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/dax.h>
  14 #include <linux/slab.h>
  15 #include <linux/kthread.h>
  16 #include <linux/freezer.h>
  17 #include <linux/uio.h>
  18
  19 #define DM_MSG_PREFIX "log-writes"
  20
  21 /*
  22  * This target will sequentially log all writes to the target device onto the
  23  * log device.  This is helpful for replaying writes to check for fs consistency
  24  * at all times.  This target provides a mechanism to mark specific events to
  25  * check data at a later time.  So for example you would:
  26  *
  27  * write data
  28  * fsync
  29  * dmsetup message /dev/whatever mark mymark
  30  * unmount /mnt/test
  31  *
  32  * Then replay the log up to mymark and check the contents of the replay to
  33  * verify it matches what was written.
  34  *
  35  * We log writes only after they have been flushed, this makes the log describe
  36  * close to the order in which the data hits the actual disk, not its cache.  So
  37  * for example the following sequence (W means write, C means complete)
  38  *
  39  * Wa,Wb,Wc,Cc,Ca,FLUSH,FUAd,Cb,CFLUSH,CFUAd
  40  *
  41  * Would result in the log looking like this:
  42  *
  43  * c,a,flush,fuad,b,<other writes>,<next flush>
  44  *
  45  * This is meant to help expose problems where file systems do not properly wait
  46  * on data being written before invoking a FLUSH.  FUA bypasses cache so once it
  47  * completes it is added to the log as it should be on disk.
  48  *
  49  * We treat DISCARDs as if they don't bypass cache so that they are logged in
  50  * order of completion along with the normal writes.  If we didn't do it this
  51  * way we would process all the discards first and then write all the data, when
  52  * in fact we want to do the data and the discard in the order that they
  53  * completed.
  54  */
  55 #define LOG_FLUSH_FLAG (1 << 0)
  56 #define LOG_FUA_FLAG (1 << 1)
  57 #define LOG_DISCARD_FLAG (1 << 2)
  58 #define LOG_MARK_FLAG (1 << 3)
  59
  60 #define WRITE_LOG_VERSION 1ULL
  61 #define WRITE_LOG_MAGIC 0x6a736677736872ULL
  62
  63 /*
  64  * The disk format for this is braindead simple.
  65  *
  66  * At byte 0 we have our super, followed by the following sequence for
  67  * nr_entries:
  68  *
  69  * [   1 sector    ][  entry->nr_sectors ]
  70  * [log_write_entry][    data written    ]
  71  *
  72  * The log_write_entry takes up a full sector so we can have arbitrary length
  73  * marks and it leaves us room for extra content in the future.
  74  */
  75
  76 /*
  77  * Basic info about the log for userspace.
  78  */
  79 struct log_write_super {
  80         __le64 magic;
  81         __le64 version;
  82         __le64 nr_entries;
  83         __le32 sectorsize;
  84 };
  85
  86 /*
  87  * sector - the sector we wrote.
  88  * nr_sectors - the number of sectors we wrote.
  89  * flags - flags for this log entry.
  90  * data_len - the size of the data in this log entry, this is for private log
  91  * entry stuff, the MARK data provided by userspace for example.
  92  */
  93 struct log_write_entry {
  94         __le64 sector;
  95         __le64 nr_sectors;
  96         __le64 flags;
  97         __le64 data_len;
  98 };
  99
 100 struct log_writes_c {
 101         struct dm_dev *dev;
 102         struct dm_dev *logdev;
 103         u64 logged_entries;
 104         u32 sectorsize;
 105         u32 sectorshift;
 106         atomic_t io_blocks;
 107         atomic_t pending_blocks;
 108         sector_t next_sector;
 109         sector_t end_sector;
 110         bool logging_enabled;
 111         bool device_supports_discard;
 112         spinlock_t blocks_lock;
 113         struct list_head unflushed_blocks;
 114         struct list_head logging_blocks;
 115         wait_queue_head_t wait;
 116         struct task_struct *log_kthread;
 117 };
 118
 119 struct pending_block {
 120         int vec_cnt;
 121         u64 flags;
 122         sector_t sector;
 123         sector_t nr_sectors;
 124         char *data;
 125         u32 datalen;
 126         struct list_head list;
 127         struct bio_vec vecs[0];
 128 };
 129
 130 struct per_bio_data {
 131         struct pending_block *block;
 132 };
 133
 134 static inline sector_t bio_to_dev_sectors(struct log_writes_c *lc,
 135                                           sector_t sectors)
 136 {
 137         return sectors >> (lc->sectorshift - SECTOR_SHIFT);
 138 }
 139
 140 static inline sector_t dev_to_bio_sectors(struct log_writes_c *lc,
 141                                           sector_t sectors)
 142 {
 143         return sectors << (lc->sectorshift - SECTOR_SHIFT);
 144 }
 145
 146 static void put_pending_block(struct log_writes_c *lc)
 147 {
 148         if (atomic_dec_and_test(&lc->pending_blocks)) {
 149                 smp_mb__after_atomic();
 150                 if (waitqueue_active(&lc->wait))
 151                         wake_up(&lc->wait);
 152         }
 153 }
 154
 155 static void put_io_block(struct log_writes_c *lc)
 156 {
 157         if (atomic_dec_and_test(&lc->io_blocks)) {
 158                 smp_mb__after_atomic();
 159                 if (waitqueue_active(&lc->wait))
 160                         wake_up(&lc->wait);
 161         }
 162 }
 163
 164 static void log_end_io(struct bio *bio)
 165 {
 166         struct log_writes_c *lc = bio->bi_private;
 167
 168         if (bio->bi_status) {
 169                 unsigned long flags;
 170
 171                 DMERR("Error writing log block, error=%d", bio->bi_status);
 172                 spin_lock_irqsave(&lc->blocks_lock, flags);
 173                 lc->logging_enabled = false;
 174                 spin_unlock_irqrestore(&lc->blocks_lock, flags);
 175         }
 176
 177         bio_free_pages(bio);
 178         put_io_block(lc);
 179         bio_put(bio);
 180 }
 181
 182 /*
 183  * Meant to be called if there is an error, it will free all the pages
 184  * associated with the block.
 185  */
 186 static void free_pending_block(struct log_writes_c *lc,
 187                                struct pending_block *block)
 188 {
 189         int i;
 190
 191         for (i = 0; i < block->vec_cnt; i++) {
 192                 if (block->vecs[i].bv_page)
 193                         __free_page(block->vecs[i].bv_page);
 194         }
 195         kfree(block->data);
 196         kfree(block);
 197         put_pending_block(lc);
 198 }
 199
 200 static int write_metadata(struct log_writes_c *lc, void *entry,
 201                           size_t entrylen, void *data, size_t datalen,
 202                           sector_t sector)
 203 {
 204         struct bio *bio;
 205         struct page *page;
 206         void *ptr;
 207         size_t ret;
 208
 209         bio = bio_alloc(GFP_KERNEL, 1);
 210         if (!bio) {
 211                 DMERR("Couldn't alloc log bio");
 212                 goto error;
 213         }
 214         bio->bi_iter.bi_size = 0;
 215         bio->bi_iter.bi_sector = sector;
 216         bio_set_dev(bio, lc->logdev->bdev);
 217         bio->bi_end_io = log_end_io;
 218         bio->bi_private = lc;
 219         bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
 220
 221         page = alloc_page(GFP_KERNEL);
 222         if (!page) {
 223                 DMERR("Couldn't alloc log page");
 224                 bio_put(bio);
 225                 goto error;
 226         }
 227
 228         ptr = kmap_atomic(page);
 229         memcpy(ptr, entry, entrylen);
 230         if (datalen)
 231                 memcpy(ptr + entrylen, data, datalen);
 232         memset(ptr + entrylen + datalen, 0,
 233                lc->sectorsize - entrylen - datalen);
 234         kunmap_atomic(ptr);
 235
 236         ret = bio_add_page(bio, page, lc->sectorsize, 0);
 237         if (ret != lc->sectorsize) {
 238                 DMERR("Couldn't add page to the log block");
 239                 goto error_bio;
 240         }
 241         submit_bio(bio);
 242         return 0;
 243 error_bio:
 244         bio_put(bio);
 245         __free_page(page);
 246 error:
 247         put_io_block(lc);
 248         return -1;
 249 }
 250
 251 static int write_inline_data(struct log_writes_c *lc, void *entry,
 252                              size_t entrylen, void *data, size_t datalen,
 253                              sector_t sector)
 254 {
 255         int num_pages, bio_pages, pg_datalen, pg_sectorlen, i;
 256         struct page *page;
 257         struct bio *bio;
 258         size_t ret;
 259         void *ptr;
 260
 261         while (datalen) {
 262                 num_pages = ALIGN(datalen, PAGE_SIZE) >> PAGE_SHIFT;
 263                 bio_pages = min(num_pages, BIO_MAX_PAGES);
 264
 265                 atomic_inc(&lc->io_blocks);
 266
 267                 bio = bio_alloc(GFP_KERNEL, bio_pages);
 268                 if (!bio) {
 269                         DMERR("Couldn't alloc inline data bio");
 270                         goto error;
 271                 }
 272
 273                 bio->bi_iter.bi_size = 0;
 274                 bio->bi_iter.bi_sector = sector;
 275                 bio_set_dev(bio, lc->logdev->bdev);
 276                 bio->bi_end_io = log_end_io;
 277                 bio->bi_private = lc;
 278                 bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
 279
 280                 for (i = 0; i < bio_pages; i++) {
 281                         pg_datalen = min_t(int, datalen, PAGE_SIZE);
 282                         pg_sectorlen = ALIGN(pg_datalen, lc->sectorsize);
