Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752171AbcDLEsa (ORCPT ); Tue, 12 Apr 2016 00:48:30 -0400 Received: from LGEAMRELO12.lge.com ([156.147.23.52]:57406 "EHLO lgeamrelo12.lge.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750795AbcDLEs3 (ORCPT ); Tue, 12 Apr 2016 00:48:29 -0400 X-Original-SENDERIP: 156.147.1.125 X-Original-MAILFROM: iamjoonsoo.kim@lge.com X-Original-SENDERIP: 10.177.222.138 X-Original-MAILFROM: iamjoonsoo.kim@lge.com Date: Tue, 12 Apr 2016 13:51:13 +0900 From: Joonsoo Kim To: Alexander Potapenko Cc: Andrey Konovalov , Christoph Lameter , Dmitriy Vyukov , Andrew Morton , Andrey Ryabinin , Steven Rostedt , Kostya Serebryany , kasan-dev , LKML , Linux Memory Management List Subject: Re: [PATCH v7 5/7] mm, kasan: Stackdepot implementation. Enable stackdepot for SLAB Message-ID: <20160412045113.GB29018@js1304-P5Q-DELUXE> References: <4f6880ee0c1545b3ae9c25cfe86a879d724c4e7b.1457949315.git.glider@google.com> <20160411074452.GC26116@js1304-P5Q-DELUXE> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1649 Lines: 44 On Mon, Apr 11, 2016 at 04:51:47PM +0200, Alexander Potapenko wrote: > On Mon, Apr 11, 2016 at 4:39 PM, Alexander Potapenko wrote: > > On Mon, Apr 11, 2016 at 9:44 AM, Joonsoo Kim wrote: > >> On Mon, Mar 14, 2016 at 11:43:43AM +0100, Alexander Potapenko wrote: > >>> +depot_stack_handle_t depot_save_stack(struct stack_trace *trace, > >>> + gfp_t alloc_flags) > >>> +{ > >>> + u32 hash; > >>> + depot_stack_handle_t retval = 0; > >>> + struct stack_record *found = NULL, **bucket; > >>> + unsigned long flags; > >>> + struct page *page = NULL; > >>> + void *prealloc = NULL; > >>> + bool *rec; > >>> + > >>> + if (unlikely(trace->nr_entries == 0)) > >>> + goto fast_exit; > >>> + > >>> + rec = this_cpu_ptr(&depot_recursion); > >>> + /* Don't store the stack if we've been called recursively. */ > >>> + if (unlikely(*rec)) > >>> + goto fast_exit; > >>> + *rec = true; > >>> + > >>> + hash = hash_stack(trace->entries, trace->nr_entries); > >>> + /* Bad luck, we won't store this stack. */ > >>> + if (hash == 0) > >>> + goto exit; > >> > >> Hello, > >> > >> why is hash == 0 skipped? > >> > >> Thanks. > > We have to keep a special value to distinguish allocations for which > > we don't have the stack trace for some reason. > > Making 0 such a value seems natural. > Well, the above statement is false. > Because we only compare the hash to the records that are already in > the depot, there's no point in reserving this value. So, could you make a patch for it? Thanks.