From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762314AbcLVAhF (ORCPT ); Wed, 21 Dec 2016 19:37:05 -0500 Received: from LGEAMRELO11.lge.com ([156.147.23.51]:53354 "EHLO lgeamrelo11.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1757527AbcLVAg1 (ORCPT ); Wed, 21 Dec 2016 19:36:27 -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: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Sergey Senozhatsky , Takashi Iwai , Hyeoncheol Lee , yjay.kim@lge.com, Sangseok Lee , Hugh Dickins , Minchan Kim , "[4.7+]" Subject: [PATCH v4 3/3] zram: support BDI_CAP_STABLE_WRITES Date: Thu, 22 Dec 2016 09:36:20 +0900 Message-Id: <1482366980-3782-4-git-send-email-minchan@kernel.org> X-Mailer: git-send-email 2.7.4 In-Reply-To: <1482366980-3782-1-git-send-email-minchan@kernel.org> References: <1482366980-3782-1-git-send-email-minchan@kernel.org> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org zram has used per-cpu stream feature from v4.7. It aims for increasing cache hit ratio of scratch buffer for compressing. Downside of that approach is that zram should ask memory space for compressed page in per-cpu context which requires stricted gfp flag which could be failed. If so, it retries to allocate memory space out of per-cpu context so it could get memory this time and compress the data again, copies it to the memory space. In this scenario, zram assumes the data should never be changed but it is not true without stable page support. So, If the data is changed under us, zram can make buffer overrun so that zsmalloc free object chain is broken so system goes crash like below https://bugzilla.suse.com/show_bug.cgi?id=997574 This patch adds BDI_CAP_STABLE_WRITES to zram for declaring "I am block device needing *stable write*". Fixes: da9556a2367c ("zram: user per-cpu compression streams") Cc: [4.7+] Signed-off-by: Minchan Kim --- * from v3 * add comment why we should set BDI_CAP_STABLE_WRITES again drivers/block/zram/zram_drv.c | 13 +++++++++++-- 1 file changed, 11 insertions(+), 2 deletions(-) diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c index 195376b4472b..e5ab7d9e8c45 100644 --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -25,6 +25,7 @@ #include #include #include +#include #include #include #include @@ -112,6 +113,14 @@ static inline bool is_partial_io(struct bio_vec *bvec) return bvec->bv_len != PAGE_SIZE; } +static void zram_revalidate_disk(struct zram *zram) +{ + revalidate_disk(zram->disk); + /* revalidate_disk reset the BDI_CAP_STABLE_WRITES so set again */ + zram->disk->queue->backing_dev_info.capabilities |= + BDI_CAP_STABLE_WRITES; +} + /* * Check if request is within bounds and aligned on zram logical blocks. */ @@ -1095,7 +1104,7 @@ static ssize_t disksize_store(struct device *dev, zram->comp = comp; zram->disksize = disksize; set_capacity(zram->disk, zram->disksize >> SECTOR_SHIFT); - revalidate_disk(zram->disk); + zram_revalidate_disk(zram); up_write(&zram->init_lock); return len; @@ -1143,7 +1152,7 @@ static ssize_t reset_store(struct device *dev, /* Make sure all the pending I/O are finished */ fsync_bdev(bdev); zram_reset_device(zram); - revalidate_disk(zram->disk); + zram_revalidate_disk(zram); bdput(bdev); mutex_lock(&bdev->bd_mutex); -- 2.7.4