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[209.85.208.169]) by smtp.gmail.com with ESMTPSA id p16-20020a056512313000b00471956e0bddsm314183lfd.49.2022.04.22.11.41.54 for (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 22 Apr 2022 11:41:55 -0700 (PDT) Received: by mail-lj1-f169.google.com with SMTP id 17so10719775lji.1 for ; Fri, 22 Apr 2022 11:41:54 -0700 (PDT) X-Received: by 2002:a2e:9d46:0:b0:24c:7f1d:73cc with SMTP id y6-20020a2e9d46000000b0024c7f1d73ccmr3579356ljj.358.1650652914703; Fri, 22 Apr 2022 11:41:54 -0700 (PDT) MIME-Version: 1.0 References: <20220422060107.781512-1-npiggin@gmail.com> <20220422060107.781512-3-npiggin@gmail.com> In-Reply-To: From: Linus Torvalds Date: Fri, 22 Apr 2022 11:41:38 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 2/2] Revert "vmalloc: replace VM_NO_HUGE_VMAP with VM_ALLOW_HUGE_VMAP" To: Nicholas Piggin Cc: Paul Menzel , "the arch/x86 maintainers" , Song Liu , "Edgecombe, Rick P" , Andrew Morton , Linux Kernel Mailing List , Linux-MM Content-Type: multipart/mixed; boundary="000000000000a114e105dd429420" X-Stat-Signature: 4msg5pqza9ntx9xf3oitmw99uwguctq1 X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 9763316002E Authentication-Results: imf08.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=google header.b=f9blmSpi; spf=pass (imf08.hostedemail.com: domain of torvalds@linuxfoundation.org designates 209.85.167.46 as permitted sender) smtp.mailfrom=torvalds@linuxfoundation.org; dmarc=none X-Rspam-User: X-HE-Tag: 1650652916-216055 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: --000000000000a114e105dd429420 Content-Type: text/plain; charset="UTF-8" On Fri, Apr 22, 2022 at 10:08 AM Linus Torvalds wrote: > > Just opt-in with the mappings that matter. Actually, we could automatically opt-in a few common cases that we know are fundamentally ok, because they already can't play protection games. In particular, kvmalloc(). So I think something like this patch - along with Song's patch to enable it for alloc_large_system_hash() - would be fairly safe, and avoid any nasty cases. And probably catch quite a lot of the cases that matter that can grow large. 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