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         bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
 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(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         bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
 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(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                         bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
 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(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         int ret;
 424
 425         as.argc = argc;
 426         as.argv = argv;
 427
 428         if (argc < 2) {
 429                 ti->error = "Invalid argument count";
 430                 return -EINVAL;
 431         }
 432
 433         lc = kzalloc(sizeof(struct log_writes_c), GFP_KERNEL);
 434         if (!lc) {
 435                 ti->error = "Cannot allocate context";
 436                 return -ENOMEM;
 437         }
 438         spin_lock_init(&lc->blocks_lock);
 439         INIT_LIST_HEAD(&lc->unflushed_blocks);
 440         INIT_LIST_HEAD(&lc->logging_blocks);
 441         init_waitqueue_head(&lc->wait);
 442         lc->sectorsize = 1 << SECTOR_SHIFT;
 443         atomic_set(&lc->io_blocks, 0);
 444         atomic_set(&lc->pending_blocks, 0);
 445
 446         devname = dm_shift_arg(&as);
 447         ret = dm_get_device(ti, devname, dm_table_get_mode(ti->table), &lc->dev);
 448         if (ret) {
 449                 ti->error = "Device lookup failed";
 450                 goto bad;
 451         }
 452
 453         logdevname = dm_shift_arg(&as);
 454         ret = dm_get_device(ti, logdevname, dm_table_get_mode(ti->table),
 455                             &lc->logdev);
 456         if (ret) {
 457                 ti->error = "Log device lookup failed";
 458                 dm_put_device(ti, lc->dev);
 459                 goto bad;
 460         }
 461
 462         ret = -EINVAL;
 463         lc->log_kthread = kthread_run(log_writes_kthread, lc, "log-write");
 464         if (!lc->log_kthread) {
 465                 ti->error = "Couldn't alloc kthread";
 466                 dm_put_device(ti, lc->dev);
 467                 dm_put_device(ti, lc->logdev);
 468                 goto bad;
 469         }
 470
 471         /* We put the super at sector 0, start logging at sector 1 */
 472         lc->next_sector = 1;
 473         lc->logging_enabled = true;
 474         lc->end_sector = logdev_last_sector(lc);
 475         lc->device_supports_discard = true;
 476
 477         ti->num_flush_bios = 1;
 478         ti->flush_supported = true;
 479         ti->num_discard_bios = 1;
 480         ti->discards_supported = true;
 481         ti->per_io_data_size = sizeof(struct per_bio_data);
 482         ti->private = lc;
 483         return 0;
 484
 485 bad:
 486         kfree(lc);
 487         return ret;
 488 }
 489
 490 static int log_mark(struct log_writes_c *lc, char *data)
 491 {
 492         struct pending_block *block;
 493         size_t maxsize = lc->sectorsize - sizeof(struct log_write_entry);
 494
 495         block = kzalloc(sizeof(struct pending_block), GFP_KERNEL);
 496         if (!block) {
 497                 DMERR("Error allocating pending block");
 498                 return -ENOMEM;
 499         }
 500
 501         block->data = kstrndup(data, maxsize, GFP_KERNEL);
 502         if (!block->data) {
 503                 DMERR("Error copying mark data");
 504                 kfree(block);
 505                 return -ENOMEM;
 506         }
 507         atomic_inc(&lc->pending_blocks);
 508         block->datalen = strlen(block->data);
 509         block->flags |= LOG_MARK_FLAG;
 510         spin_lock_irq(&lc->blocks_lock);
 511         list_add_tail(&block->list, &lc->logging_blocks);
 512         spin_unlock_irq(&lc->blocks_lock);
 513         wake_up_process(lc->log_kthread);
 514         return 0;
 515 }
 516
 517 static void log_writes_dtr(struct dm_target *ti)
 518 {
 519         struct log_writes_c *lc = ti->private;
 520
 521         spin_lock_irq(&lc->blocks_lock);
 522         list_splice_init(&lc->unflushed_blocks, &lc->logging_blocks);
 523         spin_unlock_irq(&lc->blocks_lock);
 524
 525         /*
 526          * This is just nice to have since it'll update the super to include the
 527          * unflushed blocks, if it fails we don't really care.
