Btrfs: fix heavy delalloc related deadlock (9ffba8cd) · Commits · 戴 / test

I added a patch where we started taking the ordered operations mutex when we waited on ordered extents. We need this because we splice the list and process it, so if a flusher came in during this scenario it would think the list was empty and we'd usually get an early ENOSPC. The problem with this is that this lock is used in transaction committing. So we end up with something like this Transaction commit -> wait on writers Delalloc flusher -> run_ordered_operations (holds mutex) ->wait for filemap-flush to do its thing flush task -> cow_file_range ->wait on btrfs_join_transaction because we're commiting some other task -> commit_transaction because we notice trans->transaction->flush is set -> run_ordered_operations (hang on mutex) We need to disentangle the ordered operations flushing from the delalloc flushing, since they are separate things. This solves the deadlock issue I was seeing. Thanks, Signed-off-by:

Josef Bacik <jbacik@fusionio.com> Signed-off-by:

Chris Mason <chris.mason@fusionio.com>

fs/btrfs/ctree.h

+7 −0

Original line number	Diff line number	Diff line
		@@ -1413,6 +1413,13 @@ struct btrfs_fs_info {
		* before jumping into the main commit.
		*/
		struct mutex ordered_operations_mutex;

		/*
		* Same as ordered_operations_mutex except this is for ordered extents
		* and not the operations.
		*/
		struct mutex ordered_extent_flush_mutex;

		struct rw_semaphore extent_commit_sem;

		struct rw_semaphore cleanup_work_sem;

fs/btrfs/disk-io.c

+1 −0

Original line number	Diff line number	Diff line
		@@ -2277,6 +2277,7 @@ int open_ctree(struct super_block *sb,


		mutex_init(&fs_info->ordered_operations_mutex);
		mutex_init(&fs_info->ordered_extent_flush_mutex);
		mutex_init(&fs_info->tree_log_mutex);
		mutex_init(&fs_info->chunk_mutex);
		mutex_init(&fs_info->transaction_kthread_mutex);

fs/btrfs/ordered-data.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -671,7 +671,7 @@ int btrfs_run_ordered_operations(struct btrfs_trans_handle *trans,
		INIT_LIST_HEAD(&splice);
		INIT_LIST_HEAD(&works);

		mutex_lock(&root->fs_info->ordered_operations_mutex);
		mutex_lock(&root->fs_info->ordered_extent_flush_mutex);
		spin_lock(&root->fs_info->ordered_root_lock);
		list_splice_init(&cur_trans->ordered_operations, &splice);
		while (!list_empty(&splice)) {
		@@ -718,7 +718,7 @@ out:
		list_del_init(&work->list);
		btrfs_wait_and_free_delalloc_work(work);
		}
		mutex_unlock(&root->fs_info->ordered_operations_mutex);
		mutex_unlock(&root->fs_info->ordered_extent_flush_mutex);
		return ret;
		}

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