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Remove O_FSYNC and associated macros.

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O_FSYNC was a pre-POSIX way of spelling O_SYNC, supported since commit
9d645fd84c for non-conforming operating systems of the time.  It's not
needed on any modern system.  We can just use standard O_SYNC directly
if it exists (= all targeted systems except Windows), and get rid of our
OPEN_SYNC_FLAG macro.

Similarly for standard O_DSYNC, we can just use that directly if it
exists (= all targeted systems except DragonFlyBSD), and get rid of our
OPEN_DATASYNC_FLAG macro.

We still avoid choosing open_datasync as a default value for
wal_sync_method if O_DSYNC has the same value as O_SYNC (= only
OpenBSD), so there is no change in default behavior.

Discussion: https://postgr.es/m/CA%2BhUKGJE7y92NY7FG2ftUbZUaqohBU65_Ys_7xF5mUHo4wirTQ%40mail.gmail.com
This commit is contained in:
Thomas Munro
2022-07-22 12:30:37 +12:00
parent 4f1f5a7f85
commit a1b56090eb
3 changed files with 19 additions and 35 deletions
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20
src/backend/access/transam/xlog.c
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@@ -171,10 +171,10 @@ const struct config_enum_entry sync_method_options[] = {
#ifdef HAVE_FDATASYNC
{"fdatasync", SYNC_METHOD_FDATASYNC, false},
#endif
#ifdef OPEN_SYNC_FLAG
#ifdef O_SYNC
{"open_sync", SYNC_METHOD_OPEN, false},
#endif
#ifdef OPEN_DATASYNC_FLAG
#ifdef O_DSYNC
{"open_datasync", SYNC_METHOD_OPEN_DSYNC, false},
#endif
{NULL, 0, false}
@@ -7894,10 +7894,10 @@ get_sync_bit(int method)
/*
* Optimize writes by bypassing kernel cache with O_DIRECT when using
* O_SYNC/O_FSYNC and O_DSYNC. But only if archiving and streaming are
* disabled, otherwise the archive command or walsender process will read
* the WAL soon after writing it, which is guaranteed to cause a physical
* read if we bypassed the kernel cache. We also skip the
* O_SYNC and O_DSYNC. But only if archiving and streaming are disabled,
* otherwise the archive command or walsender process will read the WAL
* soon after writing it, which is guaranteed to cause a physical read if
* we bypassed the kernel cache. We also skip the
* posix_fadvise(POSIX_FADV_DONTNEED) call in XLogFileClose() for the same
* reason.
*
@@ -7921,13 +7921,13 @@ get_sync_bit(int method)
case SYNC_METHOD_FSYNC_WRITETHROUGH:
case SYNC_METHOD_FDATASYNC:
return 0;
#ifdef OPEN_SYNC_FLAG
#ifdef O_SYNC
case SYNC_METHOD_OPEN:
return OPEN_SYNC_FLAG | o_direct_flag;
return O_SYNC | o_direct_flag;
#endif
#ifdef OPEN_DATASYNC_FLAG
#ifdef O_DSYNC
case SYNC_METHOD_OPEN_DSYNC:
return OPEN_DATASYNC_FLAG | o_direct_flag;
return O_DSYNC | o_direct_flag;
#endif
default:
/* can't happen (unless we are out of sync with option array) */