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