Horton

Re: Use pg_pwritev_with_retry() instead of write() in dir_open_for_write() to avoid partial writes?

Michael Paquier <michael@paquier.xyz>

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From: Michael Paquier <michael@paquier.xyz>
To: Thomas Munro <thomas.munro@gmail.com>
Cc: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>, Andres Freund <andres@anarazel.de>, Alvaro Herrera <alvherre@alvh.no-ip.org>, Nathan Bossart <nathandbossart@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2023-03-07T04:32:22Z
Lists: pgsql-hackers 
On Tue, Mar 07, 2023 at 03:44:46PM +1300, Thomas Munro wrote:
> On Tue, Mar 7, 2023 at 3:42 PM Thomas Munro <thomas.munro@gmail.com> wrote:
>> Apparently ye olde GCC 4.7 on "lapwing" doesn't like the way you
>> initialised that struct.  I guess it wants {{0}} instead of {0}.
>> Apparently old GCC was wrong about that warning[1], but that system
>> doesn't have the back-patched fixes?  Not sure.

6392f2a was one such case.

> Oh, you already pushed a fix.  But now I'm wondering if it's useful to
> have old buggy compilers set to run with -Werror.

Yes, as far as I can see when investigating the issue, this is an old
bug of gcc when detecting where the initialization needs to be
applied.  And at the same time the fix is deadly simple, so the
current statu-quo does not sound that bad to me.  Note that lapwing is
one of the only animals testing 32b builds, and it has saved from
quite few bugs over the years.
--
Michael

Commits

  1. Revise pg_pwrite_zeros()

  2. Use pg_pwrite_zeros() in walmethods.c

  3. Introduce pg_pwrite_zeros() in fileutils.c

  4. Move pg_pwritev_with_retry() to src/common/file_utils.c

  5. Restore pg_pread and friends.

  6. Remove dead pread and pwrite replacement code.