Re: Protecting against unexpected zero-pages: proposal

Aidan Van Dyk <aidan@highrise.ca>

From: Aidan Van Dyk <aidan@highrise.ca>
To: Greg Stark <gsstark@mit.edu>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Gurjeet Singh <singh.gurjeet@gmail.com>, PGSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2010-11-09T14:28:36Z
Lists: pgsql-hackers
On Tue, Nov 9, 2010 at 8:45 AM, Greg Stark <gsstark@mit.edu> wrote:

> But buffering the page only means you've got some consistent view of
> the page. It doesn't mean the checksum will actually match the data in
> the page that gets written out. So when you read it back in the
> checksum may be invalid.

I was assuming that if the code went through the trouble to buffer the
shared page to get a "stable, non-changing" copy to use for
checksumming/writing it, it would write() the buffered copy it just
made, not the original in shared memory...  I'm not sure how that
write could be in-consistent.

a.

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