On Fri, Mar 04, 2011 at 09:41:05AM +1100, Dave Chinner wrote:
> On Thu, Mar 03, 2011 at 10:34:10AM -0500, Christoph Hellwig wrote:
> > I still don't see any point in having the ENOSPC flushing moved to a
> > different context.
> IIRC, stack usage has always been an issue, and we also call
> xfs_flush_inodes() with the XFS_IOLOCK held (from
> xfs_iomap_write_delay()) so the alternate context was used to avoid
> deadlocks. I don't think we have that deadlock problem now thanks to
> being able to combine SYNC_TRYLOCK | SYNC_WAIT flags, but I'm not
> sure we can ignore the stack issues.
Given that we wait for completion of the syncing in the caller moving it
to a different context does not help with any deadlocks. It just makes
them impossible to detect using lockdep.
> I've also realised the work_pending() check is unnecessary, as is
> the lock, because queue_work() will only queue new work if the work
> item isn't already pending so there's no need to check it here.
> Hence all this actually needs to do is:
or in fact only use the writeback_inodes_sb_if_idle call you added
later. That also causes writeback of data from the flusher threads.