 283
 284                         page = alloc_page(GFP_KERNEL);
 285                         if (!page) {
 286                                 DMERR("Couldn't alloc inline data page");
 287                                 goto error_bio;
 288                         }
 289
 290                         ptr = kmap_atomic(page);
 291                         memcpy(ptr, data, pg_datalen);
 292                         if (pg_sectorlen > pg_datalen)
 293                                 memset(ptr + pg_datalen, 0, pg_sectorlen - pg_datalen);
 294                         kunmap_atomic(ptr);
 295
 296                         ret = bio_add_page(bio, page, pg_sectorlen, 0);
 297                         if (ret != pg_sectorlen) {
 298                                 DMERR("Couldn't add page of inline data");
 299                                 __free_page(page);
 300                                 goto error_bio;
 301                         }
 302
 303                         datalen -= pg_datalen;
 304                         data    += pg_datalen;
 305                 }
 306                 submit_bio(bio);
 307
 308                 sector += bio_pages * PAGE_SECTORS;
 309         }
 310         return 0;
 311 error_bio:
 312         bio_free_pages(bio);
 313         bio_put(bio);
 314 error:
 315         put_io_block(lc);
 316         return -1;
 317 }
 318
 319 static int log_one_block(struct log_writes_c *lc,
 320                          struct pending_block *block, sector_t sector)
 321 {
 322         struct bio *bio;
 323         struct log_write_entry entry;
 324         size_t metadatalen, ret;
 325         int i;
 326
 327         entry.sector = cpu_to_le64(block->sector);
 328         entry.nr_sectors = cpu_to_le64(block->nr_sectors);
 329         entry.flags = cpu_to_le64(block->flags);
 330         entry.data_len = cpu_to_le64(block->datalen);
 331
 332         metadatalen = (block->flags & LOG_MARK_FLAG) ? block->datalen : 0;
 333         if (write_metadata(lc, &entry, sizeof(entry), block->data,
 334                            metadatalen, sector)) {
 335                 free_pending_block(lc, block);
 336                 return -1;
 337         }
 338
 339         sector += dev_to_bio_sectors(lc, 1);
 340
 341         if (block->datalen && metadatalen == 0) {
 342                 if (write_inline_data(lc, &entry, sizeof(entry), block->data,
 343                                       block->datalen, sector)) {
 344                         free_pending_block(lc, block);
 345                         return -1;
 346                 }
 347                 /* we don't support both inline data & bio data */
 348                 goto out;
 349         }
 350
 351         if (!block->vec_cnt)
 352                 goto out;
 353
 354         atomic_inc(&lc->io_blocks);
 355         bio = bio_alloc(GFP_KERNEL, min(block->vec_cnt, BIO_MAX_PAGES));
 356         if (!bio) {
 357                 DMERR("Couldn't alloc log bio");
 358                 goto error;
 359         }
 360         bio->bi_iter.bi_size = 0;
 361         bio->bi_iter.bi_sector = sector;
 362         bio_set_dev(bio, lc->logdev->bdev);
 363         bio->bi_end_io = log_end_io;
 364         bio->bi_private = lc;
 365         bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
 366
 367         for (i = 0; i < block->vec_cnt; i++) {
 368                 /*
 369                  * The page offset is always 0 because we allocate a new page
 370                  * for every bvec in the original bio for simplicity sake.
