From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Martin K. Petersen" Subject: Re: sd_setup_discard_cmnd: BUG: unable to handle kernel NULL pointer dereference at (null) Date: Wed, 25 Jun 2014 21:44:11 -0400 Message-ID: References: <53A28B21.7070500@profihost.ag> <20140620155321.GA24389@soda.linbit> <20140620182956.GB24389@soda.linbit> <20140624115324.GB17123@soda.linbit> <20140625101421.GE17123@soda.linbit> Mime-Version: 1.0 Content-Type: text/plain Return-path: Received: from userp1040.oracle.com ([156.151.31.81]:23703 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756697AbaFZBof (ORCPT ); Wed, 25 Jun 2014 21:44:35 -0400 In-Reply-To: <20140625101421.GE17123@soda.linbit> (Lars Ellenberg's message of "Wed, 25 Jun 2014 12:14:21 +0200") Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Lars Ellenberg Cc: "Martin K. Petersen" , NeilBrown , linux-raid@vger.kernel.org, linux-scsi , JBottomley@parallels.com, Jens Axboe , konrad.wilk@oracle.com, elder@linaro.org, Josh Durgin , Greg KH >>>>> "Lars" == Lars Ellenberg writes: Lars> Because the way we do some internal bookkeeping, we announce a max Lars> discard of 4 MiB. Yikes! Lars> Similar for the WRITE_SAME interface (which we do not properly Lars> support on the DRBD protocol level yet -- backward compatibility Lars> concerns -- but intend to support "soon"). Yeah, WRITE SAME can take a long time to complete too. However, we're typically issuing them 32 megs at a time. Lars> If we only have a synchronous interface, we will probably have to Lars> either add some "async wrapper", or defer such submissions to Lars> worker threads. I'd prefer to have an async submit path. OK, I'll chew on it. -- Martin K. Petersen Oracle Linux Engineering