linux-kernel - Re: [PATCH 2/2] umem: fix up unplugging

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Date:	Mon, 4 Jun 2012 22:49:17 +0800
From:	Tao Guo <glorioustao@...il.com>
To:	linux-kernel@...r.kernel.org
Cc:	Tao Guo <glorioustao@...il.com>, Tao Guo <Tao.Guo@....com>,
	Neil Brown <neilb@...e.de>, Jens Axboe <axboe@...nel.dk>,
	stable@...r.kernel.org, Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 2/2] umem: fix up unplugging

This patch is to fix a regression introduced by 7eaceaccab5f40
("block: remove per-queueplugging").

-Tao

On Mon, Jun 4, 2012 at 10:41 PM, Tao Guo <glorioustao@...il.com> wrote:
> In that patch, Jens removed the whole mm_unplug_device()
> function, which used to be the trigger to make umem start to work.
>
> We need to implement unplugging to make umem start to work, or I/O
> will never be triggered.
>
> Signed-off-by: Tao Guo <Tao.Guo@....com>
> Cc: Neil Brown <neilb@...e.de>
> Cc: Jens Axboe <axboe@...nel.dk>
> Cc: <stable@...r.kernel.org>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: <stable@...r.kernel.org>
> ---
>  drivers/block/umem.c |   11 +++++++++++
>  1 files changed, 11 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/block/umem.c b/drivers/block/umem.c
> index aa27120..89cc9a6 100644
> --- a/drivers/block/umem.c
> +++ b/drivers/block/umem.c
> @@ -513,6 +513,15 @@ static void process_page(unsigned long data)
>        }
>  }
>
> +static void mm_unplug(struct blk_plug_cb *cb)
> +{
> +       struct cardinfo *card = cb->q->queuedata;
> +
> +       spin_lock_irq(&card->lock);
> +       activate(card);
> +       spin_unlock_irq(&card->lock);
> +}
> +
>  static void mm_make_request(struct request_queue *q, struct bio *bio)
>  {
>        struct cardinfo *card = q->queuedata;
> @@ -523,6 +532,8 @@ static void mm_make_request(struct request_queue *q, struct bio *bio)
>        *card->biotail = bio;
>        bio->bi_next = NULL;
>        card->biotail = &bio->bi_next;
> +       if (bio->bi_rw & REQ_SYNC || !blk_check_plugged(q, mm_unplug))
> +               activate(card);
>        spin_unlock_irq(&card->lock);
>
>        return;
> --
> 1.7.7.6
>
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