fs: Convert buffer to XArray

EXPORT_SYMBOL(mark_buffer_dirty_inode);

/*

 * Mark the page dirty, and set it dirty in the radix tree, and mark the inode

 * Mark the page dirty, and set it dirty in the page cache, and mark the inode

 * dirty.

 *

 * If warn is true, then emit a warning if the page is not uptodate and has

	if (page->mapping) {	/* Race with truncate? */

		WARN_ON_ONCE(warn && !PageUptodate(page));

		account_page_dirtied(page, mapping);

		radix_tree_tag_set(&mapping->i_pages,

				page_index(page), PAGECACHE_TAG_DIRTY);

		__xa_set_mark(&mapping->i_pages, page_index(page),

				PAGECACHE_TAG_DIRTY);

	}

	xa_unlock_irqrestore(&mapping->i_pages, flags);

}

 * 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 is tagged dirty in its radix tree.

 * the page is tagged dirty in the page cache.

 *

 * 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

 * mark_buffer_dirty - mark a buffer_head as needing writeout

 * @bh: the buffer_head to mark dirty

 *

 * 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

 * mark_buffer_dirty() will set the dirty bit against the buffer, then set

 * its backing page dirty, then tag the page as dirty in the page cache

 * 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,