 371                  */
 372                 ret = bio_add_page(bio, block->vecs[i].bv_page,
 373                                    block->vecs[i].bv_len, 0);
 374                 if (ret != block->vecs[i].bv_len) {
 375                         atomic_inc(&lc->io_blocks);
 376                         submit_bio(bio);
 377                         bio = bio_alloc(GFP_KERNEL, min(block->vec_cnt - i, BIO_MAX_PAGES));
 378                         if (!bio) {
 379                                 DMERR("Couldn't alloc log bio");
 380                                 goto error;
 381                         }
 382                         bio->bi_iter.bi_size = 0;
 383                         bio->bi_iter.bi_sector = sector;
 384                         bio_set_dev(bio, lc->logdev->bdev);
 385                         bio->bi_end_io = log_end_io;
 386                         bio->bi_private = lc;
 387                         bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
 388
 389                         ret = bio_add_page(bio, block->vecs[i].bv_page,
 390                                            block->vecs[i].bv_len, 0);
 391                         if (ret != block->vecs[i].bv_len) {
 392                                 DMERR("Couldn't add page on new bio?");
 393                                 bio_put(bio);
 394                                 goto error;
 395                         }
 396                 }
 397                 sector += block->vecs[i].bv_len >> SECTOR_SHIFT;
 398         }
 399         submit_bio(bio);
 400 out:
 401         kfree(block->data);
 402         kfree(block);
 403         put_pending_block(lc);
 404         return 0;
 405 error:
 406         free_pending_block(lc, block);
 407         put_io_block(lc);
 408         return -1;
 409 }
 410
 411 static int log_super(struct log_writes_c *lc)
 412 {
 413         struct log_write_super super;
 414
 415         super.magic = cpu_to_le64(WRITE_LOG_MAGIC);
 416         super.version = cpu_to_le64(WRITE_LOG_VERSION);
 417         super.nr_entries = cpu_to_le64(lc->logged_entries);
 418         super.sectorsize = cpu_to_le32(lc->sectorsize);
 419
 420         if (write_metadata(lc, &super, sizeof(super), NULL, 0, 0)) {
 421                 DMERR("Couldn't write super");
 422                 return -1;
 423         }
 424
 425         return 0;
 426 }
 427
 428 static inline sector_t logdev_last_sector(struct log_writes_c *lc)
 429 {
 430         return i_size_read(lc->logdev->bdev->bd_inode) >> SECTOR_SHIFT;
 431 }
 432
 433 static int log_writes_kthread(void *arg)
 434 {
 435         struct log_writes_c *lc = (struct log_writes_c *)arg;
 436         sector_t sector = 0;
 437
 438         while (!kthread_should_stop()) {
 439                 bool super = false;
 440                 bool logging_enabled;
 441                 struct pending_block *block = NULL;
 442                 int ret;
 443
 444                 spin_lock_irq(&lc->blocks_lock);
 445                 if (!list_empty(&lc->logging_blocks)) {
 446                         block = list_first_entry(&lc->logging_blocks,
 447                                                  struct pending_block, list);
 448                         list_del_init(&block->list);
 449                         if (!lc->logging_enabled)
 450                                 goto next;
 451
 452                         sector = lc->next_sector;
 453                         if (!(block->flags & LOG_DISCARD_FLAG))
 454                                 lc->next_sector += dev_to_bio_sectors(lc, block->nr_sectors);
 455                         lc->next_sector += dev_to_bio_sectors(lc, 1);
 456
 457                         /*
 458                          * Apparently the size of the device may not be known
 459                          * right away, so handle this properly.
 460                          */
 461                         if (!lc->end_sector)
 462                                 lc->end_sector = logdev_last_sector(lc);
 463                         if (lc->end_sector &&
 464                             lc->next_sector >= lc->end_sector) {
 465                                 DMERR("Ran out of space on the logdev");
 466                                 lc->logging_enabled = false;
 467                                 goto next;
 468                         }
 469                         lc->logged_entries++;
 470                         atomic_inc(&lc->io_blocks);
 471
 472                         super = (block->flags & (LOG_FUA_FLAG | LOG_MARK_FLAG));
 473                         if (super)
 474                                 atomic_inc(&lc->io_blocks);
 475                 }
 476 next:
 477                 logging_enabled = lc->logging_enabled;
 478                 spin_unlock_irq(&lc->blocks_lock);
 479                 if (block) {
 480                         if (logging_enabled) {
 481                                 ret = log_one_block(lc, block, sector);
 482                                 if (!ret && super)
 483                                         ret = log_super(lc);
 484                                 if (ret) {
 485                                         spin_lock_irq(&lc->blocks_lock);
 486                                         lc->logging_enabled = false;
 487                                         spin_unlock_irq(&lc->blocks_lock);
 488                                 }
 489                         } else
 490                                 free_pending_block(lc, block);
 491                         continue;
 492                 }
 493
 494                 if (!try_to_freeze()) {
 495                         set_current_state(TASK_INTERRUPTIBLE);
 496                         if (!kthread_should_stop() &&
 497                             list_empty(&lc->logging_blocks))
 498                                 schedule();
 499                         __set_current_state(TASK_RUNNING);
 500                 }
 501         }
 502         return 0;
 503 }
 504
 505 /*
 506  * Construct a log-writes mapping:
 507  * log-writes <dev_path> <log_dev_path>
 508  */
 509 static int log_writes_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 510 {
 511         struct log_writes_c *lc;
 512         struct dm_arg_set as;
 513         const char *devname, *logdevname;
 514         int ret;
 515
 516         as.argc = argc;
 517         as.argv = argv;
 518
 519         if (argc < 2) {
 520                 ti->error = "Invalid argument count";
 521                 return -EINVAL;
 522         }
 523
 524         lc = kzalloc(sizeof(struct log_writes_c), GFP_KERNEL);
 525         if (!lc) {
 526                 ti->error = "Cannot allocate context";
 527                 return -ENOMEM;
 528         }
 529         spin_lock_init(&lc->blocks_lock);
 530         INIT_LIST_HEAD(&lc->unflushed_blocks);
 531         INIT_LIST_HEAD(&lc->logging_blocks);
 532         init_waitqueue_head(&lc->wait);
 533         atomic_set(&lc->io_blocks, 0);
 534         atomic_set(&lc->pending_blocks, 0);
 535
 536         devname = dm_shift_arg(&as);
 537         ret = dm_get_device(ti, devname, dm_table_get_mode(ti->table), &lc->dev);
 538         if (ret) {
 539                 ti->error = "Device lookup failed";
 540                 goto bad;
 541         }
 542
 543         logdevname = dm_shift_arg(&as);
 544         ret = dm_get_device(ti, logdevname, dm_table_get_mode(ti->table),
 545                             &lc->logdev);
 546         if (ret) {
 547                 ti->error = "Log device lookup failed";
 548                 dm_put_device(ti, lc->dev);
 549                 goto bad;
 550         }
 551
 552         lc->sectorsize = bdev_logical_block_size(lc->dev->bdev);
 553         lc->sectorshift = ilog2(lc->sectorsize);
 554         lc->log_kthread = kthread_run(log_writes_kthread, lc, "log-write");
 555         if (IS_ERR(lc->log_kthread)) {
 556                 ret = PTR_ERR(lc->log_kthread);
 557                 ti->error = "Couldn't alloc kthread";
 558                 dm_put_device(ti, lc->dev);
 559                 dm_put_device(ti, lc->logdev);
 560                 goto bad;
 561         }
 562
 563         /*
 564          * next_sector is in 512b sectors to correspond to what bi_sector expects.
 565          * The super starts at sector 0, and the next_sector is the next logical
 566          * one based on the sectorsize of the device.
 567          */
 568         lc->next_sector = lc->sectorsize >> SECTOR_SHIFT;
 569         lc->logging_enabled = true;
 570         lc->end_sector = logdev_last_sector(lc);
 571         lc->device_supports_discard = true;
 572
 573         ti->num_flush_bios = 1;
 574         ti->flush_supported = true;
 575         ti->num_discard_bios = 1;
 576         ti->discards_supported = true;
 577         ti->per_io_data_size = sizeof(struct per_bio_data);
 578         ti->private = lc;
 579         return 0;
 580
 581 bad:
 582         kfree(lc);
 583         return ret;
 584 }
 585
 586 static int log_mark(struct log_writes_c *lc, char *data)
 587 {
 588         struct pending_block *block;
 589         size_t maxsize = lc->sectorsize - sizeof(struct log_write_entry);
 590
 591         block = kzalloc(sizeof(struct pending_block), GFP_KERNEL);
 592         if (!block) {
 593                 DMERR("Error allocating pending block");
 594                 return -ENOMEM;
 595         }
 596
 597         block->data = kstrndup(data, maxsize, GFP_KERNEL);
 598         if (!block->data) {
 599                 DMERR("Error copying mark data");
 600                 kfree(block);
 601                 return -ENOMEM;
 602         }
 603         atomic_inc(&lc->pending_blocks);
 604         block->datalen = strlen(block->data);
 605         block->flags |= LOG_MARK_FLAG;
 606         spin_lock_irq(&lc->blocks_lock);
 607         list_add_tail(&block->list, &lc->logging_blocks);
 608         spin_unlock_irq(&lc->blocks_lock);
 609         wake_up_process(lc->log_kthread);
 610         return 0;
 611 }
 612
 613 static int log_dax(struct log_writes_c *lc, sector_t sector, size_t bytes,
 614                    struct iov_iter *i)
 615 {
 616         struct pending_block *block;
 617
 618         if (!bytes)
 619                 return 0;
 620
 621         block = kzalloc(sizeof(struct pending_block), GFP_KERNEL);
 622         if (!block) {
 623                 DMERR("Error allocating dax pending block");
 624                 return -ENOMEM;
 625         }
 626
 627         block->data = kzalloc(bytes, GFP_KERNEL);
 628         if (!block->data) {
 629                 DMERR("Error allocating dax data space");
 630                 kfree(block);
 631                 return -ENOMEM;
 632         }
 633
 634         /* write data provided via the iterator */
 635         if (!copy_from_iter(block->data, bytes, i)) {
 636                 DMERR("Error copying dax data");
 637                 kfree(block->data);
 638                 kfree(block);
 639                 return -EIO;
 640         }
 641
 642         /* rewind the iterator so that the block driver can use it */
 643         iov_iter_revert(i, bytes);
 644
 645         block->datalen = bytes;
 646         block->sector = bio_to_dev_sectors(lc, sector);
 647         block->nr_sectors = ALIGN(bytes, lc->sectorsize) >> lc->sectorshift;
 648
 649         atomic_inc(&lc->pending_blocks);
 650         spin_lock_irq(&lc->blocks_lock);
 651         list_add_tail(&block->list, &lc->unflushed_blocks);
 652         spin_unlock_irq(&lc->blocks_lock);
 653         wake_up_process(lc->log_kthread);
 654
 655         return 0;
 656 }
 657
 658 static void log_writes_dtr(struct dm_target *ti)
 659 {
 660         struct log_writes_c *lc = ti->private;
 661
 662         spin_lock_irq(&lc->blocks_lock);
 663         list_splice_init(&lc->unflushed_blocks, &lc->logging_blocks);
 664         spin_unlock_irq(&lc->blocks_lock);
 665
 666         /*
 667          * This is just nice to have since it'll update the super to include the
 668          * unflushed blocks, if it fails we don't really care.
