Re: silent data loss with ext4 / all current versions

From: Andres Freund <andres(at)anarazel(dot)de>
To: Michael Paquier <michael(dot)paquier(at)gmail(dot)com>
Cc: Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>, PostgreSQL mailing lists <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: silent data loss with ext4 / all current versions
Date: 2016-03-06 03:54:05
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On 2016-03-05 22:25:36 +0900, Michael Paquier wrote:
> OK, I hacked a v7:
> - Move the link()/rename() group with HAVE_WORKING_LINK into a single
> routine, making the previous link_safe renamed to replace_safe. This
> is sharing a lot of things with rename_safe. I am not sure it is worth
> complicating the code more this way by having a common single routine
> for whole. Thoughts welcome. Honestly, I kind of liked the separation
> with link_safe/rename_safe of previous patches because link_safe could
> have been directly used by extensions and plugins btw.
> - Remove the call of stat() in rename_safe() and implement a logic
> depending on OpenTransientFile()/pg_fsync() to flush any existing
> target file before performing the rename.
> Andres, feel free to use this patch as a base, perhaps that will help.

I started working on this; delayed by taking longer than planned on the
logical decoding stuff (quite a bit complicated by
e1a11d93111ff3fba7a91f3f2ac0b0aca16909a8). I'm not very happy with the
error handling as it is right now. For one, you have rename_safe return
error codes, and act on them in the callers, but on the other hand you
call fsync_fname which always errors out in case of failure. I also
don't like the new messages much.

Will continue working on this tomorrow.

Andres Freund

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