From b0d97557ebfc9d5ba5f2939339a9fdd267abafeb Mon Sep 17 00:00:00 2001
From: Jeffle Xu <jefflexu@linux.alibaba.com>
Date: Wed, 2 Dec 2020 19:11:45 +0800
Subject: [PATCH] block: fix inflight statistics of part0
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Git-commit: b0d97557ebfc9d5ba5f2939339a9fdd267abafeb
Patch-mainline: v5.11-rc1
References: bsc#1182445

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")
Signed-off-by: Jeffle Xu <jefflexu@linux.alibaba.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
[axboe: adapt for 5.11 partition change]
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Acked-by: Jan Kara <jack@suse.cz>

---
 block/blk-mq.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -105,7 +105,7 @@ static bool blk_mq_check_inflight(struct
 	/*
 	 * index[0] counts the specific partition that was asked for.
 	 */
-	if (rq->part == mi->part)
+	if (!mi->part->partno || rq->part == mi->part)
 		mi->inflight[0]++;
 
 	return true;
@@ -128,7 +128,7 @@ static bool blk_mq_check_inflight_rw(str
 {
 	struct mq_inflight *mi = priv;
 
-	if (rq->part == mi->part)
+	if (!mi->part->partno || rq->part == mi->part)
 		mi->inflight[rq_data_dir(rq)]++;
 
 	return true;