From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from zimbra13.linbit.com (zimbra.linbit.com [212.69.161.123]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by mail09.linbit.com (LINBIT Mail Daemon) with ESMTPS id E7A2F1019A36 for ; Thu, 19 Mar 2015 21:08:22 +0100 (CET) Received: from localhost (localhost [127.0.0.1]) by zimbra13.linbit.com (Postfix) with ESMTP id C6F5C453C93 for ; Thu, 19 Mar 2015 21:08:22 +0100 (CET) Received: from zimbra13.linbit.com ([127.0.0.1]) by localhost (zimbra13.linbit.com [127.0.0.1]) (amavisd-new, port 10032) with ESMTP id scfhTVLkIkIs for ; Thu, 19 Mar 2015 21:08:22 +0100 (CET) Received: from localhost (localhost [127.0.0.1]) by zimbra13.linbit.com (Postfix) with ESMTP id 753B9453C9C for ; Thu, 19 Mar 2015 21:08:22 +0100 (CET) Received: from zimbra13.linbit.com ([127.0.0.1]) by localhost (zimbra13.linbit.com [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id NMg2mS2CTJIr for ; Thu, 19 Mar 2015 21:08:22 +0100 (CET) Received: from soda.linbit (tuerlsteher.linbit.com [86.59.100.100]) by zimbra13.linbit.com (Postfix) with ESMTPS id 04CA8453C93 for ; Thu, 19 Mar 2015 21:08:21 +0100 (CET) Resent-Message-ID: <20150319200821.GC3556@soda.linbit> Received: from mail-ie0-f173.google.com (mail-ie0-f173.google.com [209.85.223.173]) (using TLSv1 with cipher RC4-SHA (128/128 bits)) (No client certificate requested) by mail09.linbit.com (LINBIT Mail Daemon) with ESMTPS id C7A301028A59 for ; Sat, 14 Mar 2015 00:24:35 +0100 (CET) Received: by iegc3 with SMTP id c3so134383484ieg.3 for ; Fri, 13 Mar 2015 16:24:33 -0700 (PDT) Date: Fri, 13 Mar 2015 16:24:32 -0700 (PDT) From: David Rientjes To: Jens Axboe In-Reply-To: Message-ID: References: <54FB98F3.2050308@fb.com> <54FB9FE2.5040707@fb.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Cc: linux-kernel@vger.kernel.org, drbd-user@lists.linbit.com, Lars Ellenberg Subject: Re: [Drbd-dev] [patch 1/2] block, drbd: fix drbd_req_new() initialization List-Id: "*Coordination* of development, patches, contributions -- *Questions* \(even to developers\) go to drbd-user, please." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , On Sat, 7 Mar 2015, David Rientjes wrote: > > >>> mempool_alloc() does not support __GFP_ZERO since elements may come from > > >>> memory that has already been released by mempool_free(). > > >>> > > >>> Remove __GFP_ZERO from mempool_alloc() in drbd_req_new() and properly > > >>> initialize it to 0. > > >> > > >> You should add it to mempool instead, avoid having this issue show up for > > >> other folks as well. It'd be trivial to do. Normal ->alloc() should honor > > >> __GFP_ZERO, just do the same manually for removing an item from the internal > > >> pool. > > >> > > > > > > Umm, it's not trivial to do and wouldn't make sense to do it. Mempools > > > > Uhm, it would make sense, though. > > > > Disagree, I don't think we should extend mempool to know the element size, > modify every user of mempool to pass it in, and keep it consistent with > mempool_alloc_t for the benefit of __GFP_ZERO for this one buggy caller. > Most users don't need __GFP_ZERO and just overwrite the entire element > after mempool_alloc() and it would be an unnecessary overhead to even > check for the bit set. So it wouldn't make sense in terms of performance > or maintainability. > > > > don't know the element size, in other words it wouldn't know the length to > > > memset() to 0 for mempool_alloc(). It shouldn't be modified to know the > > > element size since elements are allocated by the implementation of > > > mempool_alloc_t and they could easily become inconsistent. This patch is > > > what you want to merge, really. > > > > > > > I forgot we don't have the size in there. Then I would suggest adding a > > WARN_ON() for __GFP_ZERO being set in mempool_alloc(), at the very least. > > > > There is, it's a VM_WARN_ON_ONCE() that will show up if you configure > CONFIG_DEBUG_VM. > Jens, are these two patches going to be merged into linux-block? Thanks.