Hi,
While experimenting with the ionice I came across the scenario where
I cannot see the bio's priority field been set when use blkdiscard
for REQ_OP_DISCARD and REQ_OP_WRITE_ZEROES.
This is a small patch-series which initializes the bio->bi_ioprio
(iopriority) field under different operations like REQ_OP_DISCARD and
REQ_OP_WRITE_ZEROES. It helps to track the priority when debugging.
In order to test this I've modified the null_blk and enabled the
write_zeroes through module param. Following are the results.
Without this patches :-
# git log -1 --oneline
4443f8e6ac77 (HEAD -> master, origin/master, origin/HEAD) Merge tag 'for-linus-20190412' of git://git.kernel.dk/linux-block
# modprobe null_blk gb=5 nr_devices=1 write_zeroes=1
# for prio in `seq 0 3`; do ionice -c ${prio} blkdiscard -z -o 0 -l 4096 /dev/nullb0; done
# dmesg -c
[ 402.958458] null_handle_cmd 1220 REQ_OP_WRITE_ZEROES priority class 0
[ 402.966024] null_handle_cmd 1220 REQ_OP_WRITE_ZEROES priority class 0
[ 402.973960] null_handle_cmd 1220 REQ_OP_WRITE_ZEROES priority class 0
[ 402.981373] null_handle_cmd 1220 REQ_OP_WRITE_ZEROES priority class 0
#
After thiese patches :-
# git log --oneline -2
7a54a31cad5c (HEAD -> master) block: add task priority to init bio iopriority
149603fbd421 block: adjust code for get_task_ioprio()
# modprobe null_blk gb=5 nr_devices=1 write_zeroes=1
# for prio in `seq 0 3`; do ionice -c ${prio} blkdiscard -z -o 0 -l 4096 /dev/nullb0; done
# dmesg -c
[ 1426.091772] null_handle_cmd 1220 REQ_OP_WRITE_ZEROES priority class 0
[ 1426.100177] null_handle_cmd 1220 REQ_OP_WRITE_ZEROES priority class 1
[ 1426.108035] null_handle_cmd 1220 REQ_OP_WRITE_ZEROES priority class 2
[ 1426.115768] null_handle_cmd 1220 REQ_OP_WRITE_ZEROES priority class 3
#
Regards,
Chaitanya
Chaitanya Kulkarni (2):
block: adjust code for get_task_ioprio()
block: add task priority to init bio iopriority
block/blk-lib.c | 6 ++++++
block/ioprio.c | 20 ++++++++++++++++----
include/linux/ioprio.h | 2 ++
3 files changed, 24 insertions(+), 4 deletions(-)
--
2.19.1
