dm crypt: use wake_up_process() instead of a wait queue

This is a small simplification of dm-crypt - use wake_up_process()
instead of a wait queue in a case where only one process may be
waiting.  dm-writecache uses a similar pattern.

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Mike Snitzer <snitzer@redhat.com>

1 files changed, 10 insertions, 15 deletions

diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index b61b069c33af..c406767cb9b7 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -144,7 +144,7 @@ struct crypt_config {
         struct workqueue_struct *io_queue;
         struct workqueue_struct *crypt_queue;
 
-        wait_queue_head_t write_thread_wait;
+        spinlock_t write_thread_lock;
         struct task_struct *write_thread;
         struct rb_root write_tree;
 
@@ -1620,36 +1620,31 @@ static int dmcrypt_write(void *data)
                 struct rb_root write_tree;
                 struct blk_plug plug;
 
-                DECLARE_WAITQUEUE(wait, current);
-
-                spin_lock_irq(&cc->write_thread_wait.lock);
+                spin_lock_irq(&cc->write_thread_lock);
 continue_locked:
 
                 if (!RB_EMPTY_ROOT(&cc->write_tree))
                         goto pop_from_list;
 
                 set_current_state(TASK_INTERRUPTIBLE);
-                __add_wait_queue(&cc->write_thread_wait, &wait);
 
-                spin_unlock_irq(&cc->write_thread_wait.lock);
+                spin_unlock_irq(&cc->write_thread_lock);
 
                 if (unlikely(kthread_should_stop())) {
                         set_current_state(TASK_RUNNING);
-                        remove_wait_queue(&cc->write_thread_wait, &wait);
                         break;
                 }
 
                 schedule();
 
                 set_current_state(TASK_RUNNING);
-                spin_lock_irq(&cc->write_thread_wait.lock);
-                __remove_wait_queue(&cc->write_thread_wait, &wait);
+                spin_lock_irq(&cc->write_thread_lock);
                 goto continue_locked;
 
 pop_from_list:
                 write_tree = cc->write_tree;
                 cc->write_tree = RB_ROOT;
-                spin_unlock_irq(&cc->write_thread_wait.lock);
+                spin_unlock_irq(&cc->write_thread_lock);
 
                 BUG_ON(rb_parent(write_tree.rb_node));
 
@@ -1693,7 +1688,9 @@ static void kcryptd_crypt_write_io_submit(struct dm_crypt_io *io, int async)
                 return;
         }
 
-        spin_lock_irqsave(&cc->write_thread_wait.lock, flags);
+        spin_lock_irqsave(&cc->write_thread_lock, flags);
+        if (RB_EMPTY_ROOT(&cc->write_tree))
+                wake_up_process(cc->write_thread);
         rbp = &cc->write_tree.rb_node;
         parent = NULL;
         sector = io->sector;
@@ -1706,9 +1703,7 @@ static void kcryptd_crypt_write_io_submit(struct dm_crypt_io *io, int async)
         }
         rb_link_node(&io->rb_node, parent, rbp);
         rb_insert_color(&io->rb_node, &cc->write_tree);
-
-        wake_up_locked(&cc->write_thread_wait);
-        spin_unlock_irqrestore(&cc->write_thread_wait.lock, flags);
+        spin_unlock_irqrestore(&cc->write_thread_lock, flags);
 }
 
 static void kcryptd_crypt_write_convert(struct dm_crypt_io *io)
@@ -2831,7 +2826,7 @@ static int crypt_ctr(struct dm_target *ti, unsigned int argc, char **argv)
                 goto bad;
         }
 
-        init_waitqueue_head(&cc->write_thread_wait);
+        spin_lock_init(&cc->write_thread_lock);
         cc->write_tree = RB_ROOT;
 
         cc->write_thread = kthread_create(dmcrypt_write, cc, "dmcrypt_write");