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authorChris Mason <chris.mason@oracle.com>2011-03-07 11:10:24 -0500
committerChris Mason <chris.mason@oracle.com>2011-03-07 11:10:24 -0500
commit31339acd07b4ba687906702085127895a56eb920 (patch)
treec1f2d464acfc97e8c5faecf57e644578cccce94d /fs
parentb1bf862e9dad431175a1174379476299dbfdc017 (diff)
downloadlinux-linaro-stable-31339acd07b4ba687906702085127895a56eb920.tar.gz
Btrfs: deal with short returns from copy_from_user
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 <chris.mason@oracle.com> cc: stable@kernel.org
Diffstat (limited to 'fs')
-rw-r--r--fs/btrfs/file.c13
1 files changed, 13 insertions, 0 deletions
diff --git a/fs/btrfs/file.c b/fs/btrfs/file.c
index 13664b315fe2..ab22ca4f237f 100644
--- a/fs/btrfs/file.c
+++ b/fs/btrfs/file.c
@@ -69,6 +69,19 @@ static noinline int btrfs_copy_from_user(loff_t pos, int num_pages,
/* 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;