Hi,
Am Mittwoch, den 26.09.2018, 13:23 +0200 schrieb Fabien COELHO:
> Patch v3 applies cleanly, code compiles and make check is ok, but the
> command is probably not tested anywhere, as already mentioned on other
> threads.
Right.
> The patch is missing a documentation update.
I've added that now. I think the only change needed was removing the
"server needs to be offline" part?
> There are debatable changes of behavior:
>
> if (errno == ENOENT) return / continue...
>
> For instance, a file disappearing is ok online, but not so if offline. On
> the other hand, the probability that a file suddenly disappears while the
> server offline looks remote, so reporting such issues does not seem
> useful.
>
> However I'm more wary with other continues/skips added. ISTM that skipping
> a block because of a read error, or because it is new, or some other
> reasons, is not the same thing, so should be counted & reported
> differently?
I think that would complicate things further without a lot of benefit.
After all, we are interested in checksum failures, not necessarily read
failures etc. so exiting on them (and skip checking possibly large parts
of PGDATA) looks undesirable to me.
So I have done no changes in this part so far, what do others think
about this?
> + if (block_retry == false)
>
> Why not trust boolean operations?
>
> if (!block_retry)
I've changed that as well.
Version 4 is attached.
Michael
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diff --git a/doc/src/sgml/ref/pg_verify_checksums.sgml b/doc/src/sgml/ref/pg_verify_checksums.sgml
index 905b8f1222..4ad6edcde6 100644
--- a/doc/src/sgml/ref/pg_verify_checksums.sgml
+++ b/doc/src/sgml/ref/pg_verify_checksums.sgml
@@ -37,9 +37,8 @@ PostgreSQL documentation
<title>Description</title>
<para>
<command>pg_verify_checksums</command> verifies data checksums in a
- <productname>PostgreSQL</productname> cluster. The server must be shut
- down cleanly before running <application>pg_verify_checksums</application>.
- The exit status is zero if there are no checksum errors, otherwise nonzero.
+ <productname>PostgreSQL</productname> cluster. The exit status is zero if
+ there are no checksum errors, otherwise nonzero.
</para>
</refsect1>
diff --git a/src/bin/pg_verify_checksums/pg_verify_checksums.c b/src/bin/pg_verify_checksums/pg_verify_checksums.c
index 1bc020ab6c..30c26e7a84 100644
--- a/src/bin/pg_verify_checksums/pg_verify_checksums.c
+++ b/src/bin/pg_verify_checksums/pg_verify_checksums.c
@@ -1,7 +1,7 @@
/*
* pg_verify_checksums
*
- * Verifies page level checksums in an offline cluster
+ * Verifies page level checksums in a cluster
*
* Copyright (c) 2010-2018, PostgreSQL Global Development Group
*
@@ -25,7 +25,9 @@
static int64 files = 0;
static int64 blocks = 0;
static int64 badblocks = 0;
+static int64 skippedblocks = 0;
static ControlFileData *ControlFile;
+static XLogRecPtr checkpointLSN;
static char *only_relfilenode = NULL;
static bool verbose = false;
@@ -54,6 +56,7 @@ static const char *const skip[] = {
"pg_filenode.map",
"pg_internal.init",
"PG_VERSION",
+ "pgsql_tmp",
NULL,
};
@@ -67,8 +70,14 @@ skipfile(const char *fn)
return true;
for (f = skip; *f; f++)
+ {
if (strcmp(*f, fn) == 0)
return true;
+ if (strcmp(*f, "pg_internal.init") == 0)
+ if (strncmp(*f, fn, strlen(*f)) == 0)
+ return true;
+ }
+
return false;
}
@@ -79,10 +88,17 @@ scan_file(const char *fn, BlockNumber segmentno)
PageHeader header = (PageHeader) buf.data;
int f;
BlockNumber blockno;
+ bool block_retry = false;
f = open(fn, O_RDONLY | PG_BINARY, 0);
if (f < 0)
{
+ if (errno == ENOENT)
+ {
+ /* File was removed in the meantime */
+ return;
+ }
+
fprintf(stderr, _("%s: could not open file \"%s\": %s\n"),
progname, fn, strerror(errno));
exit(1);
@@ -99,24 +115,71 @@ scan_file(const char *fn, BlockNumber segmentno)
break;
if (r != BLCKSZ)
{
- fprintf(stderr, _("%s: could not read block %u in file \"%s\": read %d of %d\n"),
- progname, blockno, fn, r, BLCKSZ);
- exit(1);
+ /* Skip partially read blocks */
+ skippedblocks++;
+ continue;
}
- blocks++;
/* New pages have no checksum yet */
if (PageIsNew(header))
+ {
+ skippedblocks++;
continue;
+ }
+
+ blocks++;
csum = pg_checksum_page(buf.data, blockno + segmentno * RELSEG_SIZE);
if (csum != header->pd_checksum)
{
+ /*
+ * Retry the block on the first failure. It's
+ * possible that we read the first 4K page of
+ * the block just before postgres updated the
+ * entire block so it ends up looking torn to
+ * us. We only need to retry once because the
+ * LSN should be updated to something we can
+ * ignore on the next pass. If the error
+ * happens again then it is a true validation
+ * failure.
