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Subject[PATCH v2 3/7] blkcg: associate a request with its blkcg_gq instead of request_list
From c856a199ec70e4022e997609f1b17b9106408777 Mon Sep 17 00:00:00 2001
From: Tejun Heo <tj@kernel.org>
Date: Mon, 13 Nov 2017 12:11:57 -0800

On the legacy request_queue, each blkcg_gq has a dedicated
request_list that requests for the cgroup are allocated from. Each
request points to the originating request_list and cgroup membership
can be determined by examining which cgroup the associated
request_list belongs to.

This doesn't work for blk-mq which doesn't use request_list. Let's
associate each request with the blkcg_gq directly. Except for minor
wrapper changes, this doesn't affect the legacy request_queue and will
allow blk-mq to track each request's cgroup association.

v2: Build fix for !CONFIG_BLK_CGROUP.

Signed-off-by: Tejun Heo <tj@kernel.org>
---
block/blk-mq.c | 2 +-
include/linux/blk-cgroup.h | 7 +++++--
include/linux/blkdev.h | 2 +-
3 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/block/blk-mq.c b/block/blk-mq.c
index 98a1860..af958c4 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -306,7 +306,7 @@ static struct request *blk_mq_rq_ctx_init(struct blk_mq_alloc_data *data,
rq->part = NULL;
rq->start_time = jiffies;
#ifdef CONFIG_BLK_CGROUP
- rq->rl = NULL;
+ rq->blkg = NULL;
set_start_time_ns(rq);
rq->io_start_time_ns = 0;
#endif
diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h
index c0d4736..47db75a 100644
--- a/include/linux/blk-cgroup.h
+++ b/include/linux/blk-cgroup.h
@@ -463,7 +463,7 @@ static inline void blk_put_rl(struct request_list *rl)
*/
static inline void blk_rq_set_rl(struct request *rq, struct request_list *rl)
{
- rq->rl = rl;
+ rq->blkg = rl->blkg;
}

/**
@@ -474,7 +474,10 @@ static inline void blk_rq_set_rl(struct request *rq, struct request_list *rl)
*/
static inline struct request_list *blk_rq_rl(struct request *rq)
{
- return rq->rl;
+ if (!rq->blkg->parent)
+ return &rq->q->root_rl;
+ else
+ return &rq->blkg->rl;
}

struct request_list *__blk_queue_next_rl(struct request_list *rl,
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 8da6637..6ec1067 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -206,7 +206,7 @@ struct request {
unsigned long start_time;
struct blk_issue_stat issue_stat;
#ifdef CONFIG_BLK_CGROUP
- struct request_list *rl; /* rl this rq is alloced from */
+ struct blkcg_gq *blkg; /* blkg of this rq */
unsigned long long start_time_ns;
unsigned long long io_start_time_ns; /* when passed to hardware */
#endif
--
2.9.5
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