From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com ([209.132.183.28]:51604 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725895AbeKOLMq (ORCPT ); Thu, 15 Nov 2018 06:12:46 -0500 Date: Thu, 15 Nov 2018 09:06:52 +0800 From: Ming Lei Subject: Re: [PATCH] block: fix 32 bit overflow in __blkdev_issue_discard() Message-ID: <20181115010651.GD32603@ming.t460p> References: <20181113214337.20581-1-david@fromorbit.com> <10a8dd78-7c00-8593-9f4e-b20eb1161b92@kernel.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <10a8dd78-7c00-8593-9f4e-b20eb1161b92@kernel.dk> Sender: linux-xfs-owner@vger.kernel.org List-ID: List-Id: xfs To: Jens Axboe Cc: Dave Chinner , linux-xfs@vger.kernel.org, linux-block@vger.kernel.org On Wed, Nov 14, 2018 at 08:18:24AM -0700, Jens Axboe wrote: > On 11/13/18 2:43 PM, Dave Chinner wrote: > > From: Dave Chinner > > > > A discard cleanup merged into 4.20-rc2 causes fstests xfs/259 to > > fall into an endless loop in the discard code. The test is creating > > a device that is exactly 2^32 sectors in size to test mkfs boundary > > conditions around the 32 bit sector overflow region. > > > > mkfs issues a discard for the entire device size by default, and > > hence this throws a sector count of 2^32 into > > blkdev_issue_discard(). It takes the number of sectors to discard as > > a sector_t - a 64 bit value. > > > > The commit ba5d73851e71 ("block: cleanup __blkdev_issue_discard") > > takes this sector count and casts it to a 32 bit value before > > comapring it against the maximum allowed discard size the device > > has. This truncates away the upper 32 bits, and so if the lower 32 > > bits of the sector count is zero, it starts issuing discards of > > length 0. This causes the code to fall into an endless loop, issuing > > a zero length discards over and over again on the same sector. > > Applied, thanks. Ming, can you please add a blktests test for > this case? This is the 2nd time it's been broken. OK, I will add zram discard test in blktests, which should cover the 1st report. For the xfs/259, I need to investigate if it is easy to do in blktests. Thanks, Ming