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Subject[ 086/187] umem: fix up unplugging
Date
From: Greg KH <gregkh@linuxfoundation.org>

3.4-stable review patch. If anyone has any objections, please let me know.

------------------

From: Tao Guo <glorioustao@gmail.com>

commit 32587371ad3db2f9d335de10dbd8cffd4fff5669 upstream.

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: Shaohua Li <shli@kernel.org>
Acked-by: NeilBrown <neilb@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/block/umem.c | 40 ++++++++++++++++++++++++++++++++++++++++
1 file changed, 40 insertions(+)

--- a/drivers/block/umem.c
+++ b/drivers/block/umem.c
@@ -513,6 +513,44 @@ static void process_page(unsigned long d
}
}

+struct mm_plug_cb {
+ struct blk_plug_cb cb;
+ struct cardinfo *card;
+};
+
+static void mm_unplug(struct blk_plug_cb *cb)
+{
+ struct mm_plug_cb *mmcb = container_of(cb, struct mm_plug_cb, cb);
+
+ spin_lock_irq(&mmcb->card->lock);
+ activate(mmcb->card);
+ spin_unlock_irq(&mmcb->card->lock);
+ kfree(mmcb);
+}
+
+static int mm_check_plugged(struct cardinfo *card)
+{
+ struct blk_plug *plug = current->plug;
+ struct mm_plug_cb *mmcb;
+
+ if (!plug)
+ return 0;
+
+ list_for_each_entry(mmcb, &plug->cb_list, cb.list) {
+ if (mmcb->cb.callback == mm_unplug && mmcb->card == card)
+ return 1;
+ }
+ /* Not currently on the callback list */
+ mmcb = kmalloc(sizeof(*mmcb), GFP_ATOMIC);
+ if (!mmcb)
+ return 0;
+
+ mmcb->card = card;
+ mmcb->cb.callback = mm_unplug;
+ list_add(&mmcb->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 +561,8 @@ static void mm_make_request(struct reque
*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;



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