/* * Copyright (C) 2014 Facebook. All rights reserved. * * This file is released under the GPL. */ #include #include #include #include #include #include #include #include #define DM_MSG_PREFIX "log-writes" /* * This target will sequentially log all writes to the target device onto the * log device. This is helpful for replaying writes to check for fs consistency * at all times. This target provides a mechanism to mark specific events to * check data at a later time. So for example you would: * * write data * fsync * dmsetup message /dev/whatever mark mymark * unmount /mnt/test * * Then replay the log up to mymark and check the contents of the replay to * verify it matches what was written. * * We log writes only after they have been flushed, this makes the log describe * close to the order in which the data hits the actual disk, not its cache. So * for example the following sequence (W means write, C means complete) * * Wa,Wb,Wc,Cc,Ca,FLUSH,FUAd,Cb,CFLUSH,CFUAd * * Would result in the log looking like this: * * c,a,flush,fuad,b,, * * This is meant to help expose problems where file systems do not properly wait * on data being written before invoking a FLUSH. FUA bypasses cache so once it * completes it is added to the log as it should be on disk. * * We treat DISCARDs as if they don't bypass cache so that they are logged in * order of completion along with the normal writes. If we didn't do it this * way we would process all the discards first and then write all the data, when * in fact we want to do the data and the discard in the order that they * completed. */ #define LOG_FLUSH_FLAG (1 << 0) #define LOG_FUA_FLAG (1 << 1) #define LOG_DISCARD_FLAG (1 << 2) #define LOG_MARK_FLAG (1 << 3) #define WRITE_LOG_VERSION 1ULL #define WRITE_LOG_MAGIC 0x6a736677736872ULL /* * The disk format for this is braindead simple. * * At byte 0 we have our super, followed by the following sequence for * nr_entries: * * [ 1 sector ][ entry->nr_sectors ] * [log_write_entry][ data written ] * * The log_write_entry takes up a full sector so we can have arbitrary length * marks and it leaves us room for extra content in the future. */ /* * Basic info about the log for userspace. */ struct log_write_super { __le64 magic; __le64 version; __le64 nr_entries; __le32 sectorsize; }; /* * sector - the sector we wrote. * nr_sectors - the number of sectors we wrote. * flags - flags for this log entry. * data_len - the size of the data in this log entry, this is for private log * entry stuff, the MARK data provided by userspace for example. */ struct log_write_entry { __le64 sector; __le64 nr_sectors; __le64 flags; __le64 data_len; }; struct log_writes_c { struct dm_dev *dev; struct dm_dev *logdev; u64 logged_entries; u32 sectorsize; atomic_t io_blocks; atomic_t pending_blocks; sector_t next_sector; sector_t end_sector; bool logging_enabled; bool device_supports_discard; spinlock_t blocks_lock; struct list_head unflushed_blocks; struct list_head logging_blocks; wait_queue_head_t wait; struct task_struct *log_kthread; }; struct pending_block { int vec_cnt; u64 flags; sector_t sector; sector_t nr_sectors; char *data; u32 datalen; struct list_head list; struct bio_vec vecs[0]; }; struct per_bio_data { struct pending_block *block; }; static void put_pending_block(struct log_writes_c *lc) { if (atomic_dec_and_test(&lc->pending_blocks)) { smp_mb__after_atomic(); if (waitqueue_active(&lc->wait)) wake_up(&lc->wait); } } static void put_io_block(struct log_writes_c *lc) { if (atomic_dec_and_test(&lc->io_blocks)) { smp_mb__after_atomic(); if (waitqueue_active(&lc->wait)) wake_up(&lc->wait); } } static void log_end_io(struct bio *bio) { struct log_writes_c *lc = bio->bi_private; if (bio->bi_error) { unsigned long flags; DMERR("Error writing log