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t=1685043179; bh=6UobrKBXIGhe2eUQTgBJPED9+bJgDbD/miYgiY64fQI=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=PcQK9c9EREG4YKZhM4pdUTAf6OggbyNsdHXCf/2K1OpwOUwcqpW4ZVTBOLYcHbTQF NX6SWvPe5znnFXJBbQAQ811rD8ETp8tL8p3UPTQXp2hxmwTpMqYOLY+clwKia6xleX VFQsrL5Dvb7eAh9GUNw649P/3o/rI+p4wNPR0PnxXai3GSiwtVEarne4mXgNBdFEYl TfJSClRSYf1VeXjdHiB5chZvYyCh2wjqRHRcSGJIM+SWjTgsAMgiepbc0VtWkbT1mv DKxdeTKbzaIl5lpU+fSC7qeRVHwLAbdKMQhXH/YLXO/qVYnv9PJoAgVK9BEPkDOLZ0 4lJKDAJjaiXHg== Received: by mail-wm1-f44.google.com with SMTP id 5b1f17b1804b1-3f6094cb2d2so10481035e9.2 for ; Thu, 25 May 2023 12:32:59 -0700 (PDT) X-Gm-Message-State: AC+VfDyAL4a8wVf8ntbODvtMD+05Xivn1xWWPGVO9dGa6TNs3xbSZX21 X9GNUJXuRlEtkf/OrwX+3jFFmJOEynWnHlI7Hco= X-Google-Smtp-Source: ACHHUZ4aeMTw09mMjfqXPUFnCiuZAbomSUSRRfwvCVtW6z9ZsKNKLNK2xI+Aluo+xANppdWVouLl7+1DSFFxC7prqxM= X-Received: by 2002:a05:600c:21cf:b0:3f6:3bd:77dc with SMTP id x15-20020a05600c21cf00b003f603bd77dcmr3032498wmj.23.1685043178000; Thu, 25 May 2023 12:32:58 -0700 (PDT) MIME-Version: 1.0 References: <20230524213620.3509138-1-mcgrof@kernel.org> <20230524213620.3509138-2-mcgrof@kernel.org> In-Reply-To: From: Luis Chamberlain Date: Thu, 25 May 2023 12:32:45 -0700 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 1/2] fs/kernel_read_file: add support for duplicate detection To: Linus Torvalds Cc: Linux FS Devel , hch@lst.de, brauner@kernel.org, david@redhat.com, tglx@linutronix.de, patches@lists.linux.dev, linux-modules@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, pmladek@suse.com, petr.pavlu@suse.com, prarit@redhat.com, lennart@poettering.net, gregkh@linuxfoundation.org, rafael@kernel.org, song@kernel.org, lucas.de.marchi@gmail.com, lucas.demarchi@intel.com, christophe.leroy@csgroup.eu, peterz@infradead.org, rppt@kernel.org, dave@stgolabs.net, willy@infradead.org, vbabka@suse.cz, mhocko@suse.com, dave.hansen@linux.intel.com, colin.i.king@gmail.com, jim.cromie@gmail.com, catalin.marinas@arm.com, jbaron@akamai.com, rick.p.edgecombe@intel.com, yujie.liu@intel.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: 29ECA20014 X-Stat-Signature: qymgwjs83kxxkmdyhuqc1wt1gaynodme X-HE-Tag: 1685043181-122741 X-HE-Meta: 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 as72xZFF VW2BmoEUcuNjTy2sjanM2vp2lkriooT43jTNEBSPD/E4EyxNoWPv2fJTayn0KGnuyg+V/Gh4pL8UBH3zit/o764iUXetkshguvs/KJZIidJbehLZ8+CLNyhX+A1iqdK1VFc+zEjsyqjFl0+55BLtTnBmhp7+SgXEuf+iEjvIx4OV5BZ0EwGw+SbcKp/YlucnUJ9IioBlRuUe5XfsBapwsvYb1Ko6gGW7Ffw719p+WuH0yTWIZvJKo2NyOOSCS0LdCGf6SGfTwRp5BJp8Jl06r74GGHOjrXgCkHjF7KpoQhofUOkd7hUHc+gNDUBw4jQAQtHEsRKu+yR4J1dsteww/AW55kjRIPq1qRYfX5+sl83RMLXbBbwe6LbFJA1BLD/75gcdQ7ofTGneDIx+fH38ux3pxhwSRnmS3+MjMYrr3AgQbkotXR5jdY9Pt+ItGDRvBvRxXVITWNktey+vRj6pQU65VOJFmymslsdYhYXlCZiLfIxY= 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 Thu, May 25, 2023 at 11:50=E2=80=AFAM Linus Torvalds wrote: > So it would probably improve on those numbers a bit more, but you'd > still have the fundamental race where *serial* duplicates end up > always wasting CPU effort and temporary vmalloc space. The known failed boots are with KASAN with a large number of CPUs, so the value in the mitigation would be to help those boot until userspace fixes it and we have enough time for propagation. But since it is not a full proof solution, it may seem like an odd thing to have in place later and this being lost as odd tribal knowledge. I'd be in favor of only applying the mitigation if we really are chasing userspace to fix this, and we'd be OK in later removing it after userspace gets this fixed / propagated. If we're going to have userspace fix this, who is volunteering? Luis