ret;
 793 }
 794 
 795 static ssize_t loop_attr_offset_show(struct loop_device *lo, char *buf)
 796 {
 797         return sprintf(buf, "%llu\n", (unsigned long long)lo->lo_offset);
 798 }
 799 
 800 static ssize_t loop_attr_sizelimit_show(struct loop_device *lo, char *buf)
 801 {
 802         return sprintf(buf, "%llu\n", (unsigned long long)lo->lo_sizelimit);
 803 }
 804 
 805 static ssize_t loop_attr_autoclear_show(struct loop_device *lo, char *buf)
 806 {
 807         int autoclear = (lo->lo_flags & LO_FLAGS_AUTOCLEAR);
 808 
 809         return sprintf(buf, "%s\n", autoclear ? "1" : "0");
 810 }
 811 
 812 static ssize_t loop_attr_partscan_show(struct loop_device *lo, char *buf)
 813 {
 814         int partscan = (lo->lo_flags & LO_FLAGS_PARTSCAN);
 815 
 816         return sprintf(buf, "%s\n", partscan ? "1" : "0");
 817 }
 818 
 819 static ssize_t loop_attr_dio_show(struct loop_device *lo, char *buf)
 820 {
 821         int dio = (lo->lo_flags & LO_FLAGS_DIRECT_IO);
 822 
 823         return sprintf(buf, "%s\n", dio ? "1" : "0");
 824 }
 825 
 826 LOOP_ATTR_RO(backing_file);
 827 LOOP_ATTR_RO(offset);
 828 LOOP_ATTR_RO(sizelimit);
 829 LOOP_ATTR_RO(autoclear);
 830 LOOP_ATTR_RO(partscan);
 831 LOOP_ATTR_RO(dio);
 832 
 833 static struct attribute *loop_attrs[] = {
 834         &loop_attr_backing_file.attr,
 835         &loop_attr_offset.attr,
 836         &loop_attr_sizelimit.attr,
 837         &loop_attr_autoclear.attr,
 838         &loop_attr_partscan.attr,
 839         &loop_attr_dio.attr,
 840         NULL,
 841 };
 842 
 843 static struct attribute_group loop_attribute_group = {
 844         .name = "loop",
 845         .attrs= loop_attrs,
 846 };
 847 
 848 static void loop_sysfs_init(struct loop_device *lo)
 849 {
 850         lo->sysfs_inited = !sysfs_create_group(&disk_to_dev(lo->lo_disk)->kobj,
 851                                                 &loop_attribute_group);
 852 }
 853 
 854 static void loop_sysfs_exit(struct loop_device *lo)
 855 {
 856         if (lo->sysfs_inited)
 857                 sysfs_remove_group(&disk_to_dev(lo->lo_disk)->kobj,
 858                                    &loop_attribute_group);
 859 }
 860 
 861 static void loop_config_discard(struct loop_device *lo)
 862 {
 863         struct file *file = lo->lo_backing_file;
 864         struct inode *inode = file->f_mapping->host;
 865         struct request_queue *q = lo->lo_queue;
 866 
 867         /*
 868          * If the backing device is a block device, mirror its zeroing
 869          * capability. Set the discard sectors to the block device's zeroing
 870          * capabilities because loop discards result in blkdev_issue_zeroout(),
 871          * not blkdev_issue_discard(). This maintains consistent behavior with
 872          * file-backed loop devices: discarded regions read back as zero.
 873          */
 874         if (S_ISBLK(inode->i_mode) && !lo->lo_encrypt_key_size) {
 875                 struct request_queue *backingq;
 876 
 877                 backingq = bdev_get_queue(inode->i_bdev);
 878                 blk_queue_max_discard_sectors(q,
 879                         backingq->limits.max_write_zeroes_sectors);
 880 
 881                 blk_queue_max_write_zeroes_sectors(q,
 882                         backingq->limits.max_write_zeroes_sectors);
 883 
 884         /*
 885          * We use punch hole to reclaim the free space used by the
 886          * image a.k.a. discard. However we do not support discard if
 887          * encryption is enabled, because it may give an attacker
 888          * useful information.
 889          */
 890         } else if (!file->f_op->fallocate || lo->lo_encrypt_key_size) {
 891                 q->limits.discard_granularity = 0;
 892                 q->limits.discard_alignment = 0;
 893                 blk_queue_max_discard_sectors(q, 0);
 894                 blk_queue_max_write_zeroes_sectors(q, 0);
 895 
 896         } else {
 897                 q->limits.discard_granularity = inode->i_sb->s_blocksize;
 898                 q->limits.discard_alignment = 0;
 899 
 900                 blk_queue_max_discard_sectors(q, UINT_MAX >> 9);
 901                 blk_queue_max_write_zeroes_sectors(q, UINT_MAX >> 9);
 902         }
 903 
 904         if (q->limits.max_write_zeroes_sectors)
 905                 blk_queue_flag_set(QUEUE_FLAG_DISCARD, q);
 906         else
 907                 blk_queue_flag_clear(QUEUE_FLAG_DISCARD, q);
 908 }
 909 
 910 static void loop_unprepare_queue(struct loop_device *lo)
 911 {
 912         kthread_flush_worker(&lo->worker);
 913         kthread_stop(lo->worker_task);
 914 }
 915 
 916 static int loop_kthread_worker_fn(void *worker_ptr)
 917 {
 918         current->flags |= PF_LESS_THROTTLE | PF_MEMALLOC_NOIO;
 919         return kthread_worker_fn(worker_ptr);
 920 }
 921 
 922 static int loop_prepare_queue(struct loop_device *lo)
 923 {
 924         kthread_init_worker(&lo->worker);
 925         lo->worker_task = kthread_run(loop_kthread_worker_fn,
 926                         &lo->worker, "loop%d", lo->lo_number);
 927         if (IS_ERR(lo->worker_task))
 928                 return -ENOMEM;
 929         set_user_nice(lo->worker_task, MIN_NICE);
 930         return 0;
 931 }
 932 
 933 static void loop_update_rotational(struct loop_device *lo)
 934 {
 935         struct file *file = lo->lo_backing_file;
 936         struct inode *file_inode = file->f_mapping->host;
 937         struct block_device *file_bdev = file_inode->i_sb->s_bdev;
 938         struct request_queue *q = lo->lo_queue;
 939         bool nonrot = true;
 940 
 941         /* not all filesystems (e.g. tmpfs) have a sb->s_bdev */
 942         if (file_bdev)
 943                 nonrot = blk_queue_nonrot(bdev_get_queue(file_bdev));
 944 
 945         if (nonrot)
 946                 blk_queue_flag_set(QUEUE_FLAG_NONROT, q);
 947         else
 948                 blk_queue_flag_clear(QUEUE_FLAG_NONROT, q);
 949 }
 950 
 951 static int loop_set_fd(struct loop_device *lo, fmode_t mode,
 952                        struct block_device *bdev, unsigned int arg)
 953 {
 954         struct file     *file;
 955         struct inode    *inode;
 956         struct address_space *mapping;
 957         struct block_device *claimed_bdev = NULL;
 958         int             lo_flags = 0;
 959         int             error;
 960         loff_t          size;
 961         bool            partscan;
 962 
 963         /* This is safe, since we have a reference from open(). */
 964         __module_get(THIS_MODULE);
 965 
 966         error = -EBADF;
 967         file = fget(arg);
 968         if (!file)
 969                 goto out;
 970 
 971         /*
 972          * If we don't hold exclusive handle for the device, upgrade to it
 973          * here to avoid changing device under exclusive owner.
