[PATCH] md/bitmap: remove bitmap writeback daemon

md/bitmap currently has a separate thread to wait for writes to the bitmap
file to complete (as we cannot get a callback on that action).

However this isn't needed as bitmap_unplug is called from process context and
waits for the writeback thread to do it's work.  The same result can be
achieved by doing the waiting directly in bitmap_unplug.

Signed-off-by: Neil Brown <neilb@suse.de>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

2 files changed, 8 insertions, 113 deletions

diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index f8ffaee20ff..814f412a410 100644
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -7,7 +7,6 @@
  * additions, Copyright (C) 2003-2004, Paul Clements, SteelEye Technology, Inc.:
  * - added disk storage for bitmap
  * - changes to allow various bitmap chunk sizes
- * - added bitmap daemon (to asynchronously clear bitmap bits from disk)
  */
 
 /*
@@ -330,14 +329,13 @@ static int write_page(struct bitmap *bitmap, struct page *page, int wait)
         set_page_dirty(page); /* force it to be written out */
 
         if (!wait) {
-                /* add to list to be waited for by daemon */
+                /* add to list to be waited for */
                 struct page_list *item = mempool_alloc(bitmap->write_pool, GFP_NOIO);
                 item->page = page;
                 get_page(page);
                 spin_lock(&bitmap->write_lock);
                 list_add(&item->list, &bitmap->complete_pages);
                 spin_unlock(&bitmap->write_lock);
-                md_wakeup_thread(bitmap->writeback_daemon);
         }
         return write_one_page(page, wait);
 }
@@ -621,8 +619,6 @@ static void bitmap_file_unmap(struct bitmap *bitmap)
         safe_put_page(sb_page);
 }
 
-static void bitmap_stop_daemon(struct bitmap *bitmap);
-
 /* dequeue the next item in a page list -- don't call from irq context */
 static struct page_list *dequeue_page(struct bitmap *bitmap)
 {
@@ -648,8 +644,6 @@ static void drain_write_queues(struct bitmap *bitmap)
                 put_page(item->page);
                 mempool_free(item, bitmap->write_pool);
         }
-
-        wake_up(&bitmap->write_wait);
 }
 
 static void bitmap_file_put(struct bitmap *bitmap)
@@ -663,8 +657,6 @@ static void bitmap_file_put(struct bitmap *bitmap)
         bitmap->file = NULL;
         spin_unlock_irqrestore(&bitmap->lock, flags);
 
-        bitmap_stop_daemon(bitmap);
-
         drain_write_queues(bitmap);
 
         bitmap_file_unmap(bitmap);
@@ -770,6 +762,8 @@ static void bitmap_file_set_bit(struct bitmap *bitmap, sector_t block)
 
 }
 
+static void bitmap_writeback(struct bitmap *bitmap);
+
 /* this gets called when the md device is ready to unplug its underlying
  * (slave) device queues -- before we let any writes go down, we need to
  * sync the dirty pages of the bitmap file to disk */
@@ -812,13 +806,9 @@ int bitmap_unplug(struct bitmap *bitmap)
                 }
         }
         if (wait) { /* if any writes were performed, we need to wait on them */
-                if (bitmap->file) {
-                        spin_lock_irq(&bitmap->write_lock);
-                        wait_event_lock_irq(bitmap->write_wait,
-                                            list_empty(&bitmap->complete_pages), bitmap->write_lock,
-                                            wake_up_process(bitmap->writeback_daemon->tsk));
-                        spin_unlock_irq(&bitmap->write_lock);
-                } else
+                if (bitmap->file)
+                        bitmap_writeback(bitmap);
+                else
                         md_super_wait(bitmap->mddev);
         }
         return 0;
@@ -1126,41 +1116,12 @@ int bitmap_daemon_work(struct bitmap *bitmap)
         return err;
 }
 
-static void daemon_exit(struct bitmap *bitmap, mdk_thread_t **daemon)
+static void bitmap_writeback(struct bitmap *bitmap)
 {
-        mdk_thread_t *dmn;
-        unsigned long flags;
-
-        /* if no one is waiting on us, we'll free the md thread struct
-         * and exit, otherwise we let the waiter clean things up */
-        spin_lock_irqsave(&bitmap->lock, flags);
-        if ((dmn = *daemon)) { /* no one is waiting, cleanup and exit */
-                *daemon = NULL;
-                spin_unlock_irqrestore(&bitmap->lock, flags);
-                kfree(dmn);
-                complete_and_exit(NULL, 0); /* do_exit not exported */
-        }
-        spin_unlock_irqrestore(&bitmap->lock, flags);
-}
-
-static void bitmap_writeback_daemon(mddev_t *mddev)
-{
-        struct bitmap *bitmap = mddev->bitmap;
         struct page *page;
         struct page_list *item;
         int err = 0;
 
