bcache: Allocation kthread fixes

The alloc kthread should've been using try_to_freeze() - and also there
was the potential for the alloc kthread to get woken up after it had
shut down, which would have been bad.

Signed-off-by: Kent Overstreet <kmo@daterainc.com>

3 files changed, 15 insertions, 18 deletions

diff --git a/drivers/md/bcache/alloc.c b/drivers/md/bcache/alloc.c
index b54b73b9b2b7..e45f5575fd4d 100644
--- a/drivers/md/bcache/alloc.c
+++ b/drivers/md/bcache/alloc.c
@@ -63,6 +63,7 @@
 #include "bcache.h"
 #include "btree.h"
 
+#include <linux/freezer.h>
 #include <linux/kthread.h>
 #include <linux/random.h>
 #include <trace/events/bcache.h>
@@ -363,11 +364,10 @@ do {									\
                         break;                                          \
                                                                         \
                 mutex_unlock(&(ca)->set->bucket_lock);                  \
-                if (test_bit(CACHE_SET_STOPPING_2, &ca->set->flags)) {  \
-                        closure_put(&ca->set->cl);                      \
+                if (kthread_should_stop())                              \
                         return 0;                                       \
-                }                                                       \
                                                                         \
+                try_to_freeze();                                        \
                 schedule();                                             \
                 mutex_lock(&(ca)->set->bucket_lock);                    \
         }                                                               \
@@ -547,14 +547,12 @@ int bch_bucket_alloc_set(struct cache_set *c, unsigned watermark,
 
 int bch_cache_allocator_start(struct cache *ca)
 {
-        ca->alloc_thread = kthread_create(bch_allocator_thread,
-                                          ca, "bcache_allocator");
-        if (IS_ERR(ca->alloc_thread))
-                return PTR_ERR(ca->alloc_thread);
-
-        closure_get(&ca->set->cl);
-        wake_up_process(ca->alloc_thread);
+        struct task_struct *k = kthread_run(bch_allocator_thread,
+                                            ca, "bcache_allocator");
+        if (IS_ERR(k))
+                return PTR_ERR(k);
 
+        ca->alloc_thread = k;
         return 0;
 }
 
diff --git a/drivers/md/bcache/bcache.h b/drivers/md/bcache/bcache.h
index 68f1ded81ae0..b39f6f0b45f2 100644
--- a/drivers/md/bcache/bcache.h
+++ b/drivers/md/bcache/bcache.h
@@ -664,13 +664,9 @@ struct gc_stat {
  * CACHE_SET_STOPPING always gets set first when we're closing down a cache set;
  * we'll continue to run normally for awhile with CACHE_SET_STOPPING set (i.e.
  * flushing dirty data).
- *
- * CACHE_SET_STOPPING_2 gets set at the last phase, when it's time to shut down
- * the allocation thread.
  */
 #define CACHE_SET_UNREGISTERING         0
 #define CACHE_SET_STOPPING              1
-#define CACHE_SET_STOPPING_2            2
 
 struct cache_set {
         struct closure          cl;
diff --git a/drivers/md/bcache/super.c b/drivers/md/bcache/super.c
index f6a62174e8f6..547c4c57b052 100644
--- a/drivers/md/bcache/super.c
+++ b/drivers/md/bcache/super.c
@@ -16,6 +16,7 @@
 #include <linux/buffer_head.h>
 #include <linux/debugfs.h>
 #include <linux/genhd.h>
+#include <linux/kthread.h>
 #include <linux/module.h>
 #include <linux/random.h>
 #include <linux/reboot.h>
@@ -1329,11 +1330,9 @@ static void cache_set_free(struct closure *cl)
 static void cache_set_flush(struct closure *cl)
 {
         struct cache_set *c = container_of(cl, struct cache_set, caching);
+        struct cache *ca;
         struct btree *b;
-
-        /* Shut down allocator threads */
-        set_bit(CACHE_SET_STOPPING_2, &c->flags);
-        wake_up_allocators(c);
+        unsigned i;
 
         bch_cache_accounting_destroy(&c->accounting);
 
@@ -1348,6 +1347,10 @@ static void cache_set_flush(struct closure *cl)
                 if (btree_node_dirty(b))
                         bch_btree_node_write(b, NULL);
 
+        for_each_cache(ca, c, i)
+                if (ca->alloc_thread)
+                        kthread_stop(ca->alloc_thread);
+
         closure_return(cl);
 }