btrfs: subpage: reject raid56 filesystem and profile conversion

RAID56 is not only unsafe due to its write-hole problem, but also has
tons of hardcoded PAGE_SIZE.

Disable it for subpage support for now.
Reviewed-by: Anand Jain <anand.jain@oracle.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

fs/btrfs/disk-io.c

@@ -3402,6 +3402,16 @@ int __cold open_ctree(struct super_block *sb, struct btrfs_fs_devices *fs_device
 			goto fail_alloc;
 		}
 	}
+	if (sectorsize != PAGE_SIZE) {
+		if (btrfs_super_incompat_flags(fs_info->super_copy) &
+			BTRFS_FEATURE_INCOMPAT_RAID56) {
+			btrfs_err(fs_info,
+		"RAID56 is not yet supported for sector size %u with page size %lu",
+				sectorsize, PAGE_SIZE);
+			err = -EINVAL;
+			goto fail_alloc;
+		}
+	}
 
 	ret = btrfs_init_workqueues(fs_info, fs_devices);
 	if (ret) {

fs/btrfs/volumes.c

@@ -3968,6 +3968,13 @@ static inline int validate_convert_profile(struct btrfs_fs_info *fs_info,
 	if (!(bargs->flags & BTRFS_BALANCE_ARGS_CONVERT))
 		return true;
 
+	if (fs_info->sectorsize < PAGE_SIZE &&
+		bargs->target & BTRFS_BLOCK_GROUP_RAID56_MASK) {
+		btrfs_err(fs_info,
+		"RAID56 is not yet supported for sectorsize %u with page size %lu",
+			  fs_info->sectorsize, PAGE_SIZE);
+		return false;
+	}
 	/* Profile is valid and does not have bits outside of the allowed set */
 	if (alloc_profile_is_valid(bargs->target, 1) &&
 	    (bargs->target & ~allowed) == 0)