Messages in this thread | | | Date | Fri, 17 Feb 2012 16:58:14 -0500 | From | Vivek Goyal <> | Subject | Re: [PATCH 9/9] block: make blk-throttle preserve the issuing task on delayed bios |
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On Thu, Feb 16, 2012 at 02:37:58PM -0800, Tejun Heo wrote: > 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);
blk-throttle is just one of places where we lose submitter's context info. There are others too.
As Kent said, doing this at more generic level will probably make sense. I think dm layer also might benefit from it. We had issues with losing this process context info while bio is being submitted with a helper thread.
https://lkml.org/lkml/2010/10/24/59
But I guess this will require some changes at dm layer too so that it takes extra bio->ioc and bio->blkcg references at cloning time.
Thanks Vivek
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