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