f2fs: remove inmem radix tree

Previously, we use radix tree to index all registered page entries for
atomic file, but now we only use radix tree to see whether current page
is indexed or not, since the other user of radix tree is gone in commit
042b7816aaeb ("f2fs: remove unnecessary call to invalidate inmemory pages").

So in this patch, we try to use one more efficient way:
Introducing a macro ATOMIC_WRITTEN_PAGE, and setting it as page private
value to indicate page indexing status. By using this way, we can save
memory and lookup time.

Signed-off-by: Chao Yu <chao2.yu@samsung.com>
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>

fs/f2fs/data.c

@@ -1558,6 +1558,11 @@ void f2fs_invalidate_page(struct page *page, unsigned int offset,
 		else
 			inode_dec_dirty_pages(inode);
 	}
+
+	/* This is atomic written page, keep Private */
+	if (IS_ATOMIC_WRITTEN_PAGE(page))
+		return;
+
 	ClearPagePrivate(page);
 }
 
@@ -1567,6 +1572,10 @@ int f2fs_release_page(struct page *page, gfp_t wait)
 	if (PageDirty(page))
 		return 0;
 
+	/* This is atomic written page, keep Private */
+	if (IS_ATOMIC_WRITTEN_PAGE(page))
+		return 0;
+
 	ClearPagePrivate(page);
 	return 1;
 }
@@ -1581,8 +1590,15 @@ static int f2fs_set_data_page_dirty(struct page *page)
 	SetPageUptodate(page);
 
 	if (f2fs_is_atomic_file(inode)) {
-		register_inmem_page(inode, page);
-		return 1;
+		if (!IS_ATOMIC_WRITTEN_PAGE(page)) {
+			register_inmem_page(inode, page);
+			return 1;
+		}
+		/*
+		 * Previously, this page has been registered, we just
+		 * return here.
+		 */
+		return 0;
 	}
 
 	if (!PageDirty(page)) {

fs/f2fs/f2fs.h

@@ -424,7 +424,6 @@ struct f2fs_inode_info {
 	unsigned long long xattr_ver;	/* cp version of xattr modification */
 	struct inode_entry *dirty_dir;	/* the pointer of dirty dir */
 
-	struct radix_tree_root inmem_root;	/* radix tree for inmem pages */
 	struct list_head inmem_pages;	/* inmemory pages managed by f2fs */
 	struct mutex inmem_lock;	/* lock for inmemory pages */
 

fs/f2fs/segment.c

@@ -197,28 +197,20 @@ void register_inmem_page(struct inode *inode, struct page *page)
 {
 	struct f2fs_inode_info *fi = F2FS_I(inode);
 	struct inmem_pages *new;
-	int err;
 
-	SetPagePrivate(page);
 	f2fs_trace_pid(page);
 
+	set_page_private(page, (unsigned long)ATOMIC_WRITTEN_PAGE);
+	SetPagePrivate(page);
+
 	new = f2fs_kmem_cache_alloc(inmem_entry_slab, GFP_NOFS);
 
 	/* add atomic page indices to the list */
 	new->page = page;
 	INIT_LIST_HEAD(&new->list);
-retry:
+
 	/* increase reference count with clean state */
 	mutex_lock(&fi->inmem_lock);
-	err = radix_tree_insert(&fi->inmem_root, page->index, new);
-	if (err == -EEXIST) {
-		mutex_unlock(&fi->inmem_lock);
-		kmem_cache_free(inmem_entry_slab, new);
-		return;
-	} else if (err) {
-		mutex_unlock(&fi->inmem_lock);
-		goto retry;
-	}
 	get_page(page);
 	list_add_tail(&new->list, &fi->inmem_pages);
 	inc_page_count(F2FS_I_SB(inode), F2FS_INMEM_PAGES);
@@ -255,8 +247,8 @@ int commit_inmem_pages(struct inode *inode, bool abort)
 
 	mutex_lock(&fi->inmem_lock);
 	list_for_each_entry_safe(cur, tmp, &fi->inmem_pages, list) {
+		lock_page(cur->page);
 		if (!abort) {
-			lock_page(cur->page);
 			if (cur->page->mapping == inode->i_mapping) {
 				set_page_dirty(cur->page);
 				f2fs_wait_on_page_writeback(cur->page, DATA);
@@ -271,12 +263,13 @@ int commit_inmem_pages(struct inode *inode, bool abort)
 					break;
 				}
 			}
-			f2fs_put_page(cur->page, 1);
 		} else {
 			trace_f2fs_commit_inmem_page(cur->page, INMEM_DROP);
-			put_page(cur->page);
 		}
-		radix_tree_delete(&fi->inmem_root, cur->page->index);
+		set_page_private(cur->page, 0);
+		ClearPagePrivate(cur->page);
+		f2fs_put_page(cur->page, 1);
+
 		list_del(&cur->list);
 		kmem_cache_free(inmem_entry_slab, cur);
 		dec_page_count(F2FS_I_SB(inode), F2FS_INMEM_PAGES);

fs/f2fs/segment.h

@@ -177,6 +177,15 @@ struct segment_allocation {
 	void (*allocate_segment)(struct f2fs_sb_info *, int, bool);
 };
 
+/*
+ * this value is set in page as a private data which indicate that
+ * the page is atomically written, and it is in inmem_pages list.
+ */
+#define ATOMIC_WRITTEN_PAGE		0x0000ffff
+
+#define IS_ATOMIC_WRITTEN_PAGE(page)			\
+		(page_private(page) == (unsigned long)ATOMIC_WRITTEN_PAGE)
+
 struct inmem_pages {
 	struct list_head list;
 	struct page *page;

fs/f2fs/super.c

@@ -423,7 +423,6 @@ static struct inode *f2fs_alloc_inode(struct super_block *sb)
 	fi->i_current_depth = 1;
 	fi->i_advise = 0;
 	init_rwsem(&fi->i_sem);
-	INIT_RADIX_TREE(&fi->inmem_root, GFP_NOFS);
 	INIT_LIST_HEAD(&fi->inmem_pages);
 	mutex_init(&fi->inmem_lock);