+ */
+ if (!block_retry)
+ {
+ /* Seek to the beginning of the failed block */
+ if (lseek(f, -BLCKSZ, SEEK_CUR) == -1)
+ {
+ fprintf(stderr, _("%s: could not lseek in file \"%s\": %m\n"),
+ progname, fn);
+ exit(1);
+ }
+
+ /* Set flag so we know a retry was attempted */
+ block_retry = true;
+
+ /* Reset loop to validate the block again */
+ blockno--;
+
+ continue;
+ }
+
+ /* The checksum verification failed on retry as well.
+ * Check if the page has been modified since the
+ * checkpoint and skip it in this case.
+ */
+ if (PageGetLSN(buf.data) > checkpointLSN)
+ {
+ block_retry = false;
+ blocks--;
+ skippedblocks++;
+ continue;
+ }
+
if (ControlFile->data_checksum_version == PG_DATA_CHECKSUM_VERSION)
fprintf(stderr, _("%s: checksum verification failed in file \"%s\", block %u: calculated checksum %X but block contains %X\n"),
progname, fn, blockno, csum, header->pd_checksum);
badblocks++;
}
+ block_retry = false;
}
if (verbose)
@@ -152,6 +215,12 @@ scan_directory(const char *basedir, const char *subdir)
snprintf(fn, sizeof(fn), "%s/%s", path, de->d_name);
if (lstat(fn, &st) < 0)
{
+ if (errno == ENOENT)
+ {
+ /* File was removed in the meantime */
+ continue;
+ }
+
fprintf(stderr, _("%s: could not stat file \"%s\": %s\n"),
progname, fn, strerror(errno));
exit(1);
@@ -285,7 +354,7 @@ main(int argc, char *argv[])
exit(1);
}
- /* Check if cluster is running */
+ /* Check if checksums are enabled */
ControlFile = get_controlfile(DataDir, progname, &crc_ok);
if (!crc_ok)
{
@@ -293,19 +362,15 @@ main(int argc, char *argv[])
exit(1);
}
- if (ControlFile->state != DB_SHUTDOWNED &&
- ControlFile->state != DB_SHUTDOWNED_IN_RECOVERY)
- {
- fprintf(stderr, _("%s: cluster must be shut down to verify checksums\n"), progname);
- exit(1);
- }
-
if (ControlFile->data_checksum_version == 0)
{
fprintf(stderr, _("%s: data checksums are not enabled in cluster\n"), progname);
exit(1);
}
+ /* Get checkpoint LSN */
+ checkpointLSN = ControlFile->checkPoint;
+
/* Scan all files */
scan_directory(DataDir, "global");
scan_directory(DataDir, "base");
@@ -315,6 +380,8 @@ main(int argc, char *argv[])
printf(_("Data checksum version: %d\n"), ControlFile->data_checksum_version);
printf(_("Files scanned: %s\n"), psprintf(INT64_FORMAT, files));
printf(_("Blocks scanned: %s\n"), psprintf(INT64_FORMAT, blocks));
+ if (skippedblocks > 0)
+ printf(_("Blocks skipped: %s\n"), psprintf(INT64_FORMAT, skippedblocks));
printf(_("Bad checksums: %s\n"), psprintf(INT64_FORMAT, badblocks));
if (badblocks > 0)
