xen/blkback: remove per-queue plugging

[firefly-linux-kernel-4.4.55.git] / drivers / xen / blkback / blkback.c

diff --git a/drivers/xen/blkback/blkback.c b/drivers/xen/blkback/blkback.c
index 2d413930f235de8e56b04fe5ff79b80dd1e24e01..464f2e0b5a61ac83f6f637fc72107f0fb84a3b1b 100644 (file)
--- a/drivers/xen/blkback/blkback.c
+++ b/drivers/xen/blkback/blkback.c
@@ -166,38 +166,6 @@ static void free_req(struct pending_req *req)
                wake_up(&blkbk->pending_free_wq);
 }
 
-/*
- * Give back a reference count on the underlaying storage.
- * It is OK to make multiple calls in this function as it
- * resets the plug to NULL when it is done on the first call.
- */
-static void unplug_queue(struct blkif_st *blkif)
-{
-       if (blkif->plug == NULL)
-               return;
-       if (blkif->plug->unplug_fn)
-               blkif->plug->unplug_fn(blkif->plug);
-       blk_put_queue(blkif->plug);
-       blkif->plug = NULL;
-}
-
-/*
- * Take a reference count on the underlaying storage.
- * It is OK to call this multiple times as we check to make sure
- * not to double reference. We also give back a reference count
- * if it corresponds to another queue.
- */
-static void plug_queue(struct blkif_st *blkif, struct block_device *bdev)
-{
-       struct request_queue *q = bdev_get_queue(bdev);
-
-       if (q == blkif->plug)
-               return;
-       unplug_queue(blkif);
-       blk_get_queue(q);
-       blkif->plug = q;
-}
-
 /*
  * Unmap the grant references, and also remove the M2P over-rides
  * used in the 'pending_req'.
@@ -280,7 +248,6 @@ int blkif_schedule(void *arg)
 
                if (do_block_io_op(blkif))
                        blkif->waiting_reqs = 1;
-               unplug_queue(blkif);
 
                if (log_stats && time_after(jiffies, blkif->st_print))
                        print_stats(blkif);
@@ -456,6 +423,8 @@ static void dispatch_rw_block_io(struct blkif_st *blkif,
        struct bio *bio = NULL;
        int ret, i;
        int operation;
+       struct blk_plug plug;
+       struct request_queue *q;
 
        switch (req->operation) {
        case BLKIF_OP_READ:
@@ -561,7 +530,8 @@ static void dispatch_rw_block_io(struct blkif_st *blkif,
        }
 
        /* Get a reference count for the disk queue and start sending I/O */
-       plug_queue(blkif, preq.bdev);
+       blk_get_queue(q);
+       blk_start_plug(&plug);
 
        /* We set it one so that the last submit_bio does not have to call
         * atomic_inc.
@@ -620,11 +590,14 @@ static void dispatch_rw_block_io(struct blkif_st *blkif,
        else if (operation == WRITE || operation == WRITE_BARRIER)
                blkif->st_wr_sect += preq.nr_sects;
 
+       blk_finish_plug(&plug);
+       blk_put_queue(q);
        return;
 
  fail_flush:
        fast_flush_area(pending_req);
  fail_response:
+       /* Haven't submitted any bio's yet. */
        make_response(blkif, req->id, req->operation, BLKIF_RSP_ERROR);
        free_req(pending_req);
        msleep(1); /* back off a bit */
@@ -634,7 +607,8 @@ static void dispatch_rw_block_io(struct blkif_st *blkif,
        __end_block_io_op(pending_req, -EINVAL);
        if (bio)
                bio_put(bio);
-       unplug_queue(blkif);
+       blk_finish_plug(&plug);
+       blk_put_queue(q);
        msleep(1); /* back off a bit */
        return;
 }