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, int err)
 150 {
 151         struct log_writes_c *lc = bio->bi_private;
 152         struct bio_vec *bvec;
 153         int i;
 154
 155         if (err) {
 156                 unsigned long flags;
 157
 158                 DMERR("Error writing log block, error=%d", err);
 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         set_bit(BIO_UPTODATE, &bio->bi_flags);
 209
 210         page = alloc_page(GFP_KERNEL);
 211         if (!page) {
 212                 DMERR("Couldn't alloc log page");
 213                 bio_put(bio);
 214                 goto error;
 215         }
 216
 217         ptr = kmap_atomic(page);
 218         memcpy(ptr, entry, entrylen);
 219         if (datalen)
 220                 memcpy(ptr + entrylen, data, datalen);
 221         memset(ptr + entrylen + datalen, 0,
 222                lc->sectorsize - entrylen - datalen);
 223         kunmap_atomic(ptr);
 224
 225         ret = bio_add_page(bio, page, lc->sectorsize, 0);
 226         if (ret != lc->sectorsize) {
 227                 DMERR("Couldn't add page to the log block");
 228                 goto error_bio;
 229         }
 230         submit_bio(WRITE, bio);
 231         return 0;
 232 error_bio:
 233         bio_put(bio);
 234         __free_page(page);
 235 error:
 236         put_io_block(lc);
 237         return -1;
 238 }
 239
 240 static int log_one_block(struct log_writes_c *lc,
 241                          struct pending_block *block, sector_t sector)
 242 {
 243         struct bio *bio;
 244         struct log_write_entry entry;
 245         size_t ret;
 246         int i;
 247
 248         entry.sector = cpu_to_le64(block->sector);
 249         entry.nr_sectors = cpu_to_le64(block->nr_sectors);
 250         entry.flags = cpu_to_le64(block->flags);
 251         entry.data_len = cpu_to_le64(block->datalen);
 252         if (write_metadata(lc, &entry, sizeof(entry), block->data,
 253                            block->datalen, sector)) {
 254                 free_pending_block(lc, block);
 255                 return -1;
 256         }
 257
 258         if (!block->vec_cnt)
 259                 goto out;
 260         sector++;
 261
 262         bio = bio_alloc(GFP_KERNEL, block->vec_cnt);
 263         if (!bio) {
 264                 DMERR("Couldn't alloc log bio");
 265                 goto error;
 266         }
 267         atomic_inc(&lc->io_blocks);
 268         bio->bi_iter.bi_size = 0;
 269         bio->bi_iter.bi_sector = sector;
 270         bio->bi_bdev = lc->logdev->bdev;
 271         bio->bi_end_io = log_end_io;
 272         bio->bi_private = lc;
 273         set_bit(BIO_UPTODATE, &bio->bi_flags);
 274
 275         for (i = 0; i < block->vec_cnt; i++) {
 276                 /*
 277                  * The page offset is always 0 because we allocate a new page
 278                  * for every bvec in the original bio for simplicity sake.
