From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-ie0-f180.google.com (mail-ie0-f180.google.com [209.85.223.180]) by kanga.kvack.org (Postfix) with ESMTP id 7D4AB6B0038 for ; Tue, 18 Nov 2014 18:23:39 -0500 (EST) Received: by mail-ie0-f180.google.com with SMTP id rp18so5139856iec.11 for ; Tue, 18 Nov 2014 15:23:39 -0800 (PST) Received: from mail.linuxfoundation.org (mail.linuxfoundation.org. [140.211.169.12]) by mx.google.com with ESMTPS id om6si19808755igb.15.2014.11.18.15.23.37 for (version=TLSv1.2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 18 Nov 2014 15:23:38 -0800 (PST) Date: Tue, 18 Nov 2014 15:23:36 -0800 From: Andrew Morton Subject: Re: [PATCH] zram: rely on the bi_end_io for zram_rw_page fails Message-Id: <20141118152336.d58b7b61a711b7d9982deb9d@linux-foundation.org> In-Reply-To: <1415926147-9023-1-git-send-email-minchan@kernel.org> References: <1415926147-9023-1-git-send-email-minchan@kernel.org> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Minchan Kim Cc: Nitin Gupta , Jerome Marchand , Sergey Senozhatsky , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Matthew Wilcox , Karam Lee , Dave Chinner On Fri, 14 Nov 2014 09:49:07 +0900 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 > > ... > > --- 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; > > - /* > - * 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; Losing the comment makes me sad. The code is somewhat odd-looking. We should add some words explaining why we're not reporting errors at this point. -- 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