 974          */
 975         if (!(mode & FMODE_EXCL)) {
 976                 claimed_bdev = bd_start_claiming(bdev, loop_set_fd);
 977                 if (IS_ERR(claimed_bdev)) {
 978                         error = PTR_ERR(claimed_bdev);
 979                         goto out_putf;
 980                 }
 981         }
 982 
 983         error = mutex_lock_killable(&loop_ctl_mutex);
 984         if (error)
 985                 goto out_bdev;
 986 
 987         error = -EBUSY;
 988         if (lo->lo_state != Lo_unbound)
 989                 goto out_unlock;
 990 
 991         error = loop_validate_file(file, bdev);
 992         if (error)
 993                 goto out_unlock;
 994 
 995         mapping = file->f_mapping;
 996         inode = mapping->host;
 997 
 998         if (!(file->f_mode & FMODE_WRITE) || !(mode & FMODE_WRITE) ||
 999             !file->f_op->write_iter)
1000                 lo_flags |= LO_FLAGS_READ_ONLY;
1001 
1002         error = -EFBIG;
1003         size = get_loop_size(lo, file);
1004         if ((loff_t)(sector_t)size != size)
1005                 goto out_unlock;
1006         error = loop_prepare_queue(lo);
1007         if (error)
1008                 goto out_unlock;
1009 
1010         error = 0;
1011 
1012         set_device_ro(bdev, (lo_flags & LO_FLAGS_READ_ONLY) != 0);
1013 
1014         lo->use_dio = false;
1015         lo->lo_device = bdev;
1016         lo->lo_flags = lo_flags;
1017         lo->lo_backing_file = file;
1018         lo->transfer = NULL;
1019         lo->ioctl = NULL;
1020         lo->lo_sizelimit = 0;
1021         lo->old_gfp_mask = mapping_gfp_mask(mapping);
1022         mapping_set_gfp_mask(mapping, lo->old_gfp_mask & ~(__GFP_IO|__GFP_FS));
1023 
1024         if (!(lo_flags & LO_FLAGS_READ_ONLY) && file->f_op->fsync)
1025                 blk_queue_write_cache(lo->lo_queue, true, false);
1026 
1027         if (io_is_direct(lo->lo_backing_file) && inode->i_sb->s_bdev) {
1028                 /* In case of direct I/O, match underlying block size */
1029                 unsigned short bsize = bdev_logical_block_size(
1030                         inode->i_sb->s_bdev);
1031 
1032                 blk_queue_logical_block_size(lo->lo_queue, bsize);
1033                 blk_queue_physical_block_size(lo->lo_queue, bsize);
1034                 blk_queue_io_min(lo->lo_queue, bsize);
1035         }
1036 
1037         loop_update_rotational(lo);
1038         loop_update_dio(lo);
1039         set_capacity(lo->lo_disk, size);
1040         bd_set_size(bdev, size << 9);
1041         loop_sysfs_init(lo);
1042         /* let user-space know about the new size */
1043         kobject_uevent(&disk_to_dev(bdev->bd_disk)->kobj, KOBJ_CHANGE);
1044 
1045         set_blocksize(bdev, S_ISBLK(inode->i_mode) ?
1046                       block_size(inode->i_bdev) : PAGE_SIZE);
1047 
1048         lo->lo_state = Lo_bound;
1049         if (part_shift)
1050                 lo->lo_flags |= LO_FLAGS_PARTSCAN;
1051         partscan = lo->lo_flags & LO_FLAGS_PARTSCAN;
1052 
1053         /* Grab the block_device to prevent its destruction after we
1054          * put /dev/loopXX inode. Later in __loop_clr_fd() we bdput(bdev).
1055          */
1056         bdgrab(bdev);
1057         mutex_unlock(&loop_ctl_mutex);
1058         if (partscan)
1059                 loop_reread_partitions(lo, bdev);
1060         if (claimed_bdev)
1061                 bd_abort_claiming(bdev, claimed_bdev, loop_set_fd);
1062         return 0;
1063 
1064 out_unlock:
1065         mutex_unlock(&loop_ctl_mutex);
1066 out_bdev:
1067         if (claimed_bdev)
1068                 bd_abort_claiming(bdev, claimed_bdev, loop_set_fd);
1069 out_putf:
1070         fput(file);
1071 out:
1072         /* This is safe: open() is still holding a reference. */
1073         module_put(THIS_MODULE);
1074         return error;
1075 }
1076 
1077 static int
1078 loop_release_xfer(struct loop_device *lo)
1079 {
1080         int err = 0;
1081         struct loop_func_table *xfer = lo->lo_encryption;
1082 
1083         if (xfer) {
1084                 if (xfer->release)
1085                         err = xfer->release(lo);
1086                 lo->transfer = NULL;
1087                 lo->lo_encryption = NULL;
1088                 module_put(xfer->owner);
1089         }
1090         return err;
1091 }
1092 
1093 static int
1094 loop_init_xfer(struct loop_device *lo, struct loop_func_table *xfer,
1095                const struct loop_info64 *i)
1096 {
1097         int err = 0;
1098 
1099         if (xfer) {
1100                 struct module *owner = xfer->owner;
1101 
1102                 if (!try_module_get(owner))
1103                         return -EINVAL;
1104                 if (xfer->init)
1105                         err = xfer->init(lo, i);
1106                 if (err)
1107                         module_put(owner);
1108                 else
1109                         lo->lo_encryption = xfer;
1110         }
1111         return err;
1112 }
1113 
1114 static int __loop_clr_fd(struct loop_device *lo, bool release)
1115 {
1116         struct file *filp = NULL;
1117         gfp_t gfp = lo->old_gfp_mask;
1118         struct block_device *bdev = lo->lo_device;
1119         int err = 0;
1120         bool partscan = false;
1121         int lo_number;
1122 
1123         mutex_lock(&loop_ctl_mutex);
1124         if (WARN_ON_ONCE(lo->lo_state != Lo_rundown)) {
1125                 err = -ENXIO;
1126                 goto out_unlock;
1127         }
1128 
1129         filp = lo->lo_backing_file;
1130         if (filp == NULL) {
1131                 err = -EINVAL;
1132                 goto out_unlock;
1133         }
1134 
1135         /* freeze request queue during the transition */
1136         blk_mq_freeze_queue(lo->lo_queue);
1137 
1138         spin_lock_irq(&lo->lo_lock);
1139         lo->lo_backing_file = NULL;
1140         spin_unlock_irq(&lo->lo_lock);
1141 
1142         loop_release_xfer(lo);
1143         lo->transfer = NULL;
1144         lo->ioctl = NULL;
1145         lo->lo_device = NULL;
1146         lo->lo_encryption = NULL;
1147         lo->lo_offset = 0;
1148         lo->lo_sizelimit = 0;
1149         lo->lo_encrypt_key_size = 0;
1150         memset(lo->lo_encrypt_key, 0, LO_KEY_SIZE);
1151         memset(lo->lo_crypt_name, 0, LO_NAME_SIZE);
1152         memset(lo->lo_file_name, 0, LO_NAME_SIZE);
1153         blk_queue_logical_block_size(lo->lo_queue, 512);
1154         blk_queue_physical_block_size(lo->lo_queue, 512);
1155         blk_queue_io_min(lo->lo_queue, 512);
1156         if (bdev) {
1157                 bdput(bdev);
1158                 invalidate_bdev(bdev);
1159                 bdev->bd_inode->i_mapping->wb_err = 0;
1160         }
1161         set_capacity(lo->lo_disk, 0);
1162         loop_sysfs_exit(lo);
1163         if (bdev) {
1164                 bd_set_size(bdev, 0);
1165                 /* let user-space know about this change */
1166                 kobject_uevent(&disk_to_dev(bdev->bd_disk)->kobj, KOBJ_CHANGE);
1167         }
1168         mapping_set_gfp_mask(filp->f_mapping, gfp);
1169         /* This is safe: open() is still holding a reference. */
1170         module_put(THIS_MODULE);
1171         blk_mq_unfreeze_queue(lo->lo_queue);
1172 
1173         partscan = lo->lo_flags & LO_FLAGS_PARTSCAN && bdev;
1174         lo_number = lo->lo_number;
1175         loop_unprepare_queue(lo);
1176 out_unlock:
1177         mutex_unlock(&loop_ctl_mutex);
1178         if (partscan) {
1179                 /*
1180                  * bd_mutex has been held already in release path, so don't
1181                  * acquire it if this function is called in such case.