block, error=%d", bio->bi_error); spin_lock_irqsave(&lc->blocks_lock, flags); lc->logging_enabled = false; spin_unlock_irqrestore(&lc->blocks_lock, flags); } bio_free_pages(bio); put_io_block(lc); bio_put(bio); } /* * Meant to be called if there is an error, it will free all the pages * associated with the block. */ static void free_pending_block(struct log_writes_c *lc, struct pending_block *block) { int i; for (i = 0; i < block->vec_cnt; i++) { if (block->vecs[i].bv_page) __free_page(block->vecs[i].bv_page); } kfree(block->data); kfree(block); put_pending_block(lc); } static int write_metadata(struct log_writes_c *lc, void *entry, size_t entrylen, void *data, size_t datalen, sector_t sector) { struct bio *bio; struct page *page; void *ptr; size_t ret; bio = bio_alloc(GFP_KERNEL, 1); if (!bio) { DMERR("Couldn't alloc log bio"); goto error; } bio->bi_iter.bi_size = 0; bio->bi_iter.bi_sector = sector; bio->bi_bdev = lc->logdev->bdev; bio->bi_end_io = log_end_io; bio->bi_private = lc; bio_set_op_attrs(bio, REQ_OP_WRITE, 0); page = alloc_page(GFP_KERNEL); if (!page) { DMERR("Couldn't alloc log page"); bio_put(bio); goto error; } ptr = kmap_atomic(page); memcpy(ptr, entry, entrylen); if (datalen) memcpy(ptr + entrylen, data, datalen); memset(ptr + entrylen + datalen, 0, lc->sectorsize - entrylen - datalen); kunmap_atomic(ptr); ret = bio_add_page(bio, page, lc->sectorsize, 0); if (ret != lc->sectorsize) { DMERR("Couldn't add page to the log block"); goto error_bio; } submit_bio(bio); return 0; error_bio: bio_put(bio); __free_page(page); error: put_io_block(lc); return -1; } static int log_one_block(struct log_writes_c *lc, struct pending_block *block, sector_t sector) { struct bio *bio; struct log_write_entry entry; size_t ret; int i; entry.sector = cpu_to_le64(block->sector); entry.nr_sectors = cpu_to_le64(block->nr_sectors); entry.flags = cpu_to_le64(block->flags); entry.data_len = cpu_to_le64(block->datalen); if (write_metadata(lc, &entry, sizeof(entry), block->data, block->datalen, sector)) { free_pending_block(lc, block); return -1; } if (!block->vec_cnt) goto out; sector++; atomic_inc(&lc->io_blocks); bio = bio_alloc(GFP_KERNEL, min(block->vec_cnt, BIO_MAX_PAGES)); if (!bio) { DMERR("Couldn't alloc log bio"); goto error; } bio->bi_iter.bi_size = 0; bio->bi_iter.bi_sector = sector; bio->bi_bdev = lc->logdev->bdev; bio->bi_end_io = log_end_io; bio->bi_private = lc; bio_set_op_attrs(bio, REQ_OP_WRITE, 0); for (i = 0; i < block->vec_cnt; i++) { /* * The page offset is always 0 because we allocate a new page * for every bvec in the original bio for simplicity sake. */ ret = bio_add_page(bio, block->vecs[i].bv_page, block->vecs[i].bv_len, 0); if (ret != block->vecs[i].bv_len) { atomic_inc(&lc->io_blocks); submit_bio(bio); bio = bio_alloc(GFP_KERNEL, min(block->vec_cnt - i, BIO_MAX_PAGES)); if (!bio) { DMERR("Couldn't alloc log bio"); goto error; } bio->bi_iter.bi_size = 0; bio->bi_iter.bi_sector = sector; bio->bi_bdev = lc->logdev->bdev; bio->bi_end_io = log_end_io; bio->bi_private = lc; bio_set_op_attrs(bio, REQ_OP_WRITE, 0); ret = bio_add_page(bio, block->vecs[i].bv_page, block->vecs[i].bv_len, 0); if (ret != block->vecs[i].bv_len) { DMERR("Couldn't add page on new bio?"); bio_put(bio); goto error; } } sector += block->vecs[i].bv_len >> SECTOR_SHIFT; } submit_bio(bio); out: kfree(block->data); kfree(block); put_pending_block(lc); return 0; error: free_pending_block(lc, block); put_io_block(lc); return -1; } static int log_super(struct log_writes_c *lc) { struct log_write_super super; super.magic = cpu_to_le64(WRITE_LOG_MAGIC); super.version = cpu_to_le64(WRITE_LOG_VERSION); super.nr_entries = cpu_to_le64(lc->logged_entries); super.sectorsize = cpu_to_le32(lc->sectorsize); if (write_metadata(lc, &super, sizeof(super), NULL, 0, 0)) { DMERR("Couldn't write super"); return -1; } return 0; } static inline sector_t logdev_last_sector(struct log_writes_c *lc) { return i_size_read(lc->logdev->bdev->bd_inode) >> SECTOR_SHIFT; } static int log_writes_kthread(void *arg) { struct log_writes_c *lc = (struct log_writes_c *)arg; sector_t sector = 0; while (!kthread_should_stop()) { bool super = false; bool logging_enabled; struct pending_block *block = NULL; int ret; spin_lock_irq(&lc->blocks_lock); if (!list_empty(&lc->logging_blocks)) { block = list_first_entry(&lc->logging_blocks, struct pending_block, list); list_del_init(&block->list); if (!lc->logging_enabled) goto next; sector = lc->next_sector; if (block->flags & LOG_DISCARD_FLAG) lc->next_sector++; else lc->next_sector += block->nr_sectors + 1; /* * Apparently the size of the device may not be known * right away, so handle this properly. */ if (!lc->end_sector) lc->end_sector = logdev_last_sector(lc); if (lc->end_sector && lc->next_sector >= lc->end_sector) { DMERR("Ran out of space on the logdev"); lc->logging_enabled = false; goto next; } lc->logged_entries++; atomic_inc(&lc->io_blocks); super = (block->flags & (LOG_FUA_FLAG | LOG_MARK_FLAG)); if (super) atomic_inc(&lc->io_blocks); } next: logging_enabled = lc->logging_enabled; spin_unlock_irq(&lc->blocks_lock); if (block) { if (logging_enabled) { ret = log_one_block(lc, block, sector); if (!ret && super) ret = log_super(lc); if (ret) { spin_lock_irq(&lc->blocks_lock); lc->logging_enabled = false; spin_unlock_irq(&lc->blocks_lock); } } else free_pending_block(lc, block); continue; } if (!try_to_freeze()) { set_current_state(TASK_INTERRUPTIBLE); if (!kthread_should_stop() && !atomic_read(&lc->pending_blocks)) schedule(); __set_current_state(TASK_RUNNING); } } return 0; } /* * Construct a log-writes mapping: * log-writes */ static int log_writes_ctr(struct dm_target *ti, unsigned int argc, char **argv) { struct log_writes_c *lc; struct dm_arg_set as; const char *devname, *logdevname; int ret; as.argc = argc; as.argv = argv; if (argc < 2) { ti->error = "Invalid argument count"; return -EINVAL; } lc = kzalloc(sizeof(struct log_writes_c), GFP_KERNEL); if (!lc) { ti->error = "Cannot allocate context"; return -ENOMEM; } spin_lock_init(&lc->blocks_lock); INIT_LIST_HEAD(&lc->unflushed_blocks); INIT_LIST_HEAD(&lc->logging_blocks); init_waitqueue_head(&lc->wait); lc->sectorsize = 1 << SECTOR_SHIFT; atomic_set(&lc->io_blocks, 0); atomic_set(&lc->pending_blocks, 0); devname = dm_shift_arg(&as); ret = dm_get_device(ti, devname, dm_table_get_mode(ti->table), &lc->dev); if (ret) { ti->error = "Device lookup failed"; goto bad; } logdevname = dm_shift_arg(&as); ret = dm_get_device(ti, logdevname, dm_table_get_mode(ti->table), &lc->logdev); if (ret) { ti->error = "Log device lookup failed"; dm_put_device(ti, lc->dev); goto bad; } lc->log_kthread = kthread_run(log_writes_kthread, lc, "log-write"); if (IS_ERR(lc->log_kthread)) { ret = PTR_ERR(lc->log_kthread); ti->error = "Couldn't alloc kthread"; dm_put_device(ti, lc->dev); dm_put_device(ti, lc->logdev); goto bad; } /* We put the super at sector 0, start logging at sector 1 */ lc->next_sector = 1; lc->logging_enabled = true; lc->end_sector = logdev_last_sector(lc); lc->device_supports_discard = true; ti->num_flush_bios = 1; ti->flush_supported = true; ti->num_discard_bios = 1; ti->discards_supported = true; ti->per_io_data_size = sizeof(struct per_bio_data); ti->private = lc; return 0; bad: kfree(lc); return ret; } static int log_mark(struct log_writes_c *lc, char *data) { struct pending_block *block; size_t maxsize = lc->sectorsize - sizeof(struct log_write_entry); block = kzalloc(sizeof(struct pending_block), GFP_KERNEL); if (!block) { DMERR("Error allocating pending block"); return -ENOMEM; } block->data = kstrndup(data, maxsize, GFP_KERNEL); if (!block->data) { DMERR("Error