drivers/md/dm-log-writes.c

   1 /*
   2  * Copyright (C) 2014 Facebook. All rights reserved.
   3  *
   4  * This file is released under the GPL.
   5  */
   6
   7 #include <linux/device-mapper.h>
   8
   9 #include <linux/module.h>
  10 #include <linux/init.h>
  11 #include <linux/blkdev.h>
  12 #include <linux/bio.h>
  13 #include <linux/slab.h>
  14 #include <linux/kthread.h>
  15 #include <linux/freezer.h>
  16
  17 #define DM_MSG_PREFIX "log-writes"
  18
  19 /*
  20  * This target will sequentially log all writes to the target device onto the
  21  * log device.  This is helpful for replaying writes to check for fs consistency
  22  * at all times.  This target provides a mechanism to mark specific events to
  23  * check data at a later time.  So for example you would:
  24  *
  25  * write data
  26  * fsync
  27  * dmsetup message /dev/whatever mark mymark
  28  * unmount /mnt/test
  29  *
  30  * Then replay the log up to mymark and check the contents of the replay to
  31  * verify it matches what was written.
  32  *
  33  * We log writes only after they have been flushed, this makes the log describe
  34  * close to the order in which the data hits the actual disk, not its cache.  So
  35  * for example the following sequence (W means write, C means complete)
  36  *
  37  * Wa,Wb,Wc,Cc,Ca,FLUSH,FUAd,Cb,CFLUSH,CFUAd
  38  *
  39  * Would result in the log looking like this:
  40  *
  41  * c,a,flush,fuad,b,<other writes>,<next flush>
  42  *
  43  * This is meant to help expose problems where file systems do not properly wait
  44  * on data being written before invoking a FLUSH.  FUA bypasses cache so once it
  45  * completes it is added to the log as it should be on disk.
  46  *
  47  * We treat DISCARDs as if they don't bypass cache so that they are logged in
  48  * order of completion along with the normal writes.  If we didn't do it this
  49  * way we would process all the discards first and then write all the data, when
  50  * in fact we want to do the data and the discard in the order that they
  51  * completed.
  52  */
  53 #define LOG_FLUSH_FLAG (1 << 0)
  54 #define LOG_FUA_FLAG (1 << 1)
  55 #define LOG_DISCARD_FLAG (1 << 2)
  56 #define LOG_MARK_FLAG (1 << 3)
  57
  58 #define WRITE_LOG_VERSION 1ULL
  59 #define WRITE_LOG_MAGIC 0x6a736677736872ULL
  60 #define WRITE_LOG_SUPER_SECTOR 0
  61
  62 /*
  63  * The disk format for this is braindead simple.
  64  *
  65  * At byte 0 we have our super, followed by the following sequence for
  66  * nr_entries:
  67  *
  68  * [   1 sector    ][  entry->nr_sectors ]
  69  * [log_write_entry][    data written    ]
  70  *
  71  * The log_write_entry takes up a full sector so we can have arbitrary length
  72  * marks and it leaves us room for extra content in the future.
  73  */
  74
  75 /*
  76  * Basic info about the log for userspace.
  77  */
  78 struct log_write_super {
  79         __le64 magic;
  80         __le64 version;
  81         __le64 nr_entries;
  82         __le32 sectorsize;
  83 };
  84
  85 /*
  86  * sector - the sector we wrote.
  87  * nr_sectors - the number of sectors we wrote.
  88  * flags - flags for this log entry.
  89  * data_len - the size of the data in this log entry, this is for private log
  90  * entry stuff, the MARK data provided by userspace for example.
