md/raid5: add simple plugging infrastructure.

md/raid5 uses the plugging infrastructure provided by the block layer
and 'struct request_queue'.  However when we plug raid5 under dm there
is no request queue so we cannot use that.

So create a similar infrastructure that is much lighter weight and use
it for raid5.

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

diff --git a/drivers/md/md.c b/drivers/md/md.c
index f877569..eec75f1 100644 (file)
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -386,6 +386,51 @@ void md_barrier_request(mddev_t *mddev, struct bio *bio)
 }
 EXPORT_SYMBOL(md_barrier_request);
 
+/* Support for plugging.
+ * This mirrors the plugging support in request_queue, but does not
+ * require having a whole queue
+ */
+static void plugger_work(struct work_struct *work)
+{
+       struct plug_handle *plug =
+               container_of(work, struct plug_handle, unplug_work);
+       plug->unplug_fn(plug);
+}
+static void plugger_timeout(unsigned long data)
+{
+       struct plug_handle *plug = (void *)data;
+       kblockd_schedule_work(NULL, &plug->unplug_work);
+}
+void plugger_init(struct plug_handle *plug,
+                 void (*unplug_fn)(struct plug_handle *))
+{
+       plug->unplug_flag = 0;
+       plug->unplug_fn = unplug_fn;
+       init_timer(&plug->unplug_timer);
+       plug->unplug_timer.function = plugger_timeout;
+       plug->unplug_timer.data = (unsigned long)plug;
+       INIT_WORK(&plug->unplug_work, plugger_work);
+}
+EXPORT_SYMBOL_GPL(plugger_init);
+
+void plugger_set_plug(struct plug_handle *plug)
+{
+       if (!test_and_set_bit(PLUGGED_FLAG, &plug->unplug_flag))
+               mod_timer(&plug->unplug_timer, jiffies + msecs_to_jiffies(3)+1);
+}
+EXPORT_SYMBOL_GPL(plugger_set_plug);
+
+int plugger_remove_plug(struct plug_handle *plug)
+{
+       if (test_and_clear_bit(PLUGGED_FLAG, &plug->unplug_flag)) {
+               del_timer(&plug->unplug_timer);
+               return 1;
+       } else
+               return 0;
+}
+EXPORT_SYMBOL_GPL(plugger_remove_plug);
+
+
 static inline mddev_t *mddev_get(mddev_t *mddev)
 {
        atomic_inc(&mddev->active);

diff --git a/drivers/md/md.h b/drivers/md/md.h
index c88b047..5be0d69 100644 (file)
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -29,6 +29,26 @@
 typedef struct mddev_s mddev_t;
 typedef struct mdk_rdev_s mdk_rdev_t;
 
+/* generic plugging support - like that provided with request_queue,
+ * but does not require a request_queue
+ */
+struct plug_handle {
+       void                    (*unplug_fn)(struct plug_handle *);
+       struct timer_list       unplug_timer;
+       struct work_struct      unplug_work;
+       unsigned long           unplug_flag;
+};
+#define        PLUGGED_FLAG 1
+void plugger_init(struct plug_handle *plug,
+                 void (*unplug_fn)(struct plug_handle *));
+void plugger_set_plug(struct plug_handle *plug);
+int plugger_remove_plug(struct plug_handle *plug);
+static inline void plugger_flush(struct plug_handle *plug)
+{
+       del_timer_sync(&plug->unplug_timer);
+       cancel_work_sync(&plug->unplug_work);
+}
+
 /*
  * MD's 'extended' device
  */

diff --git a/drivers/md/raid5.c b/drivers/md/raid5.c
index ad6694f..84bb9ae 100644 (file)
--- a/drivers/md/raid5.c
+++ b/drivers/md/raid5.c
@@ -201,11 +201,11 @@ static void __release_stripe(raid5_conf_t *conf, struct stripe_head *sh)
                if (test_bit(STRIPE_HANDLE, &sh->state)) {
                        if (test_bit(STRIPE_DELAYED, &sh->state)) {
                                list_add_tail(&sh->lru, &conf->delayed_list);
-                               blk_plug_device(conf->mddev->queue);
+                               plugger_set_plug(&conf->plug);
                        } else if (test_bit(STRIPE_BIT_DELAY, &sh->state) &&
                                   sh->bm_seq - conf->seq_write > 0) {
                                list_add_tail(&sh->lru, &conf->bitmap_list);
-                               blk_plug_device(conf->mddev->queue);
+                               plugger_set_plug(&conf->plug);
                        } else {
                                clear_bit(STRIPE_BIT_DELAY, &sh->state);
                                list_add_tail(&sh->lru, &conf->handle_list);
@@ -434,7 +434,7 @@ static int has_failed(raid5_conf_t *conf)
 }
 
