From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751749AbaKOJTH (ORCPT ); Sat, 15 Nov 2014 04:19:07 -0500 Received: from mail-pa0-f48.google.com ([209.85.220.48]:41536 "EHLO mail-pa0-f48.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751190AbaKOJTA (ORCPT ); Sat, 15 Nov 2014 04:19:00 -0500 Date: Sat, 15 Nov 2014 18:19:21 +0900 From: Sergey Senozhatsky To: Minchan Kim Cc: Andrew Morton , Nitin Gupta , Jerome Marchand , Sergey Senozhatsky , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Matthew Wilcox , Karam Lee , Dave Chinner Subject: Re: [PATCH] zram: rely on the bi_end_io for zram_rw_page fails Message-ID: <20141115091921.GA1046@swordfish> References: <1415926147-9023-1-git-send-email-minchan@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1415926147-9023-1-git-send-email-minchan@kernel.org> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, On (11/14/14 09:49), Minchan Kim wrote: > When I tested zram, I found processes got segfaulted. > The reason was zram_rw_page doesn't make the page dirty > again when swap write failed, and even it doesn't return > error by [1]. > > If error by zram internal happens, zram_rw_page should return > non-zero without calling page_endio. > It causes resubmit the IO with bio so that it ends up calling > bio->bi_end_io. > > The reason is zram could be used for a block device for FS and > swap, which they uses different bio complete callback, which > works differently. So, we should rely on the bio I/O complete > handler rather than zram_bvec_rw itself in case of I/O fail. > > This patch fixes the segfault issue as well one [1]'s > mentioned > > [1] zram: make rw_page opeartion return 0 > > Cc: Matthew Wilcox > Cc: Karam Lee > Cc: Dave Chinner > Signed-off-by: Minchan Kim > --- > drivers/block/zram/zram_drv.c | 8 +++----- > 1 file changed, 3 insertions(+), 5 deletions(-) > > diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c > index 4b4f4dbc3cfd..0e0650feab2a 100644 > --- a/drivers/block/zram/zram_drv.c > +++ b/drivers/block/zram/zram_drv.c > @@ -978,12 +978,10 @@ static int zram_rw_page(struct block_device *bdev, sector_t sector, > out_unlock: > up_read(&zram->init_lock); > out: > - page_endio(page, rw, err); > + if (unlikely(err)) > + return err; this unlikely() case can be turned into a likely() one: if (err == 0) page_endio(page, rw, 0); return err; > - /* > - * Return 0 prevents I/O fallback trial caused by rw_page fail > - * and upper layer can handle this IO error via page error. > - */ > + page_endio(page, rw, 0); > return 0; > } seems like we also can drop at least one goto (jump-to-return) for invalid request. (not sure about `goto out_unblock', yet another up_read(&zram->init_lock) just will make function bigger). Signed-off-by: Sergey Senozhatsky --- drivers/block/zram/zram_drv.c | 13 ++++--------- 1 file changed, 4 insertions(+), 9 deletions(-) diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c index 0e0650f..decca6f 100644 --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -956,8 +956,7 @@ static int zram_rw_page(struct block_device *bdev, sector_t sector, zram = bdev->bd_disk->private_data; if (!valid_io_request(zram, sector, PAGE_SIZE)) { atomic64_inc(&zram->stats.invalid_io); - err = -EINVAL; - goto out; + return -EINVAL; } down_read(&zram->init_lock); @@ -974,15 +973,11 @@ static int zram_rw_page(struct block_device *bdev, sector_t sector, bv.bv_offset = 0; err = zram_bvec_rw(zram, &bv, index, offset, rw); - out_unlock: up_read(&zram->init_lock); -out: - if (unlikely(err)) - return err; - - page_endio(page, rw, 0); - return 0; + if (err == 0) + page_endio(page, rw, 0); + return err; } static const struct block_device_operations zram_devops = {