  91  */
  92 struct log_write_entry {
  93         __le64 sector;
  94         __le64 nr_sectors;
  95         __le64 flags;
  96         __le64 data_len;
  97 };
  98
  99 struct log_writes_c {
 100         struct dm_dev *dev;
 101         struct dm_dev *logdev;
 102         u64 logged_entries;
 103         u32 sectorsize;
 104         u32 sectorshift;
 105         atomic_t io_blocks;
 106         atomic_t pending_blocks;
 107         sector_t next_sector;
 108         sector_t end_sector;
 109         bool logging_enabled;
 110         bool device_supports_discard;
 111         spinlock_t blocks_lock;
 112         struct list_head unflushed_blocks;
 113         struct list_head logging_blocks;
 114         wait_queue_head_t wait;
 115         struct task_struct *log_kthread;
 116         struct completion super_done;
 117 };
 118
 119 struct pending_block {
 120         int vec_cnt;
 121         u64 flags;
 122         sector_t sector;
 123         sector_t nr_sectors;
 124         char *data;
 125         u32 datalen;
 126         struct list_head list;
 127         struct bio_vec vecs[0];
 128 };
 129
 130 struct per_bio_data {
 131         struct pending_block *block;
 132 };
 133
 134 static inline sector_t bio_to_dev_sectors(struct log_writes_c *lc,
 135                                           sector_t sectors)
 136 {
 137         return sectors >> (lc->sectorshift - SECTOR_SHIFT);
 138 }
 139
 140 static inline sector_t dev_to_bio_sectors(struct log_writes_c *lc,
 141                                           sector_t sectors)
 142 {
 143         return sectors << (lc->sectorshift - SECTOR_SHIFT);
 144 }
 145
 146 static void put_pending_block(struct log_writes_c *lc)
 147 {
 148         if (atomic_dec_and_test(&lc->pending_blocks)) {
 149                 smp_mb__after_atomic();
 150                 if (waitqueue_active(&lc->wait))
 151                         wake_up(&lc->wait);
 152         }
 153 }
 154
 155 static void put_io_block(struct log_writes_c *lc)
 156 {
 157         if (atomic_dec_and_test(&lc->io_blocks)) {
 158                 smp_mb__after_atomic();
 159                 if (waitqueue_active(&lc->wait))
 160                         wake_up(&lc->wait);
 161         }
 162 }
 163
 164 static void log_end_io(struct bio *bio)
 165 {
 166         struct log_writes_c *lc = bio->bi_private;
 167
 168         if (bio->bi_status) {
 169                 unsigned long flags;
 170
 171                 DMERR("Error writing log block, error=%d", bio->bi_status);
 172                 spin_lock_irqsave(&lc->blocks_lock, flags);
 173                 lc->logging_enabled = false;
 174                 spin_unlock_irqrestore(&lc->blocks_lock, flags);
 175         }
 176
 177         bio_free_pages(bio);
 178         put_io_block(lc);
 179         bio_put(bio);
 180 }
 181
 182 static void log_end_super(struct bio *bio)
 183 {
 184         struct log_writes_c *lc = bio->bi_private;
 185
 186         complete(&lc->super_done);
 187         log_end_io(bio);
 188 }
 189
 190 /*
 191  * Meant to be called if there is an error, it will free all the pages
 192  * associated with the block.
 193  */
 194 static void free_pending_block(struct log_writes_c *lc,
 195                                struct pending_block *block)
 196 {
 197         int i;
 198
 199         for (i = 0; i < block->vec_cnt; i++) {
 200                 if (block->vecs[i].bv_page)
 201                         __free_page(block->vecs[i].bv_page);
 202         }
 203         kfree(block->data);
 204         kfree(block);
 205         put_pending_block(lc);
 206 }
 207
 208 static int write_metadata(struct log_writes_c *lc, void *entry,
 209                           size_t entrylen, void *data, size_t datalen,
 210                           sector_t sector)
 211 {
 212         struct bio *bio;
 213         struct page *page;
 214         void *ptr;
 215         size_t ret;
 216
 217         bio = bio_alloc(GFP_KERNEL, 1);
 218         if (!bio) {
 219                 DMERR("Couldn't alloc log bio");
 220                 goto error;
 221         }
 222         bio->bi_iter.bi_size = 0;
 223         bio->bi_iter.bi_sector = sector;
 224         bio_set_dev(bio, lc->logdev->bdev);
 225         bio->bi_end_io = (sector == WRITE_LOG_SUPER_SECTOR) ?
