[v2,03/11] lib/crc64: rename CRC64-Rocksoft to CRC64-NVME

Commit Message

Eric Biggers Jan. 30, 2025, 3:51 a.m. UTC

From: Eric Biggers <[e-mail]>

This CRC64 variant comes from the NVME NVM Command Set Specification
(https://nvmexpress.org/wp-content/uploads/NVM-Express-NVM-Command-Set-Specification-1.0e-2024.07.29-Ratified.pdf).

The "Rocksoft Model CRC Algorithm", published in 1993 and available at
https://www.zlib.net/crc_v3.txt, is a generalized CRC algorithm that can
calculate any variant of CRC, given a list of parameters such as
polynomial, bit order, etc.  It is not a CRC variant.

The NVME NVM Command Set Specification has a table that gives the
"Rocksoft Model Parameters" for the CRC variant it uses.  When support
for this CRC variant was added to Linux, this table seems to have been
misinterpreted as naming the CRC variant the "Rocksoft" CRC.  In fact,
the CRC variant is not explicitly named by the NVME spec.

Most implementations of this CRC variant outside Linux have been calling
it CRC64-NVME.  Therefore, update Linux to match.

While at it, remove the superfluous "update" from the function name, so
crc64_rocksoft_update() is now just crc64_nvme(), matching most of the
other CRC library functions.

Signed-off-by: Eric Biggers <[e-mail]>
---
 block/t10-pi.c        |  2 +-
 include/linux/crc64.h | 11 +++++++----
 lib/crc64.c           | 10 +++++-----
 lib/gen_crc64table.c  | 10 +++++-----
 4 files changed, 18 insertions(+), 15 deletions(-)

Patch

diff --git a/block/t10-pi.c b/block/t10-pi.c
index 2d05421f0fa5..2577114ff20c 100644
--- a/block/t10-pi.c
+++ b/block/t10-pi.c
@@ -208,11 +208,11 @@  static void t10_pi_type1_complete(struct request *rq, unsigned int nr_bytes)
 	}
 }
 
 static __be64 ext_pi_crc64(u64 crc, void *data, unsigned int len)
 {
-	return cpu_to_be64(crc64_rocksoft_update(crc, data, len));
+	return cpu_to_be64(crc64_nvme(crc, data, len));
 }
 
 static void ext_pi_crc64_generate(struct blk_integrity_iter *iter,
 		struct blk_integrity *bi)
 {
diff --git a/include/linux/crc64.h b/include/linux/crc64.h
index 7880aeab69d6..17cf5af3e78e 100644
--- a/include/linux/crc64.h
+++ b/include/linux/crc64.h
@@ -6,20 +6,23 @@ 
 #define _LINUX_CRC64_H
 
 #include <linux/types.h>
 
 u64 __pure crc64_be(u64 crc, const void *p, size_t len);
-u64 __pure crc64_rocksoft_generic(u64 crc, const void *p, size_t len);
+u64 __pure crc64_nvme_generic(u64 crc, const void *p, size_t len);
 
 /**
- * crc64_rocksoft_update - Calculate bitwise Rocksoft CRC64
+ * crc64_nvme - Calculate CRC64-NVME
  * @crc: seed value for computation. 0 for a new CRC calculation, or the
  *	 previous crc64 value if computing incrementally.
  * @p: pointer to buffer over which CRC64 is run
  * @len: length of buffer @p
+ *
+ * This computes the CRC64 defined in the NVME NVM Command Set Specification,
+ * *including the bitwise inversion at the beginning and end*.
  */
-static inline u64 crc64_rocksoft_update(u64 crc, const u8 *p, size_t len)
+static inline u64 crc64_nvme(u64 crc, const u8 *p, size_t len)
 {
-	return crc64_rocksoft_generic(crc, p, len);
+	return crc64_nvme_generic(crc, p, len);
 }
 
