ceph: stop copying to iter at EOF on sync reads

[ Upstream commit 1065da21e5df9d843d2c5165d5d576be000142a6 ]

If EOF is encountered, ceph_sync_read() return value is adjusted down
according to i_size, but the "to" iter is advanced by the actual number
of bytes read.  Then, when retrying, the remainder of the range may be
skipped incorrectly.

Ensure that the "to" iter is advanced only until EOF.

[ idryomov: changelog ]

Fixes: c3d8e0b5de48 ("ceph: return the real size read when it hits EOF")
Reported-by: Frank Hsiao <frankhsiao@qnap.com>
Signed-off-by: Xiubo Li <xiubli@redhat.com>
Reviewed-by: Ilya Dryomov <idryomov@gmail.com>
Tested-by: Frank Hsiao <frankhsiao@qnap.com>
Signed-off-by: Ilya Dryomov <idryomov@gmail.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/fs/ceph/file.c b/fs/ceph/file.c
index b5f8038065d7c1f952ef1cbeef569ad88ac9e0f9..bdd0a3b894b7bc7e8494cea4a95b3c6252be9ba1 100644 (file)
--- a/fs/ceph/file.c
+++ b/fs/ceph/file.c
@@ -1108,7 +1108,12 @@ ssize_t __ceph_sync_read(struct inode *inode, loff_t *ki_pos,
                }
 
                idx = 0;
-               left = ret > 0 ? ret : 0;
+               if (ret <= 0)
+                       left = 0;
+               else if (off + ret > i_size)
+                       left = i_size - off;
+               else
+                       left = ret;
                while (left > 0) {
                        size_t plen, copied;
 
@@ -1137,15 +1142,13 @@ ssize_t __ceph_sync_read(struct inode *inode, loff_t *ki_pos,
        }
 
        if (ret > 0) {
-               if (off > *ki_pos) {
-                       if (off >= i_size) {
-                               *retry_op = CHECK_EOF;
-                               ret = i_size - *ki_pos;
-                               *ki_pos = i_size;
-                       } else {
-                               ret = off - *ki_pos;
-                               *ki_pos = off;
-                       }
+               if (off >= i_size) {
+                       *retry_op = CHECK_EOF;
+                       ret = i_size - *ki_pos;
+                       *ki_pos = i_size;
+               } else {
+                       ret = off - *ki_pos;
+                       *ki_pos = off;
                }
 
                if (last_objver)