[PATCH] stop using the address_space dirty_pages list

Move everything over to walking the radix tree via the PAGECACHE_TAG_DIRTY
tag.  Remove address_space.dirty_pages.

fs/buffer.c

@@ -825,12 +825,6 @@ EXPORT_SYMBOL(mark_buffer_dirty_inode);
  * bit, see a bunch of clean buffers and we'd end up with dirty buffers/clean
  * page on the dirty page list.
  *
- * There is also a small window where the page is dirty, and not on dirty_pages.
- * Also a possibility that by the time the page is added to dirty_pages, it has
- * been set clean.  The page lists are somewhat approximate in this regard.
- * It's better to have clean pages accidentally attached to dirty_pages than to
- * leave dirty pages attached to clean_pages.
- *
  * We use private_lock to lock against try_to_free_buffers while using the
  * page's buffer list.  Also use this to protect against clean buffers being
  * added to the page after it was set dirty.
@@ -871,8 +865,6 @@ int __set_page_dirty_buffers(struct page *page)
 		if (page->mapping) {	/* Race with truncate? */
 			if (!mapping->backing_dev_info->memory_backed)
 				inc_page_state(nr_dirty);
-			list_del(&page->list);
-			list_add(&page->list, &mapping->dirty_pages);
 			radix_tree_tag_set(&mapping->page_tree, page->index,
 						PAGECACHE_TAG_DIRTY);
 		}
@@ -1228,7 +1220,7 @@ __getblk_slow(struct block_device *bdev, sector_t block, int size)
  * The relationship between dirty buffers and dirty pages:
  *
  * Whenever a page has any dirty buffers, the page's dirty bit is set, and
- * the page appears on its address_space.dirty_pages list.
+ * the page is tagged dirty in its radix tree.
  *
  * At all times, the dirtiness of the buffers represents the dirtiness of
  * subsections of the page.  If the page has buffers, the page dirty bit is
@@ -1250,10 +1242,10 @@ __getblk_slow(struct block_device *bdev, sector_t block, int size)
 /**
  * mark_buffer_dirty - mark a buffer_head as needing writeout
  *
- * mark_buffer_dirty() will set the dirty bit against the buffer,
- * then set its backing page dirty, then attach the page to its
- * address_space's dirty_pages list and then attach the address_space's
- * inode to its superblock's dirty inode list.
+ * mark_buffer_dirty() will set the dirty bit against the buffer, then set its
+ * backing page dirty, then tag the page as dirty in its address_space's radix
+ * tree and then attach the address_space's inode to its superblock's dirty
+ * inode list.
  *
  * mark_buffer_dirty() is atomic.  It takes bh->b_page->mapping->private_lock,
  * mapping->tree_lock and the global inode_lock.

fs/fs-writeback.c

@@ -129,12 +129,6 @@ static void write_inode(struct inode *inode, int sync)
  * starvation of particular inodes when others are being redirtied, prevent
  * livelocks, etc.
  *
- * So what we do is to move all pages which are to be written from dirty_pages
- * onto io_pages.  And keep on writing io_pages until it's empty.  Refusing to
- * move more pages onto io_pages until io_pages is empty.  Once that point has
- * been reached, we are ready to take another pass across the inode's dirty
- * pages.
- *
  * Called under inode_lock.
  */
 static int
@@ -159,10 +153,6 @@ __sync_single_inode(struct inode *inode, struct writeback_control *wbc)
 	 * read speculatively by this cpu before &= ~I_DIRTY  -- mikulas
 	 */
 
-	spin_lock_irq(&mapping->tree_lock);
-	if (wait || !wbc->for_kupdate || list_empty(&mapping->io_pages))
-		list_splice_init(&mapping->dirty_pages, &mapping->io_pages);
-	spin_unlock_irq(&mapping->tree_lock);
 	spin_unlock(&inode_lock);
 
 	ret = do_writepages(mapping, wbc);
@@ -180,10 +170,7 @@ __sync_single_inode(struct inode *inode, struct writeback_control *wbc)
 	spin_lock(&inode_lock);
 	inode->i_state &= ~I_LOCK;
 	if (!(inode->i_state & I_FREEING)) {
-		if (!list_empty(&mapping->io_pages)) {
-		 	/* Needs more writeback */
-			inode->i_state |= I_DIRTY_PAGES;
-		} else if (!list_empty(&mapping->dirty_pages)) {
+		if (mapping_tagged(mapping, PAGECACHE_TAG_DIRTY)) {
 			/* Redirtied */
 			inode->i_state |= I_DIRTY_PAGES;
 			inode->dirtied_when = jiffies;

