From: Dave Chinner <david@fromorbit.com>
To: Alex Elder <aelder@sgi.com>
Cc: xfs@oss.sgi.com
Subject: Re: [PATCH 2/2] xfs: don't truncate prealloc from frequently accessed inodes
Date: Fri, 15 Oct 2010 08:28:41 +1100 [thread overview]
Message-ID: <20101014212841.GE4681@dastard> (raw)
In-Reply-To: <1287076970.2362.521.camel@doink>
On Thu, Oct 14, 2010 at 12:22:50PM -0500, Alex Elder wrote:
> On Mon, 2010-10-04 at 21:13 +1100, Dave Chinner wrote:
> > diff --git a/fs/xfs/xfs_vnodeops.c b/fs/xfs/xfs_vnodeops.c
> > index b7bdc43..0c8eeba 100644
> > --- a/fs/xfs/xfs_vnodeops.c
> > +++ b/fs/xfs/xfs_vnodeops.c
>
> OK, this comment is unrelated to your exact change. But just above
> the next hunk there's a big nasty condition, which appears to
> be *almost* duplicated in xfs_inactive() (twice!). It would be
> very nice if, while you're at modifying this nearby code, you
> could encapsulate that condition in a macro that has a meaningful
> name.
I've looked at doing this factoring before, but the conditions are
subtly different and hence cannot be factored into a single macro.
The xfs_inactive case can be cleaned up (i've got old patches around
that do half the job, IIRC), but the tests in the two functions are
not the same.
> > @@ -979,14 +979,27 @@ xfs_release(
> > * chance to drop them once the last reference to
> > * the inode is dropped, so we'll never leak blocks
> > * permanently.
>
> I'm curious what the effect is if we simply don't do the truncate
> *except* when the inode becomes inactive. It means we hang onto
> the stuff for a while longer, and maybe it makes things messier
> in the event of a crash.
It doesn't change a thing in the event of a crash - speculative
preallocation is entirely in-memory state.
> Can you tell me why we do the truncate
> here as well as in xfs_inactive() (or what the problem is of
> *not* doing it here)?
the truncation in ->release is not guaranteed to succeed - it uses
trylock semantics to avoid blocking unnecessarily. It can do this
because we know that when xfs_inactive() is called, the truncation
will happen for real.
--
Dave Chinner
david@fromorbit.com
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next prev parent reply other threads:[~2010-10-14 21:27 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-10-04 10:13 [RFC, PATCH 0/2] xfs: dynamic speculative preallocation for delalloc Dave Chinner
2010-10-04 10:13 ` [PATCH 1/2] xfs: dynamic speculative EOF preallocation Dave Chinner
2010-10-14 17:22 ` Alex Elder
2010-10-14 21:33 ` Dave Chinner
2010-10-15 6:51 ` allocsize mount option, was: " Michael Monnerie
2010-10-15 11:59 ` Dave Chinner
2010-10-04 10:13 ` [PATCH 2/2] xfs: don't truncate prealloc from frequently accessed inodes Dave Chinner
2010-10-14 17:22 ` Alex Elder
2010-10-14 21:28 ` Dave Chinner [this message]
2010-10-14 17:22 ` [RFC, PATCH 0/2] xfs: dynamic speculative preallocation for delalloc Alex Elder
2010-10-14 21:16 ` Dave Chinner
2010-10-14 21:50 ` Ivan.Novick
2010-10-15 7:14 ` Michael Monnerie
2010-10-15 11:45 ` Dave Chinner
2010-10-17 14:31 ` Michael Monnerie
2010-10-17 23:49 ` Dave Chinner
2010-10-18 6:39 ` Michael Monnerie
-- strict thread matches above, loose matches on Subject: below --
2010-11-29 0:43 [PATCH 0/2] xfs: dynamic speculative allocation beyond EOF V3 Dave Chinner
2010-11-29 0:43 ` [PATCH 2/2] xfs: don't truncate prealloc from frequently accessed inodes Dave Chinner
2010-11-29 9:42 ` Andi Kleen
2010-11-30 1:00 ` Dave Chinner
2010-11-30 17:03 ` Christoph Hellwig
2010-11-30 22:00 ` Dave Chinner
2010-12-13 1:25 [PATCH 0/2] xfs: dynamic speculative allocation beyond EOF V4 Dave Chinner
2010-12-13 1:25 ` [PATCH 2/2] xfs: don't truncate prealloc from frequently accessed inodes Dave Chinner
2010-12-16 15:46 ` Christoph Hellwig
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