From 9cc0b837e14ae913581ec1ea6e979a738f71b0fd Mon Sep 17 00:00:00 2001
From: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Date: Tue, 6 Jul 2021 01:32:38 +0900
Subject: [PATCH] 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 <johannes.thumshirn@wdc.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
---
fs/btrfs/block-group.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)
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;