fs/inode.c

@@ -179,7 +179,6 @@ void inode_init_once(struct inode *inode)
 	memset(inode, 0, sizeof(*inode));
 	INIT_HLIST_NODE(&inode->i_hash);
 	INIT_LIST_HEAD(&inode->i_data.clean_pages);
-	INIT_LIST_HEAD(&inode->i_data.dirty_pages);
 	INIT_LIST_HEAD(&inode->i_data.locked_pages);
 	INIT_LIST_HEAD(&inode->i_data.io_pages);
 	INIT_LIST_HEAD(&inode->i_dentry);

fs/mpage.c

@@ -592,28 +592,12 @@ mpage_writepage(struct bio *bio, struct page *page, get_block_t get_block,
  * (The next two paragraphs refer to code which isn't here yet, but they
  *  explain the presence of address_space.io_pages)
  *
- * Pages can be moved from clean_pages or locked_pages onto dirty_pages
- * at any time - it's not possible to lock against that.  So pages which
- * have already been added to a BIO may magically reappear on the dirty_pages
- * list.  And mpage_writepages() will again try to lock those pages.
- * But I/O has not yet been started against the page.  Thus deadlock.
- *
- * To avoid this, mpage_writepages() will only write pages from io_pages. The
- * caller must place them there.  We walk io_pages, locking the pages and
- * submitting them for I/O, moving them to locked_pages.
- *
- * This has the added benefit of preventing a livelock which would otherwise
- * occur if pages are being dirtied faster than we can write them out.
- *
  * If a page is already under I/O, generic_writepages() skips it, even
  * if it's dirty.  This is desirable behaviour for memory-cleaning writeback,
  * but it is INCORRECT for data-integrity system calls such as fsync().  fsync()
  * and msync() need to guarantee that all the data which was dirty at the time
  * the call was made get new I/O started against them.  So if called_for_sync()
  * is true, we must wait for existing IO to complete.
- *
- * It's fairly rare for PageWriteback pages to be on ->dirty_pages.  It
- * means that someone redirtied the page while it was under I/O.
  */
 int
 mpage_writepages(struct address_space *mapping,
@@ -625,6 +609,9 @@ mpage_writepages(struct address_space *mapping,
 	int ret = 0;
 	int done = 0;
 	int (*writepage)(struct page *page, struct writeback_control *wbc);
+	struct pagevec pvec;
+	int nr_pages;
+	pgoff_t index;
 
 	if (wbc->nonblocking && bdi_write_congested(bdi)) {
 		wbc->encountered_congestion = 1;
@@ -635,33 +622,21 @@ mpage_writepages(struct address_space *mapping,
 	if (get_block == NULL)
 		writepage = mapping->a_ops->writepage;
 
-	spin_lock_irq(&mapping->tree_lock);
-	while (!list_empty(&mapping->io_pages) && !done) {
-		struct page *page = list_entry(mapping->io_pages.prev,
-					struct page, list);
-		list_del(&page->list);
-		if (PageWriteback(page) && wbc->sync_mode == WB_SYNC_NONE) {
-			if (PageDirty(page)) {
-				list_add(&page->list, &mapping->dirty_pages);
-				continue;
-			}
-			list_add(&page->list, &mapping->locked_pages);
-			continue;
-		}
-		if (!PageDirty(page)) {
-			list_add(&page->list, &mapping->clean_pages);
-			continue;
-		}
-		list_add(&page->list, &mapping->locked_pages);
+	pagevec_init(&pvec, 0);
+	index = 0;
+	while (!done && (nr_pages = pagevec_lookup_tag(&pvec, mapping, &index,
+					PAGECACHE_TAG_DIRTY, PAGEVEC_SIZE))) {
+		unsigned i;
 
-		page_cache_get(page);
-		spin_unlock_irq(&mapping->tree_lock);
+		for (i = 0; i < nr_pages; i++) {
+			struct page *page = pvec.pages[i];
 