1182                  *
1183                  * If the reread partition isn't from release path, lo_refcnt
1184                  * must be at least one and it can only become zero when the
1185                  * current holder is released.
1186                  */
1187                 if (release)
1188                         err = __blkdev_reread_part(bdev);
1189                 else
1190                         err = blkdev_reread_part(bdev);
1191                 if (err)
1192                         pr_warn("%s: partition scan of loop%d failed (rc=%d)\n",
1193                                 __func__, lo_number, err);
1194                 /* Device is gone, no point in returning error */
1195                 err = 0;
1196         }
1197 
1198         /*
1199          * lo->lo_state is set to Lo_unbound here after above partscan has
1200          * finished.
1201          *
1202          * There cannot be anybody else entering __loop_clr_fd() as
1203          * lo->lo_backing_file is already cleared and Lo_rundown state
1204          * protects us from all the other places trying to change the 'lo'
1205          * device.
1206          */
1207         mutex_lock(&loop_ctl_mutex);
1208         lo->lo_flags = 0;
1209         if (!part_shift)
1210                 lo->lo_disk->flags |= GENHD_FL_NO_PART_SCAN;
1211         lo->lo_state = Lo_unbound;
1212         mutex_unlock(&loop_ctl_mutex);
1213 
1214         /*
1215          * Need not hold loop_ctl_mutex to fput backing file.
1216          * Calling fput holding loop_ctl_mutex triggers a circular
1217          * lock dependency possibility warning as fput can take
1218          * bd_mutex which is usually taken before loop_ctl_mutex.
1219          */
1220         if (filp)
1221                 fput(filp);
1222         return err;
1223 }
1224 
1225 static int loop_clr_fd(struct loop_device *lo)
1226 {
1227         int err;
1228 
1229         err = mutex_lock_killable(&loop_ctl_mutex);
1230         if (err)
1231                 return err;
1232         if (lo->lo_state != Lo_bound) {
1233                 mutex_unlock(&loop_ctl_mutex);
1234                 return -ENXIO;
1235         }
1236         /*
1237          * If we've explicitly asked to tear down the loop device,
1238          * and it has an elevated reference count, set it for auto-teardown when
1239          * the last reference goes away. This stops $!~#$@ udev from
1240          * preventing teardown because it decided that it needs to run blkid on
1241          * the loopback device whenever they appear. xfstests is notorious for
1242          * failing tests because blkid via udev races with a losetup
1243          * <dev>/do something like mkfs/losetup -d <dev> causing the losetup -d
1244          * command to fail with EBUSY.
1245          */
1246         if (atomic_read(&lo->lo_refcnt) > 1) {
1247                 lo->lo_flags |= LO_FLAGS_AUTOCLEAR;
1248                 mutex_unlock(&loop_ctl_mutex);
1249                 return 0;
1250         }
1251         lo->lo_state = Lo_rundown;
1252         mutex_unlock(&loop_ctl_mutex);
1253 
1254         return __loop_clr_fd(lo, false);
1255 }
1256 
1257 static int
1258 loop_set_status(struct loop_device *lo, const struct loop_info64 *info)
1259 {
1260         int err;
1261         struct loop_func_table *xfer;
1262         kuid_t uid = current_uid();
1263         struct block_device *bdev;
1264         bool partscan = false;
1265 
1266         err = mutex_lock_killable(&loop_ctl_mutex);
1267         if (err)
1268                 return err;
1269         if (lo->lo_encrypt_key_size &&
1270             !uid_eq(lo->lo_key_owner, uid) &&
1271             !capable(CAP_SYS_ADMIN)) {
1272                 err = -EPERM;
1273                 goto out_unlock;
1274         }
1275         if (lo->lo_state != Lo_bound) {
1276                 err = -ENXIO;
1277                 goto out_unlock;
1278         }
1279         if ((unsigned int) info->lo_encrypt_key_size > LO_KEY_SIZE) {
1280                 err = -EINVAL;
1281                 goto out_unlock;
1282         }
1283 
1284         if (lo->lo_offset != info->lo_offset ||
1285             lo->lo_sizelimit != info->lo_sizelimit) {
1286                 sync_blockdev(lo->lo_device);
1287                 kill_bdev(lo->lo_device);
1288         }
1289 
1290         /* I/O need to be drained during transfer transition */
1291         blk_mq_freeze_queue(lo->lo_queue);
1292 
1293         err = loop_release_xfer(lo);
1294         if (err)
1295                 goto out_unfreeze;
1296 
1297         if (info->lo_encrypt_type) {
1298                 unsigned int type = info->lo_encrypt_type;
1299 
1300                 if (type >= MAX_LO_CRYPT) {
1301                         err = -EINVAL;
1302                         goto out_unfreeze;
1303                 }
1304                 xfer = xfer_funcs[type];
1305                 if (xfer == NULL) {
1306                         err = -EINVAL;
1307                         goto out_unfreeze;
1308                 }
1309         } else
1310                 xfer = NULL;
1311 
1312         err = loop_init_xfer(lo, xfer, info);
1313         if (err)
1314                 goto out_unfreeze;
1315 
1316         if (lo->lo_offset != info->lo_offset ||
1317             lo->lo_sizelimit != info->lo_sizelimit) {
1318                 /* kill_bdev should have truncated all the pages */
1319                 if (lo->lo_device->bd_inode->i_mapping->nrpages) {
1320                         err = -EAGAIN;
1321                         pr_warn("%s: loop%d (%s) has still dirty pages (nrpages=%lu)\n",
1322                                 __func__, lo->lo_number, lo->lo_file_name,
1323                                 lo->lo_device->bd_inode->i_mapping->nrpages);
1324                         goto out_unfreeze;
1325                 }
1326                 if (figure_loop_size(lo, info->lo_offset, info->lo_sizelimit)) {
1327                         err = -EFBIG;
1328                         goto out_unfreeze;
1329                 }
1330         }
1331 
1332         loop_config_discard(lo);
1333 
1334         memcpy(lo->lo_file_name, info->lo_file_name, LO_NAME_SIZE);
1335         memcpy(lo->lo_crypt_name, info->lo_crypt_name, LO_NAME_SIZE);
1336         lo->lo_file_name[LO_NAME_SIZE-1] = 0;
1337         lo->lo_crypt_name[LO_NAME_SIZE-1] = 0;
1338 
1339         if (!xfer)
1340                 xfer = &none_funcs;
1341         lo->transfer = xfer->transfer;
1342         lo->ioctl = xfer->ioctl;
1343 
1344         if ((lo->lo_flags & LO_FLAGS_AUTOCLEAR) !=
1345              (info->lo_flags & LO_FLAGS_AUTOCLEAR))
1346                 lo->lo_flags ^= LO_FLAGS_AUTOCLEAR;
1347 
