block: count 'ios' and 'sectors' when io is done for bio-based device

While using iostat for raid, I observed very strange 'await'
occasionally, and turns out it's due to that 'ios' and 'sectors' is
counted in bdev_start_io_acct(), while 'nsecs' is counted in
bdev_end_io_acct(). I'm not sure why they are ccounted like that
but I think this behaviour is obviously wrong because user will get
wrong disk stats.

Fix the problem by counting 'ios' and 'sectors' when io is done, like
what rq-based device does.

Fixes: 394ffa50 ("blk: introduce generic io stat accounting help function")
Signed-off-by: Yu Kuai <yukuai3@huawei.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Link: https://lore.kernel.org/r/20230223091226.1135678-1-yukuai1@huaweicloud.comSigned-off-by: Jens Axboe <axboe@kernel.dk>

block/blk-core.c

@@ -959,16 +959,11 @@ void update_io_ticks(struct block_device *part, unsigned long now, bool end)
 	}
 }
 
-unsigned long bdev_start_io_acct(struct block_device *bdev,
-				 unsigned int sectors, enum req_op op,
+unsigned long bdev_start_io_acct(struct block_device *bdev, enum req_op op,
 				 unsigned long start_time)
 {
-	const int sgrp = op_stat_group(op);
-
 	part_stat_lock();
 	update_io_ticks(bdev, start_time, false);
-	part_stat_inc(bdev, ios[sgrp]);
-	part_stat_add(bdev, sectors[sgrp], sectors);
 	part_stat_local_inc(bdev, in_flight[op_is_write(op)]);
 	part_stat_unlock();
 
@@ -984,13 +979,12 @@ EXPORT_SYMBOL(bdev_start_io_acct);
  */
 unsigned long bio_start_io_acct(struct bio *bio)
 {
-	return bdev_start_io_acct(bio->bi_bdev, bio_sectors(bio),
-				  bio_op(bio), jiffies);
+	return bdev_start_io_acct(bio->bi_bdev, bio_op(bio), jiffies);
 }
 EXPORT_SYMBOL_GPL(bio_start_io_acct);
 
 void bdev_end_io_acct(struct block_device *bdev, enum req_op op,
-		      unsigned long start_time)
+		      unsigned int sectors, unsigned long start_time)
 {
 	const int sgrp = op_stat_group(op);
 	unsigned long now = READ_ONCE(jiffies);
@@ -998,6 +992,8 @@ void bdev_end_io_acct(struct block_device *bdev, enum req_op op,
 
 	part_stat_lock();
 	update_io_ticks(bdev, now, true);
+	part_stat_inc(bdev, ios[sgrp]);
+	part_stat_add(bdev, sectors[sgrp], sectors);
 	part_stat_add(bdev, nsecs[sgrp], jiffies_to_nsecs(duration));
 	part_stat_local_dec(bdev, in_flight[op_is_write(op)]);
 	part_stat_unlock();
@@ -1007,7 +1003,7 @@ EXPORT_SYMBOL(bdev_end_io_acct);
 void bio_end_io_acct_remapped(struct bio *bio, unsigned long start_time,
 			      struct block_device *orig_bdev)
 {
-	bdev_end_io_acct(orig_bdev, bio_op(bio), start_time);
+	bdev_end_io_acct(orig_bdev, bio_op(bio), bio_sectors(bio), start_time);
 }
 EXPORT_SYMBOL_GPL(bio_end_io_acct_remapped);
 

drivers/md/dm.c

@@ -512,10 +512,10 @@ static void dm_io_acct(struct dm_io *io, bool end)
 		sectors = io->sectors;
 
 	if (!end)
-		bdev_start_io_acct(bio->bi_bdev, sectors, bio_op(bio),
-				   start_time);
+		bdev_start_io_acct(bio->bi_bdev, bio_op(bio), start_time);
 	else
-		bdev_end_io_acct(bio->bi_bdev, bio_op(bio), start_time);
+		bdev_end_io_acct(bio->bi_bdev, bio_op(bio), sectors,
+				 start_time);
 
 	if (static_branch_unlikely(&stats_enabled) &&
 	    unlikely(dm_stats_used(&md->stats))) {

drivers/nvme/host/multipath.c

@@ -123,9 +123,8 @@ void nvme_mpath_start_request(struct request *rq)
 		return;
 
 	nvme_req(rq)->flags |= NVME_MPATH_IO_STATS;
-	nvme_req(rq)->start_time = bdev_start_io_acct(disk->part0,
-					blk_rq_bytes(rq) >> SECTOR_SHIFT,
-					req_op(rq), jiffies);
+	nvme_req(rq)->start_time = bdev_start_io_acct(disk->part0, req_op(rq),
+						      jiffies);
 }
 EXPORT_SYMBOL_GPL(nvme_mpath_start_request);
 
@@ -136,6 +135,7 @@ void nvme_mpath_end_request(struct request *rq)
 	if (!(nvme_req(rq)->flags & NVME_MPATH_IO_STATS))
 		return;
 	bdev_end_io_acct(ns->head->disk->part0, req_op(rq),
+			 blk_rq_bytes(rq) >> SECTOR_SHIFT,
 			 nvme_req(rq)->start_time);
 }
 

include/linux/blkdev.h

@@ -1446,11 +1446,10 @@ static inline void blk_wake_io_task(struct task_struct *waiter)
 		wake_up_process(waiter);
 }
 
-unsigned long bdev_start_io_acct(struct block_device *bdev,
-				 unsigned int sectors, enum req_op op,
+unsigned long bdev_start_io_acct(struct block_device *bdev, enum req_op op,
 				 unsigned long start_time);
 void bdev_end_io_acct(struct block_device *bdev, enum req_op op,
-		unsigned long start_time);
+		      unsigned int sectors, unsigned long start_time);
 
 unsigned long bio_start_io_acct(struct bio *bio);
 void bio_end_io_acct_remapped(struct bio *bio, unsigned long start_time,