ext4: fix to check return value of freeze_bdev() in ext4_shutdown()

freeze_bdev() can fail due to a lot of reasons, it needs to check its
reason before later process.

Fixes: 783d948 ("ext4: add EXT4_IOC_GOINGDOWN ioctl")
Cc: [email protected]
Signed-off-by: Chao Yu <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Theodore Ts'o <[email protected]>

Author: chaseyu

fs/ext4/ioctl.c

@@ -797,6 +797,7 @@ static int ext4_shutdown(struct super_block *sb, unsigned long arg)
 {
 	struct ext4_sb_info *sbi = EXT4_SB(sb);
 	__u32 flags;
+	int ret;
 
 	if (!capable(CAP_SYS_ADMIN))
 		return -EPERM;
@@ -815,7 +816,9 @@ static int ext4_shutdown(struct super_block *sb, unsigned long arg)
 
 	switch (flags) {
 	case EXT4_GOING_FLAGS_DEFAULT:
-		freeze_bdev(sb->s_bdev);
+		ret = freeze_bdev(sb->s_bdev);
+		if (ret)
+			return ret;
 		set_bit(EXT4_FLAGS_SHUTDOWN, &sbi->s_ext4_flags);
 		thaw_bdev(sb->s_bdev);
 		break;