ovl: punt write aio completion to workqueue

We want to protect concurrent updates of ovl inode size and mtime
(i.e. ovl_copyattr()) from aio completion context.

Punt write aio completion to a workqueue so that we can protect
ovl_copyattr() with a spinlock.

Export sb_init_dio_done_wq(), so that overlayfs can use its own
dio workqueue to punt aio completions.

Suggested-by: Jens Axboe <axboe@kernel.dk>
Link: https://lore.kernel.org/r/8620dfd3-372d-4ae0-aa3f-2fe97dda1bca@kernel.dk/
Signed-off-by: Amir Goldstein <amir73il@gmail.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/fs/super.c b/fs/super.c
index c7b452e12e4c..4cedeb7a7d79 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -2157,3 +2157,4 @@ int sb_init_dio_done_wq(struct super_block *sb)
 		destroy_workqueue(wq);
 	return 0;
 }
+EXPORT_SYMBOL_GPL(sb_init_dio_done_wq);