 			/*
 			 * At this point we hold neither mapping->tree_lock nor
 			 * lock on the page itself: the page may be truncated or
 			 * invalidated (changing page->mapping to NULL), or even
-		 * swizzled back from swapper_space to tmpfs file mapping.
+			 * swizzled back from swapper_space to tmpfs file
+			 * mapping
 			 */
 
 			lock_page(page);
@@ -682,25 +657,23 @@ mpage_writepages(struct address_space *mapping,
 							  &mapping->flags);
 					}
 				} else {
-				bio = mpage_writepage(bio, page, get_block,
-					&last_block_in_bio, &ret, wbc);
+					bio = mpage_writepage(bio, page,
+						get_block, &last_block_in_bio,
+						&ret, wbc);
 				}
 				if (ret || (--(wbc->nr_to_write) <= 0))
 					done = 1;
-			if (wbc->nonblocking && bdi_write_congested(bdi)) {
+				if (wbc->nonblocking &&
+						bdi_write_congested(bdi)) {
 					wbc->encountered_congestion = 1;
 					done = 1;
 				}
 			} else {
 				unlock_page(page);
 			}
-		page_cache_release(page);
-		spin_lock_irq(&mapping->tree_lock);
 		}
-	/*
-	 * Leave any remaining dirty pages on ->io_pages
-	 */
-	spin_unlock_irq(&mapping->tree_lock);
+		pagevec_release(&pvec);
+	}
 	if (bio)
 		mpage_bio_submit(WRITE, bio);
 	return ret;

fs/xfs/linux/xfs_vnode.h

@@ -600,7 +600,8 @@ static __inline__ void vn_flagclr(struct vnode *vp, uint flag)
 	(!list_empty(&(LINVFS_GET_IP(vp)->i_mapping->i_mmap)) || \
 	(!list_empty(&(LINVFS_GET_IP(vp)->i_mapping->i_mmap_shared))))
 #define VN_CACHED(vp)	(LINVFS_GET_IP(vp)->i_mapping->nrpages)
-#define VN_DIRTY(vp)	(!list_empty(&(LINVFS_GET_IP(vp)->i_mapping->dirty_pages)))
+#define VN_DIRTY(vp)	mapping_tagged(LINVFS_GET_IP(vp)->i_mapping, \
+					PAGECACHE_TAG_DIRTY)
 #define VMODIFY(vp)	VN_FLAGSET(vp, VMODIFIED)
 #define VUNMODIFY(vp)	VN_FLAGCLR(vp, VMODIFIED)
 

include/linux/fs.h

@@ -324,7 +324,6 @@ struct address_space {
 	struct radix_tree_root	page_tree;	/* radix tree of all pages */
 	spinlock_t		tree_lock;	/* and spinlock protecting it */
 	struct list_head	clean_pages;	/* list of clean pages */
-	struct list_head	dirty_pages;	/* list of dirty pages */
 	struct list_head	locked_pages;	/* list of locked pages */
 	struct list_head	io_pages;	/* being prepared for I/O */
 	unsigned long		nrpages;	/* number of total pages */
@@ -371,6 +370,8 @@ struct block_device {
 #define PAGECACHE_TAG_DIRTY	0
 #define PAGECACHE_TAG_WRITEBACK	1
 
+int mapping_tagged(struct address_space *mapping, int tag);
+
 /*
  * Use sequence counter to get consistent i_size on 32-bit processors.
  */

include/linux/pagemap.h

@@ -69,9 +69,10 @@ extern struct page * find_trylock_page(struct address_space *mapping,
 				unsigned long index);
 extern struct page * find_or_create_page(struct address_space *mapping,
 				unsigned long index, unsigned int gfp_mask);
-extern unsigned int find_get_pages(struct address_space *mapping,
-				pgoff_t start, unsigned int nr_pages,
-				struct page **pages);
+unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
+			unsigned int nr_pages, struct page **pages);
+unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
+			int tag, unsigned int nr_pages, struct page **pages);
 
 /*
  * Returns locked page at given index in given cache, creating it if needed.

