page cache: Rearrange address_space

Change i_pages from a radix_tree_root to an xarray, convert the
documentation into kernel-doc format and change the order of the elements
to pack them better on 64-bit systems.

Signed-off-by: Matthew Wilcox <willy@infradead.org>

1 files changed, 31 insertions, 15 deletions

diff --git a/include/linux/fs.h b/include/linux/fs.h
index 6c0b4a1c22ff..d126cad0f621 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