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pg_test_fsync: add C comment about direct I/O and write size failure

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Report from Marti Raudsepp
This commit is contained in:
Bruce Momjian
2014-02-12 15:38:14 -05:00
parent 6f2aead1ff
commit f9bb944cd8
1 changed files with 6 additions and 0 deletions
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6
contrib/pg_test_fsync/pg_test_fsync.c
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@ -369,6 +369,12 @@ test_sync(int writes_per_op)
{ {
for (writes = 0; writes < writes_per_op; writes++) for (writes = 0; writes < writes_per_op; writes++)
if (write(tmpfile, buf, XLOG_BLCKSZ) != XLOG_BLCKSZ) 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"); die("write failed");
if (lseek(tmpfile, 0, SEEK_SET) == -1) if (lseek(tmpfile, 0, SEEK_SET) == -1)
die("seek failed"); die("seek failed");