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

[majianpeng]

Hi Sage:
        This patch based on my previous patch"ceph: fix bugs about handling 
short-read for sync read mode".
I can't see this patch in ceph-client#testing.Maybe you forget it ?

Thanks!
Jianpeng Ma

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 <majianp...@gmail.com>
---
 fs/ceph/file.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/fs/ceph/file.c b/fs/ceph/file.c
index 69c4669..dd525c5 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)
@@ -611,7 +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;
 }
 
-- 
1.8.1.2