 528          */
 529         log_mark(lc, "dm-log-writes-end");
 530         wake_up_process(lc->log_kthread);
 531         wait_event(lc->wait, !atomic_read(&lc->io_blocks) &&
 532                    !atomic_read(&lc->pending_blocks));
 533         kthread_stop(lc->log_kthread);
 534
 535         WARN_ON(!list_empty(&lc->logging_blocks));
 536         WARN_ON(!list_empty(&lc->unflushed_blocks));
 537         dm_put_device(ti, lc->dev);
 538         dm_put_device(ti, lc->logdev);
 539         kfree(lc);
 540 }
 541
 542 static void normal_map_bio(struct dm_target *ti, struct bio *bio)
 543 {
 544         struct log_writes_c *lc = ti->private;
 545
 546         bio->bi_bdev = lc->dev->bdev;
 547 }
 548
 549 static int log_writes_map(struct dm_target *ti, struct bio *bio)
 550 {
 551         struct log_writes_c *lc = ti->private;
 552         struct per_bio_data *pb = dm_per_bio_data(bio, sizeof(struct per_bio_data));
 553         struct pending_block *block;
 554         struct bvec_iter iter;
 555         struct bio_vec bv;
 556         size_t alloc_size;
 557         int i = 0;
 558         bool flush_bio = (bio->bi_opf & REQ_PREFLUSH);
 559         bool fua_bio = (bio->bi_opf & REQ_FUA);
 560         bool discard_bio = (bio_op(bio) == REQ_OP_DISCARD);
 561
 562         pb->block = NULL;
 563
 564         /* Don't bother doing anything if logging has been disabled */
 565         if (!lc->logging_enabled)
 566                 goto map_bio;
 567
 568         /*
 569          * Map reads as normal.
 570          */
 571         if (bio_data_dir(bio) == READ)
 572                 goto map_bio;
 573
 574         /* No sectors and not a flush?  Don't care */
 575         if (!bio_sectors(bio) && !flush_bio)
 576                 goto map_bio;
 577
 578         /*
 579          * Discards will have bi_size set but there's no actual data, so just
 580          * allocate the size of the pending block.
 581          */
 582         if (discard_bio)
 583                 alloc_size = sizeof(struct pending_block);
 584         else
 585                 alloc_size = sizeof(struct pending_block) + sizeof(struct bio_vec) * bio_segments(bio);
 586
 587         block = kzalloc(alloc_size, GFP_NOIO);
 588         if (!block) {
 589                 DMERR("Error allocating pending block");
 590                 spin_lock_irq(&lc->blocks_lock);
 591                 lc->logging_enabled = false;
 592                 spin_unlock_irq(&lc->blocks_lock);
 593                 return -ENOMEM;
 594         }
 595         INIT_LIST_HEAD(&block->list);
 596         pb->block = block;
 597         atomic_inc(&lc->pending_blocks);
 598
 599         if (flush_bio)
 600                 block->flags |= LOG_FLUSH_FLAG;
 601         if (fua_bio)
 602                 block->flags |= LOG_FUA_FLAG;
 603         if (discard_bio)
 604                 block->flags |= LOG_DISCARD_FLAG;
 605
 606         block->sector = bio->bi_iter.bi_sector;
 607         block->nr_sectors = bio_sectors(bio);
 608
 609         /* We don't need the data, just submit */
 610         if (discard_bio) {
 611                 WARN_ON(flush_bio || fua_bio);
 612                 if (lc->device_supports_discard)
 613                         goto map_bio;
 614                 bio_endio(bio);
 615                 return DM_MAPIO_SUBMITTED;
 616         }
 617
 618         /* Flush bio, splice the unflushed blocks onto this list and submit */
 619         if (flush_bio && !bio_sectors(bio)) {
 620                 spin_lock_irq(&lc->blocks_lock);
 621                 list_splice_init(&lc->unflushed_blocks, &block->list);
 622                 spin_unlock_irq(&lc->blocks_lock);
 623                 goto map_bio;
 624         }
 625
 626         /*
 627          * We will write this bio somewhere else way later so we need to copy
 628          * the actual contents into new pages so we know the data will always be
 629          * there.
