[PATCH] kthread: convert loop.c to kthread

Convert loop.c from the deprecated kernel_thread to kthread.  This patch
simplifies the code quite a bit and passes similar testing to the previous
submission on both emulated x86 and s390.

Changes since last submission:
	switched to using a rather simple loop based on
	wait_event_interruptible.

Signed-off-by: Serge E. Hallyn <serue@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 26 insertions, 48 deletions

diff --git a/drivers/block/loop.c b/drivers/block/loop.c
index c774121684d7..e87b88731adc 100644
--- a/drivers/block/loop.c
+++ b/drivers/block/loop.c
@@ -72,6 +72,7 @@
 #include <linux/completion.h>
 #include <linux/highmem.h>
 #include <linux/gfp.h>
+#include <linux/kthread.h>
 
 #include <asm/uaccess.h>
 
@@ -522,15 +523,12 @@ static int loop_make_request(request_queue_t *q, struct bio *old_bio)
                 goto out;
         if (unlikely(rw == WRITE && (lo->lo_flags & LO_FLAGS_READ_ONLY)))
                 goto out;
-        lo->lo_pending++;
         loop_add_bio(lo, old_bio);
+        wake_up(&lo->lo_event);
         spin_unlock_irq(&lo->lo_lock);
-        complete(&lo->lo_bh_done);
         return 0;
 
 out:
-        if (lo->lo_pending == 0)
-                complete(&lo->lo_bh_done);
         spin_unlock_irq(&lo->lo_lock);
         bio_io_error(old_bio, old_bio->bi_size);
         return 0;
@@ -570,14 +568,18 @@ static inline void loop_handle_bio(struct loop_device *lo, struct bio *bio)
  * to avoid blocking in our make_request_fn. it also does loop decrypting
  * on reads for block backed loop, as that is too heavy to do from
  * b_end_io context where irqs may be disabled.
+ *
+ * Loop explanation:  loop_clr_fd() sets lo_state to Lo_rundown before
+ * calling kthread_stop().  Therefore once kthread_should_stop() is
+ * true, make_request will not place any more requests.  Therefore
+ * once kthread_should_stop() is true and lo_bio is NULL, we are
+ * done with the loop.
  */
 static int loop_thread(void *data)
 {
         struct loop_device *lo = data;
         struct bio *bio;
 
-        daemonize("loop%d", lo->lo_number);
-
         /*
          * loop can be used in an encrypted device,
          * hence, it mustn't be stopped at all
@@ -587,47 +589,21 @@ static int loop_thread(void *data)
 
         set_user_nice(current, -20);
 
-        lo->lo_state = Lo_bound;
-        lo->lo_pending = 1;
-
-        /*
-         * complete it, we are running
-         */
-        complete(&lo->lo_done);
+        while (!kthread_should_stop() || lo->lo_bio) {
 
-        for (;;) {
-                int pending;
+                wait_event_interruptible(lo->lo_event,
+                                lo->lo_bio || kthread_should_stop());
 
-                if (wait_for_completion_interruptible(&lo->lo_bh_done))
+                if (!lo->lo_bio)
                         continue;
-
                 spin_lock_irq(&lo->lo_lock);
-
-                /*
-                 * could be completed because of tear-down, not pending work
-                 */
-                if (unlikely(!lo->lo_pending)) {
-                        spin_unlock_irq(&lo->lo_lock);
-                        break;
-                }
-
                 bio = loop_get_bio(lo);
-                lo->lo_pending--;
-                pending = lo->lo_pending;
                 spin_unlock_irq(&lo->lo_lock);
 
                 BUG_ON(!bio);
                 loop_handle_bio(lo, bio);
-
-                /*
-                 * upped both for pending work and tear-down, lo_pending
-                 * will hit zero then
-                 */
-                if (unlikely(!pending))
-                        break;
         }
 
-        complete(&lo->lo_done);
         return 0;
 }
 
@@ -840,10 +816,15 @@ static int loop_set_fd(struct loop_device *lo, struct file *lo_file,
 
         set_blocksize(bdev, lo_blocksize);
 
-        error = kernel_thread(loop_thread, lo, CLONE_KERNEL);
-        if (error < 0)
+        lo->lo_thread = kthread_create(loop_thread, lo, "loop%d",
+                                                lo->lo_number);
+        if (IS_ERR(lo->lo_thread)) {
+                error = PTR_ERR(lo->lo_thread);
+                lo->lo_thread = NULL;
                 goto out_putf;
-        wait_for_completion(&lo->lo_done);
+        }
+        lo->lo_state = Lo_bound;
+        wake_up_process(lo->lo_thread);
         return 0;
 
  out_putf:
@@ -907,12 +888,9 @@ static int loop_clr_fd(struct loop_device *lo, struct block_device *bdev)
 
         spin_lock_irq(&lo->lo_lock);
         lo->lo_state = Lo_rundown;
-        lo->lo_pending--;
-        if (!lo->lo_pending)
-                complete(&lo->lo_bh_done);
         spin_unlock_irq(&lo->lo_lock);
 
-        wait_for_completion(&lo->lo_done);
+        kthread_stop(lo->lo_thread);
 
         lo->lo_backing_file = NULL;
 
@@ -925,6 +903,7 @@ static int loop_clr_fd(struct loop_device *lo, struct block_device *bdev)
         lo->lo_sizelimit = 0;
         lo->lo_encrypt_key_size = 0;
         lo->lo_flags = 0;
+        lo->lo_thread = NULL;
         memset(lo->lo_encrypt_key, 0, LO_KEY_SIZE);
         memset(lo->lo_crypt_name, 0, LO_NAME_SIZE);
         memset(lo->lo_file_name, 0, LO_NAME_SIZE);
@@ -1287,9 +1266,9 @@ static int __init loop_init(void)
                 if (!lo->lo_queue)
                         goto out_mem4;
                 mutex_init(&lo->lo_ctl_mutex);
-                init_completion(&lo->lo_done);
-                init_completion(&lo->lo_bh_done);
                 lo->lo_number = i;
+                lo->lo_thread = NULL;
+                init_waitqueue_head(&lo->lo_event);
                 spin_lock_init(&lo->lo_lock);
                 disk->major = LOOP_MAJOR;
                 disk->first_minor = i;
diff --git a/include/linux/loop.h b/include/linux/loop.h
index e76c7611d6cc..191a595055f0 100644
--- a/include/linux/loop.h
+++ b/include/linux/loop.h
@@ -59,10 +59,9 @@ struct loop_device {
         struct bio              *lo_bio;
         struct bio              *lo_biotail;
         int                     lo_state;
-        struct completion       lo_done;
-        struct completion       lo_bh_done;
         struct mutex            lo_ctl_mutex;
-        int                     lo_pending;
+        struct task_struct      *lo_thread;
+        wait_queue_head_t       lo_event;
 
         request_queue_t         *lo_queue;
 };