Date: Tue, 26 Apr 2022 11:33:49 -0700
From: Nathan Bossart <nathandbossart@gmail.com>
To: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Cc: pgsql-hackers@lists.postgresql.org, masao.fujii@oss.nttdata.com
Subject: Re: Possible corruption by CreateRestartPoint at promotion
Message-ID: <20220426183349.GA3002960@nathanxps13>
References: <20220316.102444.2193181487576617583.horikyota.ntt@gmail.com>
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On Wed, Mar 16, 2022 at 10:24:44AM +0900, Kyotaro Horiguchi wrote:
> While discussing on additional LSNs in checkpoint log message,
> Fujii-san pointed out [2] that there is a case where
> CreateRestartPoint leaves unrecoverable database when concurrent
> promotion happens. That corruption is "fixed" by the next checkpoint
> so it is not a severe corruption.

I suspect we'll start seeing this problem more often once end-of-recovery
checkpoints are removed [0].  Would you mind creating a commitfest entry
for this thread?  I didn't see one.

> AFAICS since 9.5, no check(/restart)pionts won't run concurrently with
> restartpoint [3].  So I propose to remove the code path as attached.

Yeah, this "quick hack" has been around for some time (2de48a8), and I
believe much has changed since then, so something like what you're
proposing is probably the right thing to do.

>  	/* Also update the info_lck-protected copy */
>  	SpinLockAcquire(&XLogCtl->info_lck);
> -	XLogCtl->RedoRecPtr = lastCheckPoint.redo;
> +	XLogCtl->RedoRecPtr = RedoRecPtr;
>  	SpinLockRelease(&XLogCtl->info_lck);
>  
>  	/*
> @@ -6984,7 +6987,10 @@ CreateRestartPoint(int flags)
>  	/* Update the process title */
>  	update_checkpoint_display(flags, true, false);
>  
> -	CheckPointGuts(lastCheckPoint.redo, flags);
> +	CheckPointGuts(RedoRecPtr, flags);

I don't understand the purpose of these changes.  Are these related to the
fix, or is this just tidying up?

[0] https://postgr.es/m/CA%2BTgmoY%2BSJLTjma4Hfn1sA7S6CZAgbihYd%3DKzO6srd7Ut%3DXVBQ%40mail.gmail.com

-- 
Nathan Bossart
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