Re: [PATCH 02/27] xfs: remove the unused ilock_nowait codepath in writepage

Christoph Hellwig
2011-06-30T06:55:31Z

On Thu, Jun 30, 2011 at 10:15:25AM +1000, Dave Chinner wrote:
> On Wed, Jun 29, 2011 at 10:01:11AM -0400, Christoph Hellwig wrote:
> > wbc->nonblocking is never set, so this whole code has been unreachable
> > for a long time. I'm also not sure it would make a lot of sense -
> > we'd rather finish our writeout after a short wait for the ilock
> > instead of cancelling the whole ioend.
>
> I'd suggest that the only thing that should be dropped is the
> wbc->nonblocking check. Numbers would be good to validate that this
> is still relevant, but I don't have a storage subsystem with enough
> bandwidth to drive a flusher thread to being CPU bound...

I don't mind re-introducing this if we actuall have a testcase for it.
Note that simply keeping the code won't work for the writepages
implementation as we'd cancel the whole ioend if one lock fails,
discarding potentially a lot of I/O. It's already bad enough with
the simpler clustering we have in the current code. Back in SLES10 /
2.6.16 when the code could still be reached we only did it for the
bmap calls directly from writepage, but not from the writeout
clustering.