[PATCH 6/9] crypto, zstd: Implement zbufsize()

[Kees Cook]

This implements the worst-case compression size querying interface for
zstd, based on the logic originally used by pstore.

Signed-off-by: Kees Cook <keesc...@chromium.org>
---
 crypto/zstd.c | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/crypto/zstd.c b/crypto/zstd.c
index 9a76b3ed8b8b..ce8efd40f27f 100644
--- a/crypto/zstd.c
+++ b/crypto/zstd.c
@@ -212,6 +212,24 @@ static int zstd_sdecompress(struct crypto_scomp *tfm, 
const u8 *src,
        return __zstd_decompress(src, slen, dst, dlen, ctx);
 }
 
+static int __zstd_zbufsize(unsigned int slen, unsigned int *dlen)
+{
+       *dlen = ZSTD_compressBound(slen);
+       return 0;
+}
+
+static int zstd_zbufsize(struct crypto_tfm *tfm, unsigned int slen,
+                        unsigned int *dlen)
+{
+       return __zstd_zbufsize(slen, dlen);
+}
+
+static int zstd_szbufsize(struct crypto_scomp *tfm, unsigned int slen,
+                         unsigned int *dlen, void *ctx)
+{
+       return __zstd_zbufsize(slen, dlen);
+}
+
 static struct crypto_alg alg = {
        .cra_name               = "zstd",
        .cra_flags              = CRYPTO_ALG_TYPE_COMPRESS,
@@ -221,7 +239,8 @@ static struct crypto_alg alg = {
        .cra_exit               = zstd_exit,
        .cra_u                  = { .compress = {
        .coa_compress           = zstd_compress,
-       .coa_decompress         = zstd_decompress } }
+       .coa_decompress         = zstd_decompress,
+       .coa_zbufsize           = zstd_zbufsize } }
 };
 
 static struct scomp_alg scomp = {
@@ -229,6 +248,7 @@ static struct scomp_alg scomp = {
        .free_ctx               = zstd_free_ctx,
        .compress               = zstd_scompress,
        .decompress             = zstd_sdecompress,
+       .zbufsize               = zstd_szbufsize,
        .base                   = {
                .cra_name       = "zstd",
                .cra_driver_name = "zstd-scomp",
-- 
2.17.1