 226                           log_end_super : log_end_io;
 227         bio->bi_private = lc;
 228         bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
 229
 230         page = alloc_page(GFP_KERNEL);
 231         if (!page) {
 232                 DMERR("Couldn't alloc log page");
 233                 bio_put(bio);
 234                 goto error;
 235         }
 236
 237         ptr = kmap_atomic(page);
 238         memcpy(ptr, entry, entrylen);
 239         if (datalen)
 240                 memcpy(ptr + entrylen, data, datalen);
 241         memset(ptr + entrylen + datalen, 0,
 242                lc->sectorsize - entrylen - datalen);
 243         kunmap_atomic(ptr);
 244
 245         ret = bio_add_page(bio, page, lc->sectorsize, 0);
 246         if (ret != lc->sectorsize) {
 247                 DMERR("Couldn't add page to the log block");
 248                 goto error_bio;
 249         }
 250         submit_bio(bio);
 251         return 0;
 252 error_bio:
 253         bio_put(bio);
 254         __free_page(page);
 255 error:
 256         put_io_block(lc);
 257         return -1;
 258 }
 259
 260 static int log_one_block(struct log_writes_c *lc,
 261                          struct pending_block *block, sector_t sector)
 262 {
 263         struct bio *bio;
 264         struct log_write_entry entry;
 265         size_t ret;
 266         int i;
 267
 268         entry.sector = cpu_to_le64(block->sector);
 269         entry.nr_sectors = cpu_to_le64(block->nr_sectors);
 270         entry.flags = cpu_to_le64(block->flags);
 271         entry.data_len = cpu_to_le64(block->datalen);
 272         if (write_metadata(lc, &entry, sizeof(entry), block->data,
 273                            block->datalen, sector)) {
 274                 free_pending_block(lc, block);
 275                 return -1;
 276         }
 277
 278         if (!block->vec_cnt)
 279                 goto out;
 280         sector += dev_to_bio_sectors(lc, 1);
 281
 282         atomic_inc(&lc->io_blocks);
 283         bio = bio_alloc(GFP_KERNEL, min(block->vec_cnt, BIO_MAX_PAGES));
 284         if (!bio) {
 285                 DMERR("Couldn't alloc log bio");
 286                 goto error;
 287         }
 288         bio->bi_iter.bi_size = 0;
 289         bio->bi_iter.bi_sector = sector;
 290         bio_set_dev(bio, lc->logdev->bdev);
 291         bio->bi_end_io = log_end_io;
 292         bio->bi_private = lc;
 293         bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
 294
 295         for (i = 0; i < block->vec_cnt; i++) {
 296                 /*
 297                  * The page offset is always 0 because we allocate a new page
 298                  * for every bvec in the original bio for simplicity sake.
 299                  */
 300                 ret = bio_add_page(bio, block->vecs[i].bv_page,
 301                                    block->vecs[i].bv_len, 0);
 302                 if (ret != block->vecs[i].bv_len) {
 303                         atomic_inc(&lc->io_blocks);
 304                         submit_bio(bio);
 305                         bio = bio_alloc(GFP_KERNEL, min(block->vec_cnt - i, BIO_MAX_PAGES));
 306                         if (!bio) {
 307                                 DMERR("Couldn't alloc log bio");
 308                                 goto error;
 309                         }
 310                         bio->bi_iter.bi_size = 0;
 311                         bio->bi_iter.bi_sector = sector;
 312                         bio_set_dev(bio, lc->logdev->bdev);
 313                         bio->bi_end_io = log_end_io;
 314                         bio->bi_private = lc;
 315                         bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
 316
 317                         ret = bio_add_page(bio, block->vecs[i].bv_page,
 318                                            block->vecs[i].bv_len, 0);
 319                         if (ret != block->vecs[i].bv_len) {
 320                                 DMERR("Couldn't add page on new bio?");
 321                                 bio_put(bio);
 322                                 goto error;
 323                         }
 324                 }
 325                 sector += block->vecs[i].bv_len >> SECTOR_SHIFT;
 326         }
 327         submit_bio(bio);
 328 out:
 329         kfree(block->data);
 330         kfree(block);
 331         put_pending_block(lc);
 332         return 0;
 333 error:
 334         free_pending_block(lc, block);
 335         put_io_block(lc);
 336         return -1;
 337 }
 338
 339 static int log_super(struct log_writes_c *lc)
 340 {
 341         struct log_write_super super;
 342
 343         super.magic = cpu_to_le64(WRITE_LOG_MAGIC);
 344         super.version = cpu_to_le64(WRITE_LOG_VERSION);
 345         super.nr_entries = cpu_to_le64(lc->logged_entries);
 346         super.sectorsize = cpu_to_le32(lc->sectorsize);
 347
 348         if (write_metadata(lc, &super, sizeof(super), NULL, 0,
 349                            WRITE_LOG_SUPER_SECTOR)) {
 350                 DMERR("Couldn't write super");
 351                 return -1;
 352         }
 353
 354         /*
 355          * Super sector should be writen in-order, otherwise the
 356          * nr_entries could be rewritten incorrectly by an old bio.
