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From: Tom Lane <[email protected]>
To: Robert Haas <[email protected]>
Cc: Thomas Munro <[email protected]>
Cc: Peter Eisentraut <[email protected]>
Cc: Larry Rosenman <[email protected]>
Cc: Pgsql hackers <[email protected]>
Subject: Re: Fwd: Re: A new look at old NFS readdir() problems?
Date: Mon, 06 Jan 2025 09:49:22 -0500
Message-ID: <[email protected]> (raw)
In-Reply-To: <CA+TgmoZdxsnA81pADXuoMJZzPd9oWp+w-D253+RnObyY_OqjrQ@mail.gmail.com>
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Robert Haas <[email protected]> writes:
> Yeah, that seems like very strong evidence against FreeBSD, but I
> think Thomas Munro's point about CIFS is worth considering. That is
> rather widely used, and if the same workarounds would help both that
> and FreeBSD's NFS, we might want to adopt it even if it's not a
> complete fix.

TBH, I am happy that PG is now failing in a fairly visible way on
filesystems that are broken in this fashion.  I think that is better
than silent data corruption in obscure circumstances, which is where
we were before and would be again if we band-aid rmtree() and do
nothing else.  Nor do I think it's worth the effort to try to become
fully bulletproof on the point.

I think we should document that CIFS is unsupported.  The docs
could say something like:

	Storing databases on filesystems with unreliable readdir() is
	not supported and can lead to data corruption.  If you observe
	warnings like "directory is not empty" when trying to drop a
	database, that is strong evidence that the filesystem has
	unreliable readdir().  Filesystems known to have this problem
	include NFS on FreeBSD and CIFS on all platforms.

We could s/FreeBSD/older FreeBSD/ if something comes of Thomas'
efforts to fix that situation.

			regards, tom lane






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