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authorFilipe Manana <fdmanana@suse.com>2022-09-08 14:31:50 +0300
committerDavid Sterba <dsterba@suse.com>2022-09-13 15:05:08 +0300
commit8a1f1e3d1eecf9d2359a2709e276743a67e145db (patch)
treed1e4b2b6da17904cddb079e168ffde3bf04e4916 /fs
parent5da431b71d4b9be3c8cf6786eff9e2d41a5f9f65 (diff)
downloadlinux-8a1f1e3d1eecf9d2359a2709e276743a67e145db.tar.xz
btrfs: fix hang during unmount when stopping block group reclaim worker
During early unmount, at close_ctree(), we try to stop the block group reclaim task with cancel_work_sync(), but that may hang if the block group reclaim task is currently at btrfs_relocate_block_group() waiting for the flag BTRFS_FS_UNFINISHED_DROPS to be cleared from fs_info->flags. During unmount we only clear that flag later, after trying to stop the block group reclaim task. Fix that by clearing BTRFS_FS_UNFINISHED_DROPS before trying to stop the block group reclaim task and after setting BTRFS_FS_CLOSING_START, so that if the reclaim task is waiting on that bit, it will stop immediately after being woken, because it sees the filesystem is closing (with a call to btrfs_fs_closing()), and then returns immediately with -EINTR. Fixes: 31e70e527806c5 ("btrfs: fix hang during unmount when block group reclaim task is running") CC: stable@vger.kernel.org # 5.15+ Reviewed-by: Josef Bacik <josef@toxicpanda.com> Signed-off-by: Filipe Manana <fdmanana@suse.com> Signed-off-by: David Sterba <dsterba@suse.com>
Diffstat (limited to 'fs')
-rw-r--r--fs/btrfs/disk-io.c17
1 files changed, 11 insertions, 6 deletions
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 129711773ae5..9f844328b1e2 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -4477,6 +4477,17 @@ void __cold close_ctree(struct btrfs_fs_info *fs_info)
set_bit(BTRFS_FS_CLOSING_START, &fs_info->flags);
/*
+ * If we had UNFINISHED_DROPS we could still be processing them, so
+ * clear that bit and wake up relocation so it can stop.
+ * We must do this before stopping the block group reclaim task, because
+ * at btrfs_relocate_block_group() we wait for this bit, and after the
+ * wait we stop with -EINTR if btrfs_fs_closing() returns non-zero - we
+ * have just set BTRFS_FS_CLOSING_START, so btrfs_fs_closing() will
+ * return 1.
+ */
+ btrfs_wake_unfinished_drop(fs_info);
+
+ /*
* We may have the reclaim task running and relocating a data block group,
* in which case it may create delayed iputs. So stop it before we park
* the cleaner kthread otherwise we can get new delayed iputs after
@@ -4494,12 +4505,6 @@ void __cold close_ctree(struct btrfs_fs_info *fs_info)
*/
kthread_park(fs_info->cleaner_kthread);
- /*
- * If we had UNFINISHED_DROPS we could still be processing them, so
- * clear that bit and wake up relocation so it can stop.
- */
- btrfs_wake_unfinished_drop(fs_info);
-
/* wait for the qgroup rescan worker to stop */
btrfs_qgroup_wait_for_completion(fs_info, false);