-        if (signal_pending(current)) {
-                printk(KERN_INFO
-                       "%s: bitmap writeback daemon got signal, exiting...\n",
-                       bmname(bitmap));
-                err = -EINTR;
-                goto out;
-        }
-        if (bitmap == NULL)
-                /* about to be stopped. */
-                return;
-
         PRINTK("%s: bitmap writeback daemon woke up...\n", bmname(bitmap));
         /* wait on bitmap page writebacks */
         while ((item = dequeue_page(bitmap))) {
@@ -1177,59 +1138,9 @@ static void bitmap_writeback_daemon(mddev_t *mddev)
                                "failed (page %lu): %d\n",
                                bmname(bitmap), page->index, err);
                         bitmap_file_kick(bitmap);
-                        goto out;
+                        break;
                 }
         }
- out:
-        wake_up(&bitmap->write_wait);
-        if (err) {
-                printk(KERN_INFO "%s: bitmap writeback daemon exiting (%d)\n",
-                       bmname(bitmap), err);
-                daemon_exit(bitmap, &bitmap->writeback_daemon);
-        }
-}
-
-static mdk_thread_t *bitmap_start_daemon(struct bitmap *bitmap,
-                                void (*func)(mddev_t *), char *name)
-{
-        mdk_thread_t *daemon;
-        char namebuf[32];
-
-#ifdef INJECT_FATAL_FAULT_2
-        daemon = NULL;
-#else
-        sprintf(namebuf, "%%s_%s", name);
-        daemon = md_register_thread(func, bitmap->mddev, namebuf);
-#endif
-        if (!daemon) {
-                printk(KERN_ERR "%s: failed to start bitmap daemon\n",
-                        bmname(bitmap));
-                return ERR_PTR(-ECHILD);
-        }
-
-        md_wakeup_thread(daemon); /* start it running */
-
-        PRINTK("%s: %s daemon (pid %d) started...\n",
-                bmname(bitmap), name, daemon->tsk->pid);
-
-        return daemon;
-}
-
-static void bitmap_stop_daemon(struct bitmap *bitmap)
-{
-        /* the daemon can't stop itself... it'll just exit instead... */
-        if (bitmap->writeback_daemon && ! IS_ERR(bitmap->writeback_daemon) &&
-            current->pid != bitmap->writeback_daemon->tsk->pid) {
-                mdk_thread_t *daemon;
-                unsigned long flags;
-
-                spin_lock_irqsave(&bitmap->lock, flags);
-                daemon = bitmap->writeback_daemon;
-                bitmap->writeback_daemon = NULL;
-                spin_unlock_irqrestore(&bitmap->lock, flags);
-                if (daemon && ! IS_ERR(daemon))
-                        md_unregister_thread(daemon); /* destroy the thread */
-        }
 }
 
 static bitmap_counter_t *bitmap_get_counter(struct bitmap *bitmap,
@@ -1553,7 +1464,6 @@ int bitmap_create(mddev_t *mddev)
 
         spin_lock_init(&bitmap->write_lock);
         INIT_LIST_HEAD(&bitmap->complete_pages);
-        init_waitqueue_head(&bitmap->write_wait);
         bitmap->write_pool = mempool_create_kmalloc_pool(WRITE_POOL_SIZE,
                                                 sizeof(struct page_list));
         err = -ENOMEM;
@@ -1613,15 +1523,6 @@ int bitmap_create(mddev_t *mddev)
 
         mddev->bitmap = bitmap;
 
-        if (file)
-                /* kick off the bitmap writeback daemon */
-                bitmap->writeback_daemon =
-                        bitmap_start_daemon(bitmap,
-                                            bitmap_writeback_daemon,
-                                            "bitmap_wb");
-
-        if (IS_ERR(bitmap->writeback_daemon))
-                return PTR_ERR(bitmap->writeback_daemon);
         mddev->thread->timeout = bitmap->daemon_sleep * HZ;
 
         return bitmap_update_sb(bitmap);
diff --git a/include/linux/raid/bitmap.h b/include/linux/raid/bitmap.h
index 899437802ae..9c8907ca60a 100644
--- a/include/linux/raid/bitmap.h
+++ b/include/linux/raid/bitmap.h
@@ -244,13 +244,7 @@ struct bitmap {
         unsigned long daemon_lastrun; /* jiffies of last run */
         unsigned long daemon_sleep; /* how many seconds between updates? */
 
-        /*
-         * bitmap_writeback_daemon waits for file-pages that have been written,
-         * as there is no way to get a call-back when a page write completes.
-         */
-        mdk_thread_t *writeback_daemon;
         spinlock_t write_lock;
-        wait_queue_head_t write_wait;
         struct list_head complete_pages;
         mempool_t *write_pool;
 };