From mboxrd@z Thu Jan 1 00:00:00 1970 Date: Sat, 22 Sep 2007 00:06:55 +0900 From: KAMEZAWA Hiroyuki Subject: Re: [RFC][PATCH] page->mapping clarification [1/3] base functions Message-Id: <20070922000655.6ab383bf.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20070921134828.45ca967e@twins> References: <20070919164308.281f9960.kamezawa.hiroyu@jp.fujitsu.com> <20070921134828.45ca967e@twins> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org Return-Path: To: Peter Zijlstra Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, akpm@linux-foundation.org, nickpiggin@yahoo.com.au, ricknu-0@student.ltu.se List-ID: On Fri, 21 Sep 2007 13:48:28 +0200 Peter Zijlstra wrote: > > Followings are moved > > * page_mapping() ... returns swapper_space or address_space a page is on. > > (from mm.h) > > * page_index() ... returns position of a page in its inode > > (from mm.h) > > * remove_mapping() ... a safe routine to remove page->mapping from page. > > (from swap.h) > > I have two other functions that might want integration with this scheme: > > page_file_mapping() ... returns backing address space > page_file_index() ... returns the index therein > > They are identical to page_mapping_cache() and page_index() for > page cache pages, but they also work on swap cache pages. > > That is, for swapcache pages they return: > > page_file_mapping: > page_swap_info(page)->swap_file->f_mapping > > page_file_index: > swp_offset((swp_offset_t)page_private(page)) > > When a filesystem uses these functions instead of page->mapping and > page->index, it allows passing swap cache pages into the regular > filesystem read/write paths. > Oh, > This is useful for things like swap over NFS, where swap is backed by a > swapfile on a 'regular' filesystem. > Okay, I'll try to add them in the next set. Thanks, -Kame -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org