 357          */
 358         wait_for_completion_io(&lc->super_done);
 359
 360         return 0;
 361 }
 362
 363 static inline sector_t logdev_last_sector(struct log_writes_c *lc)
 364 {
 365         return i_size_read(lc->logdev->bdev->bd_inode) >> SECTOR_SHIFT;
 366 }
 367
 368 static int log_writes_kthread(void *arg)
 369 {
 370         struct log_writes_c *lc = (struct log_writes_c *)arg;
 371         sector_t sector = 0;
 372
 373         while (!kthread_should_stop()) {
 374                 bool super = false;
 375                 bool logging_enabled;
 376                 struct pending_block *block = NULL;
 377                 int ret;
 378
 379                 spin_lock_irq(&lc->blocks_lock);
 380                 if (!list_empty(&lc->logging_blocks)) {
 381                         block = list_first_entry(&lc->logging_blocks,
 382                                                  struct pending_block, list);
 383                         list_del_init(&block->list);
 384                         if (!lc->logging_enabled)
 385                                 goto next;
 386
 387                         sector = lc->next_sector;
 388                         if (!(block->flags & LOG_DISCARD_FLAG))
 389                                 lc->next_sector += dev_to_bio_sectors(lc, block->nr_sectors);
 390                         lc->next_sector += dev_to_bio_sectors(lc, 1);
 391
 392                         /*
 393                          * Apparently the size of the device may not be known
 394                          * right away, so handle this properly.
 395                          */
 396                         if (!lc->end_sector)
 397                                 lc->end_sector = logdev_last_sector(lc);
 398                         if (lc->end_sector &&
 399                             lc->next_sector >= lc->end_sector) {
 400                                 DMERR("Ran out of space on the logdev");
 401                                 lc->logging_enabled = false;
 402                                 goto next;
 403                         }
 404                         lc->logged_entries++;
 405                         atomic_inc(&lc->io_blocks);
 406
 407                         super = (block->flags & (LOG_FUA_FLAG | LOG_MARK_FLAG));
 408                         if (super)
 409                                 atomic_inc(&lc->io_blocks);
 410                 }
 411 next:
 412                 logging_enabled = lc->logging_enabled;
 413                 spin_unlock_irq(&lc->blocks_lock);
 414                 if (block) {
 415                         if (logging_enabled) {
 416                                 ret = log_one_block(lc, block, sector);
 417                                 if (!ret && super)
 418                                         ret = log_super(lc);
 419                                 if (ret) {
 420                                         spin_lock_irq(&lc->blocks_lock);
 421                                         lc->logging_enabled = false;
 422                                         spin_unlock_irq(&lc->blocks_lock);
 423                                 }
 424                         } else
 425                                 free_pending_block(lc, block);
 426                         continue;
 427                 }
 428
 429                 if (!try_to_freeze()) {
 430                         set_current_state(TASK_INTERRUPTIBLE);
 431                         if (!kthread_should_stop() &&
 432                             list_empty(&lc->logging_blocks))
 433                                 schedule();
 434                         __set_current_state(TASK_RUNNING);
 435                 }
 436         }
 437         return 0;
 438 }
 439
 440 /*
 441  * Construct a log-writes mapping:
 442  * log-writes <dev_path> <log_dev_path>
 443  */
 444 static int log_writes_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 445 {
 446         struct log_writes_c *lc;
 447         struct dm_arg_set as;
 448         const char *devname, *logdevname;
 449         int ret;
 450
 451         as.argc = argc;
 452         as.argv = argv;
 453
