From: Al Viro <viro@zeniv.linux.org.uk>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: "Tobin C. Harding" <tobin@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Roman Gushchin <guro@fb.com>,
Alexander Viro <viro@ftp.linux.org.uk>,
Christoph Hellwig <hch@infradead.org>,
Pekka Enberg <penberg@cs.helsinki.fi>,
David Rientjes <rientjes@google.com>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Christopher Lameter <cl@linux.com>,
Matthew Wilcox <willy@infradead.org>,
Miklos Szeredi <mszeredi@redhat.com>,
Andreas Dilger <adilger@dilger.ca>,
Waiman Long <longman@redhat.com>, Tycho Andersen <tycho@tycho.ws>,
Theodore Ts'o <tytso@mit.edu>, Andi Kleen <ak@linux.intel.com>,
David Chinner <david@fromorbit.com>,
Nick Piggin <npiggin@gmail.com>, Rik van Riel <riel@redhat.com>,
Hugh Dickins <hughd@google.com>, Jonathan Corbet <corbet@lwn.net>,
linux-mm@kvack.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: shrink_dentry_list() logics change (was Re: [RFC PATCH v3 14/15] dcache: Implement partial shrink via Slab Movable Objects)
Date: Sat, 29 Jun 2019 05:38:03 +0100 [thread overview]
Message-ID: <20190629043803.GT17978@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20190629040844.GS17978@ZenIV.linux.org.uk>
On Sat, Jun 29, 2019 at 05:08:44AM +0100, Al Viro wrote:
> > The reason we don't hit that problem with regular memory shrinker is
> > this:
> > unregister_shrinker(&s->s_shrink);
> > fs->kill_sb(s);
> > in deactivate_locked_super(). IOW, shrinker for this fs is gone
> > before we get around to shutdown. And so are all normal sources
> > of dentry eviction for that fs.
> >
> > Your earlier variants all suffer the same problem - picking a page
> > shared by dentries from several superblocks can run into trouble
> > if it overlaps with umount of one of those.
PS: the problem is not gone in the next iteration of the patchset in
question. The patch I'm proposing (including dput_to_list() and _ONLY_
compile-tested) follows. Comments?
diff --git a/fs/dcache.c b/fs/dcache.c
index 8136bda27a1f..dfe21a649c96 100644
--- a/fs/dcache.c
+++ b/fs/dcache.c
@@ -860,6 +860,32 @@ void dput(struct dentry *dentry)
}
EXPORT_SYMBOL(dput);
+static void __dput_to_list(struct dentry *dentry, struct list_head *list)
+__must_hold(&dentry->d_lock)
+{
+ if (dentry->d_flags & DCACHE_SHRINK_LIST) {
+ /* let the owner of the list it's on deal with it */
+ --dentry->d_lockref.count;
+ } else {
+ if (dentry->d_flags & DCACHE_LRU_LIST)
+ d_lru_del(dentry);
+ if (!--dentry->d_lockref.count)
+ d_shrink_add(dentry, list);
+ }
+}
+
+void dput_to_list(struct dentry *dentry, struct list_head *list)
+{
+ rcu_read_lock();
+ if (likely(fast_dput(dentry))) {
+ rcu_read_unlock();
+ return;
+ }
+ rcu_read_unlock();
+ if (!retain_dentry(dentry))
+ __dput_to_list(dentry, list);
+ spin_unlock(&dentry->d_lock);
+}
/* This must be called with d_lock held */
static inline void __dget_dlock(struct dentry *dentry)
@@ -1088,18 +1114,9 @@ static void shrink_dentry_list(struct list_head *list)
rcu_read_unlock();
d_shrink_del(dentry);
parent = dentry->d_parent;
+ if (parent != dentry)
+ __dput_to_list(parent, list);
__dentry_kill(dentry);
- if (parent == dentry)
- continue;
- /*
- * We need to prune ancestors too. This is necessary to prevent
- * quadratic behavior of shrink_dcache_parent(), but is also
- * expected to be beneficial in reducing dentry cache
- * fragmentation.
- */
- dentry = parent;
- while (dentry && !lockref_put_or_lock(&dentry->d_lockref))
- dentry = dentry_kill(dentry);
}
}
next prev parent reply other threads:[~2019-06-29 4:38 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-04-11 1:34 [RFC PATCH v3 00/15] Slab Movable Objects (SMO) Tobin C. Harding
2019-04-11 1:34 ` [RFC PATCH v3 01/15] slub: Add isolate() and migrate() methods Tobin C. Harding
2019-04-11 1:34 ` [RFC PATCH v3 02/15] tools/vm/slabinfo: Add support for -C and -M options Tobin C. Harding
2019-04-11 1:34 ` [RFC PATCH v3 03/15] slub: Sort slab cache list Tobin C. Harding
2019-04-11 1:34 ` [RFC PATCH v3 04/15] slub: Slab defrag core Tobin C. Harding
2019-04-11 1:34 ` [RFC PATCH v3 05/15] tools/vm/slabinfo: Add remote node defrag ratio output Tobin C. Harding
2019-04-11 1:34 ` [RFC PATCH v3 06/15] tools/vm/slabinfo: Add defrag_used_ratio output Tobin C. Harding
2019-04-11 1:34 ` [RFC PATCH v3 07/15] tools/testing/slab: Add object migration test module Tobin C. Harding
2019-04-11 1:34 ` [RFC PATCH v3 08/15] tools/testing/slab: Add object migration test suite Tobin C. Harding
2019-04-11 1:34 ` [RFC PATCH v3 09/15] xarray: Implement migration function for objects Tobin C. Harding
2019-04-11 1:34 ` [RFC PATCH v3 10/15] tools/testing/slab: Add XArray movable objects tests Tobin C. Harding
2019-04-11 1:34 ` [RFC PATCH v3 11/15] slub: Enable moving objects to/from specific nodes Tobin C. Harding
2019-04-11 1:34 ` [RFC PATCH v3 12/15] slub: Enable balancing slabs across nodes Tobin C. Harding
2019-04-11 1:34 ` [RFC PATCH v3 13/15] dcache: Provide a dentry constructor Tobin C. Harding
2019-04-11 1:34 ` [RFC PATCH v3 14/15] dcache: Implement partial shrink via Slab Movable Objects Tobin C. Harding
2019-04-11 2:33 ` Al Viro
2019-04-11 2:48 ` Tobin C. Harding
2019-04-11 4:47 ` Al Viro
2019-04-11 5:05 ` Tobin C. Harding
2019-04-11 20:01 ` Al Viro
2019-04-11 21:02 ` Al Viro
2019-06-29 4:08 ` Al Viro
2019-06-29 4:38 ` Al Viro [this message]
2019-06-29 19:06 ` shrink_dentry_list() logics change (was Re: [RFC PATCH v3 14/15] dcache: Implement partial shrink via Slab Movable Objects) Al Viro
2019-06-29 22:29 ` Al Viro
2019-06-29 22:34 ` Al Viro
2019-07-01 9:26 ` Tobin C. Harding
2019-04-11 1:34 ` [RFC PATCH v3 15/15] dcache: Add CONFIG_DCACHE_SMO Tobin C. Harding
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