From: Tom Lane <tgl@sss.pgh.pa.us>
To: Michael Paquier <michael@paquier.xyz>
cc: Thomas Munro <thomas.munro@gmail.com>,
        Heikki Linnakangas <hlinnaka@iki.fi>,
        Alexander Lakhin <exclusion@gmail.com>,
        PostgreSQL mailing lists <pgsql-bugs@lists.postgresql.org>
Subject: Re: BUG #17064: Parallel VACUUM operations cause the error
 "global/pg_filenode.map contains incorrect checksum"
In-reply-to: <YNKBazxEayjtyb1x@paquier.xyz>
References: <17064-bb0d7904ef72add3@postgresql.org>
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 <CA+hUKGJ98=MOjDCnMAC5gSpkzrrey=O+aEQJ1OY03C=cVtiwkA@mail.gmail.com>
 <1715251.1624371066@sss.pgh.pa.us> <YNKBazxEayjtyb1x@paquier.xyz>
Comments: In-reply-to Michael Paquier <michael@paquier.xyz>
	message dated "Wed, 23 Jun 2021 09:33:47 +0900"
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Date: Tue, 22 Jun 2021 20:41:19 -0400
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Michael Paquier <michael@paquier.xyz> writes:
> On Tue, Jun 22, 2021 at 10:11:06AM -0400, Tom Lane wrote:
>> Shouldn't we instead file a kernel bug report?  I seem to recall that
>> POSIX guarantees atomicity of these things up to some operation size.
>> Or is that just for pipe I/O?

> Even if this is recognized as a bug report, it seems to me that we'd
> better cope with an extra lock for instances that may run into this
> issue anyway in the future, no?  Just to be on the safe side.

Based on the evidence at hand, we can't really say whether the writes
are non-atomic.  If that's the case then we have much worse problems
than just needing to add a lock.  Thus, I think we need to get some
kernel people involved.

			regards, tom lane