 669          */
 670         log_mark(lc, "dm-log-writes-end");
 671         wake_up_process(lc->log_kthread);
 672         wait_event(lc->wait, !atomic_read(&lc->io_blocks) &&
 673                    !atomic_read(&lc->pending_blocks));
 674         kthread_stop(lc->log_kthread);
 675
 676         WARN_ON(!list_empty(&lc->logging_blocks));
 677         WARN_ON(!list_empty(&lc->unflushed_blocks));
 678         dm_put_device(ti, lc->dev);
 679         dm_put_device(ti, lc->logdev);
 680         kfree(lc);
 681 }
 682
 683 static void normal_map_bio(struct dm_target *ti, struct bio *bio)
 684 {
 685         struct log_writes_c *lc = ti->private;
 686
 687         bio_set_dev(bio, lc->dev->bdev);
 688 }
 689
 690 static int log_writes_map(struct dm_target *ti, struct bio *bio)
 691 {
 692         struct log_writes_c *lc = ti->private;
 693         struct per_bio_data *pb = dm_per_bio_data(bio, sizeof(struct per_bio_data));
 694         struct pending_block *block;
 695         struct bvec_iter iter;
 696         struct bio_vec bv;
 697         size_t alloc_size;
 698         int i = 0;
 699         bool flush_bio = (bio->bi_opf & REQ_PREFLUSH);
 700         bool fua_bio = (bio->bi_opf & REQ_FUA);
 701         bool discard_bio = (bio_op(bio) == REQ_OP_DISCARD);
 702
 703         pb->block = NULL;
 704
 705         /* Don't bother doing anything if logging has been disabled */
 706         if (!lc->logging_enabled)
 707                 goto map_bio;
 708
 709         /*
 710          * Map reads as normal.
 711          */
 712         if (bio_data_dir(bio) == READ)
 713                 goto map_bio;
 714
 715         /* No sectors and not a flush?  Don't care */
 716         if (!bio_sectors(bio) && !flush_bio)
 717                 goto map_bio;
 718
 719         /*
 720          * Discards will have bi_size set but there's no actual data, so just
 721          * allocate the size of the pending block.
 722          */
 723         if (discard_bio)
 724                 alloc_size = sizeof(struct pending_block);
 725         else
 726                 alloc_size = sizeof(struct pending_block) + sizeof(struct bio_vec) * bio_segments(bio);
 727
 728         block = kzalloc(alloc_size, GFP_NOIO);
 729         if (!block) {
 730                 DMERR("Error allocating pending block");
 731                 spin_lock_irq(&lc->blocks_lock);
 732                 lc->logging_enabled = false;
 733                 spin_unlock_irq(&lc->blocks_lock);
 734                 return DM_MAPIO_KILL;
 735         }
 736         INIT_LIST_HEAD(&block->list);
 737         pb->block = block;
 738         atomic_inc(&lc->pending_blocks);
 739
 740         if (flush_bio)
 741                 block->flags |= LOG_FLUSH_FLAG;
 742         if (fua_bio)
 743                 block->flags |= LOG_FUA_FLAG;
 744         if (discard_bio)
 745                 block->flags |= LOG_DISCARD_FLAG;
 746
 747         block->sector = bio_to_dev_sectors(lc, bio->bi_iter.bi_sector);
 748         block->nr_sectors = bio_to_dev_sectors(lc, bio_sectors(bio));
 749
 750         /* We don't need the data, just submit */
 751         if (discard_bio) {
 752                 WARN_ON(flush_bio || fua_bio);
 753                 if (lc->device_supports_discard)
 754                         goto map_bio;
 755                 bio_endio(bio);
 756                 return DM_MAPIO_SUBMITTED;
 757         }
 758
 759         /* Flush bio, splice the unflushed blocks onto this list and submit */
 760         if (flush_bio && !bio_sectors(bio)) {
 761                 spin_lock_irq(&lc->blocks_lock);
 762                 list_splice_init(&lc->unflushed_blocks, &block->list);
 763                 spin_unlock_irq(&lc->blocks_lock);
 764                 goto map_bio;
 765         }
 766
 767         /*
 768          * We will write this bio somewhere else way later so we need to copy
 769          * the actual contents into new pages so we know the data will always be
 770          * there.
