From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-f199.google.com (mail-qk0-f199.google.com [209.85.220.199]) by kanga.kvack.org (Postfix) with ESMTP id 153DC6B0005 for ; Tue, 24 Apr 2018 11:50:36 -0400 (EDT) Received: by mail-qk0-f199.google.com with SMTP id m21so13644732qkk.12 for ; Tue, 24 Apr 2018 08:50:36 -0700 (PDT) Received: from mx1.redhat.com (mx3-rdu2.redhat.com. [66.187.233.73]) by mx.google.com with ESMTPS id x4-v6si502293qtk.160.2018.04.24.08.50.34 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 24 Apr 2018 08:50:35 -0700 (PDT) Date: Tue, 24 Apr 2018 11:50:30 -0400 (EDT) From: Mikulas Patocka Subject: Re: [PATCH v3] kvmalloc: always use vmalloc if CONFIG_DEBUG_SG In-Reply-To: <20180424125121.GA17484@dhcp22.suse.cz> Message-ID: References: <20180420130852.GC16083@dhcp22.suse.cz> <20180420210200.GH10788@bombadil.infradead.org> <20180421144757.GC14610@bombadil.infradead.org> <20180423151545.GU17484@dhcp22.suse.cz> <20180424125121.GA17484@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-linux-mm@kvack.org List-ID: To: Michal Hocko Cc: Matthew Wilcox , David Miller , Andrew Morton , linux-mm@kvack.org, eric.dumazet@gmail.com, edumazet@google.com, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, mst@redhat.com, jasowang@redhat.com, virtualization@lists.linux-foundation.org, dm-devel@redhat.com, Vlastimil Babka On Tue, 24 Apr 2018, Michal Hocko wrote: > On Mon 23-04-18 20:06:16, Mikulas Patocka wrote: > [...] > > @@ -404,6 +405,12 @@ void *kvmalloc_node(size_t size, gfp_t f > > */ > > WARN_ON_ONCE((flags & GFP_KERNEL) != GFP_KERNEL); > > > > +#ifdef CONFIG_DEBUG_SG > > + /* Catch bugs when the caller uses DMA API on the result of kvmalloc. */ > > + if (!(prandom_u32_max(2) & 1)) > > + goto do_vmalloc; > > +#endif > > I really do not think there is anything DEBUG_SG specific here. Why you > simply do not follow should_failslab path or even reuse the function? CONFIG_DEBUG_SG is enabled by default in RHEL and Fedora debug kernel (if you don't like CONFIG_DEBUG_SG, pick any other option that is enabled there). Fail-injection framework is if off by default and it must be explicitly enabled and configured by the user - and most users won't enable it. Mikulas > > + > > /* > > * We want to attempt a large physically contiguous block first because > > * it is less likely to fragment multiple larger blocks and therefore > > @@ -427,6 +434,9 @@ void *kvmalloc_node(size_t size, gfp_t f > > if (ret || size <= PAGE_SIZE) > > return ret; > > > > +#ifdef CONFIG_DEBUG_SG > > +do_vmalloc: > > +#endif > > return __vmalloc_node_flags_caller(size, node, flags, > > __builtin_return_address(0)); > > } > > -- > Michal Hocko > SUSE Labs >