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>

diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index b61b069c33afbafd17af1951f0f5d8fee4ddf9d0..c406767cb9b7b1c6e21d25aa991c84399691b39f 100644 (file)
--- 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");