ext4: Block writes to journal device

Ask block layer to not allow other writers to open block device used
for ext4 journal.
Signed-off-by: Jan Kara <jack@suse.cz>
Link: https://lore.kernel.org/r/20231101174325.10596-7-jack@suse.czReviewed-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Christian Brauner <brauner@kernel.org>

fs/ext4/super.c

@@ -5864,8 +5864,9 @@ static struct bdev_handle *ext4_get_journal_blkdev(struct super_block *sb,
 	struct ext4_super_block *es;
 	int errno;
 
-	bdev_handle = bdev_open_by_dev(j_dev, BLK_OPEN_READ | BLK_OPEN_WRITE,
-				       sb, &fs_holder_ops);
+	bdev_handle = bdev_open_by_dev(j_dev,
+		BLK_OPEN_READ | BLK_OPEN_WRITE | BLK_OPEN_RESTRICT_WRITES,
+		sb, &fs_holder_ops);
 	if (IS_ERR(bdev_handle)) {
 		ext4_msg(sb, KERN_ERR,
 			 "failed to open journal device unknown-block(%u,%u) %ld",