[PATCH 3.11 105/208] ceph: Avoid data inconsistency due to d-cache aliasing in readpage()

[Luis Henriques]

3.11.10.3 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Li Wang <liwang at ubuntukylin.com>

commit 56f91aad69444d650237295f68c195b74d888d95 upstream.

If the length of data to be read in readpage() is exactly
PAGE_CACHE_SIZE, the original code does not flush d-cache
for data consistency after finishing reading. This patches fixes
this.

Signed-off-by: Li Wang <liwang at ubuntukylin.com>
Signed-off-by: Sage Weil <sage at inktank.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 fs/ceph/addr.c | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/fs/ceph/addr.c b/fs/ceph/addr.c
index 5318a3b..0d2e0f1 100644
--- a/fs/ceph/addr.c
+++ b/fs/ceph/addr.c
@@ -214,9 +214,13 @@ static int readpage_nounlock(struct file *filp, struct page *page)
 	if (err < 0) {
 		SetPageError(page);
 		goto out;
-	} else if (err < PAGE_CACHE_SIZE) {
+	} else {
+		if (err < PAGE_CACHE_SIZE) {
 		/* zero fill remainder of page */
-		zero_user_segment(page, err, PAGE_CACHE_SIZE);
+			zero_user_segment(page, err, PAGE_CACHE_SIZE);
+		} else {
+			flush_dcache_page(page);
+		}
 	}
 	SetPageUptodate(page);
 
-- 
1.8.3.2