[dm-devel] [PATCH 3/4] add manual failover support for HP storage works

[Mike Christie <michaelc cs wisc edu>]

blk-req-callback2.patch - was discussed here 
https://www.redhat.com/archives/dm-devel/2004-May/msg00047.html. This version 
incorporates Jens's comments.
diff -arup linux-2.6.7-rc1/drivers/block/ll_rw_blk.c linux-2.6.7-rc1-patch/drivers/block/ll_rw_blk.c
--- linux-2.6.7-rc1/drivers/block/ll_rw_blk.c	2004-05-24 18:54:18.000000000 -0700
+++ linux-2.6.7-rc1-patch/drivers/block/ll_rw_blk.c	2004-05-25 18:00:41.935174675 -0700
@@ -1598,6 +1598,7 @@ static struct request *get_request(reque
 	rq->ref_count = 1;
 	rq->q = q;
 	rq->rl = rl;
+	rq->end_request = NULL;
 	rq->waiting = NULL;
 	rq->special = NULL;
 	rq->data_len = 0;
@@ -1841,6 +1842,21 @@ int blk_rq_unmap_user(struct request *rq
 EXPORT_SYMBOL(blk_rq_unmap_user);
 
 /**
+ * blk_end_sync_rq - executes a completion event on a request
+ *			when it has completed.
+ * @rq: request to complete.
+ *
+ * Caveat: If you set this function as your end_request_fn
+ * you must set a valid completion structure to rq->waiting.
+ */
+void blk_end_sync_rq(struct request *rq)
+{
+	struct completion *waiting = rq->waiting;
+
+	complete(waiting);
+}
+
+/**
  * blk_execute_rq - insert a request into queue for execution
  * @q:		queue to insert the request in
  * @bd_disk:	matching gendisk
@@ -1873,6 +1889,7 @@ int blk_execute_rq(request_queue_t *q, s
 
 	rq->flags |= REQ_NOMERGE;
 	rq->waiting = &wait;
+	rq->end_request = blk_end_sync_rq;
 	elv_add_request(q, rq, ELEVATOR_INSERT_BACK, 1);
 	generic_unplug_device(q);
 	wait_for_completion(&wait);
@@ -1970,6 +1987,7 @@ void __blk_put_request(request_queue_t *
 	req->rq_status = RQ_INACTIVE;
 	req->q = NULL;
 	req->rl = NULL;
+	req->end_request = NULL;
 
 	/*
 	 * Request may not have originated from ll_rw_blk. if not,
@@ -2732,6 +2750,7 @@ void end_that_request_last(struct reques
 {
 	struct gendisk *disk = req->rq_disk;
 	struct completion *waiting = req->waiting;
+	end_request_fn *end_fn = req->end_request;
 
 	if (unlikely(laptop_mode) && blk_fs_request(req))
 		laptop_io_completion();
@@ -2753,7 +2772,9 @@ void end_that_request_last(struct reques
 	}
 	__blk_put_request(req->q, req);
 	/* Do this LAST! The structure may be freed immediately afterwards */
-	if (waiting)
+	if (end_fn)
+		end_fn(req);
+	else if (waiting)
 		complete(waiting);
 }
 
diff -arup linux-2.6.7-rc1/include/linux/blkdev.h linux-2.6.7-rc1-patch/include/linux/blkdev.h
--- linux-2.6.7-rc1/include/linux/blkdev.h	2004-05-24 18:55:05.000000000 -0700
+++ linux-2.6.7-rc1-patch/include/linux/blkdev.h	2004-05-25 18:00:23.000000000 -0700
@@ -17,6 +17,7 @@
 
 #include <asm/scatterlist.h>
 
+struct request;
 struct request_queue;
 typedef struct request_queue request_queue_t;
 struct elevator_s;
@@ -85,6 +86,13 @@ struct request_list {
 #define BLK_MAX_CDB	16
 
 /*
+ * When using the end_request_fn, you should get a handle
+ * to the request, then release it in the end_request_fn
+ * (or whenever you are done with the rq).
+ */
+typedef void end_request_fn(struct request *rq);
+
+/*
  * try to put the fields that are referenced together in the same cacheline
  */
 struct request {
@@ -144,6 +152,7 @@ struct request {
 
 	struct completion *waiting;
 	void *special;
+	end_request_fn *end_request;
 
 	/*
 	 * when request is used as a packet command carrier