linux/drivers/md/dm-log-writes.c
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   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#define LOG_METADATA_FLAG       (1 << 4)
  60
  61#define WRITE_LOG_VERSION 1ULL
  62#define WRITE_LOG_MAGIC 0x6a736677736872ULL
  63#define WRITE_LOG_SUPER_SECTOR 0
  64
  65/*
  66 * The disk format for this is braindead simple.
  67 *
  68 * At byte 0 we have our super, followed by the following sequence for
  69 * nr_entries:
  70 *
  71 * [   1 sector    ][  entry->nr_sectors ]
  72 * [log_write_entry][    data written    ]
  73 *
  74 * The log_write_entry takes up a full sector so we can have arbitrary length
  75 * marks and it leaves us room for extra content in the future.
  76 */
  77
  78/*
  79 * Basic info about the log for userspace.
  80 */
  81struct log_write_super {
  82        __le64 magic;
  83        __le64 version;
  84        __le64 nr_entries;
  85        __le32 sectorsize;
  86};
  87
  88/*
  89 * sector - the sector we wrote.
  90 * nr_sectors - the number of sectors we wrote.
  91 * flags - flags for this log entry.
  92 * data_len - the size of the data in this log entry, this is for private log
  93 * entry stuff, the MARK data provided by userspace for example.
  94 */
  95struct log_write_entry {
  96        __le64 sector;
  97        __le64 nr_sectors;
  98        __le64 flags;
  99        __le64 data_len;
 100};
 101
 102struct log_writes_c {
 103        struct dm_dev *dev;
 104        struct dm_dev *logdev;
 105        u64 logged_entries;
 106        u32 sectorsize;
 107        u32 sectorshift;
 108        atomic_t io_blocks;
 109        atomic_t pending_blocks;
 110        sector_t next_sector;
 111        sector_t end_sector;
 112        bool logging_enabled;
 113        bool device_supports_discard;
 114        spinlock_t blocks_lock;
 115        struct list_head unflushed_blocks;
 116        struct list_head logging_blocks;
 117        wait_queue_head_t wait;
 118        struct task_struct *log_kthread;
 119        struct completion super_done;
 120};
 121
 122struct pending_block {
 123        int vec_cnt;
 124        u64 flags;
 125        sector_t sector;
 126        sector_t nr_sectors;
 127        char *data;
 128        u32 datalen;
 129        struct list_head list;
 130        struct bio_vec vecs[0];
 131};
 132
 133struct per_bio_data {
 134        struct pending_block *block;
 135};
 136
 137static inline sector_t bio_to_dev_sectors(struct log_writes_c *lc,
 138                                          sector_t sectors)
 139{
 140        return sectors >> (lc->sectorshift - SECTOR_SHIFT);
 141}
 142
 143static inline sector_t dev_to_bio_sectors(struct log_writes_c *lc,
 144                                          sector_t sectors)
 145{
 146        return sectors << (lc->sectorshift - SECTOR_SHIFT);
 147}
 148
 149static void put_pending_block(struct log_writes_c *lc)
 150{
 151        if (atomic_dec_and_test(&lc->pending_blocks)) {
 152                smp_mb__after_atomic();
 153                if (waitqueue_active(&lc->wait))
 154                        wake_up(&lc->wait);
 155        }
 156}
 157
 158static void put_io_block(struct log_writes_c *lc)
 159{
 160        if (atomic_dec_and_test(&lc->io_blocks)) {
 161                smp_mb__after_atomic();
 162                if (waitqueue_active(&lc->wait))
 163                        wake_up(&lc->wait);
 164        }
 165}
 166
 167static void log_end_io(struct bio *bio)
 168{
 169        struct log_writes_c *lc = bio->bi_private;
 170
 171        if (bio->bi_status) {
 172                unsigned long flags;
 173
 174                DMERR("Error writing log block, error=%d", bio->bi_status);
 175                spin_lock_irqsave(&lc->blocks_lock, flags);
 176                lc->logging_enabled = false;
 177                spin_unlock_irqrestore(&lc->blocks_lock, flags);
 178        }
 179
 180        bio_free_pages(bio);
 181        put_io_block(lc);
 182        bio_put(bio);
 183}
 184
 185static void log_end_super(struct bio *bio)
 186{
 187        struct log_writes_c *lc = bio->bi_private;
 188
 189        complete(&lc->super_done);
 190        log_end_io(bio);
 191}
 192
 193/*
 194 * Meant to be called if there is an error, it will free all the pages
 195 * associated with the block.
