Merge branch 'xarray' of git://git.infradead.org/users/willy/linux-dax

Pull XArray conversion from Matthew Wilcox:
 "The XArray provides an improved interface to the radix tree data
  structure, providing locking as part of the API, specifying GFP flags
  at allocation time, eliminating preloading, less re-walking the tree,
  more efficient iterations and not exposing RCU-protected pointers to
  its users.

  This patch set

   1. Introduces the XArray implementation

   2. Converts the pagecache to use it

   3. Converts memremap to use it

  The page cache is the most complex and important user of the radix
  tree, so converting it was most important. Converting the memremap
  code removes the only other user of the multiorder code, which allows
  us to remove the radix tree code that supported it.

  I have 40+ followup patches to convert many other users of the radix
  tree over to the XArray, but I'd like to get this part in first. The
  other conversions haven't been in linux-next and aren't suitable for
  applying yet, but you can see them in the xarray-conv branch if you're
  interested"

* 'xarray' of git://git.infradead.org/users/willy/linux-dax: (90 commits)
  radix tree: Remove multiorder support
  radix tree test: Convert multiorder tests to XArray
  radix tree tests: Convert item_delete_rcu to XArray
  radix tree tests: Convert item_kill_tree to XArray
  radix tree tests: Move item_insert_order
  radix tree test suite: Remove multiorder benchmarking
  radix tree test suite: Remove __item_insert
  memremap: Convert to XArray
  xarray: Add range store functionality
  xarray: Move multiorder_check to in-kernel tests
  xarray: Move multiorder_shrink to kernel tests
  xarray: Move multiorder account test in-kernel
  radix tree test suite: Convert iteration test to XArray
  radix tree test suite: Convert tag_tagged_items to XArray
  radix tree: Remove radix_tree_clear_tags
  radix tree: Remove radix_tree_maybe_preload_order
  radix tree: Remove split/join code
  radix tree: Remove radix_tree_update_node_t
  page cache: Finish XArray conversion
  dax: Convert page fault handlers to XArray
  ...

1 files changed, 41 insertions, 22 deletions

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 897eae8faee1..771341470bce 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -403,24 +403,40 @@ int pagecache_write_end(struct file *, struct address_space *mapping,
 				loff_t pos, unsigned len, unsigned copied,
 				struct page *page, void *fsdata);
 
+/**
+ * struct address_space - Contents of a cacheable, mappable object.
+ * @host: Owner, either the inode or the block_device.
+ * @i_pages: Cached pages.
+ * @gfp_mask: Memory allocation flags to use for allocating pages.
+ * @i_mmap_writable: Number of VM_SHARED mappings.
+ * @i_mmap: Tree of private and shared mappings.
+ * @i_mmap_rwsem: Protects @i_mmap and @i_mmap_writable.
+ * @nrpages: Number of page entries, protected by the i_pages lock.
+ * @nrexceptional: Shadow or DAX entries, protected by the i_pages lock.
+ * @writeback_index: Writeback starts here.
+ * @a_ops: Methods.
+ * @flags: Error bits and flags (AS_*).
+ * @wb_err: The most recent error which has occurred.
+ * @private_lock: For use by the owner of the address_space.
+ * @private_list: For use by the owner of the address_space.
+ * @private_data: For use by the owner of the address_space.
+ */
 struct address_space {
-	struct inode		*host;		/* owner: inode, block_device */
-	struct radix_tree_root	i_pages;	/* cached pages */
-	atomic_t		i_mmap_writable;/* count VM_SHARED mappings */
-	struct rb_root_cached	i_mmap;		/* tree of private and shared mappings */
-	struct rw_semaphore	i_mmap_rwsem;	/* protect tree, count, list */
-	/* Protected by the i_pages lock */
-	unsigned long		nrpages;	/* number of total pages */
-	/* number of shadow or DAX exceptional entries */
+	struct inode		*host;
+	struct xarray		i_pages;
+	gfp_t			gfp_mask;
+	atomic_t		i_mmap_writable;
+	struct rb_root_cached	i_mmap;
+	struct rw_semaphore	i_mmap_rwsem;
+	unsigned long		nrpages;
 	unsigned long		nrexceptional;
-	pgoff_t			writeback_index;/* writeback starts here */
-	const struct address_space_operations *a_ops;	/* methods */
-	unsigned long		flags;		/* error bits */
-	spinlock_t		private_lock;	/* for use by the address_space */
-	gfp_t			gfp_mask;	/* implicit gfp mask for allocations */
-	struct list_head	private_list;	/* for use by the address_space */
-	void			*private_data;	/* ditto */
+	pgoff_t			writeback_index;
+	const struct address_space_operations *a_ops;
+	unsigned long		flags;
 	errseq_t		wb_err;
+	spinlock_t		private_lock;
+	struct list_head	private_list;
+	void			*private_data;
 } __attribute__((aligned(sizeof(long)))) __randomize_layout;
 	/*
 	 * On most architectures that alignment is already the case; but
@@ -467,15 +483,18 @@ struct block_device {
 	struct mutex		bd_fsfreeze_mutex;
 } __randomize_layout;
 
+/* XArray tags, for tagging dirty and writeback pages in the pagecache. */
+#define PAGECACHE_TAG_DIRTY	XA_MARK_0
+#define PAGECACHE_TAG_WRITEBACK	XA_MARK_1
+#define PAGECACHE_TAG_TOWRITE	XA_MARK_2
+
 /*
- * Radix-tree tags, for tagging dirty and writeback pages within the pagecache
- * radix trees
+ * Returns true if any of the pages in the mapping are marked with the tag.
  */
-#define PAGECACHE_TAG_DIRTY	0
-#define PAGECACHE_TAG_WRITEBACK	1
-#define PAGECACHE_TAG_TOWRITE	2
-
-int mapping_tagged(struct address_space *mapping, int tag);
+static inline bool mapping_tagged(struct address_space *mapping, xa_mark_t tag)
+{
+	return xa_marked(&mapping->i_pages, tag);
+}
 
 static inline void i_mmap_lock_write(struct address_space *mapping)
 {