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[109.81.92.122]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-5c04a3cb04csm5819961a12.31.2024.08.26.09.51.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 26 Aug 2024 09:51:56 -0700 (PDT) Date: Mon, 26 Aug 2024 18:51:55 +0200 From: Michal Hocko To: Matthew Wilcox Cc: Andrew Morton , Christoph Hellwig , Yafang Shao , Kent Overstreet , jack@suse.cz, Christian Brauner , Alexander Viro , Paul Moore , James Morris , "Serge E. Hallyn" , linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-bcachefs@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 2/2] mm: drop PF_MEMALLOC_NORECLAIM Message-ID: References: <20240826085347.1152675-1-mhocko@kernel.org> <20240826085347.1152675-3-mhocko@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: F1C3940009 X-Rspam-User: X-Rspamd-Server: rspam05 X-Stat-Signature: h3o6rskmhrstxcyi1mqcewi9b5c1pdot X-HE-Tag: 1724691117-97589 X-HE-Meta: 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 3HYjQTwV dsm8fm/UfrZDCarUK1M818b3SDGkvaF2iyIs9geREC3aqRRq0lES7//qpzp9wPjX3TK4Ff5c0BxqG5bLjRT+nNmfynnyDZB7JVsohEam2sj7mZrSIVedgUONN0a8I18SEDc2xUUeUcIES4JvDZTwWRMyqsTNl0ccsSzouGQ9b+DrwYoSmqcbrzMWhJ76HZD9BL0CY7fS9aiOmjzq1Pfl4A8ZhBURRAN8xMe1ZF45qa38RbOVTqFGKYruymN+ka6ehd22IRG4MscEpl5R4f0AmgmAQAYRPg31pqlDRFDdNOxlMYN3g7SymUXYmEgZ1IxneTL+H8xAT/aOOewrSDwRSVzpNBFSxViMenOkzeLYVYvoBh8NzZZCJV0DIRMN9LfbEcslF7t2IRBIy66E4EKulQyeILoQnLL7RMnkrZeYQpHLb3FTNWOUO2j9Ln1BtPFDoxunQnKHtsYIrEnK63Za6KwQ3eQ== 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: List-Subscribe: List-Unsubscribe: On Mon 26-08-24 14:59:29, Matthew Wilcox wrote: > On Mon, Aug 26, 2024 at 10:47:13AM +0200, Michal Hocko wrote: > > From: Michal Hocko > > > > There is no existing user of the flag and the flag is dangerous because > > a nested allocation context can use GFP_NOFAIL which could cause > > unexpected failure. Such a code would be hard to maintain because it > > could be deeper in the call chain. > > > > PF_MEMALLOC_NORECLAIM has been added even when it was pointed out [1] > > that such a allocation contex is inherently unsafe if the context > > doesn't fully control all allocations called from this context. > > Wouldn't a straight-up revert of eab0af905bfc be cleaner? Or is there > a reason to keep PF_MEMALLOC_NOWARN? I wanted to make it PF_MEMALLOC_NORECLAIM specific. I do not have a strong case against PF_MEMALLOC_NOWARN TBH. It is a hack because the scope is claiming something about all allocations within the scope without necessarily knowing all of them (including potential future changes). But NOWARN is not really harmful so I do not care strongly. If a plan revert is preferably, I will go with it. -- Michal Hocko SUSE Labs