From 25ce459c1af138f95a3fd318461193397ebb825b Mon Sep 17 00:00:00 2001 From: Liu Bo Date: Wed, 10 Sep 2014 12:58:50 +0800 Subject: [PATCH] Btrfs: fix loop writing of async reclaim One of my tests shows that when we really don't have space to reclaim via flush_space and also run out of space, this async reclaim work loops on adding itself into the workqueue and keeps writing something to disk according to iostat's results, and these writes mainly comes from commit_transaction which writes super_block. This's unacceptable as it can be bad to disks, especially memeory storages. This adds a check to avoid the above situation. Signed-off-by: Liu Bo Signed-off-by: Chris Mason --- fs/btrfs/extent-tree.c | 17 ++++++++++++++--- 1 file changed, 14 insertions(+), 3 deletions(-) diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c index e10555823fde..2191a2c7496b 100644 --- a/fs/btrfs/extent-tree.c +++ b/fs/btrfs/extent-tree.c @@ -4343,11 +4343,21 @@ static inline int need_do_async_reclaim(struct btrfs_space_info *space_info, } static int btrfs_need_do_async_reclaim(struct btrfs_space_info *space_info, - struct btrfs_fs_info *fs_info) + struct btrfs_fs_info *fs_info, + int flush_state) { u64 used; spin_lock(&space_info->lock); + /* + * We run out of space and have not got any free space via flush_space, + * so don't bother doing async reclaim. + */ + if (flush_state > COMMIT_TRANS && space_info->full) { + spin_unlock(&space_info->lock); + return 0; + } + used = space_info->bytes_used + space_info->bytes_reserved + space_info->bytes_pinned + space_info->bytes_readonly + space_info->bytes_may_use; @@ -4380,11 +4390,12 @@ static void btrfs_async_reclaim_metadata_space(struct work_struct *work) flush_space(fs_info->fs_root, space_info, to_reclaim, to_reclaim, flush_state); flush_state++; - if (!btrfs_need_do_async_reclaim(space_info, fs_info)) + if (!btrfs_need_do_async_reclaim(space_info, fs_info, + flush_state)) return; } while (flush_state <= COMMIT_TRANS); - if (btrfs_need_do_async_reclaim(space_info, fs_info)) + if (btrfs_need_do_async_reclaim(space_info, fs_info, flush_state)) queue_work(system_unbound_wq, work); }