 279                  */
 280                 ret = bio_add_page(bio, block->vecs[i].bv_page,
 281                                    block->vecs[i].bv_len, 0);
 282                 if (ret != block->vecs[i].bv_len) {
 283                         atomic_inc(&lc->io_blocks);
 284                         submit_bio(WRITE, bio);
 285                         bio = bio_alloc(GFP_KERNEL, block->vec_cnt - i);
 286                         if (!bio) {
 287                                 DMERR("Couldn't alloc log bio");
 288                                 goto error;
 289                         }
 290                         bio->bi_iter.bi_size = 0;
 291                         bio->bi_iter.bi_sector = sector;
 292                         bio->bi_bdev = lc->logdev->bdev;
 293                         bio->bi_end_io = log_end_io;
 294                         bio->bi_private = lc;
 295                         set_bit(BIO_UPTODATE, &bio->bi_flags);
 296
 297                         ret = bio_add_page(bio, block->vecs[i].bv_page,
 298                                            block->vecs[i].bv_len, 0);
 299                         if (ret != block->vecs[i].bv_len) {
 300                                 DMERR("Couldn't add page on new bio?");
 301                                 bio_put(bio);
 302                                 goto error;
 303                         }
 304                 }
 305                 sector += block->vecs[i].bv_len >> SECTOR_SHIFT;
 306         }
 307         submit_bio(WRITE, bio);
 308 out:
 309         kfree(block->data);
 310         kfree(block);
 311         put_pending_block(lc);
 312         return 0;
 313 error:
 314         free_pending_block(lc, block);
 315         put_io_block(lc);
 316         return -1;
 317 }
 318
 319 static int log_super(struct log_writes_c *lc)
 320 {
 321         struct log_write_super super;
 322
 323         super.magic = cpu_to_le64(WRITE_LOG_MAGIC);
 324         super.version = cpu_to_le64(WRITE_LOG_VERSION);
 325         super.nr_entries = cpu_to_le64(lc->logged_entries);
 326         super.sectorsize = cpu_to_le32(lc->sectorsize);
 327
 328         if (write_metadata(lc, &super, sizeof(super), NULL, 0, 0)) {
 329                 DMERR("Couldn't write super");
 330                 return -1;
 331         }
 332
 333         return 0;
 334 }
 335
 336 static inline sector_t logdev_last_sector(struct log_writes_c *lc)
 337 {
 338         return i_size_read(lc->logdev->bdev->bd_inode) >> SECTOR_SHIFT;
 339 }
 340
 341 static int log_writes_kthread(void *arg)
 342 {
 343         struct log_writes_c *lc = (struct log_writes_c *)arg;
 344         sector_t sector = 0;
 345
 346         while (!kthread_should_stop()) {
 347                 bool super = false;
 348                 bool logging_enabled;
 349                 struct pending_block *block = NULL;
 350                 int ret;
 351
 352                 spin_lock_irq(&lc->blocks_lock);
 353                 if (!list_empty(&lc->logging_blocks)) {
 354                         block = list_first_entry(&lc->logging_blocks,
 355                                                  struct pending_block, list);
 356                         list_del_init(&block->list);
 357                         if (!lc->logging_enabled)
 358                                 goto next;
 359
 360                         sector = lc->next_sector;
 361                         if (block->flags & LOG_DISCARD_FLAG)
 362                                 lc->next_sector++;
 363                         else
 364                                 lc->next_sector += block->nr_sectors + 1;
 365
 366                         /*
 367                          * Apparently the size of the device may not be known
 368                          * right away, so handle this properly.
 369                          */
 370                         if (!lc->end_sector)
 371                                 lc->end_sector = logdev_last_sector(lc);
 372                         if (lc->end_sector &&
 373                             lc->next_sector >= lc->end_sector) {
 374                                 DMERR("Ran out of space on the logdev");
 375                                 lc->logging_enabled = false;
 376                                 goto next;
 377                         }
 378                         lc->logged_entries++;
 379                         atomic_inc(&lc->io_blocks);
 380
 381                         super = (block->flags & (LOG_FUA_FLAG | LOG_MARK_FLAG));
 382                         if (super)
 383                                 atomic_inc(&lc->io_blocks);
 384                 }
 385 next:
 386                 logging_enabled = lc->logging_enabled;
 387                 spin_unlock_irq(&lc->blocks_lock);
 388                 if (block) {
 389                         if (logging_enabled) {
 390                                 ret = log_one_block(lc, block, sector);
