ext4: split ext4_shutdown

Split ext4_shutdown into a low-level helper that will be reused for
implementing the shutdown super operation and a wrapper for the ioctl
handling.
Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Acked-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Link: https://lore.kernel.org/r/20230601094459.1350643-15-hch@lst.deSigned-off-by: Jens Axboe <axboe@kernel.dk>

fs/ext4/ext4.h

@@ -2965,6 +2965,7 @@ int ext4_fileattr_set(struct mnt_idmap *idmap,
 int ext4_fileattr_get(struct dentry *dentry, struct fileattr *fa);
 extern void ext4_reset_inode_seed(struct inode *inode);
 int ext4_update_overhead(struct super_block *sb, bool force);
+int ext4_force_shutdown(struct super_block *sb, u32 flags);
 
 /* migrate.c */
 extern int ext4_ext_migrate(struct inode *);

fs/ext4/ioctl.c

@@ -793,16 +793,9 @@ static int ext4_ioctl_setproject(struct inode *inode, __u32 projid)
 }
 #endif
 
-static int ext4_shutdown(struct super_block *sb, unsigned long arg)
+int ext4_force_shutdown(struct super_block *sb, u32 flags)
 {
 	struct ext4_sb_info *sbi = EXT4_SB(sb);
-	__u32 flags;
-
-	if (!capable(CAP_SYS_ADMIN))
-		return -EPERM;
-
-	if (get_user(flags, (__u32 __user *)arg))
-		return -EFAULT;
 
 	if (flags > EXT4_GOING_FLAGS_NOLOGFLUSH)
 		return -EINVAL;
@@ -838,6 +831,19 @@ static int ext4_shutdown(struct super_block *sb, unsigned long arg)
 	return 0;
 }
 
+static int ext4_ioctl_shutdown(struct super_block *sb, unsigned long arg)
+{
+	u32 flags;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	if (get_user(flags, (__u32 __user *)arg))
+		return -EFAULT;
+
+	return ext4_force_shutdown(sb, flags);
+}
+
 struct getfsmap_info {
 	struct super_block	*gi_sb;
 	struct fsmap_head __user *gi_data;
@@ -1566,7 +1572,7 @@ static long __ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 		return ext4_ioctl_get_es_cache(filp, arg);
 
 	case EXT4_IOC_SHUTDOWN:
-		return ext4_shutdown(sb, arg);
+		return ext4_ioctl_shutdown(sb, arg);
 
 	case FS_IOC_ENABLE_VERITY:
 		if (!ext4_has_feature_verity(sb))