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[198.145.29.99]) by mx.google.com with ESMTPS id s16si17030072plr.292.2019.05.27.05.59.30 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 27 May 2019 05:59:31 -0700 (PDT) Received-SPF: pass (google.com: domain of srs0=gqbm=t3=goodmis.org=rostedt@kernel.org designates 198.145.29.99 as permitted sender) client-ip=198.145.29.99; Authentication-Results: mx.google.com; spf=pass (google.com: domain of srs0=gqbm=t3=goodmis.org=rostedt@kernel.org designates 198.145.29.99 as permitted sender) smtp.mailfrom="SRS0=GqBM=T3=goodmis.org=rostedt@kernel.org" Received: from gandalf.local.home (cpe-66-24-58-225.stny.res.rr.com [66.24.58.225]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 733AE20859; Mon, 27 May 2019 12:59:29 +0000 (UTC) Date: Mon, 27 May 2019 08:59:27 -0400 From: Steven Rostedt To: "Uladzislau Rezki (Sony)" Cc: Andrew Morton , linux-mm@kvack.org, Roman Gushchin , Hillf Danton , Michal Hocko , Matthew Wilcox , LKML , Thomas Garnier , Oleksiy Avramchenko , Joel Fernandes , Thomas Gleixner , Ingo Molnar , Tejun Heo Subject: Re: [PATCH v3 4/4] mm/vmap: move BUG_ON() check to the unlink_va() Message-ID: <20190527085927.19152502@gandalf.local.home> In-Reply-To: <20190527093842.10701-5-urezki@gmail.com> References: <20190527093842.10701-1-urezki@gmail.com> <20190527093842.10701-5-urezki@gmail.com> X-Mailer: Claws Mail 3.17.3 (GTK+ 2.24.32; x86_64-pc-linux-gnu) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon, 27 May 2019 11:38:42 +0200 "Uladzislau Rezki (Sony)" wrote: > Move the BUG_ON()/RB_EMPTY_NODE() check under unlink_va() > function, it means if an empty node gets freed it is a BUG > thus is considered as faulty behaviour. Can we switch it to a WARN_ON(). We are trying to remove all BUG_ON()s. If a user wants to crash on warning, there's a sysctl for that. But crashing the system can make it hard to debug. Especially if it is hit by someone without a serial console, and the machine just hangs in X. That is very annoying. With a WARN_ON, you at least get a chance to see the crash dump. -- Steve > > Signed-off-by: Uladzislau Rezki (Sony) > --- > mm/vmalloc.c | 24 +++++++++--------------- > 1 file changed, 9 insertions(+), 15 deletions(-) > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index 371aba9a4bf1..340959b81228 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -533,20 +533,16 @@ link_va(struct vmap_area *va, struct rb_root *root, > static __always_inline void > unlink_va(struct vmap_area *va, struct rb_root *root) > { > - /* > - * During merging a VA node can be empty, therefore > - * not linked with the tree nor list. Just check it. > - */ > - if (!RB_EMPTY_NODE(&va->rb_node)) { > - if (root == &free_vmap_area_root) > - rb_erase_augmented(&va->rb_node, > - root, &free_vmap_area_rb_augment_cb); > - else > - rb_erase(&va->rb_node, root); > + BUG_ON(RB_EMPTY_NODE(&va->rb_node)); > > - list_del(&va->list); > - RB_CLEAR_NODE(&va->rb_node); > - } > + if (root == &free_vmap_area_root) > + rb_erase_augmented(&va->rb_node, > + root, &free_vmap_area_rb_augment_cb); > + else > + rb_erase(&va->rb_node, root); > + > + list_del(&va->list); > + RB_CLEAR_NODE(&va->rb_node); > } > > #if DEBUG_AUGMENT_PROPAGATE_CHECK > @@ -1187,8 +1183,6 @@ EXPORT_SYMBOL_GPL(unregister_vmap_purge_notifier); > > static void __free_vmap_area(struct vmap_area *va) > { > - BUG_ON(RB_EMPTY_NODE(&va->rb_node)); > - > /* > * Remove from the busy tree/list. > */