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Date: Wed, 4 Apr 2012 15:20:16 -0700
From: Tao Guo <glorioustao@...il.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org, neilb@...e.de, axboe@...ionio.com,
Jens Axboe <axboe@...nel.dk>
Subject: Re: [PATCH] umem: fix up unplugging.
Hi Andrew,
Thanks for your reply.
Yes, without this patch the umem driver just doesn't work.
It is a bug introduced by commit 7eaceaccab5f40bbfda044629a6298616aeaed50.
In that patch, Jens removed the whole mm_unplug_device() function,
which used to be
the trigger to make umem start to work.
Thanks,
-Tao
On Wed, Apr 4, 2012 at 2:46 PM, Andrew Morton <akpm@...ux-foundation.org> wrote:
> On Fri, 30 Dec 2011 09:17:31 -0500
>
> (Long delay...)
>
> Tao Guo <glorioustao@...il.com> wrote:
>
>> We need to implement unplugging to make umem start to work, or I/O
>> will never be triggered.
>>
>
> I take it from this that umem simply doesn't work at all?
>
> If so, for how long has this been the case and should we just delete the
> thing?
>
>>
>> --- a/drivers/block/umem.c
>> +++ b/drivers/block/umem.c
>> @@ -111,7 +111,8 @@ struct cardinfo {
>> int current_idx;
>> sector_t current_sector;
>>
>> - struct request_queue *queue;
>> + struct request_queue *queue;
>> + struct blk_plug_cb plug_cb;
>>
>> struct mm_page {
>> dma_addr_t page_dma;
>> @@ -513,6 +514,33 @@ static void process_page(unsigned long data)
>> }
>> }
>>
>> +static void mm_unplug(struct blk_plug_cb *cb)
>> +{
>> + struct cardinfo *card = container_of(cb, struct cardinfo, plug_cb);
>> +
>> + spin_lock_irq(&card->lock);
>> + activate(card);
>> + spin_unlock_irq(&card->lock);
>> +}
>> +
>> +int mm_check_plugged(struct cardinfo *card)
>> +{
>> + struct blk_plug *plug = current->plug;
>> + struct cardinfo *c;
>> +
>> + if (!plug)
>> + return 0;
>> +
>> + list_for_each_entry(c, &plug->cb_list, plug_cb.list) {
>> + if (c == card)
>> + return 1;
>> + }
>> +
>> + /* set up unplug callback */
>> + list_add(&card->plug_cb.list, &plug->cb_list);
>> + return 1;
>> +}
>> +
>> static void mm_make_request(struct request_queue *q, struct bio *bio)
>> {
>> struct cardinfo *card = q->queuedata;
>> @@ -523,6 +551,8 @@ 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 || !mm_check_plugged(card))
>> + activate(card);
>> spin_unlock_irq(&card->lock);
>>
>> return;
>> @@ -884,6 +914,7 @@ static int __devinit mm_pci_probe(struct pci_dev *dev,
>> blk_queue_make_request(card->queue, mm_make_request);
>> card->queue->queue_lock = &card->lock;
>> card->queue->queuedata = card;
>> + card->plug_cb.callback = mm_unplug;
>>
>> tasklet_init(&card->tasklet, process_page, (unsigned long)card);
>
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