[RFC PATCH 2/4] btrfs: create structure to encode checksum type and length

[Johannes Thumshirn]

Create a structure to encode the type and length for the known on-disk
checksums. Also add a table and a convenience macro for adding the
checksum types to the table.

This makes it easier to add new checksums later.

Signed-off-by: Johannes Thumshirn <jthumsh...@suse.de>
---
 fs/btrfs/ctree.h | 16 +++++++++++-----
 1 file changed, 11 insertions(+), 5 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index da97ff10f421..099401f5dd47 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -82,9 +82,15 @@ struct btrfs_ref;
  */
 #define BTRFS_LINK_MAX 65535U
 
-/* four bytes for CRC32 */
-static const int btrfs_csum_sizes[] = { 4 };
-static const char *btrfs_csum_names[] = { "crc32c" };
+#define BTRFS_CHECKSUM_TYPE(_type, _size, _name) \
+       [_type] = { .size = _size, .name = _name }
+
+static const struct btrfs_csums {
+       u16             size;
+       const char      *name;
+} btrfs_csums[] = {
+       BTRFS_CHECKSUM_TYPE(BTRFS_CSUM_TYPE_CRC32, 4, "crc32c"),
+};
 
 #define BTRFS_EMPTY_DIR_SIZE 0
 
@@ -2373,13 +2379,13 @@ static inline int btrfs_super_csum_size(const struct 
btrfs_super_block *s)
        /*
         * csum type is validated at mount time
         */
-       return btrfs_csum_sizes[t];
+       return btrfs_csums[t].size;
 }
 
 static inline const char *btrfs_super_csum_name(u16 csum_type)
 {
        /* csum type is validated at mount time */
-       return btrfs_csum_names[csum_type];
+       return btrfs_csums[csum_type].name;
 }
 
 /*
-- 
2.16.4