include/linux/pagevec.h

@@ -22,8 +22,11 @@ void __pagevec_free(struct pagevec *pvec);
 void __pagevec_lru_add(struct pagevec *pvec);
 void __pagevec_lru_add_active(struct pagevec *pvec);
 void pagevec_strip(struct pagevec *pvec);
-unsigned int pagevec_lookup(struct pagevec *pvec, struct address_space *mapping,
-		pgoff_t start, unsigned int nr_pages);
+unsigned pagevec_lookup(struct pagevec *pvec, struct address_space *mapping,
+		pgoff_t start, unsigned nr_pages);
+unsigned pagevec_lookup_tag(struct pagevec *pvec,
+		struct address_space *mapping, pgoff_t *index, int tag,
+		unsigned nr_pages);
 
 static inline void pagevec_init(struct pagevec *pvec, int cold)
 {

mm/filemap.c

@@ -100,9 +100,7 @@ void __remove_from_page_cache(struct page *page)
 	struct address_space *mapping = page->mapping;
 
 	radix_tree_delete(&mapping->page_tree, page->index);
-	list_del(&page->list);
 	page->mapping = NULL;
-
 	mapping->nrpages--;
 	pagecache_acct(-1);
 }
@@ -148,9 +146,6 @@ static int __filemap_fdatawrite(struct address_space *mapping, int sync_mode)
 	if (mapping->backing_dev_info->memory_backed)
 		return 0;
 
-	spin_lock_irq(&mapping->tree_lock);
-	list_splice_init(&mapping->dirty_pages, &mapping->io_pages);
-	spin_unlock_irq(&mapping->tree_lock);
 	ret = do_writepages(mapping, &wbc);
 	return ret;
 }
@@ -190,11 +185,7 @@ int filemap_fdatawait(struct address_space * mapping)
 		struct page *page;
 
 		page = list_entry(mapping->locked_pages.next,struct page,list);
-		list_del(&page->list);
-		if (PageDirty(page))
-			list_add(&page->list, &mapping->dirty_pages);
-		else
-			list_add(&page->list, &mapping->clean_pages);
+		list_del_init(&page->list);
 
 		if (!PageWriteback(page)) {
 			if (++progress > 32) {
@@ -228,7 +219,6 @@ int filemap_fdatawait(struct address_space * mapping)
 
 	return ret;
 }
-
 EXPORT_SYMBOL(filemap_fdatawait);
 
 int filemap_write_and_wait(struct address_space *mapping)
@@ -539,7 +529,7 @@ EXPORT_SYMBOL(find_or_create_page);
  *
  * find_get_pages() returns the number of pages which were found.
  */
-unsigned int find_get_pages(struct address_space *mapping, pgoff_t start,
+unsigned find_get_pages(struct address_space *mapping, pgoff_t start,
 			    unsigned int nr_pages, struct page **pages)
 {
 	unsigned int i;
@@ -554,6 +544,27 @@ unsigned int find_get_pages(struct address_space *mapping, pgoff_t start,
 	return ret;
 }
 
+/*
+ * Like find_get_pages, except we only return pages which are tagged with
+ * `tag'.   We update *start to index the next page for the traversal.
+ */
+unsigned find_get_pages_tag(struct address_space *mapping, pgoff_t *index,
+			int tag, unsigned int nr_pages, struct page **pages)
+{
+	unsigned int i;
+	unsigned int ret;
+
+	spin_lock_irq(&mapping->tree_lock);
+	ret = radix_tree_gang_lookup_tag(&mapping->page_tree,
+				(void **)pages, *index, nr_pages, tag);
+	for (i = 0; i < ret; i++)
+		page_cache_get(pages[i]);
+	if (ret)
+		*index = pages[ret - 1]->index + 1;
+	spin_unlock_irq(&mapping->tree_lock);
+	return ret;
+}
+
 /*
  * Same as grab_cache_page, but do not wait if the page is unavailable.
  * This is intended for speculative data generators, where the data can

mm/page-writeback.c

@@ -472,12 +472,8 @@ int write_one_page(struct page *page, int wait)
 	if (wait)
 		wait_on_page_writeback(page);
 
-	spin_lock_irq(&mapping->tree_lock);
-	list_del(&page->list);
 	if (test_clear_page_dirty(page)) {
-		list_add(&page->list, &mapping->locked_pages);
 		page_cache_get(page);
-		spin_unlock_irq(&mapping->tree_lock);
 		ret = mapping->a_ops->writepage(page, &wbc);
 		if (ret == 0 && wait) {
 			wait_on_page_writeback(page);
@@ -486,8 +482,6 @@ int write_one_page(struct page *page, int wait)
 		}
 		page_cache_release(page);
 	} else {
-		list_add(&page->list, &mapping->clean_pages);
-		spin_unlock_irq(&mapping->tree_lock);
 		unlock_page(page);
 	}
 	return ret;
@@ -495,9 +489,8 @@ int write_one_page(struct page *page, int wait)
 EXPORT_SYMBOL(write_one_page);
 