 771          *
 772          * We do this because this could be a bio from O_DIRECT in which case we
 773          * can't just hold onto the page until some later point, we have to
 774          * manually copy the contents.
 775          */
 776         bio_for_each_segment(bv, bio, iter) {
 777                 struct page *page;
 778                 void *src, *dst;
 779
 780                 page = alloc_page(GFP_NOIO);
 781                 if (!page) {
 782                         DMERR("Error allocing page");
 783                         free_pending_block(lc, block);
 784                         spin_lock_irq(&lc->blocks_lock);
 785                         lc->logging_enabled = false;
 786                         spin_unlock_irq(&lc->blocks_lock);
 787                         return DM_MAPIO_KILL;
 788                 }
 789
 790                 src = kmap_atomic(bv.bv_page);
 791                 dst = kmap_atomic(page);
 792                 memcpy(dst, src + bv.bv_offset, bv.bv_len);
 793                 kunmap_atomic(dst);
 794                 kunmap_atomic(src);
 795                 block->vecs[i].bv_page = page;
 796                 block->vecs[i].bv_len = bv.bv_len;
 797                 block->vec_cnt++;
 798                 i++;
 799         }
 800
 801         /* Had a flush with data in it, weird */
 802         if (flush_bio) {
 803                 spin_lock_irq(&lc->blocks_lock);
 804                 list_splice_init(&lc->unflushed_blocks, &block->list);
 805                 spin_unlock_irq(&lc->blocks_lock);
 806         }
 807 map_bio:
 808         normal_map_bio(ti, bio);
 809         return DM_MAPIO_REMAPPED;
 810 }
 811
 812 static int normal_end_io(struct dm_target *ti, struct bio *bio,
 813                 blk_status_t *error)
 814 {
 815         struct log_writes_c *lc = ti->private;
 816         struct per_bio_data *pb = dm_per_bio_data(bio, sizeof(struct per_bio_data));
 817
 818         if (bio_data_dir(bio) == WRITE && pb->block) {
 819                 struct pending_block *block = pb->block;
 820                 unsigned long flags;
 821
 822                 spin_lock_irqsave(&lc->blocks_lock, flags);
 823                 if (block->flags & LOG_FLUSH_FLAG) {
 824                         list_splice_tail_init(&block->list, &lc->logging_blocks);
 825                         list_add_tail(&block->list, &lc->logging_blocks);
 826                         wake_up_process(lc->log_kthread);
 827                 } else if (block->flags & LOG_FUA_FLAG) {
 828                         list_add_tail(&block->list, &lc->logging_blocks);
 829                         wake_up_process(lc->log_kthread);
 830                 } else
 831                         list_add_tail(&block->list, &lc->unflushed_blocks);
 832                 spin_unlock_irqrestore(&lc->blocks_lock, flags);
 833         }
 834
 835         return DM_ENDIO_DONE;
 836 }
 837
 838 /*
 839  * INFO format: <logged entries> <highest allocated sector>
 840  */
 841 static void log_writes_status(struct dm_target *ti, status_type_t type,
 842                               unsigned status_flags, char *result,
 843                               unsigned maxlen)
 844 {
 845         unsigned sz = 0;
 846         struct log_writes_c *lc = ti->private;
 847
 848         switch (type) {
 849         case STATUSTYPE_INFO:
 850                 DMEMIT("%llu %llu", lc->logged_entries,
 851                        (unsigned long long)lc->next_sector - 1);
 852                 if (!lc->logging_enabled)
 853                         DMEMIT(" logging_disabled");
 854                 break;
 855
 856         case STATUSTYPE_TABLE:
 857                 DMEMIT("%s %s", lc->dev->name, lc->logdev->name);
 858                 break;
 859         }
 860 }
 861
 862 static int log_writes_prepare_ioctl(struct dm_target *ti,
 863                 struct block_device **bdev, fmode_t *mode)
 864 {
 865         struct log_writes_c *lc = ti->private;
 866         struct dm_dev *dev = lc->dev;
 867
 868         *bdev = dev->bdev;
 869         /*
 870          * Only pass ioctls through if the device sizes match exactly.
 871          */
 872         if (ti->len != i_size_read(dev->bdev->bd_inode) >> SECTOR_SHIFT)
 873                 return 1;
 874         return 0;
 875 }
 876
 877 static int log_writes_iterate_devices(struct dm_target *ti,
 878                                       iterate_devices_callout_fn fn,
 879                                       void *data)
 880 {
 881         struct log_writes_c *lc = ti->private;
 882
 883         return fn(ti, lc->dev, 0, ti->len, data);
 884 }
 885
 886 /*
 887  * Messages supported:
 888  *   mark <mark data> - specify the marked data.