copying mark data"); kfree(block); return -ENOMEM; } atomic_inc(&lc->pending_blocks); block->datalen = strlen(block->data); block->flags |= LOG_MARK_FLAG; spin_lock_irq(&lc->blocks_lock); list_add_tail(&block->list, &lc->logging_blocks); spin_unlock_irq(&lc->blocks_lock); wake_up_process(lc->log_kthread); return 0; } static void log_writes_dtr(struct dm_target *ti) { struct log_writes_c *lc = ti->private; spin_lock_irq(&lc->blocks_lock); list_splice_init(&lc->unflushed_blocks, &lc->logging_blocks); spin_unlock_irq(&lc->blocks_lock); /* * This is just nice to have since it'll update the super to include the * unflushed blocks, if it fails we don't really care. */ log_mark(lc, "dm-log-writes-end"); wake_up_process(lc->log_kthread); wait_event(lc->wait, !atomic_read(&lc->io_blocks) && !atomic_read(&lc->pending_blocks)); kthread_stop(lc->log_kthread); WARN_ON(!list_empty(&lc->logging_blocks)); WARN_ON(!list_empty(&lc->unflushed_blocks)); dm_put_device(ti, lc->dev); dm_put_device(ti, lc->logdev); kfree(lc); } static void normal_map_bio(struct dm_target *ti, struct bio *bio) { struct log_writes_c *lc = ti->private; bio->bi_bdev = lc->dev->bdev; } static int log_writes_map(struct dm_target *ti, struct bio *bio) { struct log_writes_c *lc = ti->private; struct per_bio_data *pb = dm_per_bio_data(bio, sizeof(struct per_bio_data)); struct pending_block *block; struct bvec_iter iter; struct bio_vec bv; size_t alloc_size; int i = 0; bool flush_bio = (bio->bi_opf & REQ_PREFLUSH); bool fua_bio = (bio->bi_opf & REQ_FUA); bool discard_bio = (bio_op(bio) == REQ_OP_DISCARD); pb->block = NULL; /* Don't bother doing anything if logging has been disabled */ if (!lc->logging_enabled) goto map_bio; /* * Map reads as normal. */ if (bio_data_dir(bio) == READ) goto map_bio; /* No sectors and not a flush? Don't care */ if (!bio_sectors(bio) && !flush_bio) goto map_bio; /* * Discards will have bi_size set but there's no actual data, so just * allocate the size of the pending block. */ if (discard_bio) alloc_size = sizeof(struct pending_block); else alloc_size = sizeof(struct pending_block) + sizeof(struct bio_vec) * bio_segments(bio); block = kzalloc(alloc_size, GFP_NOIO); if (!block) { DMERR("Error allocating pending block"); spin_lock_irq(&lc->blocks_lock); lc->logging_enabled = false; spin_unlock_irq(&lc->blocks_lock); return -ENOMEM; } INIT_LIST_HEAD(&block->list); pb->block = block; atomic_inc(&lc->pending_blocks); if (flush_bio) block->flags |= LOG_FLUSH_FLAG; if (fua_bio) block->flags |= LOG_FUA_FLAG; if (discard_bio) block->flags |= LOG_DISCARD_FLAG; block->sector = bio->bi_iter.bi_sector; block->nr_sectors = bio_sectors(bio); /* We don't need the data, just submit */ if (discard_bio) { WARN_ON(flush_bio || fua_bio); if (lc->device_supports_discard) goto map_bio; bio_endio(bio); return DM_MAPIO_SUBMITTED; } /* Flush bio, splice the unflushed blocks onto this list and submit */ if (flush_bio && !bio_sectors(bio)) { spin_lock_irq(&lc->blocks_lock); list_splice_init(&lc->unflushed_blocks, &block->list); spin_unlock_irq(&lc->blocks_lock); goto map_bio; } /* * We will write this bio somewhere else way later so we need to copy * the actual contents into new pages so we know the data will always be * there. * * We do this because this could be a bio from O_DIRECT in which case we * can't just hold onto the page until some later point, we have to * manually copy the contents. */ bio_for_each_segment(bv, bio, iter) { struct page *page; void *src, *dst; page = alloc_page(GFP_NOIO); if (!page) { DMERR("Error allocing page"); free_pending_block(lc, block); spin_lock_irq(&lc->blocks_lock); lc->logging_enabled = false; spin_unlock_irq(&lc->blocks_lock); return -ENOMEM; } src = kmap_atomic(bv.bv_page); dst = kmap_atomic(page); memcpy(dst, src + bv.bv_offset, bv.bv_len); kunmap_atomic(dst); kunmap_atomic(src); block->vecs[i].bv_page = page; block->vecs[i].bv_len = bv.bv_len; block->vec_cnt++; i++; } /* Had a flush with data in it, weird */ if (flush_bio) { spin_lock_irq(&lc->blocks_lock); list_splice_init(&lc->unflushed_blocks, &block->list); spin_unlock_irq(&lc->blocks_lock); } map_bio: normal_map_bio(ti, bio); return DM_MAPIO_REMAPPED; } static int normal_end_io(struct dm_target *ti, struct bio *bio, int error) { struct log_writes_c *lc = ti->private; struct per_bio_data *pb = dm_per_bio_data(bio, sizeof(struct per_bio_data)); if (bio_data_dir(bio) == WRITE && pb->block) { struct pending_block *block = pb->block; unsigned long flags; spin_lock_irqsave(&lc->blocks_lock, flags); if (block->flags & LOG_FLUSH_FLAG) { list_splice_tail_init(&block->list, &lc->logging_blocks); list_add_tail(&block->list, &lc->logging_blocks); wake_up_process(lc->log_kthread); } else if (block->flags & LOG_FUA_FLAG) { list_add_tail(&block->list, &lc->logging_blocks); wake_up_process(lc->log_kthread); } else list_add_tail(&block->list, &lc->unflushed_blocks); spin_unlock_irqrestore(&lc->blocks_lock, flags); } return error; } /* * INFO format: */ static void log_writes_status(struct dm_target *ti, status_type_t type, unsigned status_flags, char *result, unsigned maxlen) { unsigned sz = 0; struct log_writes_c *lc = ti->private; switch (type) { case STATUSTYPE_INFO: DMEMIT("%llu %llu", lc->logged_entries, (unsigned long long)lc->next_sector - 1); if (!lc->logging_enabled) DMEMIT(" logging_disabled"); break; case STATUSTYPE_TABLE: DMEMIT("%s %s", lc->dev->name, lc->logdev->name); break; } } static int log_writes_prepare_ioctl(struct dm_target *ti, struct block_device **bdev, fmode_t *mode) { struct log_writes_c *lc = ti->private; struct dm_dev *dev = lc->dev; *bdev = dev->bdev; /* * Only pass ioctls through if the device sizes match exactly. */ if (ti->len != i_size_read(dev->bdev->bd_inode) >> SECTOR_SHIFT) return 1; return 0; } static int log_writes_iterate_devices(struct dm_target *ti, iterate_devices_callout_fn fn, void *data) { struct log_writes_c *lc = ti->private; return fn(ti, lc->dev, 0, ti->len, data); } /* * Messages supported: * mark - specify the marked data. */ static int log_writes_message(struct dm_target *ti, unsigned argc, char **argv) { int r = -EINVAL; struct log_writes_c *lc = ti->private; if (argc != 2) { DMWARN("Invalid log-writes message arguments, expect 2 arguments, got %d", argc); return r; } if (!strcasecmp(argv[0], "mark")) r = log_mark(lc, argv[1]); else DMWARN("Unrecognised log writes target message received: %s", argv[0]); return r; } static void log_writes_io_hints(struct dm_target *ti, struct queue_limits *limits) { struct log_writes_c *lc = ti->private; struct request_queue *q = bdev_get_queue(lc->dev->bdev); if (!q || !blk_queue_discard(q)) { lc->device_supports_discard = false; limits->discard_granularity = 1 << SECTOR_SHIFT; limits->max_discard_sectors = (UINT_MAX >> SECTOR_SHIFT); } } static struct target_type log_writes_target = { .name = "log-writes", .version = {1, 0, 0}, .module = THIS_MODULE, .ctr = log_writes_ctr, .dtr = log_writes_dtr, .map = log_writes_map, .end_io = normal_end_io, .status = log_writes_status, .prepare_ioctl = log_writes_prepare_ioctl, .message = log_writes_message, .iterate_devices = log_writes_iterate_devices, .io_hints = log_writes_io_hints, }; static int __init dm_log_writes_init(void) { int r = dm_register_target(&log_writes_target); if (r < 0) DMERR("register failed %d", r); return r; } static void __exit dm_log_writes_exit(void) { dm_unregister_target(&log_writes_target); } module_init(dm_log_writes_init); module_exit(dm_log_writes_exit); MODULE_DESCRIPTION(DM_NAME " log writes target"); MODULE_AUTHOR("Josef Bacik "); MODULE_LICENSE("GPL");