vmscan: fix shrinker callback bug in fs/super.c

svn path=/dists/trunk/linux-2.6/; revision=18259

debian/changelog

@@ -19,6 +19,7 @@ linux-2.6 (3.1.1-1) UNRELEASED; urgency=low
   * DFSG: Remove drivers/staging/ft1000/ft1000-*/*.img, non-free
     firmware for drivers we don't build
   * hfs: fix hfs_find_init() sb->ext_tree NULL ptr oops (CVE-2011-2203)
+  * vmscan: fix shrinker callback bug in fs/super.c
 
  -- Ben Hutchings <ben@decadent.org.uk>  Fri, 04 Nov 2011 15:05:47 +0000
 

debian/patches/bugfix/all/vmscan-fix-shrinker-callback-bug-in-fs-super.c.patch

@@ -0,0 +1,46 @@
+From: Mikulas Patocka <mpatocka@redhat.com>
+Date: Mon, 31 Oct 2011 17:08:57 -0700
+Subject: [PATCH] vmscan: fix shrinker callback bug in fs/super.c
+
+commit 09f363c7363eb10cfb4b82094bd7064e5608258b upstream.
+
+The callback must not return -1 when nr_to_scan is zero. Fix the bug in
+fs/super.c and add this requirement to the callback specification.
+
+Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
+Cc: Dave Chinner <david@fromorbit.com>
+Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
+Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
+---
+ fs/super.c               |    2 +-
+ include/linux/shrinker.h |    1 +
+ 2 files changed, 2 insertions(+), 1 deletions(-)
+
+diff --git a/fs/super.c b/fs/super.c
+index 3f56a26..32a81f3 100644
+--- a/fs/super.c
++++ b/fs/super.c
+@@ -61,7 +61,7 @@ static int prune_super(struct shrinker *shrink, struct shrink_control *sc)
+ 		return -1;
+ 
+ 	if (!grab_super_passive(sb))
+-		return -1;
++		return !sc->nr_to_scan ? 0 : -1;
+ 
+ 	if (sb->s_op && sb->s_op->nr_cached_objects)
+ 		fs_objects = sb->s_op->nr_cached_objects(sb);
+diff --git a/include/linux/shrinker.h b/include/linux/shrinker.h
+index 790651b..a83833a 100644
+--- a/include/linux/shrinker.h
++++ b/include/linux/shrinker.h
+@@ -20,6 +20,7 @@ struct shrink_control {
+  * 'nr_to_scan' entries and attempt to free them up.  It should return
+  * the number of objects which remain in the cache.  If it returns -1, it means
+  * it cannot do any scanning at this time (eg. there is a risk of deadlock).
++ * The callback must not return -1 if nr_to_scan is zero.
+  *
+  * The 'gfpmask' refers to the allocation we are currently trying to
+  * fulfil.
+-- 
+1.7.7.2
+

debian/patches/series/base

@@ -56,3 +56,4 @@
 + bugfix/all/Fix-build-break-when-freezer-not-configured.patch
 + bugfix/all/PM-Freezer-Reimplement-wait_event_freezekillable-usi.patch
 + bugfix/all/hfs-fix-hfs_find_init-sb-ext_tree-NULL-ptr-oops.patch
++ bugfix/all/vmscan-fix-shrinker-callback-bug-in-fs-super.c.patch