 196 */
 197static void free_pending_block(struct log_writes_c *lc,
 198                               struct pending_block *block)
 199{
 200        int i;
 201
 202        for (i = 0; i < block->vec_cnt; i++) {
 203                if (block->vecs[i].bv_page)
 204                        __free_page(block->vecs[i].bv_page);
 205        }
 206        kfree(block->data);
 207        kfree(block);
 208        put_pending_block(lc);
 209}
 210
 211static int write_metadata(struct log_writes_c *lc, void *entry,
 212                          size_t entrylen, void *data, size_t datalen,
 213                          sector_t sector)
 214{
 215        struct bio *bio;
 216        struct page *page;
 217        void *ptr;
 218        size_t ret;
 219
 220        bio = bio_alloc(GFP_KERNEL, 1);
 221        if (!bio) {
 222                DMERR("Couldn't alloc log bio");
 223                goto error;
 224        }
 225        bio->bi_iter.bi_size = 0;
 226        bio->bi_iter.bi_sector = sector;
 227        bio_set_dev(bio, lc->logdev->bdev);
 228        bio->bi_end_io = (sector == WRITE_LOG_SUPER_SECTOR) ?
 229                          log_end_super : log_end_io;
 230        bio->bi_private = lc;
 231        bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
 232
 233        page = alloc_page(GFP_KERNEL);
 234        if (!page) {
 235                DMERR("Couldn't alloc log page");
 236                bio_put(bio);
 237                goto error;
 238        }
 239
 240        ptr = kmap_atomic(page);
 241        memcpy(ptr, entry, entrylen);
 242        if (datalen)
 243                memcpy(ptr + entrylen, data, datalen);
 244        memset(ptr + entrylen + datalen, 0,
 245               lc->sectorsize - entrylen - datalen);
 246        kunmap_atomic(ptr);
 247
 248        ret = bio_add_page(bio, page, lc->sectorsize, 0);
 249        if (ret != lc->sectorsize) {
 250                DMERR("Couldn't add page to the log block");
 251                goto error_bio;
 252        }
 253        submit_bio(bio);
 254        return 0;
 255error_bio:
 256        bio_put(bio);
 257        __free_page(page);
 258error:
 259        put_io_block(lc);
 260        return -1;
 261}
 262
 263static int write_inline_data(struct log_writes_c *lc, void *entry,
 264                             size_t entrylen, void *data, size_t datalen,
 265                             sector_t sector)
 266{
 267        int num_pages, bio_pages, pg_datalen, pg_sectorlen, i;
 268        struct page *page;
 269        struct bio *bio;
 270        size_t ret;
 271        void *ptr;
 272
 273        while (datalen) {
 274                num_pages = ALIGN(datalen, PAGE_SIZE) >> PAGE_SHIFT;
 275                bio_pages = min(num_pages, BIO_MAX_PAGES);
 276
 277                atomic_inc(&lc->io_blocks);
 278
 279                bio = bio_alloc(GFP_KERNEL, bio_pages);
 280                if (!bio) {
 281                        DMERR("Couldn't alloc inline data bio");
 282                        goto error;
 283                }
 284
 285                bio->bi_iter.bi_size = 0;
 286                bio->bi_iter.bi_sector = sector;
 287                bio_set_dev(bio, lc->logdev->bdev);
 288                bio->bi_end_io = log_end_io;
 289                bio->bi_private = lc;
 290                bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
 291
 292                for (i = 0; i < bio_pages; i++) {
 293                        pg_datalen = min_t(int, datalen, PAGE_SIZE);
 294                        pg_sectorlen = ALIGN(pg_datalen, lc->sectorsize);
 295
 296                        page = alloc_page(GFP_KERNEL);
 297                        if (!page) {
 298                                DMERR("Couldn't alloc inline data page");
 299                                goto error_bio;
 300                        }
 301
 302                        ptr = kmap_atomic(page);
 303                        memcpy(ptr, data, pg_datalen);
 304                        if (pg_sectorlen > pg_datalen)
 305                                memset(ptr + pg_datalen, 0, pg_sectorlen - pg_datalen);
 306                        kunmap_atomic(ptr);
 307
 308                        ret = bio_add_page(bio, page, pg_sectorlen, 0);
 309                        if (ret != pg_sectorlen) {
 310                                DMERR("Couldn't add page of inline data");
 311                                __free_page(page);
 312                                goto error_bio;
 313                        }
 314
 315                        datalen -= pg_datalen;
 316                        data    += pg_datalen;
 317                }
 318                submit_bio(bio);
 319
 320                sector += bio_pages * PAGE_SECTORS;
 321        }
 322        return 0;
