[PATCH 3.11 122/208] ceph: allow sync_read/write return partial successed size of read/write.

[Luis Henriques]

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

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

From: majianpeng <majianpeng at gmail.com>

commit ee7289bfadda5f4ef60884547ebc9989c8fb314a upstream.

For sync_read/write, it may do multi stripe operations.If one of those
met erro, we return the former successed size rather than a error value.
There is a exception for write-operation met -EOLDSNAPC.If this occur,we
retry the whole write again.

Signed-off-by: Jianpeng Ma <majianpeng at gmail.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 fs/ceph/file.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/ceph/file.c b/fs/ceph/file.c
index 5f3b4ee..47f2cde 100644
--- a/fs/ceph/file.c
+++ b/fs/ceph/file.c
@@ -373,7 +373,7 @@ more:
 			goto more;
 	}
 
-	if (ret >= 0) {
+	if (read > 0) {
 		ret = read;
 		/* did we bounce off eof? */
 		if (pos + left > inode->i_size)
@@ -611,6 +611,8 @@ out:
 		if (check_caps)
 			ceph_check_caps(ceph_inode(inode), CHECK_CAPS_AUTHONLY,
 					NULL);
+	} else if (ret != -EOLDSNAPC && written > 0) {
+		ret = written;
 	}
 	return ret;
 }
-- 
1.8.3.2