 391                                 if (!ret && super)
 392                                         ret = log_super(lc);
 393                                 if (ret) {
 394                                         spin_lock_irq(&lc->blocks_lock);
 395                                         lc->logging_enabled = false;
 396                                         spin_unlock_irq(&lc->blocks_lock);
 397                                 }
 398                         } else
 399                                 free_pending_block(lc, block);
 400                         continue;
 401                 }
 402
 403                 if (!try_to_freeze()) {
 404                         set_current_state(TASK_INTERRUPTIBLE);
 405                         if (!kthread_should_stop() &&
 406                             !atomic_read(&lc->pending_blocks))
 407                                 schedule();
 408                         __set_current_state(TASK_RUNNING);
 409                 }
 410         }
 411         return 0;
 412 }
 413
 414 /*
 415  * Construct a log-writes mapping:
 416  * log-writes <dev_path> <log_dev_path>
 417  */
 418 static int log_writes_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 419 {
 420         struct log_writes_c *lc;
 421         struct dm_arg_set as;
 422         const char *devname, *logdevname;
 423
 424         as.argc = argc;
 425         as.argv = argv;
 426
 427         if (argc < 2) {
 428                 ti->error = "Invalid argument count";
 429                 return -EINVAL;
 430         }
 431
 432         lc = kzalloc(sizeof(struct log_writes_c), GFP_KERNEL);
 433         if (!lc) {
 434                 ti->error = "Cannot allocate context";
 435                 return -ENOMEM;
 436         }
 437         spin_lock_init(&lc->blocks_lock);
 438         INIT_LIST_HEAD(&lc->unflushed_blocks);
 439         INIT_LIST_HEAD(&lc->logging_blocks);
 440         init_waitqueue_head(&lc->wait);
 441         lc->sectorsize = 1 << SECTOR_SHIFT;
 442         atomic_set(&lc->io_blocks, 0);
 443         atomic_set(&lc->pending_blocks, 0);
 444
 445         devname = dm_shift_arg(&as);
 446         if (dm_get_device(ti, devname, dm_table_get_mode(ti->table), &lc->dev)) {
 447                 ti->error = "Device lookup failed";
 448                 goto bad;
 449         }
 450
 451         logdevname = dm_shift_arg(&as);
 452         if (dm_get_device(ti, logdevname, dm_table_get_mode(ti->table), &lc->logdev)) {
 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 (!lc->log_kthread) {
 460                 ti->error = "Couldn't alloc kthread";
 461                 dm_put_device(ti, lc->dev);
 462                 dm_put_device(ti, lc->logdev);
 463                 goto bad;
 464         }
 465
 466         /* We put the super at sector 0, start logging at sector 1 */
 467         lc->next_sector = 1;
 468         lc->logging_enabled = true;
 469         lc->end_sector = logdev_last_sector(lc);
 470         lc->device_supports_discard = true;
 471
 472         ti->num_flush_bios = 1;
 473         ti->flush_supported = true;
 474         ti->num_discard_bios = 1;
 475         ti->discards_supported = true;
 476         ti->per_bio_data_size = sizeof(struct per_bio_data);
 477         ti->private = lc;
 478         return 0;
 479
 480 bad:
 481         kfree(lc);
 482         return -EINVAL;
 483 }
 484
 485 static int log_mark(struct log_writes_c *lc, char *data)
 486 {
 487         struct pending_block *block;
 488         size_t maxsize = lc->sectorsize - sizeof(struct log_write_entry);
 489
 490         block = kzalloc(sizeof(struct pending_block), GFP_KERNEL);
 491         if (!block) {
 492                 DMERR("Error allocating pending block");
 493                 return -ENOMEM;
 494         }
 495
 496         block->data = kstrndup(data, maxsize, GFP_KERNEL);
 497         if (!block->data) {
 498                 DMERR("Error copying mark data");
 499                 kfree(block);
 500                 return -ENOMEM;
 501         }
 502         atomic_inc(&lc->pending_blocks);
 503         block->datalen = strlen(block->data);
 504         block->flags |= LOG_MARK_FLAG;
 505         spin_lock_irq(&lc->blocks_lock);
 506         list_add_tail(&block->list, &lc->logging_blocks);
 507         spin_unlock_irq(&lc->blocks_lock);
 508         wake_up_process(lc->log_kthread);
 509         return 0;
 510 }
 511
 512 static void log_writes_dtr(struct dm_target *ti)
 513 {
 514         struct log_writes_c *lc = ti->private;
 515
 516         spin_lock_irq(&lc->blocks_lock);
 517         list_splice_init(&lc->unflushed_blocks, &lc->logging_blocks);
 518         spin_unlock_irq(&lc->blocks_lock);
 519
 520         /*
 521          * This is just nice to have since it'll update the super to include the
 522          * unflushed blocks, if it fails we don't really care.