 454         if (argc < 2) {
 455                 ti->error = "Invalid argument count";
 456                 return -EINVAL;
 457         }
 458
 459         lc = kzalloc(sizeof(struct log_writes_c), GFP_KERNEL);
 460         if (!lc) {
 461                 ti->error = "Cannot allocate context";
 462                 return -ENOMEM;
 463         }
 464         spin_lock_init(&lc->blocks_lock);
 465         INIT_LIST_HEAD(&lc->unflushed_blocks);
 466         INIT_LIST_HEAD(&lc->logging_blocks);
 467         init_waitqueue_head(&lc->wait);
 468         init_completion(&lc->super_done);
 469         atomic_set(&lc->io_blocks, 0);
 470         atomic_set(&lc->pending_blocks, 0);
 471
 472         devname = dm_shift_arg(&as);
 473         ret = dm_get_device(ti, devname, dm_table_get_mode(ti->table), &lc->dev);
 474         if (ret) {
 475                 ti->error = "Device lookup failed";
 476                 goto bad;
 477         }
 478
 479         logdevname = dm_shift_arg(&as);
 480         ret = dm_get_device(ti, logdevname, dm_table_get_mode(ti->table),
 481                             &lc->logdev);
 482         if (ret) {
 483                 ti->error = "Log device lookup failed";
 484                 dm_put_device(ti, lc->dev);
 485                 goto bad;
 486         }
 487
 488         lc->sectorsize = bdev_logical_block_size(lc->dev->bdev);
 489         lc->sectorshift = ilog2(lc->sectorsize);
 490         lc->log_kthread = kthread_run(log_writes_kthread, lc, "log-write");
 491         if (IS_ERR(lc->log_kthread)) {
 492                 ret = PTR_ERR(lc->log_kthread);
 493                 ti->error = "Couldn't alloc kthread";
 494                 dm_put_device(ti, lc->dev);
 495                 dm_put_device(ti, lc->logdev);
 496                 goto bad;
 497         }
 498
 499         /*
 500          * next_sector is in 512b sectors to correspond to what bi_sector expects.
 501          * The super starts at sector 0, and the next_sector is the next logical
 502          * one based on the sectorsize of the device.
 503          */
 504         lc->next_sector = lc->sectorsize >> SECTOR_SHIFT;
 505         lc->logging_enabled = true;
 506         lc->end_sector = logdev_last_sector(lc);
 507         lc->device_supports_discard = true;
 508
 509         ti->num_flush_bios = 1;
 510         ti->flush_supported = true;
 511         ti->num_discard_bios = 1;
 512         ti->discards_supported = true;
 513         ti->per_io_data_size = sizeof(struct per_bio_data);
 514         ti->private = lc;
 515         return 0;
 516
 517 bad:
 518         kfree(lc);
 519         return ret;
 520 }
 521
 522 static int log_mark(struct log_writes_c *lc, char *data)
 523 {
 524         struct pending_block *block;
 525         size_t maxsize = lc->sectorsize - sizeof(struct log_write_entry);
 526
 527         block = kzalloc(sizeof(struct pending_block), GFP_KERNEL);
 528         if (!block) {
 529                 DMERR("Error allocating pending block");
 530                 return -ENOMEM;
 531         }
 532
 533         block->data = kstrndup(data, maxsize, GFP_KERNEL);
 534         if (!block->data) {
 535                 DMERR("Error copying mark data");
 536                 kfree(block);
 537                 return -ENOMEM;
 538         }
 539         atomic_inc(&lc->pending_blocks);
 540         block->datalen = strlen(block->data);
 541         block->flags |= LOG_MARK_FLAG;
 542         spin_lock_irq(&lc->blocks_lock);
 543         list_add_tail(&block->list, &lc->logging_blocks);
 544         spin_unlock_irq(&lc->blocks_lock);
 545         wake_up_process(lc->log_kthread);
 546         return 0;
 547 }
 548
 549 static void log_writes_dtr(struct dm_target *ti)
 550 {
 551         struct log_writes_c *lc = ti->private;
 552
 553         spin_lock_irq(&lc->blocks_lock);
 554         list_splice_init(&lc->unflushed_blocks, &lc->logging_blocks);
 555         spin_unlock_irq(&lc->blocks_lock);
 556
 557         /*
 558          * This is just nice to have since it'll update the super to include the
 559          * unflushed blocks, if it fails we don't really care.
 560          */
 561         log_mark(lc, "dm-log-writes-end");
 562         wake_up_process(lc->log_kthread);
 563         wait_event(lc->wait, !atomic_read(&lc->io_blocks) &&
 564                    !atomic_read(&lc->pending_blocks));
 565         kthread_stop(lc->log_kthread);
 566
 567         WARN_ON(!list_empty(&lc->logging_blocks));
 568         WARN_ON(!list_empty(&lc->unflushed_blocks));
 569         dm_put_device(ti, lc->dev);
 570         dm_put_device(ti, lc->logdev);
 571         kfree(lc);
 572 }
 573
 574 static void normal_map_bio(struct dm_target *ti, struct bio *bio)
 575 {
 576         struct log_writes_c *lc = ti->private;
 577
 578         bio_set_dev(bio, lc->dev->bdev);
 579 }
 580
 581 static int log_writes_map(struct dm_target *ti, struct bio *bio)
 582 {
 583         struct log_writes_c *lc = ti->private;
 584         struct per_bio_data *pb = dm_per_bio_data(bio, sizeof(struct per_bio_data));
 585         struct pending_block *block;
 586         struct bvec_iter iter;
 587         struct bio_vec bv;
 588         size_t alloc_size;
 589         int i = 0;
 590         bool flush_bio = (bio->bi_opf & REQ_PREFLUSH);
 591         bool fua_bio = (bio->bi_opf & REQ_FUA);
 592         bool discard_bio = (bio_op(bio) == REQ_OP_DISCARD);
 593
 594         pb->block = NULL;
 595
 596         /* Don't bother doing anything if logging has been disabled */
 597         if (!lc->logging_enabled)
 598                 goto map_bio;
 599
 600         /*
 601          * Map reads as normal.
 602          */
 603         if (bio_data_dir(bio) == READ)
 604                 goto map_bio;
 605
 606         /* No sectors and not a flush?  Don't care */
 607         if (!bio_sectors(bio) && !flush_bio)
 608                 goto map_bio;
 609
 610         /*
 611          * Discards will have bi_size set but there's no actual data, so just
 612          * allocate the size of the pending block.
 613          */
 614         if (discard_bio)
 615                 alloc_size = sizeof(struct pending_block);
 616         else
 617                 alloc_size = sizeof(struct pending_block) + sizeof(struct bio_vec) * bio_segments(bio);
 618
 619         block = kzalloc(alloc_size, GFP_NOIO);
 620         if (!block) {
 621                 DMERR("Error allocating pending block");
 622                 spin_lock_irq(&lc->blocks_lock);
 623                 lc->logging_enabled = false;
 624                 spin_unlock_irq(&lc->blocks_lock);
 625                 return DM_MAPIO_KILL;
 626         }
 627         INIT_LIST_HEAD(&block->list);
 628         pb->block = block;
 629         atomic_inc(&lc->pending_blocks);
 630
 631         if (flush_bio)
 632                 block->flags |= LOG_FLUSH_FLAG;
 633         if (fua_bio)
 634                 block->flags |= LOG_FUA_FLAG;
 635         if (discard_bio)
 636                 block->flags |= LOG_DISCARD_FLAG;
 637
 638         block->sector = bio_to_dev_sectors(lc, bio->bi_iter.bi_sector);
 639         block->nr_sectors = bio_to_dev_sectors(lc, bio_sectors(bio));
 640
 641         /* We don't need the data, just submit */
 642         if (discard_bio) {
 643                 WARN_ON(flush_bio || fua_bio);
 644                 if (lc->device_supports_discard)
 645                         goto map_bio;
 646                 bio_endio(bio);
 647                 return DM_MAPIO_SUBMITTED;
 648         }
 649
 650         /* Flush bio, splice the unflushed blocks onto this list and submit */
 651         if (flush_bio && !bio_sectors(bio)) {
 652                 spin_lock_irq(&lc->blocks_lock);
 653                 list_splice_init(&lc->unflushed_blocks, &block->list);
 654                 spin_unlock_irq(&lc->blocks_lock);
 655                 goto map_bio;
 656         }
 657
 658         /*
 659          * We will write this bio somewhere else way later so we need to copy
 660          * the actual contents into new pages so we know the data will always be
 661          * there.
