[PATCH AUTOSEL 6.1 036/212] btrfs: run btrfs_error_commit_super() early

Sasha Levin
2025-05-05T23:07:30Z

From: Qu Wenruo <wqu@suse.com>

[ Upstream commit df94a342efb451deb0e32b495d1d6cd4bb3a1648 ]

[BUG]
Even after all the error fixes related the
"ASSERT(list_empty(&fs_info->delayed_iputs));" in close_ctree(), I can
still hit it reliably with my experimental 2K block size.

[CAUSE]
In my case, all the error is triggered after the fs is already in error
status.

I find the following call trace to be the cause of race:

Main thread | endio_write_workers
---------------------------------------------+---------------------------
close_ctree() |
|- btrfs_error_commit_super() |
| |- btrfs_cleanup_transaction() |
| | |- btrfs_destroy_all_ordered_extents() |
| | |- btrfs_wait_ordered_roots() |
| |- btrfs_run_delayed_iputs() |
| | btrfs_finish_ordered_io()
| | |- btrfs_put_ordered_extent()
| | |- btrfs_add_delayed_iput()
|- ASSERT(list_empty(delayed_iputs)) |
!!! Triggered !!!

The root cause is that, btrfs_wait_ordered_roots() only wait for
ordered extents to finish their IOs, not to wait for them to finish and
removed.

[FIX]
Since btrfs_error_commit_super() will flush and wait for all ordered
extents, it should be executed early, before we start flushing the
workqueues.

And since btrfs_error_commit_super() now runs early, there is no need to
run btrfs_run_delayed_iputs() inside it, so just remove the
btrfs_run_delayed_iputs() call from btrfs_error_commit_super().

Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/btrfs/disk-io.c | 15 ++++++++-------
1 file changed, 8 insertions(+), 7 deletions(-)

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index de4f590fe30f2..6670188b9eb6b 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -4641,6 +4641,14 @@ void __cold close_ctree(struct btrfs_fs_info *fs_info)
/* clear out the rbtree of defraggable inodes */
btrfs_cleanup_defrag_inodes(fs_info);

+ /*
+ * Handle the error fs first, as it will flush and wait for all ordered
+ * extents. This will generate delayed iputs, thus we want to handle
+ * it first.
+ */
+ if (unlikely(BTRFS_FS_ERROR(fs_info)))
+ btrfs_error_commit_super(fs_info);
+
/*
* Wait for any fixup workers to complete.
* If we don't wait for them here and they are still running by the time
@@ -4730,9 +4738,6 @@ void __cold close_ctree(struct btrfs_fs_info *fs_info)
btrfs_err(fs_info, "commit super ret %d", ret);
}

- if (BTRFS_FS_ERROR(fs_info))
- btrfs_error_commit_super(fs_info);
-
kthread_stop(fs_info->transaction_kthread);
kthread_stop(fs_info->cleaner_kthread);

@@ -4888,10 +4893,6 @@ static void btrfs_error_commit_super(struct btrfs_fs_info *fs_info)
/* cleanup FS via transaction */
btrfs_cleanup_transaction(fs_info);

- mutex_lock(&fs_info->cleaner_mutex);
- btrfs_run_delayed_iputs(fs_info);
- mutex_unlock(&fs_info->cleaner_mutex);
-
down_write(&fs_info->cleanup_work_sem);
up_write(&fs_info->cleanup_work_sem);
}
--
2.39.5