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Wed, 30 Oct 2019 07:30:00 -0700 (PDT) Received: from pc636 ([37.139.158.167]) by smtp.gmail.com with ESMTPSA id s7sm32320ljo.98.2019.10.30.07.29.58 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 30 Oct 2019 07:29:59 -0700 (PDT) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Wed, 30 Oct 2019 15:29:51 +0100 To: Daniel Axtens Cc: kasan-dev@googlegroups.com, linux-mm@kvack.org, x86@kernel.org, aryabinin@virtuozzo.com, glider@google.com, luto@kernel.org, linux-kernel@vger.kernel.org, mark.rutland@arm.com, dvyukov@google.com, christophe.leroy@c-s.fr, linuxppc-dev@lists.ozlabs.org, gor@linux.ibm.com Subject: Re: [PATCH v10 1/5] kasan: support backing vmalloc space with real shadow memory Message-ID: <20191030142951.GA24958@pc636> References: <20191029042059.28541-1-dja@axtens.net> <20191029042059.28541-2-dja@axtens.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191029042059.28541-2-dja@axtens.net> User-Agent: Mutt/1.10.1 (2018-07-13) 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: Hello, Daniel > > @@ -1294,14 +1299,19 @@ static bool __purge_vmap_area_lazy(unsigned long start, unsigned long end) > spin_lock(&free_vmap_area_lock); > llist_for_each_entry_safe(va, n_va, valist, purge_list) { > unsigned long nr = (va->va_end - va->va_start) >> PAGE_SHIFT; > + unsigned long orig_start = va->va_start; > + unsigned long orig_end = va->va_end; > > /* > * Finally insert or merge lazily-freed area. It is > * detached and there is no need to "unlink" it from > * anything. > */ > - merge_or_add_vmap_area(va, > - &free_vmap_area_root, &free_vmap_area_list); > + va = merge_or_add_vmap_area(va, &free_vmap_area_root, > + &free_vmap_area_list); > + > + kasan_release_vmalloc(orig_start, orig_end, > + va->va_start, va->va_end); > I have some questions here. I have not analyzed kasan_releace_vmalloc() logic in detail, sorry for that if i miss something. __purge_vmap_area_lazy() deals with big address space, so not only vmalloc addresses it frees here, basically it can be any, starting from 1 until ULONG_MAX, whereas vmalloc space spans from VMALLOC_START - VMALLOC_END: 1) Should it be checked that vmalloc only address is freed or you handle it somewhere else? if (is_vmalloc_addr(va->va_start)) kasan_release_vmalloc(...) 2) Have you run any bencmarking just to see how much overhead it adds? I am asking, because probably it make sense to add those figures to the backlog(commit message). For example you can run: sudo ./test_vmalloc.sh performance and sudo ./test_vmalloc.sh sequential_test_order=1 Thanks! -- Vlad Rezki