From 3cb0929ad24c95c5fd8f08eb41a702a65954b4c6 Mon Sep 17 00:00:00 2001 From: Wang Shilong Date: Wed, 4 Dec 2013 21:15:19 +0800 Subject: [PATCH] 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 Signed-off-by: Wang Shilong Reviewed-by: Miao Xie Signed-off-by: Josef Bacik Signed-off-by: Chris Mason --- fs/btrfs/scrub.c | 45 ++++++++++++++++++++++++++------------------- 1 file changed, 26 insertions(+), 19 deletions(-) diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c index e5481ae12753..6acb573e7d6b 100644 --- a/fs/btrfs/scrub.c +++ b/fs/btrfs/scrub.c @@ -256,6 +256,7 @@ static int copy_nocow_pages_for_inode(u64 inum, u64 offset, u64 root, static int copy_nocow_pages(struct scrub_ctx *sctx, u64 logical, u64 len, int mirror_num, u64 physical_for_dev_replace); static void copy_nocow_pages_worker(struct btrfs_work *work); +static void scrub_blocked_if_needed(struct btrfs_fs_info *fs_info); static void scrub_pending_bio_inc(struct scrub_ctx *sctx) @@ -269,6 +270,16 @@ static void scrub_pending_bio_dec(struct scrub_ctx *sctx) wake_up(&sctx->list_wait); } +static void scrub_blocked_if_needed(struct btrfs_fs_info *fs_info) +{ + while (atomic_read(&fs_info->scrub_pause_req)) { + mutex_unlock(&fs_info->scrub_lock); + wait_event(fs_info->scrub_pause_wait, + atomic_read(&fs_info->scrub_pause_req) == 0); + mutex_lock(&fs_info->scrub_lock); + } +} + /* * used for workers that require transaction commits (i.e., for the * NOCOW case) @@ -2310,14 +2321,10 @@ static noinline_for_stack int scrub_stripe(struct scrub_ctx *sctx, btrfs_reada_wait(reada2); mutex_lock(&fs_info->scrub_lock); - while (atomic_read(&fs_info->scrub_pause_req)) { - mutex_unlock(&fs_info->scrub_lock); - wait_event(fs_info->scrub_pause_wait, - atomic_read(&fs_info->scrub_pause_req) == 0); - mutex_lock(&fs_info->scrub_lock); - } + scrub_blocked_if_needed(fs_info); atomic_dec(&fs_info->scrubs_paused); mutex_unlock(&fs_info->scrub_lock); + wake_up(&fs_info->scrub_pause_wait); /* @@ -2357,15 +2364,12 @@ static noinline_for_stack int scrub_stripe(struct scrub_ctx *sctx, atomic_set(&sctx->wr_ctx.flush_all_writes, 0); atomic_inc(&fs_info->scrubs_paused); wake_up(&fs_info->scrub_pause_wait); + mutex_lock(&fs_info->scrub_lock); - while (atomic_read(&fs_info->scrub_pause_req)) { - mutex_unlock(&fs_info->scrub_lock); - wait_event(fs_info->scrub_pause_wait, - atomic_read(&fs_info->scrub_pause_req) == 0); - mutex_lock(&fs_info->scrub_lock); - } + scrub_blocked_if_needed(fs_info); atomic_dec(&fs_info->scrubs_paused); mutex_unlock(&fs_info->scrub_lock); + wake_up(&fs_info->scrub_pause_wait); } @@ -2687,14 +2691,10 @@ int scrub_enumerate_chunks(struct scrub_ctx *sctx, atomic_read(&sctx->workers_pending) == 0); mutex_lock(&fs_info->scrub_lock); - while (atomic_read(&fs_info->scrub_pause_req)) { - mutex_unlock(&fs_info->scrub_lock); - wait_event(fs_info->scrub_pause_wait, - atomic_read(&fs_info->scrub_pause_req) == 0); - mutex_lock(&fs_info->scrub_lock); - } + scrub_blocked_if_needed(fs_info); atomic_dec(&fs_info->scrubs_paused); mutex_unlock(&fs_info->scrub_lock); + wake_up(&fs_info->scrub_pause_wait); btrfs_put_block_group(cache); @@ -2906,7 +2906,13 @@ int btrfs_scrub_dev(struct btrfs_fs_info *fs_info, u64 devid, u64 start, } sctx->readonly = readonly; dev->scrub_device = sctx; + mutex_unlock(&fs_info->fs_devices->device_list_mutex); + /* + * checking @scrub_pause_req here, we can avoid + * race between committing transaction and scrubbing. + */ + scrub_blocked_if_needed(fs_info); atomic_inc(&fs_info->scrubs_running); mutex_unlock(&fs_info->scrub_lock); @@ -2915,9 +2921,10 @@ int btrfs_scrub_dev(struct btrfs_fs_info *fs_info, u64 devid, u64 start, * by holding device list mutex, we can * kick off writing super in log tree sync. */ + mutex_lock(&fs_info->fs_devices->device_list_mutex); ret = scrub_supers(sctx, dev); + mutex_unlock(&fs_info->fs_devices->device_list_mutex); } - mutex_unlock(&fs_info->fs_devices->device_list_mutex); if (!ret) ret = scrub_enumerate_chunks(sctx, dev, start, end, -- 2.30.2