Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755891AbcKKFaN (ORCPT ); Fri, 11 Nov 2016 00:30:13 -0500 Received: from LGEAMRELO11.lge.com ([156.147.23.51]:34064 "EHLO lgeamrelo11.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754823AbcKKFaL (ORCPT ); Fri, 11 Nov 2016 00:30:11 -0500 X-Original-SENDERIP: 156.147.1.125 X-Original-MAILFROM: minchan@kernel.org X-Original-SENDERIP: 10.177.223.161 X-Original-MAILFROM: minchan@kernel.org From: Minchan Kim To: Andrew Morton Cc: Hyeoncheol Lee , yjay.kim@lge.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, Minchan Kim , Hugh Dickins , "Darrick J . Wong" Subject: [PATCH] mm: support anonymous stable page Date: Fri, 11 Nov 2016 14:30:02 +0900 Message-Id: <1478842202-24009-1-git-send-email-minchan@kernel.org> X-Mailer: git-send-email 2.7.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2041 Lines: 61 For developemnt for zram-swap asynchronous writeback, I found strange corruption of compressed page. With investigation, it reveals currently stable page doesn't support anonymous page. IOW, reuse_swap_page can reuse the page without waiting writeback completion so that it can corrupt data during zram compression. It can affect every swap device which supports asynchronous writeback and CRC checking as well as zRAM. Unfortunately, reuse_swap_page should be atomic so that we cannot wait on writeback in there so the approach in this patch is simply return false if we found it needs stable page. Although it increases memory footprint temporarily, it happens rarely and it should be reclaimed easily althoug it happened. Also, It would be better than waiting of IO completion, which is critial path for application latency. Cc: Hugh Dickins Cc: Darrick J. Wong Signed-off-by: Minchan Kim --- mm/swapfile.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-) diff --git a/mm/swapfile.c b/mm/swapfile.c index 816ca8663ae5..ea591435d8e0 100644 --- a/mm/swapfile.c +++ b/mm/swapfile.c @@ -949,7 +949,12 @@ bool reuse_swap_page(struct page *page, int *total_mapcount) delete_from_swap_cache(page); SetPageDirty(page); } else { - wait_for_stable_page(page); + struct address_space *mapping; + + mapping = page_mapping(page); + if (bdi_cap_stable_pages_required( + inode_to_bdi(mapping->host))) + return false; } } out: @@ -2185,6 +2190,7 @@ static struct swap_info_struct *alloc_swap_info(void) static int claim_swapfile(struct swap_info_struct *p, struct inode *inode) { int error; + struct address_space *swapper_space; if (S_ISBLK(inode->i_mode)) { p->bdev = bdgrab(I_BDEV(inode)); @@ -2207,6 +2213,9 @@ static int claim_swapfile(struct swap_info_struct *p, struct inode *inode) } else return -EINVAL; + swapper_space = &swapper_spaces[p->type]; + swapper_space->host = inode; + return 0; } -- 2.7.4