blk: centralize non-request unplug handling.

Both md and umem has similar code for getting notified on an
blk_finish_plug event.
Centralize this code in block/ and allow each driver to
provide its distinctive difference.

Signed-off-by: NeilBrown <neilb@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

5 files changed, 49 insertions, 83 deletions

diff --git a/block/blk-core.c b/block/blk-core.c
index dd134d834d58..177ddcf356e6 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -2927,6 +2927,31 @@ static void flush_plug_callbacks(struct blk_plug *plug)
         }
 }
 
+struct blk_plug_cb *blk_check_plugged(blk_plug_cb_fn unplug, void *data,
+                                      int size)
+{
+        struct blk_plug *plug = current->plug;
+        struct blk_plug_cb *cb;
+
+        if (!plug)
+                return NULL;
+
+        list_for_each_entry(cb, &plug->cb_list, list)
+                if (cb->callback == unplug && cb->data == data)
+                        return cb;
+
+        /* Not currently on the callback list */
+        BUG_ON(size < sizeof(*cb));
+        cb = kzalloc(size, GFP_ATOMIC);
+        if (cb) {
+                cb->data = data;
+                cb->callback = unplug;
+                list_add(&cb->list, &plug->cb_list);
+        }
+        return cb;
+}
+EXPORT_SYMBOL(blk_check_plugged);
+
 void blk_flush_plug_list(struct blk_plug *plug, bool from_schedule)
 {
         struct request_queue *q;
diff --git a/drivers/block/umem.c b/drivers/block/umem.c
index 9a72277a31df..6ef3489568e3 100644
--- a/drivers/block/umem.c
+++ b/drivers/block/umem.c
@@ -513,42 +513,19 @@ static void process_page(unsigned long data)
         }
 }
 
-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);
+        struct cardinfo *card = cb->data;
 
-        spin_lock_irq(&mmcb->card->lock);
-        activate(mmcb->card);
-        spin_unlock_irq(&mmcb->card->lock);
-        kfree(mmcb);
+        spin_lock_irq(&card->lock);
+        activate(card);
+        spin_unlock_irq(&card->lock);
+        kfree(cb);
 }
 
 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;
+        return !!blk_check_plugged(mm_unplug, card, sizeof(struct blk_plug_cb));
 }
 
 static void mm_make_request(struct request_queue *q, struct bio *bio)
diff --git a/drivers/md/md.c b/drivers/md/md.c
index 34381172a947..b493fa417387 100644
--- a/drivers/md/md.c
+++ b/drivers/md/md.c
@@ -498,59 +498,13 @@ void md_flush_request(struct mddev *mddev, struct bio *bio)
 }
 EXPORT_SYMBOL(md_flush_request);
 
-/* Support for plugging.
- * This mirrors the plugging support in request_queue, but does not
- * require having a whole queue or request structures.
- * We allocate an md_plug_cb for each md device and each thread it gets
- * plugged on.  This links tot the private plug_handle structure in the
- * personality data where we keep a count of the number of outstanding
- * plugs so other code can see if a plug is active.
- */
-struct md_plug_cb {
-        struct blk_plug_cb cb;
-        struct mddev *mddev;
-};
-
-static void plugger_unplug(struct blk_plug_cb *cb)
+void md_unplug(struct blk_plug_cb *cb)
 {
-        struct md_plug_cb *mdcb = container_of(cb, struct md_plug_cb, cb);
-        md_wakeup_thread(mdcb->mddev->thread);
-        kfree(mdcb);
-}
-
-/* Check that an unplug wakeup will come shortly.
- * If not, wakeup the md thread immediately
- */
-int mddev_check_plugged(struct mddev *mddev)
-{
-        struct blk_plug *plug = current->plug;
-        struct md_plug_cb *mdcb;
-
-        if (!plug)
-                return 0;
-
-        list_for_each_entry(mdcb, &plug->cb_list, cb.list) {
-                if (mdcb->cb.callback == plugger_unplug &&
-                    mdcb->mddev == mddev) {
-                        /* Already on the list, move to top */
-                        if (mdcb != list_first_entry(&plug->cb_list,
-                                                    struct md_plug_cb,
-                                                    cb.list))
-                                list_move(&mdcb->cb.list, &plug->cb_list);
-                        return 1;
-                }
-        }
-        /* Not currently on the callback list */
-        mdcb = kmalloc(sizeof(*mdcb), GFP_ATOMIC);
-        if (!mdcb)
-                return 0;
-
-        mdcb->mddev = mddev;
-        mdcb->cb.callback = plugger_unplug;
-        list_add(&mdcb->cb.list, &plug->cb_list);
-        return 1;
+        struct mddev *mddev = cb->data;
+        md_wakeup_thread(mddev->thread);
+        kfree(cb);
 }
-EXPORT_SYMBOL_GPL(mddev_check_plugged);
+EXPORT_SYMBOL(md_unplug);
 
 static inline struct mddev *mddev_get(struct mddev *mddev)
 {
diff --git a/drivers/md/md.h b/drivers/md/md.h
index 91786c46b85c..8f998e08fb87 100644
--- a/drivers/md/md.h
+++ b/drivers/md/md.h
@@ -627,6 +627,12 @@ extern struct bio *bio_clone_mddev(struct bio *bio, gfp_t gfp_mask,
                                    struct mddev *mddev);
 extern struct bio *bio_alloc_mddev(gfp_t gfp_mask, int nr_iovecs,
                                    struct mddev *mddev);
-extern int mddev_check_plugged(struct mddev *mddev);
 extern void md_trim_bio(struct bio *bio, int offset, int size);
+
+extern void md_unplug(struct blk_plug_cb *cb);
+static inline int mddev_check_plugged(struct mddev *mddev)
+{
+        return !!blk_check_plugged(md_unplug, mddev,
+                                   sizeof(struct blk_plug_cb));
+}
 #endif /* _MD_MD_H */
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 3816ce8a08fc..607ca228f47e 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -922,11 +922,15 @@ struct blk_plug {
 };
 #define BLK_MAX_REQUEST_COUNT 16
 
+struct blk_plug_cb;
+typedef void (*blk_plug_cb_fn)(struct blk_plug_cb *);
 struct blk_plug_cb {
         struct list_head list;
-        void (*callback)(struct blk_plug_cb *);
+        blk_plug_cb_fn callback;
+        void *data;
 };
-
+extern struct blk_plug_cb *blk_check_plugged(blk_plug_cb_fn unplug,
+                                             void *data, int size);
 extern void blk_start_plug(struct blk_plug *);
 extern void blk_finish_plug(struct blk_plug *);
 extern void blk_flush_plug_list(struct blk_plug *, bool);