[PATCH v3 0/4] io_uring: consistent behaviour with linked read/write

[Dylan Yudaken <dylany@fb.com>]

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
v3:
  * outline slow path of pos updating
  * style fixes
  * do not pass kiocb unnecessarily

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 | 118 +++++++++++++++++++++++++++++++++++++++++++-------
 1 file changed, 103 insertions(+), 15 deletions(-)


base-commit: 754e0b0e35608ed5206d6a67a791563c631cec07
-- 
2.30.2