| From: | Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com> |
|---|---|
| To: | Justin Pryzby <pryzby(at)telsasoft(dot)com> |
| Cc: | Michael Paquier <michael(at)paquier(dot)xyz>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Craig Ringer <craig(at)2ndquadrant(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: PostgreSQL's handling of fsync() errors is unsafe and risks data loss at least on XFS |
| Date: | 2018-03-29 05:06:22 |
| Message-ID: | CAEepm=1YNv1hic3MVRJiB817eofmL-wfiD=zhJnt0RjaHnfwig@mail.gmail.com |
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On Thu, Mar 29, 2018 at 6:00 PM, Justin Pryzby <pryzby(at)telsasoft(dot)com> wrote:
> The retries are the source of the problem ; the first fsync() can return EIO,
> and also *clears the error* causing a 2nd fsync (of the same data) to return
> success.
What I'm failing to grok here is how that error flag even matters,
whether it's a single bit or a counter as described in that patch. If
write back failed, *the page is still dirty*. So all future calls to
fsync() need to try to try to flush it again, and (presumably) fail
again (unless it happens to succeed this time around).
--
Thomas Munro
http://www.enterprisedb.com
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