[PATCH 1/2] btrfs: add member for a specific checksum driver

[David Sterba]

Currently all the checksum algorithms generate a fixed size digest size
and we use it.  The on-disk format can hold up to BTRFS_CSUM_SIZE bytes
and BLAKE2b produces digest of 512 bits by default. We can't do that and
will use the blake2b-256, this needs to be passed to the crypto API.

Separate that from the base algorithm name and add a member to request
specific driver, in this case with the digest size.

The only place that uses the driver name is the crypto API setup.

Signed-off-by: David Sterba <dste...@suse.com>
---
 fs/btrfs/ctree.c   | 12 ++++++++++++
 fs/btrfs/ctree.h   |  1 +
 fs/btrfs/disk-io.c |  6 +++---
 3 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
index c1561097e5a3..c211216b4524 100644
--- a/fs/btrfs/ctree.c
+++ b/fs/btrfs/ctree.c
@@ -32,6 +32,7 @@ static void del_ptr(struct btrfs_root *root, struct 
btrfs_path *path,
 static const struct btrfs_csums {
        u16             size;
        const char      *name;
+       const char      *driver;
 } btrfs_csums[] = {
        [BTRFS_CSUM_TYPE_CRC32] = { .size = 4, .name = "crc32c" },
        [BTRFS_CSUM_TYPE_XXHASH] = { .size = 8, .name = "xxhash64" },
@@ -53,6 +54,17 @@ const char *btrfs_super_csum_name(u16 csum_type)
        return btrfs_csums[csum_type].name;
 }
 
+/*
+ * Return driver name if defined, otherwise the name that's also a valid driver
+ * name
+ */
+const char *btrfs_super_csum_driver(u16 csum_type)
+{
+       /* csum type is validated at mount time */
+       return btrfs_csums[csum_type].driver ?:
+               btrfs_csums[csum_type].name;
+}
+
 size_t __const btrfs_get_num_csums(void)
 {
        return ARRAY_SIZE(btrfs_csums);
diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index b17944995e09..4a842c0fa062 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -2163,6 +2163,7 @@ BTRFS_SETGET_STACK_FUNCS(super_uuid_tree_generation, 
struct btrfs_super_block,
 
 int btrfs_super_csum_size(const struct btrfs_super_block *s);
 const char *btrfs_super_csum_name(u16 csum_type);
+const char *btrfs_super_csum_driver(u16 csum_type);
 size_t __const btrfs_get_num_csums(void);
 
 
diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 21fab336f8ca..948ed5ac0794 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -2219,13 +2219,13 @@ static int btrfs_init_workqueues(struct btrfs_fs_info 
*fs_info,
 static int btrfs_init_csum_hash(struct btrfs_fs_info *fs_info, u16 csum_type)
 {
        struct crypto_shash *csum_shash;
-       const char *csum_name = btrfs_super_csum_name(csum_type);
+       const char *csum_driver = btrfs_super_csum_driver(csum_type);
 
-       csum_shash = crypto_alloc_shash(csum_name, 0, 0);
+       csum_shash = crypto_alloc_shash(csum_driver, 0, 0);
 
        if (IS_ERR(csum_shash)) {
                btrfs_err(fs_info, "error allocating %s hash for checksum",
-                         csum_name);
+                         csum_driver);
                return PTR_ERR(csum_shash);
        }
 
-- 
2.23.0