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[86.164.169.89]) by smtp.gmail.com with ESMTPSA id f2-20020adfdb42000000b0024274a5db0asm26335772wrj.2.2023.01.16.04.24.44 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 16 Jan 2023 04:24:45 -0800 (PST) Date: Mon, 16 Jan 2023 12:24:44 +0000 From: Lorenzo Stoakes To: Baoquan He Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, urezki@gmail.com, stephen.s.brennan@oracle.com, willy@infradead.org, akpm@linux-foundation.org, hch@infradead.org Subject: Re: [PATCH v3 5/7] mm/vmalloc: skip the uninitilized vmalloc areas Message-ID: References: <20230113031921.64716-1-bhe@redhat.com> <20230113031921.64716-6-bhe@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230113031921.64716-6-bhe@redhat.com> X-Rspam-User: X-Rspamd-Server: rspam03 X-Stat-Signature: 8faqqwfxjt98kdixfq19cemdgrzbhrex X-Rspamd-Queue-Id: 341921A0003 X-HE-Tag: 1673871886-526045 X-HE-Meta: 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 CT9SygbH ZXuu+vGiqZR46UZXzBIvM3OOFqO66pVi+tx2ZkLxMyH1VkrWWmLKDq+rNgRxXy/Pvd8/1OdxTVqTHjliSnHyr0Hf9vA== 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 Fri, Jan 13, 2023 at 11:19:19AM +0800, Baoquan He wrote: > For areas allocated via vmalloc_xxx() APIs, it searches for unmapped area > to reserve and allocates new pages to map into, please see function > __vmalloc_node_range(). During the process, flag VM_UNINITIALIZED is set > in vm->flags to indicate that the pages allocation and mapping haven't > been done, until clear_vm_uninitialized_flag() is called to clear it. > > For this kind of area, if VM_UNINITIALIZED is still set, let's ignore > it in vread() because pages newly allocated and being mapped in that > area only contains zero data. reading them out by aligned_vread() is > wasting time. > > Signed-off-by: Baoquan He > --- > mm/vmalloc.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index 4a10b3b692fa..dbcdcad2276b 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -3660,6 +3660,11 @@ long vread(char *buf, char *addr, unsigned long count) > if (!vm && !flags) > continue; > > + if (vm && (vm->flags & VM_UNINITIALIZED)) > + continue; > + /* Pair with smp_wmb() in clear_vm_uninitialized_flag() */ > + smp_rmb(); > + > vaddr = (char *) va->va_start; > size = vm ? get_vm_area_size(vm) : va_size(va); > > -- > 2.34.1 > Reviewed-by: Lorenzo Stoakes