 #endif /* _LINUX_CRC64_H */
diff --git a/lib/crc64.c b/lib/crc64.c
index b5136fb4c199..d6f3f245eede 100644
--- a/lib/crc64.c
+++ b/lib/crc64.c
@@ -20,12 +20,12 @@ 
  * x^64 + x^62 + x^57 + x^55 + x^54 + x^53 + x^52 + x^47 + x^46 + x^45 +
  * x^40 + x^39 + x^38 + x^37 + x^35 + x^33 + x^32 + x^31 + x^29 + x^27 +
  * x^24 + x^23 + x^22 + x^21 + x^19 + x^17 + x^13 + x^12 + x^10 + x^9 +
  * x^7 + x^4 + x + 1
  *
- * crc64rocksoft[256] table is from the Rocksoft specification polynomial
- * defined as,
+ * crc64nvmetable[256] uses the CRC64 polynomial from the NVME NVM Command Set
+ * Specification and uses least-significant-bit first bit order:
  *
  * x^64 + x^63 + x^61 + x^59 + x^58 + x^56 + x^55 + x^52 + x^49 + x^48 + x^47 +
  * x^46 + x^44 + x^41 + x^37 + x^36 + x^34 + x^32 + x^31 + x^28 + x^26 + x^23 +
  * x^22 + x^19 + x^16 + x^13 + x^12 + x^10 + x^9 + x^6 + x^4 + x^3 + 1
  *
@@ -61,18 +61,18 @@  u64 __pure crc64_be(u64 crc, const void *p, size_t len)
 
 	return crc;
 }
 EXPORT_SYMBOL_GPL(crc64_be);
 
-u64 __pure crc64_rocksoft_generic(u64 crc, const void *p, size_t len)
+u64 __pure crc64_nvme_generic(u64 crc, const void *p, size_t len)
 {
 	const unsigned char *_p = p;
 	size_t i;
 
 	crc = ~crc;
 
 	for (i = 0; i < len; i++)
-		crc = (crc >> 8) ^ crc64rocksofttable[(crc & 0xff) ^ *_p++];
+		crc = (crc >> 8) ^ crc64nvmetable[(crc & 0xff) ^ *_p++];
 
 	return ~crc;
 }
-EXPORT_SYMBOL_GPL(crc64_rocksoft_generic);
+EXPORT_SYMBOL_GPL(crc64_nvme_generic);
diff --git a/lib/gen_crc64table.c b/lib/gen_crc64table.c
index 55e222acd0b8..e05a4230a0a0 100644
--- a/lib/gen_crc64table.c
+++ b/lib/gen_crc64table.c
@@ -15,14 +15,14 @@ 
  */
 #include <inttypes.h>
 #include <stdio.h>
 
 #define CRC64_ECMA182_POLY 0x42F0E1EBA9EA3693ULL
-#define CRC64_ROCKSOFT_POLY 0x9A6C9329AC4BC9B5ULL
+#define CRC64_NVME_POLY 0x9A6C9329AC4BC9B5ULL
 
 static uint64_t crc64_table[256] = {0};
-static uint64_t crc64_rocksoft_table[256] = {0};
+static uint64_t crc64_nvme_table[256] = {0};
 
 static void generate_reflected_crc64_table(uint64_t table[256], uint64_t poly)
 {
 	uint64_t i, j, c, crc;
 
@@ -80,16 +80,16 @@  static void print_crc64_tables(void)
 	printf("#include <linux/types.h>\n");
 	printf("#include <linux/cache.h>\n\n");
 	printf("static const u64 ____cacheline_aligned crc64table[256] = {\n");
 	output_table(crc64_table);
 
-	printf("\nstatic const u64 ____cacheline_aligned crc64rocksofttable[256] = {\n");
-	output_table(crc64_rocksoft_table);
+	printf("\nstatic const u64 ____cacheline_aligned crc64nvmetable[256] = {\n");
+	output_table(crc64_nvme_table);
 }
 
 int main(int argc, char *argv[])
 {
 	generate_crc64_table(crc64_table, CRC64_ECMA182_POLY);
-	generate_reflected_crc64_table(crc64_rocksoft_table, CRC64_ROCKSOFT_POLY);
+	generate_reflected_crc64_table(crc64_nvme_table, CRC64_NVME_POLY);
 	print_crc64_tables();
 	return 0;
 }