On Mon, Oct 15, 2018 at 12:57:27PM +1100, Dave Chinner wrote: > 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? > Looks fine to me, thanks! Brian > Cheers, > > Dave. > -- > Dave Chinner > david@xxxxxxxxxxxxx