1348         lo->lo_encrypt_key_size = info->lo_encrypt_key_size;
1349         lo->lo_init[0] = info->lo_init[0];
1350         lo->lo_init[1] = info->lo_init[1];
1351         if (info->lo_encrypt_key_size) {
1352                 memcpy(lo->lo_encrypt_key, info->lo_encrypt_key,
1353                        info->lo_encrypt_key_size);
1354                 lo->lo_key_owner = uid;
1355         }
1356 
1357         /* update dio if lo_offset or transfer is changed */
1358         __loop_update_dio(lo, lo->use_dio);
1359 
1360 out_unfreeze:
1361         blk_mq_unfreeze_queue(lo->lo_queue);
1362 
1363         if (!err && (info->lo_flags & LO_FLAGS_PARTSCAN) &&
1364              !(lo->lo_flags & LO_FLAGS_PARTSCAN)) {
1365                 lo->lo_flags |= LO_FLAGS_PARTSCAN;
1366                 lo->lo_disk->flags &= ~GENHD_FL_NO_PART_SCAN;
1367                 bdev = lo->lo_device;
1368                 partscan = true;
1369         }
1370 out_unlock:
1371         mutex_unlock(&loop_ctl_mutex);
1372         if (partscan)
1373                 loop_reread_partitions(lo, bdev);
1374 
1375         return err;
1376 }
1377 
1378 static int
1379 loop_get_status(struct loop_device *lo, struct loop_info64 *info)
1380 {
1381         struct path path;
1382         struct kstat stat;
1383         int ret;
1384 
1385         ret = mutex_lock_killable(&loop_ctl_mutex);
1386         if (ret)
1387                 return ret;
1388         if (lo->lo_state != Lo_bound) {
1389                 mutex_unlock(&loop_ctl_mutex);
1390                 return -ENXIO;
1391         }
1392 
1393         memset(info, 0, sizeof(*info));
1394         info->lo_number = lo->lo_number;
1395         info->lo_offset = lo->lo_offset;
1396         info->lo_sizelimit = lo->lo_sizelimit;
1397         info->lo_flags = lo->lo_flags;
1398         memcpy(info->lo_file_name, lo->lo_file_name, LO_NAME_SIZE);
1399         memcpy(info->lo_crypt_name, lo->lo_crypt_name, LO_NAME_SIZE);
1400         info->lo_encrypt_type =
1401                 lo->lo_encryption ? lo->lo_encryption->number : 0;
1402         if (lo->lo_encrypt_key_size && capable(CAP_SYS_ADMIN)) {
1403                 info->lo_encrypt_key_size = lo->lo_encrypt_key_size;
1404                 memcpy(info->lo_encrypt_key, lo->lo_encrypt_key,
1405                        lo->lo_encrypt_key_size);
1406         }
1407 
1408         /* Drop loop_ctl_mutex while we call into the filesystem. */
1409         path = lo->lo_backing_file->f_path;
1410         path_get(&path);
1411         mutex_unlock(&loop_ctl_mutex);
1412         ret = vfs_getattr(&path, &stat, STATX_INO, AT_STATX_SYNC_AS_STAT);
1413         if (!ret) {
1414                 info->lo_device = huge_encode_dev(stat.dev);
1415                 info->lo_inode = stat.ino;
1416                 info->lo_rdevice = huge_encode_dev(stat.rdev);
1417         }
1418         path_put(&path);
1419         return ret;
1420 }
1421 
1422 static void
1423 loop_info64_from_old(const struct loop_info *info, struct loop_info64 *info64)
1424 {
1425         memset(info64, 0, sizeof(*info64));
1426         info64->lo_number = info->lo_number;
1427         info64->lo_device = info->lo_device;
1428         info64->lo_inode = info->lo_inode;
1429         info64->lo_rdevice = info->lo_rdevice;
1430         info64->lo_offset = info->lo_offset;
1431         info64->lo_sizelimit = 0;
1432         info64->lo_encrypt_type = info->lo_encrypt_type;
1433         info64->lo_encrypt_key_size = info->lo_encrypt_key_size;
1434         info64->lo_flags = info->lo_flags;
1435         info64->lo_init[0] = info->lo_init[0];
1436         info64->lo_init[1] = info->lo_init[1];
1437         if (info->lo_encrypt_type == LO_CRYPT_CRYPTOAPI)
1438                 memcpy(info64->lo_crypt_name, info->lo_name, LO_NAME_SIZE);
1439         else
1440                 memcpy(info64->lo_file_name, info->lo_name, LO_NAME_SIZE);
1441         memcpy(info64->lo_encrypt_key, info->lo_encrypt_key, LO_KEY_SIZE);
1442 }
1443 
1444 static int
1445 loop_info64_to_old(const struct loop_info64 *info64, struct loop_info *info)
1446 {
1447         memset(info, 0, sizeof(*info));
1448         info->lo_number = info64->lo_number;
1449         info->lo_device = info64->lo_device;
1450         info->lo_inode = info64->lo_inode;
1451         info->lo_rdevice = info64->lo_rdevice;
1452         info->lo_offset = info64->lo_offset;
1453         info->lo_encrypt_type = info64->lo_encrypt_type;
1454         info->lo_encrypt_key_size = info64->lo_encrypt_key_size;
1455         info->lo_flags = info64->lo_flags;
1456         info->lo_init[0] = info64->lo_init[0];
1457         info->lo_init[1] = info64->lo_init[1];
1458         if (info->lo_encrypt_type == LO_CRYPT_CRYPTOAPI)
1459                 memcpy(info->lo_name, info64->lo_crypt_name, LO_NAME_SIZE);
1460         else
1461                 memcpy(info->lo_name, info64->lo_file_name, LO_NAME_SIZE);
1462         memcpy(info->lo_encrypt_key, info64->lo_encrypt_key, LO_KEY_SIZE);
1463 
1464         /* error in case values were truncated */
1465         if (info->lo_device != info64->lo_device ||
1466             info->lo_rdevice != info64->lo_rdevice ||
1467             info->lo_inode != info64->lo_inode ||
1468             info->lo_offset != info64->lo_offset)
1469                 return -EOVERFLOW;
1470 
1471         return 0;
1472 }
1473 
1474 static int
1475 loop_set_status_old(struct loop_device *lo, const struct loop_info __user *arg)
1476 {
1477         struct loop_info info;
1478         struct loop_info64 info64;
1479 
1480         if (copy_from_user(&info, arg, sizeof (struct loop_info)))
1481                 return -EFAULT;
1482         loop_info64_from_old(&info, &info64);
1483         return loop_set_status(lo, &info64);
1484 }
1485 
1486 static int
1487 loop_set_status64(struct loop_device *lo, const struct loop_info64 __user *arg)
1488 {
1489         struct loop_info64 info64;
1490 
1491         if (copy_from_user(&info64, arg, sizeof (struct loop_info64)))
1492                 return -EFAULT;
1493         return loop_set_status(lo, &info64);
1494 }
1495 
1496 static int
1497 loop_get_status_old(struct loop_device *lo, struct loop_info __user *arg) {
1498         struct loop_info info;
1499         struct loop_info64 info64;
1500         int err;
1501 
1502         if (!arg)
1503                 return -EINVAL;
1504         err = loop_get_status(lo, &info64);
1505         if (!err)
1506                 err = loop_info64_to_old(&info64, &info);
1507         if (!err && copy_to_user(arg, &info, sizeof(info)))
1508                 err = -EFAULT;
1509 
1510         return err;
1511 }
1512 
1513 static int
1514 loop_get_status64(struct loop_device *lo, struct loop_info64 __user *arg) {
1515         struct loop_info64 info64;
1516         int err;
1517 
1518         if (!arg)
1519                 return -EINVAL;
1520         err = loop_get_status(lo, &info64);
1521         if (!err && copy_to_user(arg, &info64, sizeof(info64)))
1522                 err = -EFAULT;
1523 
1524         return err;
1525 }
1526 
1527 static int loop_set_capacity(struct loop_device *lo)
1528 {
1529         if (unlikely(lo->lo_state != Lo_bound))
1530                 return -ENXIO;
1531 
1532         return figure_loop_size(lo, lo->lo_offset, lo->lo_sizelimit);
1533 }
1534 
1535 static int loop_set_dio(struct loop_device *lo, unsigned long arg)
1536 {
1537         int error = -ENXIO;
1538         if (lo->lo_state != Lo_bound)
1539                 goto out;
1540 
1541         __loop_update_dio(lo, !!arg);
1542         if (lo->use_dio == !!arg)
1543                 return 0;
1544         error = -EINVAL;
1545  out:
1546         return error;
1547 }
1548 
1549 static int loop_set_block_size(struct loop_device *lo, unsigned long arg)
1550 {
1551         int err = 0;
1552 
1553         if (lo->lo_state != Lo_bound)
1554                 return -ENXIO;
1555 
1556         if (arg < 512 || arg > PAGE_SIZE || !is_power_of_2(arg))
1557                 return -EINVAL;
1558 
1559         if (lo->lo_queue->limits.logical_block_size != arg) {
1560                 sync_blockdev(lo->lo_device);
1561                 kill_bdev(lo->lo_device);
1562         }
1563 
1564         blk_mq_freeze_queue(lo->lo_queue);
1565 
1566         /* kill_bdev should have truncated all the pages */
1567         if (lo->lo_queue->limits.logical_block_size != arg &&
1568                         lo->lo_device->bd_inode->i_mapping->nrpages) {
1569                 err = -EAGAIN;
1570                 pr_warn("%s: loop%d (%s) has still dirty pages (nrpages=%lu)\n",
1571                         __func__, lo->lo_number, lo->lo_file_name,
1572                         lo->lo_device->bd_inode->i_mapping->nrpages);
1573                 goto out_unfreeze;
1574         }
1575 
1576         blk_queue_logical_block_size(lo->lo_queue, arg);
1577         blk_queue_physical_block_size(lo->lo_queue, arg);
1578         blk_queue_io_min(lo->lo_queue, arg);
1579         loop_update_dio(lo);
1580 out_unfreeze:
1581         blk_mq_unfreeze_queue(lo->lo_queue);
1582 
1583         return err;
1584 }
1585 
1586 static int lo_simple_ioctl(struct loop_device *lo, unsigned int cmd,
1587                            unsigned long arg)
1588 {
1589         int err;
1590 
1591         err = mutex_lock_killable(&loop_ctl_mutex);
1592         if (err)
1593                 return err;
1594         switch (cmd) {
1595         case LOOP_SET_CAPACITY:
1596                 err = loop_set_capacity(lo);
1597                 break;
1598         case LOOP_SET_DIRECT_IO:
1599                 err = loop_set_dio(lo, arg);
1600                 break;
1601         case LOOP_SET_BLOCK_SIZE:
1602                 err = loop_set_block_size(lo, arg);
1603                 break;
1604         default:
1605                 err = lo->ioctl ? lo->ioctl(lo, cmd, arg) : -EINVAL;
1606         }
1607         mutex_unlock(&loop_ctl_mutex);
1608         return err;
1609 }
1610 
1611 static int lo_ioctl(struct block_device *bdev, fmode_t mode,
1612         unsigned int cmd, unsigned long arg)
1613 {
1614         struct loop_device *lo = bdev->bd_disk->private_data;
1615         int err;
1616 
1617         switch (cmd) {
1618         case LOOP_SET_FD:
1619                 return loop_set_fd(lo, mode, bdev, arg);
1620         case LOOP_CHANGE_FD:
1621                 return loop_change_fd(lo, bdev, arg);
1622         case LOOP_CLR_FD:
1623                 return loop_clr_fd(lo);
1624         case LOOP_SET_STATUS:
1625                 err = -EPERM;
1626                 if ((mode & FMODE_WRITE) || capable(CAP_SYS_ADMIN)) {
1627                         err = loop_set_status_old(lo,
1628                                         (struct loop_info __user *)arg);
1629                 }
1630                 break;
1631         case LOOP_GET_STATUS:
1632                 return loop_get_status_old(lo, (struct loop_info __user *) arg);
1633         case LOOP_SET_STATUS64:
1634                 err = -EPERM;
1635                 if ((mode & FMODE_WRITE) || capable(CAP_SYS_ADMIN)) {
1636                         err = loop_set_status64(lo,
1637                                         (struct loop_info64 __user *) arg);
1638                 }
1639                 break;
1640         case LOOP_GET_STATUS64:
1641                 return loop_get_status64(lo, (struct loop_info64 __user *) arg);
1642         case LOOP_SET_CAPACITY:
1643         case LOOP_SET_DIRECT_IO:
1644         case LOOP_SET_BLOCK_SIZE:
1645                 if (!(mode & FMODE_WRITE) && !capable(CAP_SYS_ADMIN))
1646                         return -EPERM;
1647                 /* Fall through */
1648         default:
1649                 err = lo_simple_ioctl(lo, cmd, arg);
1650                 break;
1651         }
1652 
1653         return err;
1654 }
1655 
1656 #ifdef CONFIG_COMPAT
1657 struct compat_loop_info {
1658         compat_int_t    lo_number;      /* ioctl r/o */
1659         compat_dev_t    lo_device;      /* ioctl r/o */
1660         compat_ulong_t  lo_inode;       /* ioctl r/o */
1661         compat_dev_t    lo_rdevice;     /* ioctl r/o */
1662         compat_int_t    lo_offset;
1663         compat_int_t    lo_encrypt_type;
1664         compat_int_t    lo_encrypt_key_size;    /* ioctl w/o */
1665         compat_int_t    lo_flags;       /* ioctl r/o */
1666         char            lo_name[LO_NAME_SIZE];
1667         unsigned char   lo_encrypt_key[LO_KEY_SIZE]; /* ioctl w/o */
1668         compat_ulong_t  lo_init[2];
1669         char            reserved[4];
1670 };
1671 
1672 /*
1673  * Transfer 32-bit compatibility structure in userspace to 64-bit loop info
1674  * - noinlined to reduce stack space usage in main part of driver
1675  */
1676 static noinline int
1677 loop_info64_from_compat(const struct compat_loop_info __user *arg,
1678                         struct loop_info64 *info64)
1679 {
1680         struct compat_loop_info info;
1681 
1682         if (copy_from_user(&info, arg, sizeof(info)))
1683                 return -EFAULT;
1684 
1685         memset(info64, 0, sizeof(*info64));
1686         info64->lo_number = info.lo_number;
1687         info64->lo_device = info.lo_device;
1688         info64->lo_inode = info.lo_inode;
1689         info64->lo_rdevice = info.lo_rdevice;
1690         info64->lo_offset = info.lo_offset;
1691         info64->lo_sizelimit = 0;
1692         info64->lo_encrypt_type = info.lo_encrypt_type;
