[PATCH v2] block: fix inflight statistics of part0

* [PATCH v2] block: fix inflight statistics of part0
@ 2020-12-02 11:11 Jeffle Xu
  2020-12-02 11:17 ` JeffleXu
  0 siblings, 1 reply; 6+ messages in thread
From: Jeffle Xu @ 2020-12-02 11:11 UTC (permalink / raw)
  To: axboe; +Cc: joseph.qi, hch, linux-block

The inflight of partition 0 doesn't include inflight IOs to all
sub-partitions, since currently mq calculates inflight of specific
partition by simply camparing the value of the partition pointer.

Thus the following case is possible:

$ cat /sys/block/vda/inflight
       0        0
$ cat /sys/block/vda/vda1/inflight
       0      128

While single queue device (on a previous version, e.g. v3.10) has no
this issue:

$cat /sys/block/sda/sda3/inflight
       0       33
$cat /sys/block/sda/inflight
       0       33

Partition 0 should be specially handled since it represents the whole
disk. This issue is introduced since commit bf0ddaba65dd ("blk-mq: fix
sysfs inflight counter").

Besides, this patch can also fix the inflight statistics of part 0 in
/proc/diskstats. Before this patch, the inflight statistics of part 0
doesn't include that of sub partitions. (I have marked the 'inflight'
field with asterisk.)

$cat /proc/diskstats
 259       0 nvme0n1 45974469 0 367814768 6445794 1 0 1 0 *0* 111062 6445794 0 0 0 0 0 0
 259       2 nvme0n1p1 45974058 0 367797952 6445727 0 0 0 0 *33* 111001 6445727 0 0 0 0 0 0

This is introduced since commit f299b7c7a9de ("blk-mq: provide internal
in-flight variant").

Fixes: bf0ddaba65dd ("blk-mq: fix sysfs inflight counter")
Fixes: f299b7c7a9de ("blk-mq: provide internal in-flight variant")
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com>
---
v2: update the commit log, adding 'Fixes' tag
---
 block/blk-mq.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 55bcee5dc032..04b6b4d21ce6 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -105,7 +105,8 @@ static bool blk_mq_check_inflight(struct blk_mq_hw_ctx *hctx,
 {
 	struct mq_inflight *mi = priv;
 
-	if (rq->part == mi->part && blk_mq_rq_state(rq) == MQ_RQ_IN_FLIGHT)
+	if ((!mi->part->partno || rq->part == mi->part) &&
+	    blk_mq_rq_state(rq) == MQ_RQ_IN_FLIGHT)
 		mi->inflight[rq_data_dir(rq)]++;
 
 	return true;
-- 
2.27.0


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