Btrfs: fix wrong super generation mismatch when scrubbing supers
We came a race condition when scrubbing superblocks, the story is: In commiting transaction, we will update @last_trans_commited after writting superblocks, if scrubber start after writting superblocks and before updating @last_trans_commited, generation mismatch happens! We fix this by checking @scrub_pause_req, and we won't start a srubber until commiting transaction is finished.(after btrfs_scrub_continue() finished.) Reported-by: Sebastian Ochmann <ochmann@informatik.uni-bonn.de> Signed-off-by: Wang Shilong <wangsl.fnst@cn.fujitsu.com> Reviewed-by: Miao Xie <miaox@cn.fujitsu.com> Signed-off-by: Josef Bacik <jbacik@fb.com> Signed-off-by: Chris Mason <clm@fb.com>
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@ -256,6 +256,7 @@ static int copy_nocow_pages_for_inode(u64 inum, u64 offset, u64 root,
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static int copy_nocow_pages(struct scrub_ctx *sctx, u64 logical, u64 len,
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int mirror_num, u64 physical_for_dev_replace);
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static void copy_nocow_pages_worker(struct btrfs_work *work);
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static void scrub_blocked_if_needed(struct btrfs_fs_info *fs_info);
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static void scrub_pending_bio_inc(struct scrub_ctx *sctx)
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@ -269,6 +270,16 @@ static void scrub_pending_bio_dec(struct scrub_ctx *sctx)
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wake_up(&sctx->list_wait);
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}
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static void scrub_blocked_if_needed(struct btrfs_fs_info *fs_info)
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{
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while (atomic_read(&fs_info->scrub_pause_req)) {
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mutex_unlock(&fs_info->scrub_lock);
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wait_event(fs_info->scrub_pause_wait,
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atomic_read(&fs_info->scrub_pause_req) == 0);
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mutex_lock(&fs_info->scrub_lock);
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}
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}
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/*
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* used for workers that require transaction commits (i.e., for the
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* NOCOW case)
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@ -2310,14 +2321,10 @@ static noinline_for_stack int scrub_stripe(struct scrub_ctx *sctx,
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btrfs_reada_wait(reada2);
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mutex_lock(&fs_info->scrub_lock);
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while (atomic_read(&fs_info->scrub_pause_req)) {
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mutex_unlock(&fs_info->scrub_lock);
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wait_event(fs_info->scrub_pause_wait,
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atomic_read(&fs_info->scrub_pause_req) == 0);
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mutex_lock(&fs_info->scrub_lock);
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}
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scrub_blocked_if_needed(fs_info);
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atomic_dec(&fs_info->scrubs_paused);
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mutex_unlock(&fs_info->scrub_lock);
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wake_up(&fs_info->scrub_pause_wait);
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/*
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@ -2357,15 +2364,12 @@ static noinline_for_stack int scrub_stripe(struct scrub_ctx *sctx,
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atomic_set(&sctx->wr_ctx.flush_all_writes, 0);
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atomic_inc(&fs_info->scrubs_paused);
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wake_up(&fs_info->scrub_pause_wait);
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mutex_lock(&fs_info->scrub_lock);
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while (atomic_read(&fs_info->scrub_pause_req)) {
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mutex_unlock(&fs_info->scrub_lock);
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wait_event(fs_info->scrub_pause_wait,
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atomic_read(&fs_info->scrub_pause_req) == 0);
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mutex_lock(&fs_info->scrub_lock);
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}
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scrub_blocked_if_needed(fs_info);
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atomic_dec(&fs_info->scrubs_paused);
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mutex_unlock(&fs_info->scrub_lock);
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wake_up(&fs_info->scrub_pause_wait);
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}
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@ -2687,14 +2691,10 @@ int scrub_enumerate_chunks(struct scrub_ctx *sctx,
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atomic_read(&sctx->workers_pending) == 0);
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mutex_lock(&fs_info->scrub_lock);
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while (atomic_read(&fs_info->scrub_pause_req)) {
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mutex_unlock(&fs_info->scrub_lock);
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wait_event(fs_info->scrub_pause_wait,
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atomic_read(&fs_info->scrub_pause_req) == 0);
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mutex_lock(&fs_info->scrub_lock);
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}
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scrub_blocked_if_needed(fs_info);
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atomic_dec(&fs_info->scrubs_paused);
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mutex_unlock(&fs_info->scrub_lock);
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wake_up(&fs_info->scrub_pause_wait);
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btrfs_put_block_group(cache);
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@ -2906,7 +2906,13 @@ int btrfs_scrub_dev(struct btrfs_fs_info *fs_info, u64 devid, u64 start,
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}
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sctx->readonly = readonly;
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dev->scrub_device = sctx;
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mutex_unlock(&fs_info->fs_devices->device_list_mutex);
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/*
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* checking @scrub_pause_req here, we can avoid
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* race between committing transaction and scrubbing.
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*/
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scrub_blocked_if_needed(fs_info);
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atomic_inc(&fs_info->scrubs_running);
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mutex_unlock(&fs_info->scrub_lock);
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@ -2915,9 +2921,10 @@ int btrfs_scrub_dev(struct btrfs_fs_info *fs_info, u64 devid, u64 start,
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* by holding device list mutex, we can
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* kick off writing super in log tree sync.
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*/
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mutex_lock(&fs_info->fs_devices->device_list_mutex);
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ret = scrub_supers(sctx, dev);
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mutex_unlock(&fs_info->fs_devices->device_list_mutex);
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}
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mutex_unlock(&fs_info->fs_devices->device_list_mutex);
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if (!ret)
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ret = scrub_enumerate_chunks(sctx, dev, start, end,
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