1693         info64->lo_encrypt_key_size = info.lo_encrypt_key_size;
1694         info64->lo_flags = info.lo_flags;
1695         info64->lo_init[0] = info.lo_init[0];
1696         info64->lo_init[1] = info.lo_init[1];
1697         if (info.lo_encrypt_type == LO_CRYPT_CRYPTOAPI)
1698                 memcpy(info64->lo_crypt_name, info.lo_name, LO_NAME_SIZE);
1699         else
1700                 memcpy(info64->lo_file_name, info.lo_name, LO_NAME_SIZE);
1701         memcpy(info64->lo_encrypt_key, info.lo_encrypt_key, LO_KEY_SIZE);
1702         return 0;
1703 }
1704 
1705 /*
1706  * Transfer 64-bit loop info to 32-bit compatibility structure in userspace
1707  * - noinlined to reduce stack space usage in main part of driver
1708  */
1709 static noinline int
1710 loop_info64_to_compat(const struct loop_info64 *info64,
1711                       struct compat_loop_info __user *arg)
1712 {
1713         struct compat_loop_info info;
1714 
1715         memset(&info, 0, sizeof(info));
1716         info.lo_number = info64->lo_number;
1717         info.lo_device = info64->lo_device;
1718         info.lo_inode = info64->lo_inode;
1719         info.lo_rdevice = info64->lo_rdevice;
1720         info.lo_offset = info64->lo_offset;
1721         info.lo_encrypt_type = info64->lo_encrypt_type;
1722         info.lo_encrypt_key_size = info64->lo_encrypt_key_size;
1723         info.lo_flags = info64->lo_flags;
1724         info.lo_init[0] = info64->lo_init[0];
1725         info.lo_init[1] = info64->lo_init[1];
1726         if (info.lo_encrypt_type == LO_CRYPT_CRYPTOAPI)
1727                 memcpy(info.lo_name, info64->lo_crypt_name, LO_NAME_SIZE);
1728         else
1729                 memcpy(info.lo_name, info64->lo_file_name, LO_NAME_SIZE);
1730         memcpy(info.lo_encrypt_key, info64->lo_encrypt_key, LO_KEY_SIZE);
1731 
1732         /* error in case values were truncated */
1733         if (info.lo_device != info64->lo_device ||
1734             info.lo_rdevice != info64->lo_rdevice ||
1735             info.lo_inode != info64->lo_inode ||
1736             info.lo_offset != info64->lo_offset ||
1737             info.lo_init[0] != info64->lo_init[0] ||
1738             info.lo_init[1] != info64->lo_init[1])
1739                 return -EOVERFLOW;
1740 
1741         if (copy_to_user(arg, &info, sizeof(info)))
1742                 return -EFAULT;
1743         return 0;
1744 }
1745 
1746 static int
1747 loop_set_status_compat(struct loop_device *lo,
1748                        const struct compat_loop_info __user *arg)
1749 {
1750         struct loop_info64 info64;
1751         int ret;
1752 
1753         ret = loop_info64_from_compat(arg, &info64);
1754         if (ret < 0)
1755                 return ret;
1756         return loop_set_status(lo, &info64);
1757 }
1758 
1759 static int
1760 loop_get_status_compat(struct loop_device *lo,
1761                        struct compat_loop_info __user *arg)
1762 {
1763         struct loop_info64 info64;
1764         int err;
1765 
1766         if (!arg)
1767                 return -EINVAL;
1768         err = loop_get_status(lo, &info64);
1769         if (!err)
1770                 err = loop_info64_to_compat(&info64, arg);
1771         return err;
1772 }
1773 
1774 static int lo_compat_ioctl(struct block_device *bdev, fmode_t mode,
1775                            unsigned int cmd, unsigned long arg)
1776 {
1777         struct loop_device *lo = bdev->bd_disk->private_data;
1778         int err;
1779 
1780         switch(cmd) {
1781         case LOOP_SET_STATUS:
1782                 err = loop_set_status_compat(lo,
1783                              (const struct compat_loop_info __user *)arg);
1784                 break;
1785         case LOOP_GET_STATUS:
1786                 err = loop_get_status_compat(lo,
1787                                      (struct compat_loop_info __user *)arg);
1788                 break;
1789         case LOOP_SET_CAPACITY:
1790         case LOOP_CLR_FD:
1791         case LOOP_GET_STATUS64:
1792         case LOOP_SET_STATUS64:
1793                 arg = (unsigned long) compat_ptr(arg);
1794                 /* fall through */
1795         case LOOP_SET_FD:
1796         case LOOP_CHANGE_FD:
1797         case LOOP_SET_BLOCK_SIZE:
1798         case LOOP_SET_DIRECT_IO:
1799                 err = lo_ioctl(bdev, mode, cmd, arg);
1800                 break;
1801         default:
1802                 err = -ENOIOCTLCMD;
1803                 break;
1804         }
1805         return err;
1806 }
1807 #endif
1808 
1809 static int lo_open(struct block_device *bdev, fmode_t mode)
1810 {
1811         struct loop_device *lo;
1812         int err;
1813 
1814         err = mutex_lock_killable(&loop_ctl_mutex);
1815         if (err)
1816                 return err;
1817         lo = bdev->bd_disk->private_data;
1818         if (!lo) {
1819                 err = -ENXIO;
1820                 goto out;
1821         }
1822 
1823         atomic_inc(&lo->lo_refcnt);
1824 out:
1825         mutex_unlock(&loop_ctl_mutex);
1826         return err;
1827 }
1828 
1829 static void lo_release(struct gendisk *disk, fmode_t mode)
1830 {
1831         struct loop_device *lo;
1832 
1833         mutex_lock(&loop_ctl_mutex);
1834         lo = disk->private_data;
1835         if (atomic_dec_return(&lo->lo_refcnt))
1836                 goto out_unlock;
1837 
1838         if (lo->lo_flags & LO_FLAGS_AUTOCLEAR) {
1839                 if (lo->lo_state != Lo_bound)
1840                         goto out_unlock;
1841                 lo->lo_state = Lo_rundown;
1842                 mutex_unlock(&loop_ctl_mutex);
1843                 /*
1844                  * In autoclear mode, stop the loop thread
1845                  * and remove configuration after last close.
1846                  */
1847                 __loop_clr_fd(lo, true);
1848                 return;
1849         } else if (lo->lo_state == Lo_bound) {
1850                 /*
1851                  * Otherwise keep thread (if running) and config,
1852                  * but flush possible ongoing bios in thread.
1853                  */
1854                 blk_mq_freeze_queue(lo->lo_queue);
1855                 blk_mq_unfreeze_queue(lo->lo_queue);
1856         }
1857 
1858 out_unlock:
1859         mutex_unlock(&loop_ctl_mutex);
1860 }
1861 
1862 static const struct block_device_operations lo_fops = {
1863         .owner =        THIS_MODULE,
1864         .open =         lo_open,
1865         .release =      lo_release,
1866         .ioctl =        lo_ioctl,
1867 #ifdef CONFIG_COMPAT
1868         .compat_ioctl = lo_compat_ioctl,
1869 #endif
1870 };
1871 
1872 /*
1873  * And now the modules code and kernel interface.
