[PATCH v4 07/13] btrfs: add common checksum type validation

[Johannes Thumshirn <jthumshirn@suse.de>]

Currently btrfs is only supporting CRC32C as checksumming algorithm. As
this is about to change provide a function to validate the checksum type in
the superblock against all possible algorithms.

This makes adding new algorithms easier as there are fewer places to adjust
when adding new algorithms.

Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>

---
Changes to v3:
- Fix callers of btrfs_supported_csum() (David)
Changes to v2:
- Only pass csum_type into btrfs_supported_csum() (David)
- Directly return in btrfs_check_super_csum() (David)
---
 fs/btrfs/disk-io.c | 29 +++++++++++++++++++----------
 1 file changed, 19 insertions(+), 10 deletions(-)

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 663efce22d98..c2aba3dc33c5 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -356,6 +356,16 @@ static int verify_parent_transid(struct extent_io_tree *io_tree,
 	return ret;
 }
 
+static bool btrfs_supported_super_csum(u16 csum_type)
+{
+	switch (csum_type) {
+	case BTRFS_CSUM_TYPE_CRC32:
+		return true;
+	default:
+		return false;
+	}
+}
+
 /*
  * Return 0 if the superblock checksum type matches the checksum value of that
  * algorithm. Pass the raw disk superblock data.
@@ -366,7 +376,12 @@ static int btrfs_check_super_csum(struct btrfs_fs_info *fs_info,
 	struct btrfs_super_block *disk_sb =
 		(struct btrfs_super_block *)raw_disk_sb;
 	u16 csum_type = btrfs_super_csum_type(disk_sb);
-	int ret = 0;
+
+	if (!btrfs_supported_super_csum(csum_type)) {
+		btrfs_err(fs_info, "unsupported checksum algorithm %u",
+			  csum_type);
+		return 1;
+	}
 
 	if (csum_type == BTRFS_CSUM_TYPE_CRC32) {
 		u32 crc = ~(u32)0;
@@ -382,16 +397,10 @@ static int btrfs_check_super_csum(struct btrfs_fs_info *fs_info,
 		btrfs_csum_final(crc, result);
 
 		if (memcmp(raw_disk_sb, result, sizeof(result)))
-			ret = 1;
+			return 1;
 	}
 
-	if (csum_type >= ARRAY_SIZE(btrfs_csum_sizes)) {
-		btrfs_err(fs_info, "unsupported checksum algorithm %u",
-				csum_type);
-		ret = 1;
-	}
-
-	return ret;
+	return 0;
 }
 
 int btrfs_verify_level_key(struct extent_buffer *eb, int level,
@@ -2577,7 +2586,7 @@ static int btrfs_validate_write_super(struct btrfs_fs_info *fs_info,
 	ret = validate_super(fs_info, sb, -1);
 	if (ret < 0)
 		goto out;
-	if (btrfs_super_csum_type(sb) != BTRFS_CSUM_TYPE_CRC32) {
+	if (!btrfs_supported_super_csum(btrfs_super_csum_type(sb))) {
 		ret = -EUCLEAN;
 		btrfs_err(fs_info, "invalid csum type, has %u want %u",
 			  btrfs_super_csum_type(sb), BTRFS_CSUM_TYPE_CRC32);
-- 
2.16.4