 323error_bio:
 324        bio_free_pages(bio);
 325        bio_put(bio);
 326error:
 327        put_io_block(lc);
 328        return -1;
 329}
 330
 331static int log_one_block(struct log_writes_c *lc,
 332                         struct pending_block *block, sector_t sector)
 333{
 334        struct bio *bio;
 335        struct log_write_entry entry;
 336        size_t metadatalen, ret;
 337        int i;
 338
 339        entry.sector = cpu_to_le64(block->sector);
 340        entry.nr_sectors = cpu_to_le64(block->nr_sectors);
 341        entry.flags = cpu_to_le64(block->flags);
 342        entry.data_len = cpu_to_le64(block->datalen);
 343
 344        metadatalen = (block->flags & LOG_MARK_FLAG) ? block->datalen : 0;
 345        if (write_metadata(lc, &entry, sizeof(entry), block->data,
 346                           metadatalen, sector)) {
 347                free_pending_block(lc, block);
 348                return -1;
 349        }
 350
 351        sector += dev_to_bio_sectors(lc, 1);
 352
 353        if (block->datalen && metadatalen == 0) {
 354                if (write_inline_data(lc, &entry, sizeof(entry), block->data,
 355                                      block->datalen, sector)) {
 356                        free_pending_block(lc, block);
 357                        return -1;
 358                }
 359                /* we don't support both inline data & bio data */
 360                goto out;
 361        }
 362
 363        if (!block->vec_cnt)
 364                goto out;
 365
 366        atomic_inc(&lc->io_blocks);
 367        bio = bio_alloc(GFP_KERNEL, min(block->vec_cnt, BIO_MAX_PAGES));
 368        if (!bio) {
 369                DMERR("Couldn't alloc log bio");
 370                goto error;
 371        }
 372        bio->bi_iter.bi_size = 0;
 373        bio->bi_iter.bi_sector = sector;
 374        bio_set_dev(bio, lc->logdev->bdev);
 375        bio->bi_end_io = log_end_io;
 376        bio->bi_private = lc;
 377        bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
 378
 379        for (i = 0; i < block->vec_cnt; i++) {
 380                /*
 381                 * The page offset is always 0 because we allocate a new page
 382                 * for every bvec in the original bio for simplicity sake.
 383                 */
 384                ret = bio_add_page(bio, block->vecs[i].bv_page,
 385                                   block->vecs[i].bv_len, 0);
 386                if (ret != block->vecs[i].bv_len) {
 387                        atomic_inc(&lc->io_blocks);
 388                        submit_bio(bio);
 389                        bio = bio_alloc(GFP_KERNEL, min(block->vec_cnt - i, BIO_MAX_PAGES));
 390                        if (!bio) {
 391                                DMERR("Couldn't alloc log bio");
 392                                goto error;
 393                        }
 394                        bio->bi_iter.bi_size = 0;
 395                        bio->bi_iter.bi_sector = sector;
 396                        bio_set_dev(bio, lc->logdev->bdev);
 397                        bio->bi_end_io = log_end_io;
 398                        bio->bi_private = lc;
 399                        bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
 400
 401                        ret = bio_add_page(bio, block->vecs[i].bv_page,
 402                                           block->vecs[i].bv_len, 0);
 403                        if (ret != block->vecs[i].bv_len) {
 404                                DMERR("Couldn't add page on new bio?");
 405                                bio_put(bio);
 406                                goto error;
 407                        }
 408                }
 409                sector += block->vecs[i].bv_len >> SECTOR_SHIFT;
 410        }
 411        submit_bio(bio);
 412out:
 413        kfree(block->data);
 414        kfree(block);
 415        put_pending_block(lc);
 416        return 0;
 417error:
 418        free_pending_block(lc, block);
 419        put_io_block(lc);
 420        return -1;
 421}
 422
 423static int log_super(struct log_writes_c *lc)
 424{
 425        struct log_write_super super;
 426
 427        super.magic = cpu_to_le64(WRITE_LOG_MAGIC);
 428        super.version = cpu_to_le64(WRITE_LOG_VERSION);
 429        super.nr_entries = cpu_to_le64(lc->logged_entries);
 430        super.sectorsize = cpu_to_le32(lc->sectorsize);
 431
 432        if (write_metadata(lc, &super, sizeof(super), NULL, 0,
 433                           WRITE_LOG_SUPER_SECTOR)) {
 434                DMERR("Couldn't write super");
 435                return -1;
 436        }
 437
 438        /*
 439         * Super sector should be writen in-order, otherwise the
 440         * nr_entries could be rewritten incorrectly by an old bio.
