block: get rid of struct blk_issue_stat

struct blk_issue_stat squashes three things into one u64:

- The time the driver started working on a request
- The original size of the request (for the io.low controller)
- Flags for writeback throttling

It turns out that on x86_64, we have a 4 byte hole in struct request
which we can fill with the non-timestamp fields from blk_issue_stat,
simplifying things quite a bit.

Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 2 insertions, 5 deletions

diff --git a/block/blk-stat.c b/block/blk-stat.c
index bd365a95fcf8..725a881723b0 100644
--- a/block/blk-stat.c
+++ b/block/blk-stat.c
@@ -55,11 +55,8 @@ void blk_stat_add(struct request *rq)
 	int bucket;
 	u64 now, value;
 
-	now = __blk_stat_time(ktime_to_ns(ktime_get()));
-	if (now < blk_stat_time(&rq->issue_stat))
-		return;
-
-	value = now - blk_stat_time(&rq->issue_stat);
+	now = ktime_get_ns();
+	value = (now >= rq->io_start_time_ns) ? now - rq->io_start_time_ns : 0;
 
 	blk_throtl_stat_add(rq, value);