ext4: consolidate checks for resize of bigalloc into ext4_resize_begin

Two different places checked for attempts to resize a filesystem with
the bigalloc feature. Move the check into ext4_resize_begin, which both
places already call.

Signed-off-by: Josh Triplett <josh@joshtriplett.org>
Link: https://lore.kernel.org/r/bee03303d999225ecb3bfa5be8576b2f4c6edbe6.1623093259.git.josh@joshtriplett.org
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

fs/ext4/ioctl.c

@@ -692,13 +692,6 @@ static long ext4_ioctl_group_add(struct file *file,
 	if (err)
 		return err;
 
-	if (ext4_has_feature_bigalloc(sb)) {
-		ext4_msg(sb, KERN_ERR,
-			 "Online resizing not supported with bigalloc");
-		err = -EOPNOTSUPP;
-		goto group_add_out;
-	}
-
 	err = mnt_want_write_file(file);
 	if (err)
 		goto group_add_out;
@@ -921,13 +914,6 @@ static long __ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 			goto group_extend_out;
 		}
 
-		if (ext4_has_feature_bigalloc(sb)) {
-			ext4_msg(sb, KERN_ERR,
-				 "Online resizing not supported with bigalloc");
-			err = -EOPNOTSUPP;
-			goto group_extend_out;
-		}
-
 		err = mnt_want_write_file(filp);
 		if (err)
 			goto group_extend_out;

fs/ext4/resize.c

@@ -74,6 +74,11 @@ int ext4_resize_begin(struct super_block *sb)
 		return -EPERM;
 	}
 
+	if (ext4_has_feature_bigalloc(sb)) {
+		ext4_msg(sb, KERN_ERR, "Online resizing not supported with bigalloc");
+		return -EOPNOTSUPP;
+	}
+
 	if (test_and_set_bit_lock(EXT4_FLAGS_RESIZING,
 				  &EXT4_SB(sb)->s_ext4_flags))
 		ret = -EBUSY;