 441         */
 442        wait_for_completion_io(&lc->super_done);
 443
 444        return 0;
 445}
 446
 447static inline sector_t logdev_last_sector(struct log_writes_c *lc)
 448{
 449        return i_size_read(lc->logdev->bdev->bd_inode) >> SECTOR_SHIFT;
 450}
 451
 452static int log_writes_kthread(void *arg)
 453{
 454        struct log_writes_c *lc = (struct log_writes_c *)arg;
 455        sector_t sector = 0;
 456
 457        while (!kthread_should_stop()) {
 458                bool super = false;
 459                bool logging_enabled;
 460                struct pending_block *block = NULL;
 461                int ret;
 462
 463                spin_lock_irq(&lc->blocks_lock);
 464                if (!list_empty(&lc->logging_blocks)) {
 465                        block = list_first_entry(&lc->logging_blocks,
 466                                                 struct pending_block, list);
 467                        list_del_init(&block->list);
 468                        if (!lc->logging_enabled)
 469                                goto next;
 470
 471                        sector = lc->next_sector;
 472                        if (!(block->flags & LOG_DISCARD_FLAG))
 473                                lc->next_sector += dev_to_bio_sectors(lc, block->nr_sectors);
 474                        lc->next_sector += dev_to_bio_sectors(lc, 1);
 475
 476                        /*
 477                         * Apparently the size of the device may not be known
 478                         * right away, so handle this properly.
 479                         */
 480                        if (!lc->end_sector)
 481                                lc->end_sector = logdev_last_sector(lc);
 482                        if (lc->end_sector &&
 483                            lc->next_sector >= lc->end_sector) {
 484                                DMERR("Ran out of space on the logdev");
 485                                lc->logging_enabled = false;
 486                                goto next;
 487                        }
 488                        lc->logged_entries++;
 489                        atomic_inc(&lc->io_blocks);
 490
 491                        super = (block->flags & (LOG_FUA_FLAG | LOG_MARK_FLAG));
 492                        if (super)
 493                                atomic_inc(&lc->io_blocks);
 494                }
 495next:
 496                logging_enabled = lc->logging_enabled;
 497                spin_unlock_irq(&lc->blocks_lock);
 498                if (block) {
 499                        if (logging_enabled) {
 500                                ret = log_one_block(lc, block, sector);
 501                                if (!ret && super)
 502                                        ret = log_super(lc);
 503                                if (ret) {
 504                                        spin_lock_irq(&lc->blocks_lock);
 505                                        lc->logging_enabled = false;
 506                                        spin_unlock_irq(&lc->blocks_lock);
 507                                }
 508                        } else
 509                                free_pending_block(lc, block);
 510                        continue;
 511                }
 512
 513                if (!try_to_freeze()) {
 514                        set_current_state(TASK_INTERRUPTIBLE);
 515                        if (!kthread_should_stop() &&
 516                            list_empty(&lc->logging_blocks))
 517                                schedule();
 518                        __set_current_state(TASK_RUNNING);
 519                }
 520        }
 521        return 0;
 522}
 523
 524/*
 525 * Construct a log-writes mapping:
 526 * log-writes <dev_path> <log_dev_path>
 527 */
 528static int log_writes_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 529{
 530        struct log_writes_c *lc;
 531        struct dm_arg_set as;
 532        const char *devname, *logdevname;
 533        int ret;
 534
 535        as.argc = argc;
 536        as.argv = argv;
 537
 538        if (argc < 2) {
 539                ti->error = "Invalid argument count";
 540                return -EINVAL;
 541        }
 542
 543        lc = kzalloc(sizeof(struct log_writes_c), GFP_KERNEL);
 544        if (!lc) {
 545                ti->error = "Cannot allocate context";
 546                return -ENOMEM;
 547        }
 548        spin_lock_init(&lc->blocks_lock);
 549        INIT_LIST_HEAD(&lc->unflushed_blocks);
 550        INIT_LIST_HEAD(&lc->logging_blocks);
 551        init_waitqueue_head(&lc->wait);
 552        init_completion(&lc->super_done);
 553        atomic_set(&lc->io_blocks, 0);
 554        atomic_set(&lc->pending_blocks, 0);
 555
 556        devname = dm_shift_arg(&as);
 557        ret = dm_get_device(ti, devname, dm_table_get_mode(ti->table), &lc->dev);
 558        if (ret) {
 559                ti->error = "Device lookup failed";
 560                goto bad;
 561        }
 562
 563        logdevname = dm_shift_arg(&as);
 564        ret = dm_get_device(ti, logdevname, dm_table_get_mode(ti->table),
 565                            &lc->logdev);
 566        if (ret) {
 567                ti->error = "Log device lookup failed";
 568                dm_put_device(ti, lc->dev);
 569                goto bad;
 570        }
 571
 572        lc->sectorsize = bdev_logical_block_size(lc->dev->bdev);
 573        lc->sectorshift = ilog2(lc->sectorsize);
 574        lc->log_kthread = kthread_run(log_writes_kthread, lc, "log-write");
 575        if (IS_ERR(lc->log_kthread)) {
 576                ret = PTR_ERR(lc->log_kthread);
 577                ti->error = "Couldn't alloc kthread";
 578                dm_put_device(ti, lc->dev);
 579                dm_put_device(ti, lc->logdev);
 580                goto bad;
 581        }
 582
 583        /*
 584         * next_sector is in 512b sectors to correspond to what bi_sector expects.
