linux-kernel - Re: [PATCH] block: call elv_bio

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Date:	Fri, 20 May 2011 18:51:48 +0900
From:	Namhyung Kim <namhyung@...il.com>
To:	Shaohua Li <shaohua.li@...el.com>
Cc:	Jens Axboe <axboe@...nel.dk>, linux-kernel@...r.kernel.org,
	Divyesh Shah <dpshah@...gle.com>
Subject: Re: [PATCH] block: call elv_bio_merged() when merged

Hello,

2011-05-20 (금), 16:31 +0800, Shaohua Li:
> 2011/5/20 Namhyung Kim <namhyung@...il.com>:
> > Commit 73c101011926 ("block: initial patch for on-stack per-task plugging")
> > removed calls to elv_bio_merged() when @bio merged with @req. Re-add them.
> >
> > Signed-off-by: Namhyung Kim <namhyung@...il.com>
> > Cc: Divyesh Shah <dpshah@...gle.com>
> > ---
> >  block/blk-core.c |    2 ++
> >  1 files changed, 2 insertions(+), 0 deletions(-)
> >
> > diff --git a/block/blk-core.c b/block/blk-core.c
> > index 3fe00a14822a..4dc02ef5fc82 100644
> > --- a/block/blk-core.c
> > +++ b/block/blk-core.c
> > @@ -1132,6 +1132,7 @@ static bool bio_attempt_back_merge(struct request_queue *q, struct request *req,
> >        req->ioprio = ioprio_best(req->ioprio, bio_prio(bio));
> >
> >        drive_stat_acct(req, 0);
> > +       elv_bio_merged(q, req, bio);
> >        return true;
> >  }
> >
> > @@ -1173,6 +1174,7 @@ static bool bio_attempt_front_merge(struct request_queue *q,
> >        req->ioprio = ioprio_best(req->ioprio, bio_prio(bio));
> >
> >        drive_stat_acct(req, 0);
> > +       elv_bio_merged(q, req, bio);
> >        return true;
> >  }
> Looks you should do this in __make_request. when the routine is called
> in attempt_plug_merge, the request isn't added to elevator yet.
> 

Hmm.. anyway it is merged. Is there any reason why we shouldn't collect
the stat - or invoke the callback routine - if the @req is not in the
elevator? Or we need to add a separate stat item for this case?

Thanks.

-- 
Regards,
Namhyung Kim


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