md/raid1: submit IO from originating thread instead of md thread.

queuing writes to the md thread means that all requests go through the
one processor which may not be able to keep up with very high request
rates.

So use the plugging infrastructure to submit all requests on unplug.
If a 'schedule' is needed, we fall back on the old approach of handing
the requests to the thread for it to handle.

Signed-off-by: NeilBrown <neilb@suse.de>

diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index 15dbe03117e473da9ce6166b6978b7f496b7bc2a..94e7f6ba2e11e1c4479d82b8e840f38cb89e0f0b 100644 (file)
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -1305,7 +1305,7 @@ int bitmap_startwrite(struct bitmap *bitmap, sector_t offset, unsigned long sect
                        prepare_to_wait(&bitmap->overflow_wait, &__wait,
                                        TASK_UNINTERRUPTIBLE);
                        spin_unlock_irq(&bitmap->counts.lock);
-                       io_schedule();
+                       schedule();
                        finish_wait(&bitmap->overflow_wait, &__wait);
                        continue;
                }

diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c
index 36a8fc059ac36efc068603c51348132324d5d399..9f01870d031cb48728c9b633f2db4404ab6759af 100644 (file)
--- a/drivers/md/raid1.c
+++ b/drivers/md/raid1.c
@@ -870,6 +870,44 @@ do_sync_io:
        pr_debug("%dB behind alloc failed, doing sync I/O\n", bio->bi_size);
 }
 
+struct raid1_plug_cb {
+       struct blk_plug_cb      cb;
+       struct bio_list         pending;
+       int                     pending_cnt;
+};
+
+static void raid1_unplug(struct blk_plug_cb *cb, bool from_schedule)
+{
+       struct raid1_plug_cb *plug = container_of(cb, struct raid1_plug_cb,
+                                                 cb);
+       struct mddev *mddev = plug->cb.data;
+       struct r1conf *conf = mddev->private;
+       struct bio *bio;
+
+       if (from_schedule) {
+               spin_lock_irq(&conf->device_lock);
+               bio_list_merge(&conf->pending_bio_list, &plug->pending);
+               conf->pending_count += plug->pending_cnt;
+               spin_unlock_irq(&conf->device_lock);
+               md_wakeup_thread(mddev->thread);
+               kfree(plug);
+               return;
+       }
+
+       /* we aren't scheduling, so we can do the write-out directly. */
+       bio = bio_list_get(&plug->pending);
+       bitmap_unplug(mddev->bitmap);
+       wake_up(&conf->wait_barrier);
+
+       while (bio) { /* submit pending writes */
+               struct bio *next = bio->bi_next;
+               bio->bi_next = NULL;
+               generic_make_request(bio);
+               bio = next;
+       }
+       kfree(plug);
+}
+
 static void make_request(struct mddev *mddev, struct bio * bio)
 {
        struct r1conf *conf = mddev->private;
@@ -883,6 +921,8 @@ static void make_request(struct mddev *mddev, struct bio * bio)
        const unsigned long do_sync = (bio->bi_rw & REQ_SYNC);
        const unsigned long do_flush_fua = (bio->bi_rw & (REQ_FLUSH | REQ_FUA));
        struct md_rdev *blocked_rdev;
+       struct blk_plug_cb *cb;
+       struct raid1_plug_cb *plug = NULL;
        int first_clone;
        int sectors_handled;
        int max_sectors;
@@ -1185,11 +1225,22 @@ read_again:
                mbio->bi_private = r1_bio;
 
                atomic_inc(&r1_bio->remaining);
+
+               cb = blk_check_plugged(raid1_unplug, mddev, sizeof(*plug));
+               if (cb)
+                       plug = container_of(cb, struct raid1_plug_cb, cb);
+               else
+                       plug = NULL;
                spin_lock_irqsave(&conf->device_lock, flags);
-               bio_list_add(&conf->pending_bio_list, mbio);
-               conf->pending_count++;
+               if (plug) {
+                       bio_list_add(&plug->pending, mbio);
+                       plug->pending_cnt++;
+               } else {
+                       bio_list_add(&conf->pending_bio_list, mbio);
+                       conf->pending_count++;
+               }
                spin_unlock_irqrestore(&conf->device_lock, flags);
-               if (!mddev_check_plugged(mddev))
+               if (!plug)
                        md_wakeup_thread(mddev->thread);
        }
        /* Mustn't call r1_bio_write_done before this next test,