 585         * The super starts at sector 0, and the next_sector is the next logical
 586         * one based on the sectorsize of the device.
 587         */
 588        lc->next_sector = lc->sectorsize >> SECTOR_SHIFT;
 589        lc->logging_enabled = true;
 590        lc->end_sector = logdev_last_sector(lc);
 591        lc->device_supports_discard = true;
 592
 593        ti->num_flush_bios = 1;
 594        ti->flush_supported = true;
 595        ti->num_discard_bios = 1;
 596        ti->discards_supported = true;
 597        ti->per_io_data_size = sizeof(struct per_bio_data);
 598        ti->private = lc;
 599        return 0;
 600
 601bad:
 602        kfree(lc);
 603        return ret;
 604}
 605
 606static int log_mark(struct log_writes_c *lc, char *data)
 607{
 608        struct pending_block *block;
 609        size_t maxsize = lc->sectorsize - sizeof(struct log_write_entry);
 610
 611        block = kzalloc(sizeof(struct pending_block), GFP_KERNEL);
 612        if (!block) {
 613                DMERR("Error allocating pending block");
 614                return -ENOMEM;
 615        }
 616
 617        block->data = kstrndup(data, maxsize - 1, GFP_KERNEL);
 618        if (!block->data) {
 619                DMERR("Error copying mark data");
 620                kfree(block);
 621                return -ENOMEM;
 622        }
 623        atomic_inc(&lc->pending_blocks);
 624        block->datalen = strlen(block->data);
 625        block->flags |= LOG_MARK_FLAG;
 626        spin_lock_irq(&lc->blocks_lock);
 627        list_add_tail(&block->list, &lc->logging_blocks);
 628        spin_unlock_irq(&lc->blocks_lock);
 629        wake_up_process(lc->log_kthread);
 630        return 0;
 631}
 632
 633static void log_writes_dtr(struct dm_target *ti)
 634{
 635        struct log_writes_c *lc = ti->private;
 636
 637        spin_lock_irq(&lc->blocks_lock);
 638        list_splice_init(&lc->unflushed_blocks, &lc->logging_blocks);
 639        spin_unlock_irq(&lc->blocks_lock);
 640
 641        /*
 642         * This is just nice to have since it'll update the super to include the
 643         * unflushed blocks, if it fails we don't really care.
 644         */
 645        log_mark(lc, "dm-log-writes-end");
 646        wake_up_process(lc->log_kthread);
 647        wait_event(lc->wait, !atomic_read(&lc->io_blocks) &&
 648                   !atomic_read(&lc->pending_blocks));
 649        kthread_stop(lc->log_kthread);
 650
 651        WARN_ON(!list_empty(&lc->logging_blocks));
 652        WARN_ON(!list_empty(&lc->unflushed_blocks));
 653        dm_put_device(ti, lc->dev);
 654        dm_put_device(ti, lc->logdev);
 655        kfree(lc);
 656}
 657
 658static void normal_map_bio(struct dm_target *ti, struct bio *bio)
 659{
 660        struct log_writes_c *lc = ti->private;
 661
 662        bio_set_dev(bio, lc->dev->bdev);
 663}
 664
 665static int log_writes_map(struct dm_target *ti, struct bio *bio)
 666{
 667        struct log_writes_c *lc = ti->private;
 668        struct per_bio_data *pb = dm_per_bio_data(bio, sizeof(struct per_bio_data));
 669        struct pending_block *block;
 670        struct bvec_iter iter;
 671        struct bio_vec bv;
 672        size_t alloc_size;
 673        int i = 0;
 674        bool flush_bio = (bio->bi_opf & REQ_PREFLUSH);
 675        bool fua_bio = (bio->bi_opf & REQ_FUA);
 676        bool discard_bio = (bio_op(bio) == REQ_OP_DISCARD);
 677        bool meta_bio = (bio->bi_opf & REQ_META);
 678
 679        pb->block = NULL;
 680
 681        /* Don't bother doing anything if logging has been disabled */
 682        if (!lc->logging_enabled)
 683                goto map_bio;
 684
 685        /*
 686         * Map reads as normal.
