for-test: add 0001-bcache-fix-a-lost-wake-up-problem-caused-by-mca_cann.patch

1 files changed, 92 insertions, 0 deletions

diff --git a/for-test/0001-bcache-fix-a-lost-wake-up-problem-caused-by-mca_cann.patch b/for-test/0001-bcache-fix-a-lost-wake-up-problem-caused-by-mca_cann.patch
new file mode 100644
index 0000000..2df3ff9
--- /dev/null
+++ b/for-test/0001-bcache-fix-a-lost-wake-up-problem-caused-by-mca_cann.patch
@@ -0,0 +1,92 @@
+From 4085c87f96aa4f70d97be3ce9cd075df1616d45f Mon Sep 17 00:00:00 2001
+From: Guoju Fang <fangguoju@gmail.com>
+Date: Tue, 20 Aug 2019 06:13:55 -0400
+Subject: [PATCH] bcache: fix a lost wake-up problem caused by
+ mca_cannibalize_lock
+
+This patch fix a lost wake-up problem caused by the race between
+mca_cannibalize_lock and bch_cannibalize_unlock.
+
+Consider two processes, A and B. Process A is executing
+mca_cannibalize_lock, while process B takes c->btree_cache_alloc_lock
+and is executing bch_cannibalize_unlock. The problem happens that after
+process A executes cmpxchg and will execute prepare_to_wait. In this
+timeslice process B executes wake_up, but after that process A executes
+prepare_to_wait and set the state to TASK_INTERRUPTIBLE. Then process A
+goes to sleep but no one will wake up it. This problem may cause bcache
+device to dead.
+
+Signed-off-by: Guoju Fang <fangguoju@gmail.com>
+Signed-off-by: Coly Li <colyli@suse.de>
+---
+ drivers/md/bcache/bcache.h |  1 +
+ drivers/md/bcache/btree.c  | 12 ++++++++----
+ drivers/md/bcache/super.c  |  1 +
+ 3 files changed, 10 insertions(+), 4 deletions(-)
+
+diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h
+index 013e35a9e317..3653faf3bf48 100644
+--- a/drivers/md/bcache/bcache.h
++++ b/drivers/md/bcache/bcache.h
+@@ -582,6 +582,7 @@ struct cache_set {
+ 	 */
+ 	wait_queue_head_t	btree_cache_wait;
+ 	struct task_struct	*btree_cache_alloc_lock;
++	spinlock_t		btree_cannibalize_lock;
+ 
+ 	/*
+ 	 * When we free a btree node, we increment the gen of the bucket the
+diff --git a/drivers/md/bcache/btree.c b/drivers/md/bcache/btree.c
+index ba434d9ac720..7fcf079e0329 100644
+--- a/drivers/md/bcache/btree.c
++++ b/drivers/md/bcache/btree.c
+@@ -884,15 +884,17 @@ static struct btree *mca_find(struct cache_set *c, struct bkey *k)
+ 
+ static int mca_cannibalize_lock(struct cache_set *c, struct btree_op *op)
+ {
+-	struct task_struct *old;
+-
+-	old = cmpxchg(&c->btree_cache_alloc_lock, NULL, current);
+-	if (old && old != current) {
++	spin_lock(&c->btree_cannibalize_lock);
++	if (likely(c->btree_cache_alloc_lock == NULL)) {
++		c->btree_cache_alloc_lock = current;
++	} else if (c->btree_cache_alloc_lock != current) {
+ 		if (op)
+ 			prepare_to_wait(&c->btree_cache_wait, &op->wait,
+ 					TASK_UNINTERRUPTIBLE);
++		spin_unlock(&c->btree_cannibalize_lock);
+ 		return -EINTR;
+ 	}
++	spin_unlock(&c->btree_cannibalize_lock);
+ 
+ 	return 0;
+ }
+@@ -927,10 +929,12 @@ static struct btree *mca_cannibalize(struct cache_set *c, struct btree_op *op,
+  */
+ static void bch_cannibalize_unlock(struct cache_set *c)
+ {
++	spin_lock(&c->btree_cannibalize_lock);
+ 	if (c->btree_cache_alloc_lock == current) {
+ 		c->btree_cache_alloc_lock = NULL;
+ 		wake_up(&c->btree_cache_wait);
+ 	}
++	spin_unlock(&c->btree_cannibalize_lock);
+ }
+ 
+ static struct btree *mca_alloc(struct cache_set *c, struct btree_op *op,
+diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
+index 20ed838e9413..ebb854ed05a4 100644
+--- a/drivers/md/bcache/super.c
++++ b/drivers/md/bcache/super.c
+@@ -1769,6 +1769,7 @@ struct cache_set *bch_cache_set_alloc(struct cache_sb *sb)
+ 	sema_init(&c->sb_write_mutex, 1);
+ 	mutex_init(&c->bucket_lock);
+ 	init_waitqueue_head(&c->btree_cache_wait);
++	spin_lock_init(&c->btree_cannibalize_lock);
+ 	init_waitqueue_head(&c->bucket_wait);
+ 	init_waitqueue_head(&c->gc_wait);
+ 	sema_init(&c->uuid_write_mutex, 1);
+-- 
+2.16.4
+