[PATCH V2 0/3] block: set ioprio value

[PATCH V2 0/3] block: set ioprio value

[Chaitanya Kulkarni]

Hi,

While experimenting with the ionice, I came across the scenario where
I cannot see the bio/request priority field being set when using
blkdiscard for REQ_OP_DISCARD, REQ_OP_WRITE_ZEROES and other operations
like REQ_OP_WRITE_SAME, REQ_OP_ZONE_RESET, and flush.

This is a small patch-series which sets the ioprio value at various
places for the zone-reset, flush, write-zeroes and discard operations.
This patch series uses get_current_ioprio() so that bio associated
with the respective operation can inherit the value from current
process.

In order to test this, I've modified the null_blk and enabled the 
write_zeroes through module param. Following are the results.

Without these patches:-  

# 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 REQ_OP_WRITE_ZEROES priority class 0
[  402.966024] null_handle_cmd REQ_OP_WRITE_ZEROES priority class 0
[  402.973960] null_handle_cmd REQ_OP_WRITE_ZEROES priority class 0
[  402.981373] null_handle_cmd REQ_OP_WRITE_ZEROES priority class 0
# 

With these patches:-

# 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 REQ_OP_WRITE_ZEROES priority class 0
[ 1426.100177] null_handle_cmd REQ_OP_WRITE_ZEROES priority class 1
[ 1426.108035] null_handle_cmd REQ_OP_WRITE_ZEROES priority class 2
[ 1426.115768] null_handle_cmd REQ_OP_WRITE_ZEROES priority class 3
# 

With the block trace extension support is being worked on [1] which has
the ability to report the I/O priority, now we can track the correct
priority values with this patch-series.

Regards,
Chaitanya

[1] https://www.spinics.net/lists/linux-btrace/msg00880.html

* Changes from V1:-
1. Adjust the code for new changes from linux-block/for-next.  

Chaitanya Kulkarni (3):
  block: set ioprio for zone-reset bio
  block: set ioprio for flush bio
  block: set ioprio for discard, write-zeroes etc

 block/blk-flush.c | 1 +
 block/blk-lib.c   | 4 ++++
 block/blk-zoned.c | 2 ++
 3 files changed, 7 insertions(+)

-- 
2.17.0

[PATCH V2 1/3] block: set ioprio for zone-reset bio

[Chaitanya Kulkarni]

Set the current process's iopriority to the bio for REQ_OP_ZONE_RESET
and REQ_OP_ZONE_RESET_ALL.

Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
---
 block/blk-zoned.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/block/blk-zoned.c b/block/blk-zoned.c
index 4bc5f260248a..741759b5e302 100644
--- a/block/blk-zoned.c
+++ b/block/blk-zoned.c
@@ -214,6 +214,7 @@ static int __blkdev_reset_all_zones(struct block_device *bdev, gfp_t gfp_mask)
 	/* across the zones operations, don't need any sectors */
 	bio_set_dev(bio, bdev);
 	bio_set_op_attrs(bio, REQ_OP_ZONE_RESET_ALL, 0);
+	bio_set_prio(bio, get_current_ioprio());
 
 	ret = submit_bio_wait(bio);
 	bio_put(bio);
@@ -290,6 +291,7 @@ int blkdev_reset_zones(struct block_device *bdev,
 		bio->bi_iter.bi_sector = sector;
 		bio_set_dev(bio, bdev);
 		bio_set_op_attrs(bio, REQ_OP_ZONE_RESET, 0);
+		bio_set_prio(bio, get_current_ioprio());
 
 		sector += zone_sectors;
 
-- 
2.17.0

[PATCH V2 2/3] block: set ioprio for flush bio

[Chaitanya Kulkarni]

Set the current process's iopriority for flush bio.

Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
---
 block/blk-flush.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/block/blk-flush.c b/block/blk-flush.c
index aedd9320e605..642a01b72a8b 100644
--- a/block/blk-flush.c
+++ b/block/blk-flush.c
@@ -445,6 +445,7 @@ int blkdev_issue_flush(struct block_device *bdev, gfp_t gfp_mask,
 	bio = bio_alloc(gfp_mask, 0);
 	bio_set_dev(bio, bdev);
 	bio->bi_opf = REQ_OP_WRITE | REQ_PREFLUSH;
+	bio_set_prio(bio, get_current_ioprio());
 
 	ret = submit_bio_wait(bio);
 
-- 
2.17.0

[PATCH V2 3/3] block: set ioprio for discard, write-zeroes etc

[Chaitanya Kulkarni]

Set the current process's iopriority for discard.

Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com>
---
 block/blk-lib.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/block/blk-lib.c b/block/blk-lib.c
index 5f2c429d4378..500a857e5d9f 100644
--- a/block/blk-lib.c
+++ b/block/blk-lib.c
@@ -64,6 +64,7 @@ int __blkdev_issue_discard(struct block_device *bdev, sector_t sector,
 		bio->bi_iter.bi_sector = sector;
 		bio_set_dev(bio, bdev);
 		bio_set_op_attrs(bio, op, 0);
+		bio_set_prio(bio, get_current_ioprio());
 
 		bio->bi_iter.bi_size = req_sects << 9;
 		sector += req_sects;
@@ -162,6 +163,7 @@ static int __blkdev_issue_write_same(struct block_device *bdev, sector_t sector,
 		bio->bi_io_vec->bv_offset = 0;
 		bio->bi_io_vec->bv_len = bdev_logical_block_size(bdev);
 		bio_set_op_attrs(bio, REQ_OP_WRITE_SAME, 0);
+		bio_set_prio(bio, get_current_ioprio());
 
 		if (nr_sects > max_write_same_sectors) {
 			bio->bi_iter.bi_size = max_write_same_sectors << 9;
@@ -234,6 +236,7 @@ static int __blkdev_issue_write_zeroes(struct block_device *bdev,
 		bio->bi_iter.bi_sector = sector;
 		bio_set_dev(bio, bdev);
 		bio->bi_opf = REQ_OP_WRITE_ZEROES;
+		bio_set_prio(bio, get_current_ioprio());
 		if (flags & BLKDEV_ZERO_NOUNMAP)
 			bio->bi_opf |= REQ_NOUNMAP;
 
@@ -286,6 +289,7 @@ static int __blkdev_issue_zero_pages(struct block_device *bdev,
 		bio->bi_iter.bi_sector = sector;
 		bio_set_dev(bio, bdev);
 		bio_set_op_attrs(bio, REQ_OP_WRITE, 0);
+		bio_set_prio(bio, get_current_ioprio());
 
 		while (nr_sects != 0) {
 			sz = min((sector_t) PAGE_SIZE, nr_sects << 9);
-- 
2.17.0