[PATCH AUTOSEL 5.2 161/185] block: make rq sector size accessible for block stats

Sasha Levin
2019-09-22T18:54:09Z

From: Hou Tao <houtao1@huawei.com>

[ Upstream commit 3d24430694077313c75c6b89f618db09943621e4 ]

Currently rq->data_len will be decreased by partial completion or
zeroed by completion, so when blk_stat_add() is invoked, data_len
will be zero and there will never be samples in poll_cb because
blk_mq_poll_stats_bkt() will return -1 if data_len is zero.

We could move blk_stat_add() back to __blk_mq_complete_request(),
but that would make the effort of trying to call ktime_get_ns()
once in vain. Instead we can reuse throtl_size field, and use
it for both block stats and block throttle, and adjust the
logic in blk_mq_poll_stats_bkt() accordingly.

Fixes: 4bc6339a583c ("block: move blk_stat_add() to __blk_mq_end_request()")
Tested-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Hou Tao <houtao1@huawei.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
block/blk-mq.c | 11 +++++------
block/blk-throttle.c | 3 ++-
include/linux/blkdev.h | 15 ++++++++++++---
3 files changed, 19 insertions(+), 10 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index f934e8afe5b43..af93ca28ce4f0 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -44,12 +44,12 @@ static void blk_mq_poll_stats_fn(struct blk_stat_callback *cb);

static int blk_mq_poll_stats_bkt(const struct request *rq)
{
- int ddir, bytes, bucket;
+ int ddir, sectors, bucket;

ddir = rq_data_dir(rq);
- bytes = blk_rq_bytes(rq);
+ sectors = blk_rq_stats_sectors(rq);

- bucket = ddir + 2*(ilog2(bytes) - 9);
+ bucket = ddir + 2 * ilog2(sectors);

if (bucket < 0)
return -1;
@@ -330,6 +330,7 @@ static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data,
else
rq->start_time_ns = 0;
rq->io_start_time_ns = 0;
+ rq->stats_sectors = 0;
rq->nr_phys_segments = 0;
#if defined(CONFIG_BLK_DEV_INTEGRITY)
rq->nr_integrity_segments = 0;
@@ -679,9 +680,7 @@ void blk_mq_start_request(struct request *rq)

if (test_bit(QUEUE_FLAG_STATS, &q->queue_flags)) {
rq->io_start_time_ns = ktime_get_ns();
-#ifdef CONFIG_BLK_DEV_THROTTLING_LOW
- rq->throtl_size = blk_rq_sectors(rq);
-#endif
+ rq->stats_sectors = blk_rq_sectors(rq);
rq->rq_flags |= RQF_STATS;
rq_qos_issue(q, rq);
}
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index 8ab6c81532236..ee74bffe3504d 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -2246,7 +2246,8 @@ void blk_throtl_stat_add(struct request *rq, u64 time_ns)
struct request_queue *q = rq->q;
struct throtl_data *td = q->td;

- throtl_track_latency(td, rq->throtl_size, req_op(rq), time_ns >> 10);
+ throtl_track_latency(td, blk_rq_stats_sectors(rq), req_op(rq),
+ time_ns >> 10);
}

void blk_throtl_bio_endio(struct bio *bio)
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 93baef66b9424..4c6754e536725 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -202,9 +202,12 @@ struct request {
#ifdef CONFIG_BLK_WBT
unsigned short wbt_flags;
#endif
-#ifdef CONFIG_BLK_DEV_THROTTLING_LOW
- unsigned short throtl_size;
-#endif
+ /*
+ * rq sectors used for blk stats. It has the same value
+ * with blk_rq_sectors(rq), except that it never be zeroed
+ * by completion.
+ */
+ unsigned short stats_sectors;

/*
* Number of scatter-gather DMA addr+len pairs after
@@ -902,6 +905,7 @@ static inline struct request_queue *bdev_get_queue(struct block_device *bdev)
* blk_rq_err_bytes() : bytes left till the next error boundary
* blk_rq_sectors() : sectors left in the entire request
* blk_rq_cur_sectors() : sectors left in the current segment
+ * blk_rq_stats_sectors() : sectors of the entire request used for stats
*/
static inline sector_t blk_rq_pos(const struct request *rq)
{
@@ -930,6 +934,11 @@ static inline unsigned int blk_rq_cur_sectors(const struct request *rq)
return blk_rq_cur_bytes(rq) >> SECTOR_SHIFT;
}

+static inline unsigned int blk_rq_stats_sectors(const struct request *rq)
+{
+ return rq->stats_sectors;
+}
+
#ifdef CONFIG_BLK_DEV_ZONED
static inline unsigned int blk_rq_zone_no(struct request *rq)
{
--
2.20.1