[3.11.y.z extended stable] Patch "mm: fix page leak at nfs_symlink()" has been added to staging queue

Luis Henriques luis.henriques at canonical.com
Fri Feb 21 12:25:08 UTC 2014


This is a note to let you know that I have just added a patch titled

    mm: fix page leak at nfs_symlink()

to the linux-3.11.y-queue branch of the 3.11.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.11.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.11.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 36a02f4f0410004b333ad547b578dc3157de94bf Mon Sep 17 00:00:00 2001
From: Rafael Aquini <aquini at redhat.com>
Date: Mon, 10 Feb 2014 14:25:48 -0800
Subject: mm: fix page leak at nfs_symlink()

commit a0b54adda3fe4b4cc6d28f2a9217cd35d1aa888c upstream.

Changes in commit a0b8cab3b9b2 ("mm: remove lru parameter from
__pagevec_lru_add and remove parts of pagevec API") have introduced a
call to add_to_page_cache_lru() which causes a leak in nfs_symlink() as
now the page gets an extra refcount that is not dropped.

Jan Stancek observed and reported the leak effect while running test8
from Connectathon Testsuite.  After several iterations over the test
case, which creates several symlinks on a NFS mountpoint, the test
system was quickly getting into an out-of-memory scenario.

This patch fixes the page leak by dropping that extra refcount
add_to_page_cache_lru() is grabbing.

Signed-off-by: Jan Stancek <jstancek at redhat.com>
Signed-off-by: Rafael Aquini <aquini at redhat.com>
Acked-by: Mel Gorman <mgorman at suse.de>
Acked-by: Rik van Riel <riel at redhat.com>
Cc: Jeff Layton <jlayton at redhat.com>
Cc: Trond Myklebust <trond.myklebust at primarydata.com>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 fs/nfs/dir.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/fs/nfs/dir.c b/fs/nfs/dir.c
index e474ca2b..7d9261a 100644
--- a/fs/nfs/dir.c
+++ b/fs/nfs/dir.c
@@ -1813,6 +1813,11 @@ int nfs_symlink(struct inode *dir, struct dentry *dentry, const char *symname)
 							GFP_KERNEL)) {
 		SetPageUptodate(page);
 		unlock_page(page);
+		/*
+		 * add_to_page_cache_lru() grabs an extra page refcount.
+		 * Drop it here to avoid leaking this page later.
+		 */
+		page_cache_release(page);
 	} else
 		__free_page(page);

--
1.9.0





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