page cache: use xa_lock

Remove the address_space ->tree_lock and use the xa_lock newly added to
the radix_tree_root.  Rename the address_space ->page_tree to ->i_pages,
since we don't really care that it's a tree.

[willy@infradead.org: fix nds32, fs/dax.c]
  Link: http://lkml.kernel.org/r/20180406145415.GB20605@bombadil.infradead.orgLink: http://lkml.kernel.org/r/20180313132639.17387-9-willy@infradead.org
Signed-off-by: Matthew Wilcox <mawilcox@microsoft.com>
Acked-by: Jeff Layton <jlayton@redhat.com>
Cc: Darrick J. Wong <darrick.wong@oracle.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Ryusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/fs/nilfs2/page.c b/fs/nilfs2/page.c
index 6824151..4cb850a 100644
--- a/fs/nilfs2/page.c
+++ b/fs/nilfs2/page.c
@@ -331,15 +331,15 @@ void nilfs_copy_back_pages(struct address_space *dmap,
 			struct page *page2;
 
 			/* move the page to the destination cache */
-			spin_lock_irq(&smap->tree_lock);
-			page2 = radix_tree_delete(&smap->page_tree, offset);
+			xa_lock_irq(&smap->i_pages);
+			page2 = radix_tree_delete(&smap->i_pages, offset);
 			WARN_ON(page2 != page);
 
 			smap->nrpages--;
-			spin_unlock_irq(&smap->tree_lock);
+			xa_unlock_irq(&smap->i_pages);
 
-			spin_lock_irq(&dmap->tree_lock);
-			err = radix_tree_insert(&dmap->page_tree, offset, page);
+			xa_lock_irq(&dmap->i_pages);
+			err = radix_tree_insert(&dmap->i_pages, offset, page);
 			if (unlikely(err < 0)) {
 				WARN_ON(err == -EEXIST);
 				page->mapping = NULL;
@@ -348,11 +348,11 @@ void nilfs_copy_back_pages(struct address_space *dmap,
 				page->mapping = dmap;
 				dmap->nrpages++;
 				if (PageDirty(page))
-					radix_tree_tag_set(&dmap->page_tree,
+					radix_tree_tag_set(&dmap->i_pages,
 							   offset,
 							   PAGECACHE_TAG_DIRTY);
 			}
-			spin_unlock_irq(&dmap->tree_lock);
+			xa_unlock_irq(&dmap->i_pages);
 		}
 		unlock_page(page);
 	}
@@ -474,15 +474,15 @@ int __nilfs_clear_page_dirty(struct page *page)
 	struct address_space *mapping = page->mapping;
 
 	if (mapping) {
-		spin_lock_irq(&mapping->tree_lock);
+		xa_lock_irq(&mapping->i_pages);
 		if (test_bit(PG_dirty, &page->flags)) {
-			radix_tree_tag_clear(&mapping->page_tree,
+			radix_tree_tag_clear(&mapping->i_pages,
 					     page_index(page),
 					     PAGECACHE_TAG_DIRTY);
-			spin_unlock_irq(&mapping->tree_lock);
+			xa_unlock_irq(&mapping->i_pages);
 			return clear_page_dirty_for_io(page);
 		}
-		spin_unlock_irq(&mapping->tree_lock);
+		xa_unlock_irq(&mapping->i_pages);
 		return 0;
 	}
 	return TestClearPageDirty(page);