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>

1 files changed, 25 insertions, 0 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;