From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751642Ab3A2HTt (ORCPT ); Tue, 29 Jan 2013 02:19:49 -0500 Received: from mail-lb0-f178.google.com ([209.85.217.178]:64492 "EHLO mail-lb0-f178.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750853Ab3A2HTr (ORCPT ); Tue, 29 Jan 2013 02:19:47 -0500 Date: Tue, 29 Jan 2013 09:11:08 +0200 From: Pekka Enberg To: Minchan Kim Cc: Greg Kroah-Hartman , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Dan Magenheimer , Nitin Gupta , Konrad Rzeszutek Wilk , Seth Jennings , stable@vger.kernel.org, Jerome Marchand Message-ID: <5107760ca0614_5bf811b9fe4132b@golgotha.mail> In-Reply-To: <20130128232145.GA2666@blaptop> References: <1359333506-13599-1-git-send-email-minchan@kernel.org> <20130128232145.GA2666@blaptop> Subject: Re: [RESEND PATCH v5 1/4] zram: Fix deadlock bug in partial write Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Jan 29, 2013 at 1:21 AM, Minchan Kim wrote: > How about this? > ------------------------- >8 ------------------------------- > > From 9f8756ae0b0f2819f93cb94dcd38da372843aa12 Mon Sep 17 00:00:00 2001 > From: Minchan Kim > Date: Mon, 21 Jan 2013 13:58:52 +0900 > Subject: [RESEND PATCH v5 1/4] zram: Fix deadlock bug in partial read/write > > Now zram allocates new page with GFP_KERNEL in zram I/O path > if IO is partial. Unfortunately, It may cause deadlock with > reclaim path like below. > > write_page from fs > fs_lock > allocation(GFP_KERNEL) > reclaim > pageout > write_page from fs > fs_lock <-- deadlock > > This patch fixes it by using GFP_ATOMIC and GFP_NOIO. > In read path, we called kmap_atomic so that we need GFP_ATOMIC > while we need GFP_NOIO in write path. The patch description makes sense now. Thanks! On Tue, Jan 29, 2013 at 1:21 AM, Minchan Kim wrote: > We could use GFP_IO instead of GFP_ATOMIC in zram_bvec_read with > some modification related to buffer allocation in case of partial IO. > But it needs more churn and prevent merge this patch into stable > if we should send this to stable so I'd like to keep it as simple > as possbile. GFP_IO usage could be separate patch after we merge it. I don't see why something like below couldn't be merged for stable. Going for GFP_ATOMIC might seem like the simplest thing to go for but usually bites you in the end. Pekka ------------------------- >8 ------------------------------- >>From 936a12b423c58542628d6fd683e859f752eb3d41 Mon Sep 17 00:00:00 2001 From: Minchan Kim Date: Mon, 21 Jan 2013 13:58:52 +0900 Subject: [PATCH] zram: Fix deadlock bug in partial read/write Now zram allocates new page with GFP_KERNEL in zram I/O path if IO is partial. Unfortunately, It may cause deadlock with reclaim path like below. write_page from fs fs_lock allocation(GFP_KERNEL) reclaim pageout write_page from fs fs_lock <-- deadlock This patch fixes it by using GFP_NOIO. In read path, we reorganize code flow so that kmap_atomic is called after the GFP_NOIO allocation. Cc: stable@vger.kernel.org Cc: Jerome Marchand Acked-by: Nitin Gupta Signed-off-by: Minchan Kim [ penberg@kernel.org: don't use GFP_ATOMIC ] Signed-off-by: Pekka Enberg --- drivers/staging/zram/zram_drv.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-) diff --git a/drivers/staging/zram/zram_drv.c b/drivers/staging/zram/zram_drv.c index f2a73bd..071e058 100644 --- a/drivers/staging/zram/zram_drv.c +++ b/drivers/staging/zram/zram_drv.c @@ -228,11 +228,12 @@ static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec, return 0; } - user_mem = kmap_atomic(page); if (is_partial_io(bvec)) /* Use a temporary buffer to decompress the page */ - uncmem = kmalloc(PAGE_SIZE, GFP_KERNEL); - else + uncmem = kmalloc(PAGE_SIZE, GFP_NOIO); + + user_mem = kmap_atomic(page); + if (!is_partial_io(bvec)) uncmem = user_mem; if (!uncmem) { @@ -279,7 +280,7 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index, * This is a partial IO. We need to read the full page * before to write the changes. */ - uncmem = kmalloc(PAGE_SIZE, GFP_KERNEL); + uncmem = kmalloc(PAGE_SIZE, GFP_NOIO); if (!uncmem) { pr_info("Error allocating temp memory!\n"); ret = -ENOMEM; -- 1.7.11.7