ceph: Correctly return NXIO errors from ceph_llseek

commit 955818cd upstream.

ceph_llseek does not correctly return NXIO errors because the 'out' path
always returns 'offset'.

Fixes: 06222e49 ("fs: handle SEEK_HOLE/SEEK_DATA properly in all fs's that define their own llseek")
Signed-off-by: Phil Turnbull <phil.turnbull@oracle.com>
Signed-off-by: Yan, Zheng <zyan@redhat.com>
[bwh: Backported to 3.16; adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

fs/ceph/file.c

@@ -985,16 +985,14 @@ static ssize_t ceph_write_iter(struct kiocb *iocb, struct iov_iter *from)
 static loff_t ceph_llseek(struct file *file, loff_t offset, int whence)
 {
 	struct inode *inode = file->f_mapping->host;
-	int ret;
+	loff_t ret;
 
 	mutex_lock(&inode->i_mutex);
 
 	if (whence == SEEK_END || whence == SEEK_DATA || whence == SEEK_HOLE) {
 		ret = ceph_do_getattr(inode, CEPH_STAT_CAP_SIZE);
-		if (ret < 0) {
-			offset = ret;
+		if (ret < 0)
 			goto out;
-		}
 	}
 
 	switch (whence) {
@@ -1009,7 +1007,7 @@ static loff_t ceph_llseek(struct file *file, loff_t offset, int whence)
 		 * write() or lseek() might have altered it
 		 */
 		if (offset == 0) {
-			offset = file->f_pos;
+			ret = file->f_pos;
 			goto out;
 		}
 		offset += file->f_pos;
@@ -1029,11 +1027,11 @@ static loff_t ceph_llseek(struct file *file, loff_t offset, int whence)
 		break;
 	}
 
-	offset = vfs_setpos(file, offset, inode->i_sb->s_maxbytes);
+	ret = vfs_setpos(file, offset, inode->i_sb->s_maxbytes);
 
 out:
 	mutex_unlock(&inode->i_mutex);
-	return offset;
+	return ret;
 }
 
 static inline void ceph_zero_partial_page(