This is a note to let you know that I've just added the patch titled
nfs: always make sure page is up-to-date before extending a write to cover the entire page
to the 3.12-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
nfs-always-make-sure-page-is-up-to-date-before-extending-a-write-to-cover-the-entire-page.patch
and it can be found in the queue-3.12 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 263b4509ec4d47e0da3e753f85a39ea12d1eff24 Mon Sep 17 00:00:00 2001
From: Scott Mayhew <smayhew@xxxxxxxxxx>
Date: Fri, 17 Jan 2014 15:12:05 -0500
Subject: nfs: always make sure page is up-to-date before extending a write to cover the entire page
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From: Scott Mayhew <smayhew@xxxxxxxxxx>
commit 263b4509ec4d47e0da3e753f85a39ea12d1eff24 upstream.
We should always make sure the cached page is up-to-date when we're
determining whether we can extend a write to cover the full page -- even
if we've received a write delegation from the server.
Commit c7559663 added logic to skip this check if we have a write
delegation, which can lead to data corruption such as the following
scenario if client B receives a write delegation from the NFS server:
Client A:
# echo 123456789 > /mnt/file
Client B:
# echo abcdefghi >> /mnt/file
# cat /mnt/file
0�D0�abcdefghi
Just because we hold a write delegation doesn't mean that we've read in
the entire page contents.
Signed-off-by: Scott Mayhew <smayhew@xxxxxxxxxx>
Signed-off-by: Trond Myklebust <trond.myklebust@xxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/nfs/write.c | 11 ++++++-----
1 file changed, 6 insertions(+), 5 deletions(-)
--- a/fs/nfs/write.c
+++ b/fs/nfs/write.c
@@ -922,19 +922,20 @@ out:
* extend the write to cover the entire page in order to avoid fragmentation
* inefficiencies.
*
- * If the file is opened for synchronous writes or if we have a write delegation
- * from the server then we can just skip the rest of the checks.
+ * If the file is opened for synchronous writes then we can just skip the rest
+ * of the checks.
*/
static int nfs_can_extend_write(struct file *file, struct page *page, struct inode *inode)
{
if (file->f_flags & O_DSYNC)
return 0;
+ if (!nfs_write_pageuptodate(page, inode))
+ return 0;
if (NFS_PROTO(inode)->have_delegation(inode, FMODE_WRITE))
return 1;
- if (nfs_write_pageuptodate(page, inode) && (inode->i_flock == NULL ||
- (inode->i_flock->fl_start == 0 &&
+ if (inode->i_flock == NULL || (inode->i_flock->fl_start == 0 &&
inode->i_flock->fl_end == OFFSET_MAX &&
- inode->i_flock->fl_type != F_RDLCK)))
+ inode->i_flock->fl_type != F_RDLCK))
return 1;
return 0;
}
Patches currently in stable-queue which might be from smayhew@xxxxxxxxxx are
queue-3.12/nfs-always-make-sure-page-is-up-to-date-before-extending-a-write-to-cover-the-entire-page.patch
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