exfat: fix potential wrong error return from get_block

JIRA: https://issues.redhat.com/browse/RHEL-89708

If there is no error, get_block() should return 0. However, when bh_read()
returns 1, get_block() also returns 1 in the same manner.

Let's set err to 0, if there is no error from bh_read()

Fixes: 11a347f ("exfat: change to get file size from DataLength")
Cc: stable@vger.kernel.org
Signed-off-by: Sungjong Seo <sj1557.seo@samsung.com>
Reviewed-by: Yuezhang Mo <Yuezhang.Mo@sony.com>
Signed-off-by: Namjae Jeon <linkinjeon@kernel.org>
(cherry picked from commit 59c30e3)
Signed-off-by: Pavel Reichl <preichl@redhat.com>

Author: preichl

fs/exfat/inode.c

@@ -391,6 +391,8 @@ static int exfat_get_block(struct inode *inode, sector_t iblock,
 			/* Zero unwritten part of a block */
 			memset(bh_result->b_data + size, 0,
 			       bh_result->b_size - size);
+
+			err = 0;
 		} else {
 			/*
 			 * The range has not been written, clear the mapped flag