[PATCH] md: enable the bitmap write-back daemon and wait for it.

Currently we don't wait for updates to the bitmap to be flushed to disk
properly.  The infrastructure all there, but it isn't being used....

A separate kernel thread (bitmap_writeback_daemon) is needed to wait for each
page as we cannot get callbacks when a page write completes.

Signed-off-by: Neil Brown <neilb@cse.unsw.edu.au>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

diff --git a/drivers/md/bitmap.c b/drivers/md/bitmap.c
index 9462fdd..86b6b03 100644 (file)
--- a/drivers/md/bitmap.c
+++ b/drivers/md/bitmap.c
@@ -261,30 +261,33 @@ char *file_path(struct file *file, char *buf, int count)
 /*
  * write out a page
  */
-static int write_page(struct page *page, int wait)
+static int write_page(struct bitmap *bitmap, struct page *page, int wait)
 {
        int ret = -ENOMEM;
 
        lock_page(page);
 
-       if (page->mapping == NULL)
-               goto unlock_out;
-       else if (i_size_read(page->mapping->host) < page->index << PAGE_SHIFT) {
-               ret = -ENOENT;
-               goto unlock_out;
-       }
-
        ret = page->mapping->a_ops->prepare_write(NULL, page, 0, PAGE_SIZE);
        if (!ret)
                ret = page->mapping->a_ops->commit_write(NULL, page, 0,
                        PAGE_SIZE);
        if (ret) {
-unlock_out:
                unlock_page(page);
                return ret;
        }
 
        set_page_dirty(page); /* force it to be written out */
+
+       if (!wait) {
+               /* add to list to be waited for by daemon */
+               struct page_list *item = mempool_alloc(bitmap->write_pool, GFP_NOIO);
+               item->page = page;
+               page_cache_get(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);
 }
 
@@ -343,14 +346,13 @@ int bitmap_update_sb(struct bitmap *bitmap)
                spin_unlock_irqrestore(&bitmap->lock, flags);
                return 0;
        }
-       page_cache_get(bitmap->sb_page);
        spin_unlock_irqrestore(&bitmap->lock, flags);
        sb = (bitmap_super_t *)kmap(bitmap->sb_page);
        sb->events = cpu_to_le64(bitmap->mddev->events);
        if (!bitmap->mddev->degraded)
                sb->events_cleared = cpu_to_le64(bitmap->mddev->events);
        kunmap(bitmap->sb_page);
-       return write_page(bitmap->sb_page, 0);
+       return write_page(bitmap, bitmap->sb_page, 0);
 }
 
 /* print out the bitmap file superblock */
@@ -556,10 +558,10 @@ static void bitmap_file_unmap(struct bitmap *bitmap)
 static void bitmap_stop_daemons(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,
-                                       struct list_head *head)
+static struct page_list *dequeue_page(struct bitmap *bitmap)
 {
        struct page_list *item = NULL;
+       struct list_head *head = &bitmap->complete_pages;
 
        spin_lock(&bitmap->write_lock);
        if (list_empty(head))
@@ -573,23 +575,15 @@ out:
 
 static void drain_write_queues(struct bitmap *bitmap)
 {
-       struct list_head *queues[] = {  &bitmap->complete_pages, NULL };
-       struct list_head *head;
        struct page_list *item;
-       int i;
 
-       for (i = 0; queues[i]; i++) {
-               head = queues[i];
-               while ((item = dequeue_page(bitmap, head))) {
-                       page_cache_release(item->page);
-                       mempool_free(item, bitmap->write_pool);
-               }
+       while ((item = dequeue_page(bitmap))) {
+               /* don't bother to wait */
+               page_cache_release(item->page);
+               mempool_free(item, bitmap->write_pool);
        }
 
