From: Filipe Manana fdmanana@suse.com
[ Upstream commit cda76788f8b0f7de3171100e3164ec1ce702292e ]
At close_ctree() after we have ran delayed iputs either explicitly through calling btrfs_run_delayed_iputs() or later during the call to btrfs_commit_super() or btrfs_error_commit_super(), we assert that the delayed iputs list is empty.
We have (another) race where this assertion might fail because we have queued an async write into the fs_info->workers workqueue. Here's how it happens:
1) We are submitting a data bio for an inode that is not the data relocation inode, so we call btrfs_wq_submit_bio();
2) btrfs_wq_submit_bio() submits a work for the fs_info->workers queue that will run run_one_async_done();
3) We enter close_ctree(), flush several work queues except fs_info->workers, explicitly run delayed iputs with a call to btrfs_run_delayed_iputs() and then again shortly after by calling btrfs_commit_super() or btrfs_error_commit_super(), which also run delayed iputs;
4) run_one_async_done() is executed in the work queue, and because there was an IO error (bio->bi_status is not 0) it calls btrfs_bio_end_io(), which drops the final reference on the associated ordered extent by calling btrfs_put_ordered_extent() - and that adds a delayed iput for the inode;
5) At close_ctree() we find that after stopping the cleaner and transaction kthreads the delayed iputs list is not empty, failing the following assertion:
ASSERT(list_empty(&fs_info->delayed_iputs));
Fix this by flushing the fs_info->workers workqueue before running delayed iputs at close_ctree().
David reported this when running generic/648, which exercises IO error paths by using the DM error table.
Reported-by: David Sterba dsterba@suse.com Reviewed-by: Qu Wenruo wqu@suse.com Signed-off-by: Filipe Manana fdmanana@suse.com Signed-off-by: David Sterba dsterba@suse.com Signed-off-by: Sasha Levin sashal@kernel.org --- fs/btrfs/disk-io.c | 13 +++++++++++++ 1 file changed, 13 insertions(+)
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index 6670188b9eb6b..8c0da0025bc71 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -4669,6 +4669,19 @@ void __cold close_ctree(struct btrfs_fs_info *fs_info) */ btrfs_flush_workqueue(fs_info->delalloc_workers);
+ /* + * We can have ordered extents getting their last reference dropped from + * the fs_info->workers queue because for async writes for data bios we + * queue a work for that queue, at btrfs_wq_submit_bio(), that runs + * run_one_async_done() which calls btrfs_bio_end_io() in case the bio + * has an error, and that later function can do the final + * btrfs_put_ordered_extent() on the ordered extent attached to the bio, + * which adds a delayed iput for the inode. So we must flush the queue + * so that we don't have delayed iputs after committing the current + * transaction below and stopping the cleaner and transaction kthreads. + */ + btrfs_flush_workqueue(fs_info->workers); + /* * When finishing a compressed write bio we schedule a work queue item * to finish an ordered extent - btrfs_finish_compressed_write_work()