 523          */
 524         log_mark(lc, "dm-log-writes-end");
 525         wake_up_process(lc->log_kthread);
 526         wait_event(lc->wait, !atomic_read(&lc->io_blocks) &&
 527                    !atomic_read(&lc->pending_blocks));
 528         kthread_stop(lc->log_kthread);
 529
 530         WARN_ON(!list_empty(&lc->logging_blocks));
 531         WARN_ON(!list_empty(&lc->unflushed_blocks));
 532         dm_put_device(ti, lc->dev);
 533         dm_put_device(ti, lc->logdev);
 534         kfree(lc);
 535 }
 536
 537 static void normal_map_bio(struct dm_target *ti, struct bio *bio)
 538 {
 539         struct log_writes_c *lc = ti->private;
 540
 541         bio->bi_bdev = lc->dev->bdev;
 542 }
 543
 544 static int log_writes_map(struct dm_target *ti, struct bio *bio)
 545 {
 546         struct log_writes_c *lc = ti->private;
 547         struct per_bio_data *pb = dm_per_bio_data(bio, sizeof(struct per_bio_data));
 548         struct pending_block *block;
 549         struct bvec_iter iter;
 550         struct bio_vec bv;
 551         size_t alloc_size;
 552         int i = 0;
 553         bool flush_bio = (bio->bi_rw & REQ_FLUSH);
 554         bool fua_bio = (bio->bi_rw & REQ_FUA);
 555         bool discard_bio = (bio->bi_rw & REQ_DISCARD);
 556
 557         pb->block = NULL;
 558
 559         /* Don't bother doing anything if logging has been disabled */
 560         if (!lc->logging_enabled)
 561                 goto map_bio;
 562
 563         /*
 564          * Map reads as normal.
 565          */
 566         if (bio_data_dir(bio) == READ)
 567                 goto map_bio;
 568
 569         /* No sectors and not a flush?  Don't care */
 570         if (!bio_sectors(bio) && !flush_bio)
 571                 goto map_bio;
 572
 573         /*
 574          * Discards will have bi_size set but there's no actual data, so just
 575          * allocate the size of the pending block.
 576          */
 577         if (discard_bio)
 578                 alloc_size = sizeof(struct pending_block);
 579         else
 580                 alloc_size = sizeof(struct pending_block) + sizeof(struct bio_vec) * bio_segments(bio);
 581
 582         block = kzalloc(alloc_size, GFP_NOIO);
 583         if (!block) {
 584                 DMERR("Error allocating pending block");
 585                 spin_lock_irq(&lc->blocks_lock);
 586                 lc->logging_enabled = false;
 587                 spin_unlock_irq(&lc->blocks_lock);
 588                 return -ENOMEM;
 589         }
 590         INIT_LIST_HEAD(&block->list);
 591         pb->block = block;
 592         atomic_inc(&lc->pending_blocks);
 593
 594         if (flush_bio)
 595                 block->flags |= LOG_FLUSH_FLAG;
 596         if (fua_bio)
 597                 block->flags |= LOG_FUA_FLAG;
 598         if (discard_bio)
 599                 block->flags |= LOG_DISCARD_FLAG;
 600
 601         block->sector = bio->bi_iter.bi_sector;
 602         block->nr_sectors = bio_sectors(bio);
 603
 604         /* We don't need the data, just submit */
 605         if (discard_bio) {
 606                 WARN_ON(flush_bio || fua_bio);
 607                 if (lc->device_supports_discard)
 608                         goto map_bio;
 609                 bio_endio(bio, 0);
 610                 return DM_MAPIO_SUBMITTED;
 611         }
 612
 613         /* Flush bio, splice the unflushed blocks onto this list and submit */
 614         if (flush_bio && !bio_sectors(bio)) {
 615                 spin_lock_irq(&lc->blocks_lock);
 616                 list_splice_init(&lc->unflushed_blocks, &block->list);
 617                 spin_unlock_irq(&lc->blocks_lock);
 618                 goto map_bio;
 619         }
 620
 621         /*
 622          * We will write this bio somewhere else way later so we need to copy
 623          * the actual contents into new pages so we know the data will always be
 624          * there.
