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Subject[PATCH 9/9] block: make blk-throttle preserve the issuing task on delayed bios
Date
Make blk-throttle call bio_associate_current() on bios being delayed
such that they get issued to block layer with the original io_context.
This allows stacking blk-throttle and cfq-iosched propio policies.
bios will always be issued with the correct ioc and blkcg whether it
gets delayed by blk-throttle or not.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Vivek Goyal <vgoyal@redhat.com>
---
block/blk-throttle.c | 4 ++++
1 files changed, 4 insertions(+), 0 deletions(-)
diff --git a/block/blk-throttle.c b/block/blk-throttle.c
index a7c8e0b..ad8e16b 100644
--- a/block/blk-throttle.c
+++ b/block/blk-throttle.c
@@ -894,6 +894,9 @@ bool blk_throtl_bio(struct request_queue *q, struct bio *bio)
goto out;
}

+ /* bio_associate_current() needs ioc, try creating */
+ create_io_context(GFP_ATOMIC, q->node);
+
/*
* A throtl_grp pointer retrieved under rcu can be used to access
* basic fields like stats and io rates. If a group has no rules,
@@ -958,6 +961,7 @@ queue_bio:
tg->io_disp[rw], tg->iops[rw],
tg->nr_queued[READ], tg->nr_queued[WRITE]);

+ bio_associate_current(bio);
throtl_add_bio_tg(q->td, tg, bio);
throttled = true;

--
1.7.7.3


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