 687         */
 688        if (bio_data_dir(bio) == READ)
 689                goto map_bio;
 690
 691        /* No sectors and not a flush?  Don't care */
 692        if (!bio_sectors(bio) && !flush_bio)
 693                goto map_bio;
 694
 695        /*
 696         * Discards will have bi_size set but there's no actual data, so just
 697         * allocate the size of the pending block.
 698         */
 699        if (discard_bio)
 700                alloc_size = sizeof(struct pending_block);
 701        else
 702                alloc_size = sizeof(struct pending_block) + sizeof(struct bio_vec) * bio_segments(bio);
 703
 704        block = kzalloc(alloc_size, GFP_NOIO);
 705        if (!block) {
 706                DMERR("Error allocating pending block");
 707                spin_lock_irq(&lc->blocks_lock);
 708                lc->logging_enabled = false;
 709                spin_unlock_irq(&lc->blocks_lock);
 710                return DM_MAPIO_KILL;
 711        }
 712        INIT_LIST_HEAD(&block->list);
 713        pb->block = block;
 714        atomic_inc(&lc->pending_blocks);
 715
 716        if (flush_bio)
 717                block->flags |= LOG_FLUSH_FLAG;
 718        if (fua_bio)
 719                block->flags |= LOG_FUA_FLAG;
 720        if (discard_bio)
 721                block->flags |= LOG_DISCARD_FLAG;
 722        if (meta_bio)
 723                block->flags |= LOG_METADATA_FLAG;
 724
 725        block->sector = bio_to_dev_sectors(lc, bio->bi_iter.bi_sector);
 726        block->nr_sectors = bio_to_dev_sectors(lc, bio_sectors(bio));
 727
 728        /* We don't need the data, just submit */
 729        if (discard_bio) {
 730                WARN_ON(flush_bio || fua_bio);
 731                if (lc->device_supports_discard)
 732                        goto map_bio;
 733                bio_endio(bio);
 734                return DM_MAPIO_SUBMITTED;
 735        }
 736
 737        /* Flush bio, splice the unflushed blocks onto this list and submit */
 738        if (flush_bio && !bio_sectors(bio)) {
 739                spin_lock_irq(&lc->blocks_lock);
 740                list_splice_init(&lc->unflushed_blocks, &block->list);
 741                spin_unlock_irq(&lc->blocks_lock);
 742                goto map_bio;
 743        }
 744
 745        /*
 746         * We will write this bio somewhere else way later so we need to copy
 747         * the actual contents into new pages so we know the data will always be
 748         * there.
 749         *
 750         * We do this because this could be a bio from O_DIRECT in which case we
 751         * can't just hold onto the page until some later point, we have to
 752         * manually copy the contents.
 753         */
 754        bio_for_each_segment(bv, bio, iter) {
 755                struct page *page;
 756                void *src, *dst;
 757
 758                page = alloc_page(GFP_NOIO);
 759                if (!page) {
 760                        DMERR("Error allocing page");
 761                        free_pending_block(lc, block);
 762                        spin_lock_irq(&lc->blocks_lock);
 763                        lc->logging_enabled = false;
 764                        spin_unlock_irq(&lc->blocks_lock);
 765                        return DM_MAPIO_KILL;
 766                }
 767
 768                src = kmap_atomic(bv.bv_page);
 769                dst = kmap_atomic(page);
 770                memcpy(dst, src + bv.bv_offset, bv.bv_len);
 771                kunmap_atomic(dst);
 772                kunmap_atomic(src);
 773                block->vecs[i].bv_page = page;
 774                block->vecs[i].bv_len = bv.bv_len;
 775                block->vec_cnt++;
 776                i++;
 777        }
 778
 779        /* Had a flush with data in it, weird */
 780        if (flush_bio) {
 781                spin_lock_irq(&lc->blocks_lock);
 782                list_splice_init(&lc->unflushed_blocks, &block->list);
 783                spin_unlock_irq(&lc->blocks_lock);
 784        }
 785map_bio:
 786        normal_map_bio(ti, bio);
 787        return DM_MAPIO_REMAPPED;
 788}
 789
 790static int normal_end_io(struct dm_target *ti, struct bio *bio,
 791                blk_status_t *error)
 792{
 793        struct log_writes_c *lc = ti->private;
 794        struct per_bio_data *pb = dm_per_bio_data(bio, sizeof(struct per_bio_data));
 795
 796        if (bio_data_dir(bio) == WRITE && pb->block) {
 797                struct pending_block *block = pb->block;
