umem: fix up unplugging

Fix a regression introduced by 7eaceaccab5f40 ("block: remove per-queue
plugging").  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@emc.com>
Cc: Neil Brown <neilb@suse.de>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/drivers/block/umem.c b/drivers/block/umem.c
index aa2712060bfbcd153e446f5adcf80a9d61377e75..c3bf98e4b88c94bfe23da1d77595a712906d0ae0 100644 (file)
--- 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);