On Sat, Oct 13, 2018 at 01:29:14PM +1100, Dave Chinner wrote: > On Fri, Oct 12, 2018 at 01:46:54PM -0400, Brian Foster wrote: > > In the typical unmount case, the AIL is forced out by the unmount > > sequence before the xfsaild task is stopped. Since AIL items are > > removed on writeback completion, this means that the AIL > > ->ail_buf_list delwri queue has been drained. This is not always > > true in the shutdown case, however. > > > > It's possible for buffers to sit on a delwri queue for a period of > > time across submission attempts if said items are locked or have > > been relogged and pinned since first added to the queue. > > Can you add this as a comment to xfs_buf_delwri_submit_nowait() to > document that callers either need to check that everything was > submitted and/or cancel the delwri list before they tear it down? I added this comment to the patch when I pulled it in: --- a/fs/xfs/xfs_buf.c +++ b/fs/xfs/xfs_buf.c @@ -2055,6 +2055,13 @@ xfs_buf_delwri_submit_buffers( * is only safely useable for callers that can track I/O completion by higher * level means, e.g. AIL pushing as the @buffer_list is consumed in this * function. + * + * Note: this function will skip buffers it would block on, and in doing so + * leaves them on @buffer_list so they can be retried on a later pass. As such, + * it is up to the caller to ensure that the buffer list is fully submitted or + * cancelled appropriately when they are finished with the list. Failure to + * cancel or resubmit the list until it is empty will result in leaked buffers + * at unmount time. */ int xfs_buf_delwri_submit_nowait( Does that look reasonable? Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx
