This is a note to let you know that I've just added the patch titled
Btrfs: deal with short returns from copy_from_user
to the 2.6.37-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:
btrfs-deal-with-short-returns-from-copy_from_user.patch
and it can be found in the queue-2.6.37 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From 31339acd07b4ba687906702085127895a56eb920 Mon Sep 17 00:00:00 2001
From: Chris Mason <[email protected]>
Date: Mon, 7 Mar 2011 11:10:24 -0500
Subject: Btrfs: deal with short returns from copy_from_user
From: Chris Mason <[email protected]>
commit 31339acd07b4ba687906702085127895a56eb920 upstream.
When copy_from_user is only able to copy some of the bytes we requested,
we may end up creating a partially up to date page. To avoid garbage in
the page, we need to treat a partial copy as a zero length copy.
This makes the rest of the file_write code drop the page and
retry the whole copy instead of marking the partially up to
date page as dirty.
Signed-off-by: Chris Mason <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
fs/btrfs/file.c | 13 +++++++++++++
1 file changed, 13 insertions(+)
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -69,6 +69,19 @@ static noinline int btrfs_copy_from_user
/* Flush processor's dcache for this page */
flush_dcache_page(page);
+
+ /*
+ * if we get a partial write, we can end up with
+ * partially up to date pages. These add
+ * a lot of complexity, so make sure they don't
+ * happen by forcing this copy to be retried.
+ *
+ * The rest of the btrfs_file_write code will fall
+ * back to page at a time copies after we return 0.
+ */
+ if (!PageUptodate(page) && copied < count)
+ copied = 0;
+
iov_iter_advance(i, copied);
write_bytes -= copied;
total_copied += copied;
Patches currently in stable-queue which might be from [email protected] are
queue-2.6.37/btrfs-deal-with-short-returns-from-copy_from_user.patch
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