From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jens Axboe Subject: Re: block: eliminate potential for infinite loop in blkdev_issue_discard Date: Fri, 15 Oct 2010 13:05:48 +0200 Message-ID: <4CB8358C.8060405@fusionio.com> References: <1285605664-27027-1-git-send-email-martin.petersen@oracle.com> <1285605664-27027-3-git-send-email-martin.petersen@oracle.com> <20100927181321.GC14180@redhat.com> <20101014213744.GA24959@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20101014213744.GA24959@redhat.com> Sender: linux-scsi-owner@vger.kernel.org To: Mike Snitzer Cc: "Martin K. Petersen" , "dm-devel@redhat.com" , "linux-scsi@vger.kernel.org" List-Id: dm-devel.ids On 2010-10-14 23:37, Mike Snitzer wrote: > On Mon, Sep 27 2010 at 2:13pm -0400, > Mike Snitzer wrote: > >> Due to the recently identified overflow in read_capacity_16() it was >> possible for max_discard_sectors to be zero but still have discards >> enabled on the associated device's queue. >> >> Eliminate the possibility for blkdev_issue_discard to infinitely loop. >> >> Interestingly this issue wasn't identified until a device, whose >> discard_granularity was 0 due to read_capacity_16 overflow, was consumed >> by blk_stack_limits() to construct limits for a higher-level DM >> multipath device. The multipath device's resulting limits never had the >> discard limits stacked because blk_stack_limits() will only do so if >> the bottom device's discard_granularity != 0. This resulted in the >> multipath device's limits.max_discard_sectors being 0. > > Hi Jens, > > This patch would only serve as a future safety-net now that the > elimination of the overflow in read_capacity_16() has been staged for > 2.6.37. Defensive programming and all... > > What do you (and others) think about this patch? Agree, may as well play it safe(r). -- Jens Axboe