[PATCH v3 1/2] ceph: skip copying the data extends the file EOF

[xiubli@redhat.com]

From: Xiubo Li <xiubli@redhat.com>

If hits the EOF it will revise the return value to the i_size
instead of the real length read, but it will advance the offset
of iovc, then for the next try it may be incorrectly skipped.

This will just skip advancing the iovc's offset more than i_size.

URL: https://patchwork.kernel.org/project/ceph-devel/list/?series=819323
Reported-by: Frank Hsiao 蕭法宣 <frankhsiao@qnap.com>
Signed-off-by: Xiubo Li <xiubli@redhat.com>
Tested-by: Frank Hsiao 蕭法宣 <frankhsiao@qnap.com>
---
 fs/ceph/file.c | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/fs/ceph/file.c b/fs/ceph/file.c
index 24a003eaa5e0..c35878427985 100644
--- a/fs/ceph/file.c
+++ b/fs/ceph/file.c
@@ -1200,7 +1200,12 @@ 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;
 
@@ -1229,15 +1234,13 @@ 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)
-- 
2.43.0