 /*
- * For address_spaces which do not use buffers.  Just set the page's dirty bit
- * and move it to the dirty_pages list.  Also perform space reservation if
- * required.
+ * For address_spaces which do not use buffers.  Just tag the page as dirty in
+ * its radix tree.
  *
  * __set_page_dirty_nobuffers() may return -ENOSPC.  But if it does, the page
  * is still safe, as long as it actually manages to find some blocks at
@@ -520,8 +513,6 @@ int __set_page_dirty_nobuffers(struct page *page)
 				BUG_ON(page->mapping != mapping);
 				if (!mapping->backing_dev_info->memory_backed)
 					inc_page_state(nr_dirty);
-				list_del(&page->list);
-				list_add(&page->list, &mapping->dirty_pages);
 				radix_tree_tag_set(&mapping->page_tree,
 					page->index, PAGECACHE_TAG_DIRTY);
 			}
@@ -646,3 +637,19 @@ int test_set_page_writeback(struct page *page)
 
 }
 EXPORT_SYMBOL(test_set_page_writeback);
+
+/*
+ * Return true if any of the pages in the mapping are marged with the
+ * passed tag.
+ */
+int mapping_tagged(struct address_space *mapping, int tag)
+{
+	unsigned long flags;
+	int ret;
+
+	spin_lock_irqsave(&mapping->tree_lock, flags);
+	ret = radix_tree_tagged(&mapping->page_tree, tag);
+	spin_unlock_irqrestore(&mapping->tree_lock, flags);
+	return ret;
+}
+EXPORT_SYMBOL(mapping_tagged);

mm/page_alloc.c

@@ -682,6 +682,8 @@ __alloc_pages(unsigned int gfp_mask, unsigned int order,
 	return NULL;
 got_pg:
 	kernel_map_pages(page, 1 << order, 1);
+	INIT_LIST_HEAD(&page->list);
+	INIT_LIST_HEAD(&page->lru);
 	return page;
 }
 

mm/swap.c

@@ -353,13 +353,21 @@ void pagevec_strip(struct pagevec *pvec)
  *
  * pagevec_lookup() returns the number of pages which were found.
  */
-unsigned int pagevec_lookup(struct pagevec *pvec, struct address_space *mapping,
-		pgoff_t start, unsigned int nr_pages)
+unsigned pagevec_lookup(struct pagevec *pvec, struct address_space *mapping,
+		pgoff_t start, unsigned nr_pages)
 {
 	pvec->nr = find_get_pages(mapping, start, nr_pages, pvec->pages);
 	return pagevec_count(pvec);
 }
 
+unsigned pagevec_lookup_tag(struct pagevec *pvec, struct address_space *mapping,
+		pgoff_t *index, int tag, unsigned nr_pages)
+{
+	pvec->nr = find_get_pages_tag(mapping, index, tag,
+					nr_pages, pvec->pages);
+	return pagevec_count(pvec);
+}
+
 
 #ifdef CONFIG_SMP
 /*

mm/swap_state.c

@@ -27,7 +27,6 @@ struct address_space swapper_space = {
 	.page_tree	= RADIX_TREE_INIT(GFP_ATOMIC),
 	.tree_lock	= SPIN_LOCK_UNLOCKED,
 	.clean_pages	= LIST_HEAD_INIT(swapper_space.clean_pages),
-	.dirty_pages	= LIST_HEAD_INIT(swapper_space.dirty_pages),
 	.io_pages	= LIST_HEAD_INIT(swapper_space.io_pages),
 	.locked_pages	= LIST_HEAD_INIT(swapper_space.locked_pages),
 	.a_ops		= &swap_aops,
@@ -210,7 +209,6 @@ int move_to_swap_cache(struct page *page, swp_entry_t entry)
 	if (!err) {
 		if (!swap_duplicate(entry))
 			BUG();
-		/* shift page from clean_pages to dirty_pages list */
 		BUG_ON(PageDirty(page));
 		set_page_dirty(page);
 		INC_CACHE_INFO(add_total);
@@ -245,7 +243,6 @@ int move_from_swap_cache(struct page *page, unsigned long index,
 
 	if (!err) {
 		swap_free(entry);
-		/* shift page from clean_pages to dirty_pages list */
 		__clear_page_dirty(page);
 		set_page_dirty(page);
 	}