linux-kernel - [PATCH v2 0/4] io_uring: consistent behaviour with linked read/write

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Date:   Mon, 21 Feb 2022 06:16:45 -0800
From:   Dylan Yudaken <dylany@...com>
To:     Jens Axboe <axboe@...nel.dk>,
        Pavel Begunkov <asml.silence@...il.com>,
        <io-uring@...r.kernel.org>
CC:     <linux-kernel@...r.kernel.org>, <kernel-team@...com>,
        Dylan Yudaken <dylany@...com>
Subject: [PATCH v2 0/4] io_uring: consistent behaviour with linked read/write

Currently submitting multiple read/write for one file with offset = -1 will
not behave as if calling read(2)/write(2) multiple times. The offset may be
pinned to the same value for each submission (for example if they are
punted to the async worker) and so each read/write will have the same
offset.

This patch series fixes this.

Patch 1,3 cleans up the code a bit

Patch 2 grabs the file position at execution time, rather than when the job
is queued to be run which fixes inconsistincies when jobs are run asynchronously.

Patch 4 increments the file's f_pos when reading it, which fixes
inconsistincies with concurrent runs. 

A test for this will be submitted to liburing separately.

v2:
  * added patch 4 which fixes cases where IOSQE_IO_LINK is not set

Dylan Yudaken (4):
  io_uring: remove duplicated calls to io_kiocb_ppos
  io_uring: update kiocb->ki_pos at execution time
  io_uring: do not recalculate ppos unnecessarily
  io_uring: pre-increment f_pos on rw

 fs/io_uring.c | 103 ++++++++++++++++++++++++++++++++++++++++++--------
 1 file changed, 88 insertions(+), 15 deletions(-)

base-commit: 754e0b0e35608ed5206d6a67a791563c631cec07
-- 
2.30.2