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Commit ece9c72a authored by Jan Kara's avatar Jan Kara Committed by Jens Axboe
Browse files

block: Fix computation of merged request priority 



Priority of a merged request is computed by ioprio_best(). If one of the
requests has undefined priority (IOPRIO_CLASS_NONE) and another request
has priority from IOPRIO_CLASS_BE, the function will return the
undefined priority which is wrong. Fix the function to properly return
priority of a request with the defined priority.

Fixes: d58cdfb8
CC: stable@vger.kernel.org
Signed-off-by: default avatarJan Kara <jack@suse.cz>
Reviewed-by: default avatarJeff Moyer <jmoyer@redhat.com>
Signed-off-by: default avatarJens Axboe <axboe@fb.com>
parent 3a2f22b7

block/ioprio.c

+8 −6
Original line number Diff line number Diff line
@@ -157,14 +157,16 @@ out: 


int ioprio_best(unsigned short aprio, unsigned short bprio)

{

	unsigned short aclass = IOPRIO_PRIO_CLASS(aprio);

	unsigned short bclass = IOPRIO_PRIO_CLASS(bprio);

	unsigned short aclass;

	unsigned short bclass;



	if (aclass == IOPRIO_CLASS_NONE)

		aclass = IOPRIO_CLASS_BE;

	if (bclass == IOPRIO_CLASS_NONE)

		bclass = IOPRIO_CLASS_BE;

	if (!ioprio_valid(aprio))

		aprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM);

	if (!ioprio_valid(bprio))

		bprio = IOPRIO_PRIO_VALUE(IOPRIO_CLASS_BE, IOPRIO_NORM);



	aclass = IOPRIO_PRIO_CLASS(aprio);

	bclass = IOPRIO_PRIO_CLASS(bprio);

	if (aclass == bclass)

		return min(aprio, bprio);

	if (aclass > bclass)