[dm-devel] [PATCH] 7/9: Queue test I/Os instead of immediately driving them.

[Kevin Corry]

In test_path, instead of driving the test I/O, queue it on a list. When all
test I/Os have been queued, they can then be driven down without having to
hold the path_lock.
--- diff/drivers/md/dm-mpath.c	2004-01-13 15:15:12.000000000 -0600
+++ source/drivers/md/dm-mpath.c	2004-01-13 15:18:44.000000000 -0600
@@ -61,6 +61,7 @@
 
 	spinlock_t failed_lock;
 	struct bio_list failed_ios;
+	struct bio_list test_ios;
 
 	unsigned test_interval;
 	atomic_t trigger_event;
@@ -222,7 +223,7 @@
 	p->test_bio->bi_size = bdev_hardsect_size(p->dev->bdev);
 	p->test_bio->bi_idx = 0;
 
-	generic_make_request(p->test_bio);
+	bio_list_add(&p->pg->m->test_ios, p->test_bio);
 }
 
 /*-----------------------------------------------------------------
@@ -233,21 +234,27 @@
 static LIST_HEAD(_mpaths);
 static spinlock_t _mpath_lock = SPIN_LOCK_UNLOCKED;
 
+static void submit_ios(struct bio *bio)
+{
+	struct bio *next;
+	while (bio) {
+		next = bio->bi_next;
+		bio->bi_next = NULL;
+		generic_make_request(bio);
+		bio = next;
+	}
+}
+
 static void dispatch_failed_ios(struct multipath *m)
 {
 	unsigned long flags;
-	struct bio *bio, *next_bio;
+	struct bio *bio;
 
 	spin_lock_irqsave(&m->failed_lock, flags);
 	bio = bio_list_get(&m->failed_ios);
 	spin_unlock_irqrestore(&m->failed_lock, flags);
 
-	while (bio) {
-		next_bio = bio->bi_next;
-		bio->bi_next = NULL;
-		generic_make_request(bio);
-		bio = next_bio;
-	}
+	submit_ios(bio);
 }
 
 static void iterate_paths(struct multipath *m, void (*fn)(struct path *p))
@@ -276,6 +283,7 @@
 	list_for_each_entry (m, &_mpaths, list) {
 		dispatch_failed_ios(m);
 		iterate_paths(m, test_path);
+		submit_ios(bio_list_get(&m->test_ios));
 
 		if (atomic_dec_and_test(&m->trigger_event))
 			dm_table_event(m->ti->table);