 798                unsigned long flags;
 799
 800                spin_lock_irqsave(&lc->blocks_lock, flags);
 801                if (block->flags & LOG_FLUSH_FLAG) {
 802                        list_splice_tail_init(&block->list, &lc->logging_blocks);
 803                        list_add_tail(&block->list, &lc->logging_blocks);
 804                        wake_up_process(lc->log_kthread);
 805                } else if (block->flags & LOG_FUA_FLAG) {
 806                        list_add_tail(&block->list, &lc->logging_blocks);
 807                        wake_up_process(lc->log_kthread);
 808                } else
 809                        list_add_tail(&block->list, &lc->unflushed_blocks);
 810                spin_unlock_irqrestore(&lc->blocks_lock, flags);
 811        }
 812
 813        return DM_ENDIO_DONE;
 814}
 815
 816/*
 817 * INFO format: <logged entries> <highest allocated sector>
 818 */
 819static void log_writes_status(struct dm_target *ti, status_type_t type,
 820                              unsigned status_flags, char *result,
 821                              unsigned maxlen)
 822{
 823        unsigned sz = 0;
 824        struct log_writes_c *lc = ti->private;
 825
 826        switch (type) {
 827        case STATUSTYPE_INFO:
 828                DMEMIT("%llu %llu", lc->logged_entries,
 829                       (unsigned long long)lc->next_sector - 1);
 830                if (!lc->logging_enabled)
 831                        DMEMIT(" logging_disabled");
 832                break;
 833
 834        case STATUSTYPE_TABLE:
 835                DMEMIT("%s %s", lc->dev->name, lc->logdev->name);
 836                break;
 837        }
 838}
 839
 840static int log_writes_prepare_ioctl(struct dm_target *ti,
 841                                    struct block_device **bdev)
 842{
 843        struct log_writes_c *lc = ti->private;
 844        struct dm_dev *dev = lc->dev;
 845
 846        *bdev = dev->bdev;
 847        /*
 848         * Only pass ioctls through if the device sizes match exactly.
 849         */
 850        if (ti->len != i_size_read(dev->bdev->bd_inode) >> SECTOR_SHIFT)
 851                return 1;
 852        return 0;
 853}
 854
 855static int log_writes_iterate_devices(struct dm_target *ti,
 856                                      iterate_devices_callout_fn fn,
 857                                      void *data)
 858{
 859        struct log_writes_c *lc = ti->private;
 860
 861        return fn(ti, lc->dev, 0, ti->len, data);
 862}
 863
 864/*
 865 * Messages supported:
 866 *   mark <mark data> - specify the marked data.
 867 */
 868static int log_writes_message(struct dm_target *ti, unsigned argc, char **argv,
 869                              char *result, unsigned maxlen)
 870{
 871        int r = -EINVAL;
 872        struct log_writes_c *lc = ti->private;
 873
 874        if (argc != 2) {
 875                DMWARN("Invalid log-writes message arguments, expect 2 arguments, got %d", argc);
 876                return r;
 877        }
 878
 879        if (!strcasecmp(argv[0], "mark"))
 880                r = log_mark(lc, argv[1]);
 881        else
 882                DMWARN("Unrecognised log writes target message received: %s", argv[0]);
 883
 884        return r;
 885}
 886
 887static void log_writes_io_hints(struct dm_target *ti, struct queue_limits *limits)
 888{
 889        struct log_writes_c *lc = ti->private;
 890        struct request_queue *q = bdev_get_queue(lc->dev->bdev);
 891
 892        if (!q || !blk_queue_discard(q)) {
 893                lc->device_supports_discard = false;
 894                limits->discard_granularity = lc->sectorsize;
 895                limits->max_discard_sectors = (UINT_MAX >> SECTOR_SHIFT);
 896        }
 897        limits->logical_block_size = bdev_logical_block_size(lc->dev->bdev);
 898        limits->physical_block_size = bdev_physical_block_size(lc->dev->bdev);
 899        limits->io_min = limits->physical_block_size;
 900}
 901
 902#if IS_ENABLED(CONFIG_DAX_DRIVER)
 903static int log_dax(struct log_writes_c *lc, sector_t sector, size_t bytes,
 904                   struct iov_iter *i)
 905{
 906        struct pending_block *block;
 907
 908        if (!bytes)
 909                return 0;
 910
 911        block = kzalloc(sizeof(struct pending_block), GFP_KERNEL);
 912        if (!block) {
 913                DMERR("Error allocating dax pending block");
 914                return -ENOMEM;
 915        }
 916
 917        block->data = kzalloc(bytes, GFP_KERNEL);