 630          *
 631          * We do this because this could be a bio from O_DIRECT in which case we
 632          * can't just hold onto the page until some later point, we have to
 633          * manually copy the contents.
 634          */
 635         bio_for_each_segment(bv, bio, iter) {
 636                 struct page *page;
 637                 void *src, *dst;
 638
 639                 page = alloc_page(GFP_NOIO);
 640                 if (!page) {
 641                         DMERR("Error allocing page");
 642                         free_pending_block(lc, block);
 643                         spin_lock_irq(&lc->blocks_lock);
 644                         lc->logging_enabled = false;
 645                         spin_unlock_irq(&lc->blocks_lock);
 646                         return -ENOMEM;
 647                 }
 648
 649                 src = kmap_atomic(bv.bv_page);
 650                 dst = kmap_atomic(page);
 651                 memcpy(dst, src + bv.bv_offset, bv.bv_len);
 652                 kunmap_atomic(dst);
 653                 kunmap_atomic(src);
 654                 block->vecs[i].bv_page = page;
 655                 block->vecs[i].bv_len = bv.bv_len;
 656                 block->vec_cnt++;
 657                 i++;
 658         }
 659
 660         /* Had a flush with data in it, weird */
 661         if (flush_bio) {
 662                 spin_lock_irq(&lc->blocks_lock);
 663                 list_splice_init(&lc->unflushed_blocks, &block->list);
 664                 spin_unlock_irq(&lc->blocks_lock);
 665         }
 666 map_bio:
 667         normal_map_bio(ti, bio);
 668         return DM_MAPIO_REMAPPED;
 669 }
 670
 671 static int normal_end_io(struct dm_target *ti, struct bio *bio, int error)
 672 {
 673         struct log_writes_c *lc = ti->private;
 674         struct per_bio_data *pb = dm_per_bio_data(bio, sizeof(struct per_bio_data));
 675
 676         if (bio_data_dir(bio) == WRITE && pb->block) {
 677                 struct pending_block *block = pb->block;
 678                 unsigned long flags;
 679
 680                 spin_lock_irqsave(&lc->blocks_lock, flags);
 681                 if (block->flags & LOG_FLUSH_FLAG) {
 682                         list_splice_tail_init(&block->list, &lc->logging_blocks);
 683                         list_add_tail(&block->list, &lc->logging_blocks);
 684                         wake_up_process(lc->log_kthread);
 685                 } else if (block->flags & LOG_FUA_FLAG) {
 686                         list_add_tail(&block->list, &lc->logging_blocks);
 687                         wake_up_process(lc->log_kthread);
 688                 } else
 689                         list_add_tail(&block->list, &lc->unflushed_blocks);
 690                 spin_unlock_irqrestore(&lc->blocks_lock, flags);
 691         }
 692
 693         return error;
 694 }
 695
 696 /*
 697  * INFO format: <logged entries> <highest allocated sector>
 698  */
 699 static void log_writes_status(struct dm_target *ti, status_type_t type,
 700                               unsigned status_flags, char *result,
 701                               unsigned maxlen)
 702 {
 703         unsigned sz = 0;
 704         struct log_writes_c *lc = ti->private;
 705
 706         switch (type) {
 707         case STATUSTYPE_INFO:
 708                 DMEMIT("%llu %llu", lc->logged_entries,
 709                        (unsigned long long)lc->next_sector - 1);
 710                 if (!lc->logging_enabled)
 711                         DMEMIT(" logging_disabled");
 712                 break;
 713
 714         case STATUSTYPE_TABLE:
 715                 DMEMIT("%s %s", lc->dev->name, lc->logdev->name);
 716                 break;
 717         }
 718 }
 719
 720 static int log_writes_prepare_ioctl(struct dm_target *ti,
 721                 struct block_device **bdev, fmode_t *mode)
 722 {
 723         struct log_writes_c *lc = ti->private;
 724         struct dm_dev *dev = lc->dev;
 725
 726         *bdev = dev->bdev;
 727         /*
 728          * Only pass ioctls through if the device sizes match exactly.
