Horton

Re: Postgres, fsync, and OSs (specifically linux)

Craig Ringer <craig@2ndquadrant.com>

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From: Craig Ringer <craig@2ndquadrant.com>
To: Andres Freund <andres@anarazel.de>
Cc: Thomas Munro <thomas.munro@enterprisedb.com>, Simon Riggs <simon@2ndquadrant.com>, PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2018-05-10T01:50:03Z
Lists: pgsql-hackers

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On 10 May 2018 at 06:55, Andres Freund <andres@anarazel.de> wrote:

> Do you have a patchset including that?  I didn't find anything after a
> quick search...

There was an earlier rev on the other thread but without msync checks.

I've added panic for msync in the attached, and tidied the comments a bit.

I didn't add comments on why we panic to each individual pg_fsync or
FileSync caller that panics; instead pg_fsync points to
pg_fsync_no_writethrough which explains it briefly and has links.

I looked at callers of pg_fsync, pg_fsync_no_writethrough,
pg_fsync_writethrough, mdsync, and FileSync when writing this.

WAL writing already PANIC'd on fsync failure, which helps, though we
now know that's not sufficient for complete safety.


Patch on top of v11 HEAD @ ddc1f32ee507

-- 
 Craig Ringer                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services

Commits

  1. PANIC on fsync() failure.

  2. Fix and improve pg_atomic_flag fallback implementation.