-       spin_lock(&bitmap->write_lock);
-       bitmap->writes_pending = 0; /* make sure waiters continue */
        wake_up(&bitmap->write_wait);
-       spin_unlock(&bitmap->write_lock);
 }
 
 static void bitmap_file_put(struct bitmap *bitmap)
@@ -734,13 +728,13 @@ int bitmap_unplug(struct bitmap *bitmap)
                spin_unlock_irqrestore(&bitmap->lock, flags);
 
                if (attr & (BITMAP_PAGE_DIRTY | BITMAP_PAGE_NEEDWRITE))
-                       if (write_page(page, 0))
+                       if (write_page(bitmap, page, 0))
                                return 1;
        }
        if (wait) { /* if any writes were performed, we need to wait on them */
                spin_lock_irq(&bitmap->write_lock);
                wait_event_lock_irq(bitmap->write_wait,
-                       bitmap->writes_pending == 0, bitmap->write_lock,
+                       list_empty(&bitmap->complete_pages), bitmap->write_lock,
                        wake_up_process(bitmap->writeback_daemon->tsk));
                spin_unlock_irq(&bitmap->write_lock);
        }
@@ -841,7 +835,7 @@ static int bitmap_init_from_disk(struct bitmap *bitmap, int in_sync)
                                 */
                                memset(page_address(page) + offset, 0xff,
                                        PAGE_SIZE - offset);
-                               ret = write_page(page, 1);
+                               ret = write_page(bitmap, page, 1);
                                if (ret) {
                                        kunmap(page);
                                        /* release, page not in filemap yet */
@@ -934,7 +928,7 @@ int bitmap_daemon_work(struct bitmap *bitmap)
                        }
                        spin_unlock_irqrestore(&bitmap->lock, flags);
                        if (attr & BITMAP_PAGE_NEEDWRITE) {
-                               if (write_page(page, 0))
+                               if (write_page(bitmap, page, 0))
                                        bitmap_file_kick(bitmap);
                                page_cache_release(page);
                        }
@@ -950,7 +944,7 @@ int bitmap_daemon_work(struct bitmap *bitmap)
                                if (get_page_attr(bitmap, lastpage) & BITMAP_PAGE_NEEDWRITE) {
                                        clear_page_attr(bitmap, lastpage, BITMAP_PAGE_NEEDWRITE);
                                        spin_unlock_irqrestore(&bitmap->lock, flags);
-                                       err = write_page(lastpage, 0);
+                                       err = write_page(bitmap, lastpage, 0);
                                } else {
                                        set_page_attr(bitmap, lastpage, BITMAP_PAGE_NEEDWRITE);
                                        spin_unlock_irqrestore(&bitmap->lock, flags);
@@ -998,7 +992,7 @@ int bitmap_daemon_work(struct bitmap *bitmap)
                if (get_page_attr(bitmap, lastpage) &BITMAP_PAGE_NEEDWRITE) {
                        clear_page_attr(bitmap, lastpage, BITMAP_PAGE_NEEDWRITE);
                        spin_unlock_irqrestore(&bitmap->lock, flags);
-                       err = write_page(lastpage, 0);
+                       err = write_page(bitmap, lastpage, 0);
                } else {
                        set_page_attr(bitmap, lastpage, BITMAP_PAGE_NEEDWRITE);
                        spin_unlock_irqrestore(&bitmap->lock, flags);
@@ -1034,46 +1028,40 @@ static void bitmap_writeback_daemon(mddev_t *mddev)
        struct page_list *item;
        int err = 0;
 
-       while (1) {
-               PRINTK("%s: bitmap writeback daemon waiting...\n", bmname(bitmap));
-               down_interruptible(&bitmap->write_done);
-               if (signal_pending(current)) {
-                       printk(KERN_INFO
-                           "%s: bitmap writeback daemon got signal, exiting...\n",
-                           bmname(bitmap));
-                       break;
-               }
+       if (signal_pending(current)) {
+               printk(KERN_INFO
+                      "%s: bitmap writeback daemon got signal, exiting...\n",
+                      bmname(bitmap));
+               err = -EINTR;
+               goto out;
+       }
 