 729          */
 730         if (ti->len != i_size_read(dev->bdev->bd_inode) >> SECTOR_SHIFT)
 731                 return 1;
 732         return 0;
 733 }
 734
 735 static int log_writes_iterate_devices(struct dm_target *ti,
 736                                       iterate_devices_callout_fn fn,
 737                                       void *data)
 738 {
 739         struct log_writes_c *lc = ti->private;
 740
 741         return fn(ti, lc->dev, 0, ti->len, data);
 742 }
 743
 744 /*
 745  * Messages supported:
 746  *   mark <mark data> - specify the marked data.
 747  */
 748 static int log_writes_message(struct dm_target *ti, unsigned argc, char **argv)
 749 {
 750         int r = -EINVAL;
 751         struct log_writes_c *lc = ti->private;
 752
 753         if (argc != 2) {
 754                 DMWARN("Invalid log-writes message arguments, expect 2 arguments, got %d", argc);
 755                 return r;
 756         }
 757
 758         if (!strcasecmp(argv[0], "mark"))
 759                 r = log_mark(lc, argv[1]);
 760         else
 761                 DMWARN("Unrecognised log writes target message received: %s", argv[0]);
 762
 763         return r;
 764 }
 765
 766 static void log_writes_io_hints(struct dm_target *ti, struct queue_limits *limits)
 767 {
 768         struct log_writes_c *lc = ti->private;
 769         struct request_queue *q = bdev_get_queue(lc->dev->bdev);
 770
 771         if (!q || !blk_queue_discard(q)) {
 772                 lc->device_supports_discard = false;
 773                 limits->discard_granularity = 1 << SECTOR_SHIFT;
 774                 limits->max_discard_sectors = (UINT_MAX >> SECTOR_SHIFT);
 775         }
 776 }
 777
 778 static struct target_type log_writes_target = {
 779         .name   = "log-writes",
 780         .version = {1, 0, 0},
 781         .module = THIS_MODULE,
 782         .ctr    = log_writes_ctr,
 783         .dtr    = log_writes_dtr,
 784         .map    = log_writes_map,
 785         .end_io = normal_end_io,
 786         .status = log_writes_status,
 787         .prepare_ioctl = log_writes_prepare_ioctl,
 788         .message = log_writes_message,
 789         .iterate_devices = log_writes_iterate_devices,
 790         .io_hints = log_writes_io_hints,
 791 };
 792
 793 static int __init dm_log_writes_init(void)
 794 {
 795         int r = dm_register_target(&log_writes_target);
 796
 797         if (r < 0)
 798                 DMERR("register failed %d", r);
 799
 800         return r;
 801 }
 802
 803 static void __exit dm_log_writes_exit(void)
 804 {
 805         dm_unregister_target(&log_writes_target);
 806 }
 807
 808 module_init(dm_log_writes_init);
 809 module_exit(dm_log_writes_exit);
 810
 811 MODULE_DESCRIPTION(DM_NAME " log writes target");
 812 MODULE_AUTHOR("Josef Bacik <jbacik@fb.com>");
 813 MODULE_LICENSE("GPL");