 918        if (!block->data) {
 919                DMERR("Error allocating dax data space");
 920                kfree(block);
 921                return -ENOMEM;
 922        }
 923
 924        /* write data provided via the iterator */
 925        if (!copy_from_iter(block->data, bytes, i)) {
 926                DMERR("Error copying dax data");
 927                kfree(block->data);
 928                kfree(block);
 929                return -EIO;
 930        }
 931
 932        /* rewind the iterator so that the block driver can use it */
 933        iov_iter_revert(i, bytes);
 934
 935        block->datalen = bytes;
 936        block->sector = bio_to_dev_sectors(lc, sector);
 937        block->nr_sectors = ALIGN(bytes, lc->sectorsize) >> lc->sectorshift;
 938
 939        atomic_inc(&lc->pending_blocks);
 940        spin_lock_irq(&lc->blocks_lock);
 941        list_add_tail(&block->list, &lc->unflushed_blocks);
 942        spin_unlock_irq(&lc->blocks_lock);
 943        wake_up_process(lc->log_kthread);
 944
 945        return 0;
 946}
 947
 948static long log_writes_dax_direct_access(struct dm_target *ti, pgoff_t pgoff,
 949                                         long nr_pages, void **kaddr, pfn_t *pfn)
 950{
 951        struct log_writes_c *lc = ti->private;
 952        sector_t sector = pgoff * PAGE_SECTORS;
 953        int ret;
 954
 955        ret = bdev_dax_pgoff(lc->dev->bdev, sector, nr_pages * PAGE_SIZE, &pgoff);
 956        if (ret)
 957                return ret;
 958        return dax_direct_access(lc->dev->dax_dev, pgoff, nr_pages, kaddr, pfn);
 959}
 960
 961static size_t log_writes_dax_copy_from_iter(struct dm_target *ti,
 962                                            pgoff_t pgoff, void *addr, size_t bytes,
 963                                            struct iov_iter *i)
 964{
 965        struct log_writes_c *lc = ti->private;
 966        sector_t sector = pgoff * PAGE_SECTORS;
 967        int err;
 968
 969        if (bdev_dax_pgoff(lc->dev->bdev, sector, ALIGN(bytes, PAGE_SIZE), &pgoff))
 970                return 0;
 971
 972        /* Don't bother doing anything if logging has been disabled */
 973        if (!lc->logging_enabled)
 974                goto dax_copy;
 975
 976        err = log_dax(lc, sector, bytes, i);
 977        if (err) {
 978                DMWARN("Error %d logging DAX write", err);
 979                return 0;
 980        }
 981dax_copy:
 982        return dax_copy_from_iter(lc->dev->dax_dev, pgoff, addr, bytes, i);
 983}
 984
 985static size_t log_writes_dax_copy_to_iter(struct dm_target *ti,
 986                                          pgoff_t pgoff, void *addr, size_t bytes,
 987                                          struct iov_iter *i)
 988{
 989        struct log_writes_c *lc = ti->private;
 990        sector_t sector = pgoff * PAGE_SECTORS;
 991
 992        if (bdev_dax_pgoff(lc->dev->bdev, sector, ALIGN(bytes, PAGE_SIZE), &pgoff))
 993                return 0;
 994        return dax_copy_to_iter(lc->dev->dax_dev, pgoff, addr, bytes, i);
 995}
 996
 997#else
 998#define log_writes_dax_direct_access NULL
 999#define log_writes_dax_copy_from_iter NULL
1000#define log_writes_dax_copy_to_iter NULL
1001#endif
1002
1003static struct target_type log_writes_target = {
1004        .name   = "log-writes",
1005        .version = {1, 1, 0},
1006        .module = THIS_MODULE,
1007        .ctr    = log_writes_ctr,
1008        .dtr    = log_writes_dtr,
1009        .map    = log_writes_map,
1010        .end_io = normal_end_io,
1011        .status = log_writes_status,
1012        .prepare_ioctl = log_writes_prepare_ioctl,
1013        .message = log_writes_message,
1014        .iterate_devices = log_writes_iterate_devices,
1015        .io_hints = log_writes_io_hints,
1016        .direct_access = log_writes_dax_direct_access,
1017        .dax_copy_from_iter = log_writes_dax_copy_from_iter,
1018        .dax_copy_to_iter = log_writes_dax_copy_to_iter,
1019};
1020
1021static int __init dm_log_writes_init(void)
1022{
1023        int r = dm_register_target(&log_writes_target);
1024
1025        if (r < 0)
1026                DMERR("register failed %d", r);
1027
1028        return r;
1029}
1030
1031static void __exit dm_log_writes_exit(void)
1032{
1033        dm_unregister_target(&log_writes_target);
1034}
1035
1036module_init(dm_log_writes_init);
1037module_exit(dm_log_writes_exit);
1038
1039MODULE_DESCRIPTION(DM_NAME " log writes target");
1040MODULE_AUTHOR("Josef Bacik <jbacik@fb.com>");
1041MODULE_LICENSE("GPL");
1042