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Switch to CRC-32C in WAL and other places.

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The old algorithm was found to not be the usual CRC-32 algorithm, used by
Ethernet et al. We were using a non-reflected lookup table with code meant
for a reflected lookup table. That's a strange combination that AFAICS does
not correspond to any bit-wise CRC calculation, which makes it difficult to
reason about its properties. Although it has worked well in practice, seems
safer to use a well-known algorithm.

Since we're changing the algorithm anyway, we might as well choose a
different polynomial. The Castagnoli polynomial has better error-correcting
properties than the traditional CRC-32 polynomial, even if we had
implemented it correctly. Another reason for picking that is that some new
CPUs have hardware support for calculating CRC-32C, but not CRC-32, let
alone our strange variant of it. This patch doesn't add any support for such
hardware, but a future patch could now do that.

The old algorithm is kept around for tsquery and pg_trgm, which use the
values in indexes that need to remain compatible so that pg_upgrade works.
While we're at it, share the old lookup table for CRC-32 calculation
between hstore, ltree and core. They all use the same table, so might as
well.
This commit is contained in:
Heikki Linnakangas
2014-11-04 11:35:15 +02:00
parent 404bc51cde
commit 5028f22f6e
20 changed files with 299 additions and 340 deletions
Download Patch File Download Diff File Expand all files Collapse all files

50
src/backend/access/transam/xlog.c
View File

@ -1059,9 +1059,9 @@ begin:;
* the whole record in the order: rdata, then backup blocks, then record
* header.
*/
INIT_CRC32(rdata_crc);
INIT_CRC32C(rdata_crc);
for (rdt = rdata; rdt != NULL; rdt = rdt->next)
COMP_CRC32(rdata_crc, rdt->data, rdt->len);
COMP_CRC32C(rdata_crc, rdt->data, rdt->len);
/*
* Construct record header (prev-link is filled in later, after reserving
@ -1076,7 +1076,7 @@ begin:;
rechdr->xl_info = info;
rechdr->xl_rmid = rmid;
rechdr->xl_prev = InvalidXLogRecPtr;
COMP_CRC32(rdata_crc, ((char *) rechdr), offsetof(XLogRecord, xl_prev));
COMP_CRC32C(rdata_crc, ((char *) rechdr), offsetof(XLogRecord, xl_prev));
hdr_rdt.next = rdata;
hdr_rdt.data = (char *) rechdr;
@ -1193,8 +1193,8 @@ begin:;
* Now that xl_prev has been filled in, finish CRC calculation of the
* record header.
*/
COMP_CRC32(rdata_crc, ((char *) &rechdr->xl_prev), sizeof(XLogRecPtr));
FIN_CRC32(rdata_crc);
COMP_CRC32C(rdata_crc, ((char *) &rechdr->xl_prev), sizeof(XLogRecPtr));
FIN_CRC32C(rdata_crc);
rechdr->xl_crc = rdata_crc;
/*
@ -4344,11 +4344,11 @@ WriteControlFile(void)
ControlFile->float8ByVal = FLOAT8PASSBYVAL;
/* Contents are protected with a CRC */
INIT_CRC32(ControlFile->crc);
COMP_CRC32(ControlFile->crc,
(char *) ControlFile,
offsetof(ControlFileData, crc));
FIN_CRC32(ControlFile->crc);
INIT_CRC32C(ControlFile->crc);
COMP_CRC32C(ControlFile->crc,
(char *) ControlFile,
offsetof(ControlFileData, crc));
FIN_CRC32C(ControlFile->crc);
/*
* We write out PG_CONTROL_SIZE bytes into pg_control, zero-padding the
@ -4444,13 +4444,13 @@ ReadControlFile(void)
errhint("It looks like you need to initdb.")));
/* Now check the CRC. */
INIT_CRC32(crc);
COMP_CRC32(crc,
(char *) ControlFile,
offsetof(ControlFileData, crc));
FIN_CRC32(crc);
INIT_CRC32C(crc);
COMP_CRC32C(crc,
(char *) ControlFile,
offsetof(ControlFileData, crc));
FIN_CRC32C(crc);
if (!EQ_CRC32(crc, ControlFile->crc))
if (!EQ_CRC32C(crc, ControlFile->crc))
ereport(FATAL,
(errmsg("incorrect checksum in control file")));
@ -4593,11 +4593,11 @@ UpdateControlFile(void)
{
int fd;
INIT_CRC32(ControlFile->crc);
COMP_CRC32(ControlFile->crc,
(char *) ControlFile,
offsetof(ControlFileData, crc));
FIN_CRC32(ControlFile->crc);
INIT_CRC32C(ControlFile->crc);
COMP_CRC32C(ControlFile->crc,
(char *) ControlFile,
offsetof(ControlFileData, crc));
FIN_CRC32C(ControlFile->crc);
fd = BasicOpenFile(XLOG_CONTROL_FILE,
O_RDWR | PG_BINARY,
@ -4975,10 +4975,10 @@ BootStrapXLOG(void)
record->xl_rmid = RM_XLOG_ID;
memcpy(XLogRecGetData(record), &checkPoint, sizeof(checkPoint));
INIT_CRC32(crc);
COMP_CRC32(crc, &checkPoint, sizeof(checkPoint));
COMP_CRC32(crc, (char *) record, offsetof(XLogRecord, xl_crc));
FIN_CRC32(crc);
INIT_CRC32C(crc);
COMP_CRC32C(crc, &checkPoint, sizeof(checkPoint));
COMP_CRC32C(crc, (char *) record, offsetof(XLogRecord, xl_crc));
FIN_CRC32C(crc);
record->xl_crc = crc;
/* Create first XLOG segment file */