 662          *
 663          * We do this because this could be a bio from O_DIRECT in which case we
 664          * can't just hold onto the page until some later point, we have to
 665          * manually copy the contents.
 666          */
 667         bio_for_each_segment(bv, bio, iter) {
 668                 struct page *page;
 669                 void *src, *dst;
 670
 671                 page = alloc_page(GFP_NOIO);
 672                 if (!page) {
 673                         DMERR("Error allocing page");
 674                         free_pending_block(lc, block);
 675                         spin_lock_irq(&lc->blocks_lock);
 676                         lc->logging_enabled = false;
 677                         spin_unlock_irq(&lc->blocks_lock);
 678                         return DM_MAPIO_KILL;
 679                 }
 680
 681                 src = kmap_atomic(bv.bv_page);
 682                 dst = kmap_atomic(page);
 683                 memcpy(dst, src + bv.bv_offset, bv.bv_len);
 684                 kunmap_atomic(dst);
 685                 kunmap_atomic(src);
 686                 block->vecs[i].bv_page = page;
 687                 block->vecs[i].bv_len = bv.bv_len;
 688                 block->vec_cnt++;
 689                 i++;
 690         }
 691
 692         /* Had a flush with data in it, weird */
 693         if (flush_bio) {
 694                 spin_lock_irq(&lc->blocks_lock);
 695                 list_splice_init(&lc->unflushed_blocks, &block->list);
 696                 spin_unlock_irq(&lc->blocks_lock);
 697         }
 698 map_bio:
 699         normal_map_bio(ti, bio);
 700         return DM_MAPIO_REMAPPED;
 701 }
 702
 703 static int normal_end_io(struct dm_target *ti, struct bio *bio,
 704                 blk_status_t *error)
 705 {
 706         struct log_writes_c *lc = ti->private;
 707         struct per_bio_data *pb = dm_per_bio_data(bio, sizeof(struct per_bio_data));
 708
 709         if (bio_data_dir(bio) == WRITE && pb->block) {
 710                 struct pending_block *block = pb->block;
 711                 unsigned long flags;
 712
 713                 spin_lock_irqsave(&lc->blocks_lock, flags);
 714                 if (block->flags & LOG_FLUSH_FLAG) {
 715                         list_splice_tail_init(&block->list, &lc->logging_blocks);
 716                         list_add_tail(&block->list, &lc->logging_blocks);
 717                         wake_up_process(lc->log_kthread);
 718                 } else if (block->flags & LOG_FUA_FLAG) {
 719                         list_add_tail(&block->list, &lc->logging_blocks);
 720                         wake_up_process(lc->log_kthread);
 721                 } else
 722                         list_add_tail(&block->list, &lc->unflushed_blocks);
 723                 spin_unlock_irqrestore(&lc->blocks_lock, flags);
 724         }
 725
 726         return DM_ENDIO_DONE;
 727 }
 728
 729 /*
 730  * INFO format: <logged entries> <highest allocated sector>
 731  */
 732 static void log_writes_status(struct dm_target *ti, status_type_t type,
 733                               unsigned status_flags, char *result,
 734                               unsigned maxlen)
 735 {
 736         unsigned sz = 0;
 737         struct log_writes_c *lc = ti->private;
 738
 739         switch (type) {
 740         case STATUSTYPE_INFO:
 741                 DMEMIT("%llu %llu", lc->logged_entries,
 742                        (unsigned long long)lc->next_sector - 1);
 743                 if (!lc->logging_enabled)
 744                         DMEMIT(" logging_disabled");
 745                 break;
 746
 747         case STATUSTYPE_TABLE:
 748                 DMEMIT("%s %s", lc->dev->name, lc->logdev->name);
 749                 break;
 750         }
 751 }
 752
 753 static int log_writes_prepare_ioctl(struct dm_target *ti,
 754                 struct block_device **bdev, fmode_t *mode)
 755 {
 756         struct log_writes_c *lc = ti->private;
 757         struct dm_dev *dev = lc->dev;
 758
 759         *bdev = dev->bdev;
 760         /*
 761          * Only pass ioctls through if the device sizes match exactly.
