102 lines
3.4 KiB
Diff
102 lines
3.4 KiB
Diff
From 560d88cb5a16636acb0e350d6997fe915cc4253e Mon Sep 17 00:00:00 2001
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From: Kyle Walker <kwalker@redhat.com>
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Date: Wed, 30 Jan 2019 07:50:55 -0500
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Subject: [PATCH] sadc: Add a -f flag to force fdatasync() use
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For quite some time, the sadc utility has not used fdatasync() when writing
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stat information to disk. This resulted in instances where data files could
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be corrupted or entries lost if a system encountered a sudden reset
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condition. This change adds a "-f" flag which can be used to bring back the
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previous behaviour if end users require it.
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Note, the fdatasync() lowers the likelihood of lost data, but does so at
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the expense of performance within the write operation.
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---
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man/sadc.in | 8 +++++++-
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sa.h | 2 ++
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sadc.c | 13 ++++++++++++-
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3 files changed, 21 insertions(+), 2 deletions(-)
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diff --git a/man/sadc.in b/man/sadc.in
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index 2d754b71..ce8ee230 100644
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--- a/man/sadc.in
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+++ b/man/sadc.in
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@@ -4,7 +4,7 @@ sadc \- System activity data collector.
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.SH SYNOPSIS
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.B @SA_LIB_DIR@/sadc [ -C
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.I comment
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-.B ] [ -D ] [ -F ] [ -L ] [ -V ] [ -S { DISK | INT | IPV6 | POWER | SNMP | XDISK | ALL | XALL [,...] } ] [
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+.B ] [ -D ] [ -F ] [ -L ] [ -V ] [ -f ] [ -S { DISK | INT | IPV6 | POWER | SNMP | XDISK | ALL | XALL [,...] } ] [
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.I interval
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.B [
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.I count
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@@ -106,6 +106,12 @@ then it will be truncated. This may be useful for daily data files
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created by an older version of
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.B sadc
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and whose format is no longer compatible with current one.
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+.IP -f
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+fdatasync() will be used to ensure data is written to disk. This differs
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+from the normal operation in that a sudden system reset is less likely to
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+result in the saDD datafiles being corrupted. However, this is at the
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+expense of performance within the sadc process as forward progress will be
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+blocked while data is written to underlying disk instead of just to cache.
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.IP -L
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.B sadc
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will try to get an exclusive lock on the
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diff --git a/sa.h b/sa.h
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index 1cd0c3d9..d3236f7c 100644
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--- a/sa.h
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+++ b/sa.h
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@@ -110,5 +110,6 @@
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#define S_F_HUMAN_READ 0x01000000
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#define S_F_ZERO_OMIT 0x02000000
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+#define S_F_FDATASYNC 0x08000000
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#define WANT_SINCE_BOOT(m) (((m) & S_F_SINCE_BOOT) == S_F_SINCE_BOOT)
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#define WANT_SA_ROTAT(m) (((m) & S_F_SA_ROTAT) == S_F_SA_ROTAT)
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@@ -138,5 +139,6 @@
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#define PACK_VIEWS(m) (((m) & S_F_SVG_PACKED) == S_F_SVG_PACKED)
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#define DISPLAY_HUMAN_READ(m) (((m) & S_F_HUMAN_READ) == S_F_HUMAN_READ)
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+#define FDATASYNC(m) (((m) & S_F_FDATASYNC) == S_F_FDATASYNC)
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#define AO_F_NULL 0x00000000
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diff --git a/sadc.c b/sadc.c
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index 826f4aed..139d490a 100644
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--- a/sadc.c
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+++ b/sadc.c
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@@ -92,7 +92,7 @@ void usage(char *progname)
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progname);
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fprintf(stderr, _("Options are:\n"
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- "[ -C <comment> ] [ -D ] [ -F ] [ -L ] [ -V ]\n"
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+ "[ -C <comment> ] [ -D ] [ -F ] [ -L ] [ -V ] [ -f ]\n"
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"[ -S { INT | DISK | IPV6 | POWER | SNMP | XDISK | ALL | XALL } ]\n"));
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exit(1);
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}
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@@ -1109,6 +1109,13 @@ void rw_sa_stat_loop(long count, int stdfd, int ofd, char ofile[],
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/* Flush data */
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fflush(stdout);
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+ if (FDATASYNC(flags)) {
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+ /* If indicated, sync the data to media */
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+ if (fdatasync(ofd) < 0) {
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+ perror("fdatasync");
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+ exit(4);
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+ }
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+ }
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if (count > 0) {
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count--;
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@@ -1206,6 +1213,10 @@ int main(int argc, char **argv)
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optz = 1;
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}
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+ else if (!strcmp(argv[opt], "-f")) {
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+ flags |= S_F_FDATASYNC;
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+ }
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+
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else if (!strcmp(argv[opt], "-C")) {
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if (!argv[++opt]) {
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usage(argv[0]);
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