Re: [PATCH v5 01/19] ioprio: cleanup interface definition

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On 4/4/23 20:24, Niklas Cassel wrote:
From: Damien Le Moal <damien.lemoal@xxxxxxxxxxxxxxxxxx>

The IO priority user interface defines the 16-bits ioprio values as
the combination of the upper 3-bits for an IO priority class and the
lower 13-bits as priority data. However, the kernel only uses the
lower 3-bits of the priority data to define priority levels for the RT
and BE priority classes. The data part of an ioprio value is completely
ignored for the IDLE and NONE classes. This is enforced by checks done
in ioprio_check_cap(), which is called for all paths that allow defining
an IO priority for IOs: the per-context ioprio_set() system call, aio
interface and io-uring interface.

Clarify this fact in the uapi ioprio.h header file and introduce the
IOPRIO_PRIO_LEVEL_MASK and IOPRIO_PRIO_LEVEL() macros for users to
define and get priority levels in an ioprio value. The coarser macro
IOPRIO_PRIO_DATA() is retained for backward compatibility with old
applications already using it. There is no functional change introduced
with this.

In-kernel users of the IOPRIO_PRIO_DATA() macro which are explicitly
handling IO priority data as a priority level are modified to use the
new IOPRIO_PRIO_LEVEL() macro without any functional change. Since f2fs
is the only user of this macro not explicitly using that value as a
priority level, it is left unchanged.

Signed-off-by: Damien Le Moal <damien.lemoal@xxxxxxxxxxxxxxxxxx>
Signed-off-by: Niklas Cassel <niklas.cassel@xxxxxxx>
---
  block/bfq-iosched.c         |  8 ++++----
  block/ioprio.c              |  6 +++---
  include/uapi/linux/ioprio.h | 19 ++++++++++++++-----
  3 files changed, 21 insertions(+), 12 deletions(-)

Reviewed-by: Hannes Reinecke <hare@xxxxxxx>

Cheers,

Hannes





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