From 9cc0b837e14ae913581ec1ea6e979a738f71b0fd Mon Sep 17 00:00:00 2001 From: Johannes Thumshirn Date: Tue, 6 Jul 2021 01:32:38 +0900 Subject: btrfs: don't block if we can't acquire the reclaim lock If we can't acquire the reclaim_bgs_lock on block group reclaim, we block until it is free. This can potentially stall for a long time. While reclaim of block groups is necessary for a good user experience on a zoned file system, there still is no need to block as it is best effort only, just like when we're deleting unused block groups. CC: stable@vger.kernel.org # 5.13 Signed-off-by: Johannes Thumshirn Reviewed-by: David Sterba Signed-off-by: David Sterba --- fs/btrfs/block-group.c | 10 +++++++++- 1 file changed, 9 insertions(+), 1 deletion(-) (limited to 'fs') diff --git a/fs/btrfs/block-group.c b/fs/btrfs/block-group.c index c557327b4545..9e7d9d0c763d 100644 --- a/fs/btrfs/block-group.c +++ b/fs/btrfs/block-group.c @@ -1498,7 +1498,15 @@ void btrfs_reclaim_bgs_work(struct work_struct *work) if (!btrfs_exclop_start(fs_info, BTRFS_EXCLOP_BALANCE)) return; - mutex_lock(&fs_info->reclaim_bgs_lock); + /* + * Long running balances can keep us blocked here for eternity, so + * simply skip reclaim if we're unable to get the mutex. + */ + if (!mutex_trylock(&fs_info->reclaim_bgs_lock)) { + btrfs_exclop_finish(fs_info); + return; + } + spin_lock(&fs_info->unused_bgs_lock); while (!list_empty(&fs_info->reclaim_bgs)) { u64 zone_unusable; -- cgit v1.2.3