 625          *
 626          * We do this because this could be a bio from O_DIRECT in which case we
 627          * can't just hold onto the page until some later point, we have to
 628          * manually copy the contents.
 629          */
 630         bio_for_each_segment(bv, bio, iter) {
 631                 struct page *page;
 632                 void *src, *dst;
 633
 634                 page = alloc_page(GFP_NOIO);
 635                 if (!page) {
 636                         DMERR("Error allocing page");
 637                         free_pending_block(lc, block);
 638                         spin_lock_irq(&lc->blocks_lock);
 639                         lc->logging_enabled = false;
 640                         spin_unlock_irq(&lc->blocks_lock);
 641                         return -ENOMEM;
 642                 }
 643
 644                 src = kmap_atomic(bv.bv_page);
 645                 dst = kmap_atomic(page);
 646                 memcpy(dst, src + bv.bv_offset, bv.bv_len);
 647                 kunmap_atomic(dst);
 648                 kunmap_atomic(src);
 649                 block->vecs[i].bv_page = page;
 650                 block->vecs[i].bv_len = bv.bv_len;
 651                 block->vec_cnt++;
 652                 i++;
 653         }
 654
 655         /* Had a flush with data in it, weird */
 656         if (flush_bio) {
 657                 spin_lock_irq(&lc->blocks_lock);
 658                 list_splice_init(&lc->unflushed_blocks, &block->list);
 659                 spin_unlock_irq(&lc->blocks_lock);
 660         }
 661 map_bio:
 662         normal_map_bio(ti, bio);
 663         return DM_MAPIO_REMAPPED;
 664 }
 665
 666 static int normal_end_io(struct dm_target *ti, struct bio *bio, int error)
 667 {
 668         struct log_writes_c *lc = ti->private;
 669         struct per_bio_data *pb = dm_per_bio_data(bio, sizeof(struct per_bio_data));
 670
 671         if (bio_data_dir(bio) == WRITE && pb->block) {
 672                 struct pending_block *block = pb->block;
 673                 unsigned long flags;
 674
 675                 spin_lock_irqsave(&lc->blocks_lock, flags);
 676                 if (block->flags & LOG_FLUSH_FLAG) {
 677                         list_splice_tail_init(&block->list, &lc->logging_blocks);
 678                         list_add_tail(&block->list, &lc->logging_blocks);
 679                         wake_up_process(lc->log_kthread);
 680                 } else if (block->flags & LOG_FUA_FLAG) {
 681                         list_add_tail(&block->list, &lc->logging_blocks);
 682                         wake_up_process(lc->log_kthread);
 683                 } else
 684                         list_add_tail(&block->list, &lc->unflushed_blocks);
 685                 spin_unlock_irqrestore(&lc->blocks_lock, flags);
 686         }
 687
 688         return error;
 689 }
 690
 691 /*
 692  * INFO format: <logged entries> <highest allocated sector>
 693  */
 694 static void log_writes_status(struct dm_target *ti, status_type_t type,
 695                               unsigned status_flags, char *result,
 696                               unsigned maxlen)
 697 {
 698         unsigned sz = 0;
 699         struct log_writes_c *lc = ti->private;
 700
 701         switch (type) {
 702         case STATUSTYPE_INFO:
 703                 DMEMIT("%llu %llu", lc->logged_entries,
 704                        (unsigned long long)lc->next_sector - 1);
 705                 if (!lc->logging_enabled)
 706                         DMEMIT(" logging_disabled");
 707                 break;
 708
 709         case STATUSTYPE_TABLE:
 710                 DMEMIT("%s %s", lc->dev->name, lc->logdev->name);
 711                 break;
 712         }
 713 }
 714
 715 static int log_writes_ioctl(struct dm_target *ti, unsigned int cmd,
 716                             unsigned long arg)
 717 {
 718         struct log_writes_c *lc = ti->private;
 719         struct dm_dev *dev = lc->dev;
 720         int r = 0;
 721
 722         /*
 723          * Only pass ioctls through if the device sizes match exactly.
