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: Nathan Bossart <nathandbossart@gmail.com>
Cc: Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>, Thomas Munro <thomas.munro@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Date: 2022-10-27T05:54:00Z
Lists: pgsql-hackers 
On Thu, Sep 29, 2022 at 08:09:56PM -0700, Nathan Bossart wrote:
> Looks reasonable to me.

0001, to move pg_pwritev_with_retry() to a new home, seems fine, so
applied.

Regarding 0002, using pg_pwrite_zeros() as a routine name, as
suggested by Thomas, sounds good to me.  However, I am not really a
fan of its dependency with PGAlignedXLogBlock, because it should be
able to work with any buffers of any sizes, as long as the input
buffer is aligned, shouldn't it?  For example, what about
PGAlignedBlock?  So, should we make this more extensible?  My guess
would be the addition of the block size and the block pointer to the 
arguments of pg_pwrite_zeros(), in combination with a check to make
sure that the input buffer is MAXALIGN()'d (with an Assert() rather
than just an elog/pg_log_error?).
--
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.