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