[ 3.5.y.z extended stable ] Patch "cifs: don't instantiate new dentries in readdir for inodes" has been added to staging queue

[Luis Henriques]

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

    cifs: don't instantiate new dentries in readdir for inodes

to the linux-3.5.y-queue branch of the 3.5.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-3.5.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 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 17a3462715ffc99c2c76307eeac760cfe8450de4 Mon Sep 17 00:00:00 2001
From: Jeff Layton <jlayton at redhat.com>
Date: Wed, 7 Aug 2013 10:29:08 -0400
Subject: [PATCH] cifs: don't instantiate new dentries in readdir for inodes
 that need to be revalidated immediately

commit 757c4f6260febff982276818bb946df89c1105aa upstream.

David reported that commit c2b93e06 (cifs: only set ops for inodes in
I_NEW state) caused a regression with mfsymlinks. Prior to that patch,
if a mfsymlink dentry was instantiated at readdir time, the inode would
get a new set of ops when it was revalidated. After that patch, this
did not occur.

This patch addresses this by simply skipping instantiating dentries in
the readdir codepath when we know that they will need to be immediately
revalidated. The next attempt to use that dentry will cause a new lookup
to occur (which is basically what we want to happen anyway).

Cc: "Stefan (metze) Metzmacher" <metze at samba.org>
Cc: Sachin Prabhu <sprabhu at redhat.com>
Reported-and-Tested-by: David McBride <dwm37 at cam.ac.uk>
Signed-off-by: Jeff Layton <jlayton at redhat.com>
Signed-off-by: Steve French <smfrench at gmail.com>
[ luis: backported to 3.5: added 'NULL' return ]
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 fs/cifs/readdir.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/fs/cifs/readdir.c b/fs/cifs/readdir.c
index 6cb83b9..8ae4457 100644
--- a/fs/cifs/readdir.c
+++ b/fs/cifs/readdir.c
@@ -107,6 +107,14 @@ cifs_readdir_lookup(struct dentry *parent, struct qstr *name,
 		dput(dentry);
 	}

+	/*
+	 * If we know that the inode will need to be revalidated immediately,
+	 * then don't create a new dentry for it. We'll end up doing an on
+	 * the wire call either way and this spares us an invalidation.
+	 */
+	if (fattr->cf_flags & CIFS_FATTR_NEED_REVAL)
+		return NULL;
+
 	dentry = d_alloc(parent, name);
 	if (dentry == NULL)
 		return NULL;
--
1.8.3.2