 724          */
 725         if (ti->len != i_size_read(dev->bdev->bd_inode) >> SECTOR_SHIFT)
 726                 r = scsi_verify_blk_ioctl(NULL, cmd);
 727
 728         return r ? : __blkdev_driver_ioctl(dev->bdev, dev->mode, cmd, arg);
 729 }
 730
 731 static int log_writes_merge(struct dm_target *ti, struct bvec_merge_data *bvm,
 732                             struct bio_vec *biovec, int max_size)
 733 {
 734         struct log_writes_c *lc = ti->private;
 735         struct request_queue *q = bdev_get_queue(lc->dev->bdev);
 736
 737         if (!q->merge_bvec_fn)
 738                 return max_size;
 739
 740         bvm->bi_bdev = lc->dev->bdev;
 741         bvm->bi_sector = dm_target_offset(ti, bvm->bi_sector);
 742
 743         return min(max_size, q->merge_bvec_fn(q, bvm, biovec));
 744 }
 745
 746 static int log_writes_iterate_devices(struct dm_target *ti,
 747                                       iterate_devices_callout_fn fn,
 748                                       void *data)
 749 {
 750         struct log_writes_c *lc = ti->private;
 751
 752         return fn(ti, lc->dev, 0, ti->len, data);
 753 }
 754
 755 /*
 756  * Messages supported:
 757  *   mark <mark data> - specify the marked data.
 758  */
 759 static int log_writes_message(struct dm_target *ti, unsigned argc, char **argv)
 760 {
 761         int r = -EINVAL;
 762         struct log_writes_c *lc = ti->private;
 763
 764         if (argc != 2) {
 765                 DMWARN("Invalid log-writes message arguments, expect 2 arguments, got %d", argc);
 766                 return r;
 767         }
 768
 769         if (!strcasecmp(argv[0], "mark"))
 770                 r = log_mark(lc, argv[1]);
 771         else
 772                 DMWARN("Unrecognised log writes target message received: %s", argv[0]);
 773
 774         return r;
 775 }
 776
 777 static void log_writes_io_hints(struct dm_target *ti, struct queue_limits *limits)
 778 {
 779         struct log_writes_c *lc = ti->private;
 780         struct request_queue *q = bdev_get_queue(lc->dev->bdev);
 781
 782         if (!q || !blk_queue_discard(q)) {
 783                 lc->device_supports_discard = false;
 784                 limits->discard_granularity = 1 << SECTOR_SHIFT;
 785                 limits->max_discard_sectors = (UINT_MAX >> SECTOR_SHIFT);
 786         }
 787 }
 788
 789 static struct target_type log_writes_target = {
 790         .name   = "log-writes",
 791         .version = {1, 0, 0},
 792         .module = THIS_MODULE,
 793         .ctr    = log_writes_ctr,
 794         .dtr    = log_writes_dtr,
 795         .map    = log_writes_map,
 796         .end_io = normal_end_io,
 797         .status = log_writes_status,
 798         .ioctl  = log_writes_ioctl,
 799         .merge  = log_writes_merge,
 800         .message = log_writes_message,
 801         .iterate_devices = log_writes_iterate_devices,
 802         .io_hints = log_writes_io_hints,
 803 };
 804
 805 static int __init dm_log_writes_init(void)
 806 {
 807         int r = dm_register_target(&log_writes_target);
 808
 809         if (r < 0)
 810                 DMERR("register failed %d", r);
 811
 812         return r;
 813 }
 814
 815 static void __exit dm_log_writes_exit(void)
 816 {
 817         dm_unregister_target(&log_writes_target);
 818 }
 819
 820 module_init(dm_log_writes_init);
 821 module_exit(dm_log_writes_exit);
 822
 823 MODULE_DESCRIPTION(DM_NAME " log writes target");
 824 MODULE_AUTHOR("Josef Bacik <jbacik@fb.com>");
 825 MODULE_LICENSE("GPL");