 762          */
 763         if (ti->len != i_size_read(dev->bdev->bd_inode) >> SECTOR_SHIFT)
 764                 return 1;
 765         return 0;
 766 }
 767
 768 static int log_writes_iterate_devices(struct dm_target *ti,
 769                                       iterate_devices_callout_fn fn,
 770                                       void *data)
 771 {
 772         struct log_writes_c *lc = ti->private;
 773
 774         return fn(ti, lc->dev, 0, ti->len, data);
 775 }
 776
 777 /*
 778  * Messages supported:
 779  *   mark <mark data> - specify the marked data.
 780  */
 781 static int log_writes_message(struct dm_target *ti, unsigned argc, char **argv)
 782 {
 783         int r = -EINVAL;
 784         struct log_writes_c *lc = ti->private;
 785
 786         if (argc != 2) {
 787                 DMWARN("Invalid log-writes message arguments, expect 2 arguments, got %d", argc);
 788                 return r;
 789         }
 790
 791         if (!strcasecmp(argv[0], "mark"))
 792                 r = log_mark(lc, argv[1]);
 793         else
 794                 DMWARN("Unrecognised log writes target message received: %s", argv[0]);
 795
 796         return r;
 797 }
 798
 799 static void log_writes_io_hints(struct dm_target *ti, struct queue_limits *limits)
 800 {
 801         struct log_writes_c *lc = ti->private;
 802         struct request_queue *q = bdev_get_queue(lc->dev->bdev);
 803
 804         if (!q || !blk_queue_discard(q)) {
 805                 lc->device_supports_discard = false;
 806                 limits->discard_granularity = lc->sectorsize;
 807                 limits->max_discard_sectors = (UINT_MAX >> SECTOR_SHIFT);
 808         }
 809         limits->logical_block_size = bdev_logical_block_size(lc->dev->bdev);
 810         limits->physical_block_size = bdev_physical_block_size(lc->dev->bdev);
 811         limits->io_min = limits->physical_block_size;
 812 }
 813
 814 static struct target_type log_writes_target = {
 815         .name   = "log-writes",
 816         .version = {1, 0, 0},
 817         .module = THIS_MODULE,
 818         .ctr    = log_writes_ctr,
 819         .dtr    = log_writes_dtr,
 820         .map    = log_writes_map,
 821         .end_io = normal_end_io,
 822         .status = log_writes_status,
 823         .prepare_ioctl = log_writes_prepare_ioctl,
 824         .message = log_writes_message,
 825         .iterate_devices = log_writes_iterate_devices,
 826         .io_hints = log_writes_io_hints,
 827 };
 828
 829 static int __init dm_log_writes_init(void)
 830 {
 831         int r = dm_register_target(&log_writes_target);
 832
 833         if (r < 0)
 834                 DMERR("register failed %d", r);
 835
 836         return r;
 837 }
 838
 839 static void __exit dm_log_writes_exit(void)
 840 {
 841         dm_unregister_target(&log_writes_target);
 842 }
 843
 844 module_init(dm_log_writes_init);
 845 module_exit(dm_log_writes_exit);
 846
 847 MODULE_DESCRIPTION(DM_NAME " log writes target");
 848 MODULE_AUTHOR("Josef Bacik <jbacik@fb.com>");
 849 MODULE_LICENSE("GPL");