From: Dave Chinner <david@fromorbit.com>
To: Al Viro <viro@ZenIV.linux.org.uk>
Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
linux-mm@kvack.org, xfs@oss.sgi.com
Subject: Re: [PATCH 08/12] superblock: introduce per-sb cache shrinker infrastructure
Date: Sat, 4 Jun 2011 11:52:12 +1000 [thread overview]
Message-ID: <20110604015212.GD561@dastard> (raw)
In-Reply-To: <20110604004231.GV11521@ZenIV.linux.org.uk>
On Sat, Jun 04, 2011 at 01:42:31AM +0100, Al Viro wrote:
> > @@ -278,7 +325,12 @@ void generic_shutdown_super(struct super_block *sb)
> > {
> > const struct super_operations *sop = sb->s_op;
> >
> > -
> > + /*
> > + * shut down the shrinker first so we know that there are no possible
> > + * races when shrinking the dcache or icache. Removes the need for
> > + * external locking to prevent such races.
> > + */
> > + unregister_shrinker(&sb->s_shrink);
> > if (sb->s_root) {
> > shrink_dcache_for_umount(sb);
> > sync_filesystem(sb);
>
> What it means is that shrinker_rwsem now nests inside ->s_umount... IOW,
> if any ->shrink() gets stuck, so does every generic_shutdown_super().
> I'm still not convinced it's a good idea - especially since _this_
> superblock will be skipped anyway.
True, that's not nice.
> Is there any good reason to evict
> shrinker that early?
I wanted to put it early on in the unmount path so that the shrinker
was guaranteed to be gone before evict_inodes() was called. That
would mean that it is obviously safe to remove the iprune_sem
serialisation in that function.
The code in the umount path is quite different between 2.6.35 (the
original version of the patchset) and 3.0-rc1, so I'm not surprised
that I haven't put the unregister call in the right place.
> Note that doing that after ->s_umount is dropped
> should be reasonably safe - your shrinker will see that superblock is
> doomed if it's called anywhere in that window...
Agreed. In trying to find the best "early" place to unregister the
shrinker, I've completely missed the obvious "late is safe"
solution. I'll respin it with these changes.
Cheers,
Dave.
--
Dave Chinner
david@fromorbit.com
next prev parent reply other threads:[~2011-06-04 1:52 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-02 7:00 [PATCH 0/12] Per superblock cache reclaim Dave Chinner
2011-06-02 7:00 ` [PATCH 01/12] vmscan: add shrink_slab tracepoints Dave Chinner
2011-06-20 0:44 ` KOSAKI Motohiro
2011-06-20 0:53 ` Dave Chinner
2011-06-02 7:00 ` [PATCH 02/12] vmscan: shrinker->nr updates race and go wrong Dave Chinner
2011-06-20 0:46 ` KOSAKI Motohiro
2011-06-20 1:25 ` Dave Chinner
2011-06-20 4:30 ` KOSAKI Motohiro
2011-06-02 7:00 ` [PATCH 03/12] vmscan: reduce wind up shrinker->nr when shrinker can't do work Dave Chinner
2011-06-20 0:51 ` KOSAKI Motohiro
2011-06-21 5:09 ` Dave Chinner
2011-06-21 5:27 ` KOSAKI Motohiro
2011-06-02 7:00 ` [PATCH 04/12] vmscan: add customisable shrinker batch size Dave Chinner
2011-06-02 7:01 ` [PATCH 05/12] inode: convert inode_stat.nr_unused to per-cpu counters Dave Chinner
2011-06-02 7:01 ` [PATCH 06/12] inode: Make unused inode LRU per superblock Dave Chinner
2011-06-04 0:25 ` Al Viro
2011-06-04 1:40 ` Dave Chinner
2011-06-02 7:01 ` [PATCH 07/12] inode: move to per-sb LRU locks Dave Chinner
2011-06-02 7:01 ` [PATCH 08/12] superblock: introduce per-sb cache shrinker infrastructure Dave Chinner
2011-06-04 0:42 ` Al Viro
2011-06-04 1:52 ` Dave Chinner [this message]
2011-06-04 14:08 ` Christoph Hellwig
2011-06-04 14:19 ` Al Viro
2011-06-04 14:24 ` Al Viro
2011-06-02 7:01 ` [PATCH 09/12] inode: remove iprune_sem Dave Chinner
2011-06-02 7:01 ` [PATCH 10/12] superblock: add filesystem shrinker operations Dave Chinner
2011-06-02 7:01 ` [PATCH 11/12] vfs: increase shrinker batch size Dave Chinner
2011-06-02 9:30 ` Nicolas Kaiser
2011-06-02 7:01 ` [PATCH 12/12] xfs: make use of new shrinker callout for the inode cache Dave Chinner
2011-06-16 11:33 ` [PATCH 0/12] Per superblock cache reclaim Christoph Hellwig
2011-06-17 3:35 ` KOSAKI Motohiro
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