[3.13.y.z extended stable] Patch "xfs: don't zero partial page cache pages during O_DIRECT writes" has been added to staging queue

[Kamal Mostafa]

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

    xfs: don't zero partial page cache pages during O_DIRECT writes

to the linux-3.13.y-queue branch of the 3.13.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-3.13.y-queue

This patch is scheduled to be released in version 3.13.11.8.

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

For more information about the 3.13.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 099bfb295ef226eff642156b60182efbb0a1eedf Mon Sep 17 00:00:00 2001
From: Dave Chinner <dchinner at redhat.com>
Date: Tue, 2 Sep 2014 12:12:52 +1000
Subject: xfs: don't zero partial page cache pages during O_DIRECT writes

commit 834ffca6f7e345a79f6f2e2d131b0dfba8a4b67a upstream.

Similar to direct IO reads, direct IO writes are using
truncate_pagecache_range to invalidate the page cache. This is
incorrect due to the sub-block zeroing in the page cache that
truncate_pagecache_range() triggers.

This patch fixes things by using invalidate_inode_pages2_range
instead.  It preserves the page cache invalidation, but won't zero
any pages.

Signed-off-by: Dave Chinner <dchinner at redhat.com>
Reviewed-by: Brian Foster <bfoster at redhat.com>
Reviewed-by: Christoph Hellwig <hch at lst.de>
Signed-off-by: Dave Chinner <david at fromorbit.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 fs/xfs/xfs_file.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/fs/xfs/xfs_file.c b/fs/xfs/xfs_file.c
index 5825705..d86a7eb 100644
--- a/fs/xfs/xfs_file.c
+++ b/fs/xfs/xfs_file.c
@@ -689,7 +689,15 @@ xfs_file_dio_aio_write(
 						    pos, -1);
 		if (ret)
 			goto out;
-		truncate_pagecache_range(VFS_I(ip), pos, -1);
+		/*
+		 * Invalidate whole pages. This can return an error if
+		 * we fail to invalidate a page, but this should never
+		 * happen on XFS. Warn if it does fail.
+		 */
+		ret = invalidate_inode_pages2_range(VFS_I(ip)->i_mapping,
+						pos >> PAGE_CACHE_SHIFT, -1);
+		WARN_ON_ONCE(ret);
+		ret = 0;
 	}

 	/*
--
1.9.1