 889  */
 890 static int log_writes_message(struct dm_target *ti, unsigned argc, char **argv)
 891 {
 892         int r = -EINVAL;
 893         struct log_writes_c *lc = ti->private;
 894
 895         if (argc != 2) {
 896                 DMWARN("Invalid log-writes message arguments, expect 2 arguments, got %d", argc);
 897                 return r;
 898         }
 899
 900         if (!strcasecmp(argv[0], "mark"))
 901                 r = log_mark(lc, argv[1]);
 902         else
 903                 DMWARN("Unrecognised log writes target message received: %s", argv[0]);
 904
 905         return r;
 906 }
 907
 908 static void log_writes_io_hints(struct dm_target *ti, struct queue_limits *limits)
 909 {
 910         struct log_writes_c *lc = ti->private;
 911         struct request_queue *q = bdev_get_queue(lc->dev->bdev);
 912
 913         if (!q || !blk_queue_discard(q)) {
 914                 lc->device_supports_discard = false;
 915                 limits->discard_granularity = lc->sectorsize;
 916                 limits->max_discard_sectors = (UINT_MAX >> SECTOR_SHIFT);
 917         }
 918         limits->logical_block_size = bdev_logical_block_size(lc->dev->bdev);
 919         limits->physical_block_size = bdev_physical_block_size(lc->dev->bdev);
 920         limits->io_min = limits->physical_block_size;
 921 }
 922
 923 static long log_writes_dax_direct_access(struct dm_target *ti, pgoff_t pgoff,
 924                                          long nr_pages, void **kaddr, pfn_t *pfn)
 925 {
 926         struct log_writes_c *lc = ti->private;
 927         sector_t sector = pgoff * PAGE_SECTORS;
 928         int ret;
 929
 930         ret = bdev_dax_pgoff(lc->dev->bdev, sector, nr_pages * PAGE_SIZE, &pgoff);
 931         if (ret)
 932                 return ret;
 933         return dax_direct_access(lc->dev->dax_dev, pgoff, nr_pages, kaddr, pfn);
 934 }
 935
 936 static size_t log_writes_dax_copy_from_iter(struct dm_target *ti,
 937                                             pgoff_t pgoff, void *addr, size_t bytes,
 938                                             struct iov_iter *i)
 939 {
 940         struct log_writes_c *lc = ti->private;
 941         sector_t sector = pgoff * PAGE_SECTORS;
 942         int err;
 943
 944         if (bdev_dax_pgoff(lc->dev->bdev, sector, ALIGN(bytes, PAGE_SIZE), &pgoff))
 945                 return 0;
 946
 947         /* Don't bother doing anything if logging has been disabled */
 948         if (!lc->logging_enabled)
 949                 goto dax_copy;
 950
 951         err = log_dax(lc, sector, bytes, i);
 952         if (err) {
 953                 DMWARN("Error %d logging DAX write", err);
 954                 return 0;
 955         }
 956 dax_copy:
 957         return dax_copy_from_iter(lc->dev->dax_dev, pgoff, addr, bytes, i);
 958 }
 959
 960 static struct target_type log_writes_target = {
 961         .name   = "log-writes",
 962         .version = {1, 1, 0},
 963         .module = THIS_MODULE,
 964         .ctr    = log_writes_ctr,
 965         .dtr    = log_writes_dtr,
 966         .map    = log_writes_map,
 967         .end_io = normal_end_io,
 968         .status = log_writes_status,
 969         .prepare_ioctl = log_writes_prepare_ioctl,
 970         .message = log_writes_message,
 971         .iterate_devices = log_writes_iterate_devices,
 972         .io_hints = log_writes_io_hints,
 973         .direct_access = log_writes_dax_direct_access,
 974         .dax_copy_from_iter = log_writes_dax_copy_from_iter,
 975 };
 976
 977 static int __init dm_log_writes_init(void)
 978 {
 979         int r = dm_register_target(&log_writes_target);
 980
 981         if (r < 0)
 982                 DMERR("register failed %d", r);
 983
 984         return r;
 985 }
 986
 987 static void __exit dm_log_writes_exit(void)
 988 {
 989         dm_unregister_target(&log_writes_target);
 990 }
 991
 992 module_init(dm_log_writes_init);
 993 module_exit(dm_log_writes_exit);
 994
 995 MODULE_DESCRIPTION(DM_NAME " log writes target");
 996 MODULE_AUTHOR("Josef Bacik <jbacik@fb.com>");
 997 MODULE_LICENSE("GPL");