bcachefs: Don't use sha256 for siphash str hash key

With the refactoring that's coming to add fuse support, we want
bch2_hash_info_init() to be cheaper so we don't have to rely on anything
cached besides the inode in the btree.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/bcachefs_format.h

@@ -1318,6 +1318,7 @@ enum bch_sb_features {
 	BCH_FEATURE_EC			= 4,
 	BCH_FEATURE_JOURNAL_SEQ_BLACKLIST_V3 = 5,
 	BCH_FEATURE_REFLINK		= 6,
+	BCH_FEATURE_NEW_SIPHASH		= 7,
 	BCH_FEATURE_NR,
 };
 
@@ -1344,11 +1345,19 @@ enum bch_csum_opts {
 	BCH_CSUM_OPT_NR			= 3,
 };
 
-enum bch_str_hash_opts {
+enum bch_str_hash_type {
 	BCH_STR_HASH_CRC32C		= 0,
 	BCH_STR_HASH_CRC64		= 1,
-	BCH_STR_HASH_SIPHASH		= 2,
-	BCH_STR_HASH_NR			= 3,
+	BCH_STR_HASH_SIPHASH_OLD	= 2,
+	BCH_STR_HASH_SIPHASH		= 3,
+	BCH_STR_HASH_NR			= 4,
+};
+
+enum bch_str_hash_opts {
+	BCH_STR_HASH_OPT_CRC32C		= 0,
+	BCH_STR_HASH_OPT_CRC64		= 1,
+	BCH_STR_HASH_OPT_SIPHASH	= 2,
+	BCH_STR_HASH_OPT_NR		= 3,
 };
 
 #define BCH_COMPRESSION_TYPES()		\

fs/bcachefs/inode.c

@@ -6,8 +6,7 @@
 #include "error.h"
 #include "extents.h"
 #include "inode.h"
-#include "io.h"
-#include "keylist.h"
+#include "str_hash.h"
 
 #include <linux/random.h>
 
@@ -303,11 +302,13 @@ void bch2_inode_init(struct bch_fs *c, struct bch_inode_unpacked *inode_u,
 		     struct bch_inode_unpacked *parent)
 {
 	s64 now = bch2_current_time(c);
+	enum bch_str_hash_type str_hash =
+		bch2_str_hash_opt_to_type(c, c->opts.str_hash);
 
 	memset(inode_u, 0, sizeof(*inode_u));
 
 	/* ick */
-	inode_u->bi_flags |= c->opts.str_hash << INODE_STR_HASH_OFFSET;
+	inode_u->bi_flags |= str_hash << INODE_STR_HASH_OFFSET;
 	get_random_bytes(&inode_u->bi_hash_seed,
 			 sizeof(inode_u->bi_hash_seed));
 

fs/bcachefs/opts.h

@@ -127,7 +127,7 @@ enum opt_type {
 	x(str_hash,			u8,				\
 	  OPT_FORMAT|OPT_MOUNT|OPT_RUNTIME,				\
 	  OPT_STR(bch2_str_hash_types),					\
-	  BCH_SB_STR_HASH_TYPE,		BCH_STR_HASH_SIPHASH,		\
+	  BCH_SB_STR_HASH_TYPE,		BCH_STR_HASH_OPT_SIPHASH,	\
 	  NULL,		"Hash function for directory entries and xattrs")\
 	x(foreground_target,		u16,				\
 	  OPT_FORMAT|OPT_MOUNT|OPT_RUNTIME|OPT_INODE,			\

fs/bcachefs/str_hash.h

@@ -14,6 +14,23 @@
 #include <crypto/hash.h>
 #include <crypto/sha2.h>
 
+static inline enum bch_str_hash_type
+bch2_str_hash_opt_to_type(struct bch_fs *c, enum bch_str_hash_opts opt)
+{
+	switch (opt) {
+	case BCH_STR_HASH_OPT_CRC32C:
+		return BCH_STR_HASH_CRC32C;
+	case BCH_STR_HASH_OPT_CRC64:
+		return BCH_STR_HASH_CRC64;
+	case BCH_STR_HASH_OPT_SIPHASH:
+		return c->sb.features & (1ULL << BCH_FEATURE_NEW_SIPHASH)
+			? BCH_STR_HASH_SIPHASH
+			: BCH_STR_HASH_SIPHASH_OLD;
+	default:
+	     BUG();
+	}
+}
+
 struct bch_hash_info {
 	u8			type;
 	union {
@@ -23,21 +40,16 @@ struct bch_hash_info {
 };
 
 static inline struct bch_hash_info
-bch2_hash_info_init(struct bch_fs *c,
-		   const struct bch_inode_unpacked *bi)
+bch2_hash_info_init(struct bch_fs *c, const struct bch_inode_unpacked *bi)
 {
 	/* XXX ick */
 	struct bch_hash_info info = {
 		.type = (bi->bi_flags >> INODE_STR_HASH_OFFSET) &
-			~(~0U << INODE_STR_HASH_BITS)
+			~(~0U << INODE_STR_HASH_BITS),
+		.crc_key = bi->bi_hash_seed,
 	};
 
-	switch (info.type) {
-	case BCH_STR_HASH_CRC32C:
-	case BCH_STR_HASH_CRC64:
-		info.crc_key = bi->bi_hash_seed;
-		break;
-	case BCH_STR_HASH_SIPHASH: {
+	if (unlikely(info.type == BCH_STR_HASH_SIPHASH_OLD)) {
 		SHASH_DESC_ON_STACK(desc, c->sha256);
 		u8 digest[SHA256_DIGEST_SIZE];
 
@@ -46,10 +58,6 @@ bch2_hash_info_init(struct bch_fs *c,
 		crypto_shash_digest(desc, (void *) &bi->bi_hash_seed,
 				    sizeof(bi->bi_hash_seed), digest);
 		memcpy(&info.siphash_key, digest, sizeof(info.siphash_key));
-		break;
-	}
-	default:
-		BUG();
 	}
 
 	return info;
@@ -73,6 +81,7 @@ static inline void bch2_str_hash_init(struct bch_str_hash_ctx *ctx,
 	case BCH_STR_HASH_CRC64:
 		ctx->crc64 = crc64_be(~0, &info->crc_key, sizeof(info->crc_key));
 		break;
+	case BCH_STR_HASH_SIPHASH_OLD:
 	case BCH_STR_HASH_SIPHASH:
 		SipHash24_Init(&ctx->siphash, &info->siphash_key);
 		break;
@@ -92,6 +101,7 @@ static inline void bch2_str_hash_update(struct bch_str_hash_ctx *ctx,
 	case BCH_STR_HASH_CRC64:
 		ctx->crc64 = crc64_be(ctx->crc64, data, len);
 		break;
+	case BCH_STR_HASH_SIPHASH_OLD:
 	case BCH_STR_HASH_SIPHASH:
 		SipHash24_Update(&ctx->siphash, data, len);
 		break;
@@ -108,6 +118,7 @@ static inline u64 bch2_str_hash_end(struct bch_str_hash_ctx *ctx,
 		return ctx->crc32c;
 	case BCH_STR_HASH_CRC64:
 		return ctx->crc64 >> 1;
+	case BCH_STR_HASH_SIPHASH_OLD:
 	case BCH_STR_HASH_SIPHASH:
 		return SipHash24_End(&ctx->siphash) >> 1;
 	default: