ceph: allow sync_read/write return partial successed size of read/write.

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@gmail.com>

1 files changed, 3 insertions, 1 deletions

diff --git a/fs/ceph/file.c b/fs/ceph/file.c
index 98b9035b2e81..20d0222c2e76 100644
--- a/fs/ceph/file.c
+++ b/fs/ceph/file.c
@@ -374,7 +374,7 @@ more:
                         goto more;
         }
 
-        if (ret >= 0) {
+        if (read > 0) {
                 ret = read;
                 /* did we bounce off eof? */
                 if (pos + left > inode->i_size)
@@ -612,6 +612,8 @@ out:
                 if (check_caps)
                         ceph_check_caps(ceph_inode(inode), CHECK_CAPS_AUTHONLY,
                                         NULL);
+        } else if (ret != -EOLDSNAPC && written > 0) {
+                ret = written;
         }
         return ret;
 }