From f9bb944cd879949cf454b941f2b8fa7b00fcc1e4 Mon Sep 17 00:00:00 2001 From: Bruce Momjian Date: Wed, 12 Feb 2014 15:38:14 -0500 Subject: [PATCH] pg_test_fsync: add C comment about direct I/O and write size failure Report from Marti Raudsepp --- contrib/pg_test_fsync/pg_test_fsync.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/contrib/pg_test_fsync/pg_test_fsync.c b/contrib/pg_test_fsync/pg_test_fsync.c index 669c4190d3..682821a8d7 100644 --- a/contrib/pg_test_fsync/pg_test_fsync.c +++ b/contrib/pg_test_fsync/pg_test_fsync.c @@ -369,6 +369,12 @@ test_sync(int writes_per_op) { for (writes = 0; writes < writes_per_op; writes++) if (write(tmpfile, buf, XLOG_BLCKSZ) != XLOG_BLCKSZ) + /* + * This can generate write failures if the filesystem + * has a large block size, e.g. 4k, and there is no + * support for O_DIRECT writes smaller than the + * file system block size, e.g. XFS. + */ die("write failed"); if (lseek(tmpfile, 0, SEEK_SET) == -1) die("seek failed"); -- 2.40.0