 static void unplug_slaves(mddev_t *mddev);
-static void raid5_unplug_device(struct request_queue *q);
+static void raid5_unplug_device(raid5_conf_t *conf);
 
 static struct stripe_head *
 get_active_stripe(raid5_conf_t *conf, sector_t sector,
@@ -464,7 +464,7 @@ get_active_stripe(raid5_conf_t *conf, sector_t sector,
                                                     < (conf->max_nr_stripes *3/4)
                                                     || !conf->inactive_blocked),
                                                    conf->device_lock,
-                                                   raid5_unplug_device(conf->mddev->queue)
+                                                   raid5_unplug_device(conf)
                                        );
                                conf->inactive_blocked = 0;
                        } else
@@ -3618,7 +3618,7 @@ static void raid5_activate_delayed(raid5_conf_t *conf)
                        list_add_tail(&sh->lru, &conf->hold_list);
                }
        } else
-               blk_plug_device(conf->mddev->queue);
+               plugger_set_plug(&conf->plug);
 }
 
 static void activate_bit_delay(raid5_conf_t *conf)
@@ -3659,23 +3659,33 @@ static void unplug_slaves(mddev_t *mddev)
        rcu_read_unlock();
 }
 
-static void raid5_unplug_device(struct request_queue *q)
+static void raid5_unplug_device(raid5_conf_t *conf)
 {
-       mddev_t *mddev = q->queuedata;
-       raid5_conf_t *conf = mddev->private;
        unsigned long flags;
 
        spin_lock_irqsave(&conf->device_lock, flags);
 
-       if (blk_remove_plug(q)) {
+       if (plugger_remove_plug(&conf->plug)) {
                conf->seq_flush++;
                raid5_activate_delayed(conf);
        }
-       md_wakeup_thread(mddev->thread);
+       md_wakeup_thread(conf->mddev->thread);
 
        spin_unlock_irqrestore(&conf->device_lock, flags);
 
-       unplug_slaves(mddev);
+       unplug_slaves(conf->mddev);
+}
+
+static void raid5_unplug(struct plug_handle *plug)
+{
+       raid5_conf_t *conf = container_of(plug, raid5_conf_t, plug);
+       raid5_unplug_device(conf);
+}
+
+static void raid5_unplug_queue(struct request_queue *q)
+{
+       mddev_t *mddev = q->queuedata;
+       raid5_unplug_device(mddev->private);
 }
 
 int md_raid5_congested(mddev_t *mddev, int bits)
@@ -4085,7 +4095,7 @@ static int make_request(mddev_t *mddev, struct bio * bi)
                                 * add failed due to overlap.  Flush everything
                                 * and wait a while
                                 */
-                               raid5_unplug_device(mddev->queue);
+                               raid5_unplug_device(conf);
                                release_stripe(sh);
                                schedule();
                                goto retry;
@@ -5178,6 +5188,7 @@ static int run(mddev_t *mddev)
                       mdname(mddev));
        md_set_array_sectors(mddev, raid5_size(mddev, 0, 0));
 
+       plugger_init(&conf->plug, raid5_unplug);
        if (mddev->queue) {
                /* read-ahead size must cover two whole stripes, which
                 * is 2 * (datadisks) * chunksize where 'n' is the
@@ -5197,7 +5208,7 @@ static int run(mddev_t *mddev)
 
        mddev->queue->queue_lock = &conf->device_lock;
 
-       mddev->queue->unplug_fn = raid5_unplug_device;
+       mddev->queue->unplug_fn = raid5_unplug_queue;
 
        chunk_size = mddev->chunk_sectors << 9;
        blk_queue_io_min(mddev->queue, chunk_size);
@@ -5229,7 +5240,7 @@ static int stop(mddev_t *mddev)
        mddev->thread = NULL;
        if (mddev->queue)
                mddev->queue->backing_dev_info.congested_fn = NULL;
-       blk_sync_queue(mddev->queue); /* the unplug fn references 'conf'*/
+       plugger_flush(&conf->plug); /* the unplug fn references 'conf'*/
        free_conf(conf);
        mddev->private = NULL;
        mddev->to_remove = &raid5_attrs_group;

diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h
index d6470de..6acd458 100644 (file)
--- a/drivers/md/raid5.h
+++ b/drivers/md/raid5.h
@@ -398,6 +398,9 @@ struct raid5_private_data {
                                            * (fresh device added).
                                            * Cleared when a sync completes.
                                            */
+
+       struct plug_handle      plug;
+
        /* per cpu variables */
        struct raid5_percpu {
                struct page     *spare_page; /* Used when checking P/Q in raid6 */