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

On 2/21/22 7:16 AM, Dylan Yudaken wrote:
> 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.

Looks good to me, but the patch 2 change will bubble through to patch 3
and 4 as well. Care to respin a v3?

-- 
Jens Axboe

On Mon, 2022-02-21 at 09:33 -0700, Jens Axboe wrote:
> On 2/21/22 7:16 AM, Dylan Yudaken wrote:
> > 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.
> 
> Looks good to me, but the patch 2 change will bubble through to patch
> 3
> and 4 as well. Care to respin a v3?
> 

Yes sure - will do it combined with the test v3