1874  */
1875 static int max_loop;
1876 module_param(max_loop, int, 0444);
1877 MODULE_PARM_DESC(max_loop, "Maximum number of loop devices");
1878 module_param(max_part, int, 0444);
1879 MODULE_PARM_DESC(max_part, "Maximum number of partitions per loop device");
1880 MODULE_LICENSE("GPL");
1881 MODULE_ALIAS_BLOCKDEV_MAJOR(LOOP_MAJOR);
1882 
1883 int loop_register_transfer(struct loop_func_table *funcs)
1884 {
1885         unsigned int n = funcs->number;
1886 
1887         if (n >= MAX_LO_CRYPT || xfer_funcs[n])
1888                 return -EINVAL;
1889         xfer_funcs[n] = funcs;
1890         return 0;
1891 }
1892 
1893 static int unregister_transfer_cb(int id, void *ptr, void *data)
1894 {
1895         struct loop_device *lo = ptr;
1896         struct loop_func_table *xfer = data;
1897 
1898         mutex_lock(&loop_ctl_mutex);
1899         if (lo->lo_encryption == xfer)
1900                 loop_release_xfer(lo);
1901         mutex_unlock(&loop_ctl_mutex);
1902         return 0;
1903 }
1904 
1905 int loop_unregister_transfer(int number)
1906 {
1907         unsigned int n = number;
1908         struct loop_func_table *xfer;
1909 
1910         if (n == 0 || n >= MAX_LO_CRYPT || (xfer = xfer_funcs[n]) == NULL)
1911                 return -EINVAL;
1912 
1913         xfer_funcs[n] = NULL;
1914         idr_for_each(&loop_index_idr, &unregister_transfer_cb, xfer);
1915         return 0;
1916 }
1917 
1918 EXPORT_SYMBOL(loop_register_transfer);
1919 EXPORT_SYMBOL(loop_unregister_transfer);
1920 
1921 static blk_status_t loop_queue_rq(struct blk_mq_hw_ctx *hctx,
1922                 const struct blk_mq_queue_data *bd)
1923 {
1924         struct request *rq = bd->rq;
1925         struct loop_cmd *cmd = blk_mq_rq_to_pdu(rq);
1926         struct loop_device *lo = rq->q->queuedata;
1927 
1928         blk_mq_start_request(rq);
1929 
1930         if (lo->lo_state != Lo_bound)
1931                 return BLK_STS_IOERR;
1932 
1933         switch (req_op(rq)) {
1934         case REQ_OP_FLUSH:
1935         case REQ_OP_DISCARD:
1936         case REQ_OP_WRITE_ZEROES:
1937                 cmd->use_aio = false;
1938                 break;
1939         default:
1940                 cmd->use_aio = lo->use_dio;
1941                 break;
1942         }
1943 
1944         /* always use the first bio's css */
1945 #ifdef CONFIG_BLK_CGROUP
1946         if (cmd->use_aio && rq->bio && rq->bio->bi_blkg) {
1947                 cmd->css = &bio_blkcg(rq->bio)->css;
1948                 css_get(cmd->css);
1949         } else
1950 #endif
1951                 cmd->css = NULL;
1952         kthread_queue_work(&lo->worker, &cmd->work);
1953 
1954         return BLK_STS_OK;
1955 }
1956 
1957 static void loop_handle_cmd(struct loop_cmd *cmd)
1958 {
1959         struct request *rq = blk_mq_rq_from_pdu(cmd);
1960         const bool write = op_is_write(req_op(rq));
1961         struct loop_device *lo = rq->q->queuedata;
1962         int ret = 0;
1963 
1964         if (write && (lo->lo_flags & LO_FLAGS_READ_ONLY)) {
1965                 ret = -EIO;
1966                 goto failed;
1967         }
1968 
1969         ret = do_req_filebacked(lo, rq);
1970  failed:
1971         /* complete non-aio request */
1972         if (!cmd->use_aio || ret) {
1973                 cmd->ret = ret ? -EIO : 0;
1974                 blk_mq_complete_request(rq);
1975         }
1976 }
1977 
1978 static void loop_queue_work(struct kthread_work *work)
1979 {
1980         struct loop_cmd *cmd =
1981                 container_of(work, struct loop_cmd, work);
1982 
1983         loop_handle_cmd(cmd);
1984 }
1985 
1986 static int loop_init_request(struct blk_mq_tag_set *set, struct request *rq,
1987                 unsigned int hctx_idx, unsigned int numa_node)
1988 {
1989         struct loop_cmd *cmd = blk_mq_rq_to_pdu(rq);
1990 
1991         kthread_init_work(&cmd->work, loop_queue_work);
1992         return 0;
1993 }
1994 
1995 static const struct blk_mq_ops loop_mq_ops = {
1996         .queue_rq       = loop_queue_rq,
1997         .init_request   = loop_init_request,
1998         .complete       = lo_complete_rq,
1999 };
2000 
2001 static int loop_add(struct loop_device **l, int i)
2002 {
2003         struct loop_device *lo;
2004         struct gendisk *disk;
2005         int err;
2006 
2007         err = -ENOMEM;
2008         lo = kzalloc(sizeof(*lo), GFP_KERNEL);
2009         if (!lo)
2010                 goto out;
2011 
2012         lo->lo_state = Lo_unbound;
2013 
2014         /* allocate id, if @id >= 0, we're requesting that specific id */
2015         if (i >= 0) {
2016                 err = idr_alloc(&loop_index_idr, lo, i, i + 1, GFP_KERNEL);
2017                 if (err == -ENOSPC)
2018                         err = -EEXIST;
2019         } else {
2020                 err = idr_alloc(&loop_index_idr, lo, 0, 0, GFP_KERNEL);
2021         }
2022         if (err < 0)
2023                 goto out_free_dev;
2024         i = err;
2025 
2026         err = -ENOMEM;
2027         lo->tag_set.ops = &loop_mq_ops;
2028         lo->tag_set.nr_hw_queues = 1;
2029         lo->tag_set.queue_depth = 128;
2030         lo->tag_set.numa_node = NUMA_NO_NODE;
2031         lo->tag_set.cmd_size = sizeof(struct loop_cmd);
2032         lo->tag_set.flags = BLK_MQ_F_SHOULD_MERGE;
2033         lo->tag_set.driver_data = lo;
2034 
2035         err = blk_mq_alloc_tag_set(&lo->tag_set);
2036         if (err)
2037                 goto out_free_idr;
2038 
2039         lo->lo_queue = blk_mq_init_queue(&lo->tag_set);
2040         if (IS_ERR(lo->lo_queue)) {
2041                 err = PTR_ERR(lo->lo_queue);
2042                 goto out_cleanup_tags;
2043         }
2044         lo->lo_queue->queuedata = lo;
2045 
2046         blk_queue_max_hw_sectors(lo->lo_queue, BLK_DEF_MAX_SECTORS);
2047 
2048         /*
2049          * By default, we do buffer IO, so it doesn't make sense to enable
2050          * merge because the I/O submitted to backing file is handled page by
2051          * page. For directio mode, merge does help to dispatch bigger request
2052          * to underlayer disk. We will enable merge once directio is enabled.
2053          */
2054         blk_queue_flag_set(QUEUE_FLAG_NOMERGES, lo->lo_queue);
2055 
2056         err = -ENOMEM;
2057         disk = lo->lo_disk = alloc_disk(1 << part_shift);
2058         if (!disk)
2059                 goto out_free_queue;
2060 
2061         /*
2062          * Disable partition scanning by default. The in-kernel partition
2063          * scanning can be requested individually per-device during its
2064          * setup. Userspace can always add and remove partitions from all
2065          * devices. The needed partition minors are allocated from the
2066          * extended minor space, the main loop device numbers will continue
2067          * to match the loop minors, regardless of the number of partitions
2068          * used.
2069          *
2070          * If max_part is given, partition scanning is globally enabled for
2071          * all loop devices. The minors for the main loop devices will be
2072          * multiples of max_part.
2073          *
2074          * Note: Global-for-all-devices, set-only-at-init, read-only module
2075          * parameteters like 'max_loop' and 'max_part' make things needlessly
2076          * complicated, are too static, inflexible and may surprise
2077          * userspace tools. Parameters like this in general should be avoided.