-               PRINTK("%s: bitmap writeback daemon woke up...\n", bmname(bitmap));
-               /* wait on bitmap page writebacks */
-               while ((item = dequeue_page(bitmap, &bitmap->complete_pages))) {
-                       page = item->page;
-                       mempool_free(item, bitmap->write_pool);
-                       PRINTK("wait on page writeback: %p %lu\n", page, bitmap->writes_pending);
-                       wait_on_page_writeback(page);
-                       PRINTK("finished page writeback: %p %lu\n", page, bitmap->writes_pending);
-                       spin_lock(&bitmap->write_lock);
-                       if (!--bitmap->writes_pending)
-                               wake_up(&bitmap->write_wait);
-                       spin_unlock(&bitmap->write_lock);
-                       err = PageError(page);
-                       page_cache_release(page);
-                       if (err) {
-                               printk(KERN_WARNING "%s: bitmap file writeback "
-                                       "failed (page %lu): %d\n",
-                                       bmname(bitmap), page->index, err);
-                               bitmap_file_kick(bitmap);
-                               goto out;
-                       }
+       PRINTK("%s: bitmap writeback daemon woke up...\n", bmname(bitmap));
+       /* wait on bitmap page writebacks */
+       while ((item = dequeue_page(bitmap))) {
+               page = item->page;
+               mempool_free(item, bitmap->write_pool);
+               PRINTK("wait on page writeback: %p\n", page);
+               wait_on_page_writeback(page);
+               PRINTK("finished page writeback: %p\n", page);
+
+               err = PageError(page);
+               page_cache_release(page);
+               if (err) {
+                       printk(KERN_WARNING "%s: bitmap file writeback "
+                              "failed (page %lu): %d\n",
+                              bmname(bitmap), page->index, err);
+                       bitmap_file_kick(bitmap);
+                       goto out;
                }
        }
-out:
+ out:
+       wake_up(&bitmap->write_wait);
        if (err) {
                printk(KERN_INFO "%s: bitmap writeback daemon exiting (%d)\n",
-                       bmname(bitmap), err);
+                      bmname(bitmap), err);
                daemon_exit(bitmap, &bitmap->writeback_daemon);
        }
-       return;
 }
 
 static int bitmap_start_daemon(struct bitmap *bitmap, mdk_thread_t **ptr,
@@ -1375,7 +1363,7 @@ int bitmap_setallbits(struct bitmap *bitmap)
                spin_unlock_irqrestore(&bitmap->lock, flags);
                memset(kmap(page), 0xff, PAGE_SIZE);
                kunmap(page);
-               if (write_page(page, 0))
+               if (write_page(bitmap, page, 0))
                        return 1;
        }
 
@@ -1443,7 +1431,6 @@ int bitmap_create(mddev_t *mddev)
        mddev->bitmap = bitmap;
 
        spin_lock_init(&bitmap->write_lock);
-       init_MUTEX_LOCKED(&bitmap->write_done);
        INIT_LIST_HEAD(&bitmap->complete_pages);
        init_waitqueue_head(&bitmap->write_wait);
        bitmap->write_pool = mempool_create(WRITE_POOL_SIZE, write_pool_alloc,

diff --git a/include/linux/raid/bitmap.h b/include/linux/raid/bitmap.h
index f785cf2..cfe60cf 100644 (file)
--- a/include/linux/raid/bitmap.h
+++ b/include/linux/raid/bitmap.h
@@ -233,21 +233,12 @@ struct bitmap {
        unsigned long daemon_sleep; /* how many seconds between updates? */
 
        /*
-        * bitmap write daemon - this daemon performs writes to the bitmap file
-        * this thread is only needed because of a limitation in ext3 (jbd)
-        * that does not allow a task to have two journal transactions ongoing
-        * simultaneously (even if the transactions are for two different
-        * filesystems) -- in the case of bitmap, that would be the filesystem
-        * that the bitmap file resides on and the filesystem that is mounted
-        * on the md device -- see current->journal_info in jbd/transaction.c
+        * 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;
-       struct semaphore write_ready;
-       struct semaphore write_done;
-       unsigned long writes_pending;
        wait_queue_head_t write_wait;
-       struct list_head write_pages;
        struct list_head complete_pages;
        mempool_t *write_pool;
 };