2078          */
2079         if (!part_shift)
2080                 disk->flags |= GENHD_FL_NO_PART_SCAN;
2081         disk->flags |= GENHD_FL_EXT_DEVT;
2082         atomic_set(&lo->lo_refcnt, 0);
2083         lo->lo_number           = i;
2084         spin_lock_init(&lo->lo_lock);
2085         disk->major             = LOOP_MAJOR;
2086         disk->first_minor       = i << part_shift;
2087         disk->fops              = &lo_fops;
2088         disk->private_data      = lo;
2089         disk->queue             = lo->lo_queue;
2090         sprintf(disk->disk_name, "loop%d", i);
2091         add_disk(disk);
2092         *l = lo;
2093         return lo->lo_number;
2094 
2095 out_free_queue:
2096         blk_cleanup_queue(lo->lo_queue);
2097 out_cleanup_tags:
2098         blk_mq_free_tag_set(&lo->tag_set);
2099 out_free_idr:
2100         idr_remove(&loop_index_idr, i);
2101 out_free_dev:
2102         kfree(lo);
2103 out:
2104         return err;
2105 }
2106 
2107 static void loop_remove(struct loop_device *lo)
2108 {
2109         del_gendisk(lo->lo_disk);
2110         blk_cleanup_queue(lo->lo_queue);
2111         blk_mq_free_tag_set(&lo->tag_set);
2112         put_disk(lo->lo_disk);
2113         kfree(lo);
2114 }
2115 
2116 static int find_free_cb(int id, void *ptr, void *data)
2117 {
2118         struct loop_device *lo = ptr;
2119         struct loop_device **l = data;
2120 
2121         if (lo->lo_state == Lo_unbound) {
2122                 *l = lo;
2123                 return 1;
2124         }
2125         return 0;
2126 }
2127 
2128 static int loop_lookup(struct loop_device **l, int i)
2129 {
2130         struct loop_device *lo;
2131         int ret = -ENODEV;
2132 
2133         if (i < 0) {
2134                 int err;
2135 
2136                 err = idr_for_each(&loop_index_idr, &find_free_cb, &lo);
2137                 if (err == 1) {
2138                         *l = lo;
2139                         ret = lo->lo_number;
2140                 }
2141                 goto out;
2142         }
2143 
2144         /* lookup and return a specific i */
2145         lo = idr_find(&loop_index_idr, i);
2146         if (lo) {
2147                 *l = lo;
2148                 ret = lo->lo_number;
2149         }
2150 out:
2151         return ret;
2152 }
2153 
2154 static struct kobject *loop_probe(dev_t dev, int *part, void *data)
2155 {
2156         struct loop_device *lo;
2157         struct kobject *kobj;
2158         int err;
2159 
2160         mutex_lock(&loop_ctl_mutex);
2161         err = loop_lookup(&lo, MINOR(dev) >> part_shift);
2162         if (err < 0)
2163                 err = loop_add(&lo, MINOR(dev) >> part_shift);
2164         if (err < 0)
2165                 kobj = NULL;
2166         else
2167                 kobj = get_disk_and_module(lo->lo_disk);
2168         mutex_unlock(&loop_ctl_mutex);
2169 
2170         *part = 0;
2171         return kobj;
2172 }
2173 
2174 static long loop_control_ioctl(struct file *file, unsigned int cmd,
2175                                unsigned long parm)
2176 {
2177         struct loop_device *lo;
2178         int ret;
2179 
2180         ret = mutex_lock_killable(&loop_ctl_mutex);
2181         if (ret)
2182                 return ret;
2183 
2184         ret = -ENOSYS;
2185         switch (cmd) {
2186         case LOOP_CTL_ADD:
2187                 ret = loop_lookup(&lo, parm);
2188                 if (ret >= 0) {
2189                         ret = -EEXIST;
2190                         break;
2191                 }
2192                 ret = loop_add(&lo, parm);
2193                 break;
2194         case LOOP_CTL_REMOVE:
2195                 ret = loop_lookup(&lo, parm);
2196                 if (ret < 0)
2197                         break;
2198                 if (lo->lo_state != Lo_unbound) {
2199                         ret = -EBUSY;
2200                         break;
2201                 }
2202                 if (atomic_read(&lo->lo_refcnt) > 0) {
2203                         ret = -EBUSY;
2204                         break;
2205                 }
2206                 lo->lo_disk->private_data = NULL;
2207                 idr_remove(&loop_index_idr, lo->lo_number);
2208                 loop_remove(lo);
2209                 break;
2210         case LOOP_CTL_GET_FREE:
2211                 ret = loop_lookup(&lo, -1);
2212                 if (ret >= 0)
2213                         break;
2214                 ret = loop_add(&lo, -1);
2215         }
2216         mutex_unlock(&loop_ctl_mutex);
2217 
2218         return ret;
2219 }
2220 
2221 static const struct file_operations loop_ctl_fops = {
2222         .open           = nonseekable_open,
2223         .unlocked_ioctl = loop_control_ioctl,
2224         .compat_ioctl   = loop_control_ioctl,
2225         .owner          = THIS_MODULE,
2226         .llseek         = noop_llseek,
2227 };
2228 
2229 static struct miscdevice loop_misc = {
2230         .minor          = LOOP_CTRL_MINOR,
2231         .name           = "loop-control",
2232         .fops           = &loop_ctl_fops,
2233 };
2234 
2235 MODULE_ALIAS_MISCDEV(LOOP_CTRL_MINOR);
2236 MODULE_ALIAS("devname:loop-control");
2237 
2238 static int __init loop_init(void)
2239 {
2240         int i, nr;
2241         unsigned long range;
2242         struct loop_device *lo;
2243         int err;
2244 
2245         part_shift = 0;
2246         if (max_part > 0) {
2247                 part_shift = fls(max_part);
2248 
2249                 /*
2250                  * Adjust max_part according to part_shift as it is exported
2251                  * to user space so that user can decide correct minor number
2252                  * if [s]he want to create more devices.
2253                  *
2254                  * Note that -1 is required because partition 0 is reserved
2255                  * for the whole disk.
2256                  */
2257                 max_part = (1UL << part_shift) - 1;
2258         }
2259 
2260         if ((1UL << part_shift) > DISK_MAX_PARTS) {
2261                 err = -EINVAL;
2262                 goto err_out;
2263         }
2264 
2265         if (max_loop > 1UL << (MINORBITS - part_shift)) {
2266                 err = -EINVAL;
2267                 goto err_out;
2268         }
2269 
2270         /*
2271          * If max_loop is specified, create that many devices upfront.
2272          * This also becomes a hard limit. If max_loop is not specified,
2273          * create CONFIG_BLK_DEV_LOOP_MIN_COUNT loop devices at module
2274          * init time. Loop devices can be requested on-demand with the
2275          * /dev/loop-control interface, or be instantiated by accessing
2276          * a 'dead' device node.
2277          */
2278         if (max_loop) {
2279                 nr = max_loop;
2280                 range = max_loop << part_shift;
2281         } else {
2282                 nr = CONFIG_BLK_DEV_LOOP_MIN_COUNT;
2283                 range = 1UL << MINORBITS;
2284         }
2285 
2286         err = misc_register(&loop_misc);
2287         if (err < 0)
2288                 goto err_out;
2289 
2290 
2291         if (register_blkdev(LOOP_MAJOR, "loop")) {
2292                 err = -EIO;
2293                 goto misc_out;
2294         }
2295 
2296         blk_register_region(MKDEV(LOOP_MAJOR, 0), range,
2297                                   THIS_MODULE, loop_probe, NULL, NULL);
2298 
2299         /* pre-create number of devices given by config or max_loop */
2300         mutex_lock(&loop_ctl_mutex);
2301         for (i = 0; i < nr; i++)
2302                 loop_add(&lo, i);
2303         mutex_unlock(&loop_ctl_mutex);
2304 
2305         printk(KERN_INFO "loop: module loaded\n");
2306         return 0;
2307 
2308 misc_out:
2309         misc_deregister(&loop_misc);
2310 err_out:
2311         return err;
2312 }
2313 
2314 static int loop_exit_cb(int id, void *ptr, void *data)
2315 {
2316         struct loop_device *lo = ptr;
2317 
2318         loop_remove(lo);
2319         return 0;
2320 }
2321 
2322 static void __exit loop_exit(void)
2323 {
2324         unsigned long range;
2325 
2326         range = max_loop ? max_loop << part_shift : 1UL << MINORBITS;
2327 
2328         idr_for_each(&loop_index_idr, &loop_exit_cb, NULL);
2329         idr_destroy(&loop_index_idr);
2330 
2331         blk_unregister_region(MKDEV(LOOP_MAJOR, 0), range);
2332         unregister_blkdev(LOOP_MAJOR, "loop");
2333 
2334         misc_deregister(&loop_misc);
2335 }
2336 
2337 module_init(loop_init);
2338 module_exit(loop_exit);
2339 
2340 #ifndef MODULE
2341 static int __init max_loop_setup(char *str)
2342 {
2343         max_loop = simple_strtol(str, NULL, 0);
2344         return 1;
2345 }
2346 
2347 __setup("max_loop=", max_loop_setup);
2348 #endif
/* [<][>][^][v][top][bottom][index][help] */
root/drivers/block/loop.c

DEFINITIONS
