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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-Server: rspam07 X-Rspamd-Queue-Id: 4A20940008 X-Stat-Signature: idxyr5k59dqh4zhea3xhnxcwsb5t1c31 X-Rspam-User: X-HE-Tag: 1724694573-980395 X-HE-Meta: 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 BOKFxDzI ArGaxgwdxK7ugC2QLF7nEVWoShGll1ct3thiWpjHLg9AdJU5W+5HFSfxdEJMId8GNyJ7S80XO5vgaGTQFmj8S9w5QBL5q6DzP9xpuujditflUGQ3PIf8CUYW5es6K8CcsZNKXZTSC7g2MyT5jKDD57Q6g+i74k3gTrdfniW3zgxeLVyZ4t9rAxgQ2KwYOomQUeEPQQwNnvYnD25nBCfONlFp8PNnpY+BZDn2+1HOfn/s/V++HfIYcpXtt26LjV3i6c4PXtSr5qa6wA84HSqDHCXaDAfiIY3JwUvr1TY6uMJPOsmZJgqNrSAwi1umjqWSKDcdETeQNzxtVgQESsKFGRFSVduVTp9B6p+LopB7CeF6vQ+253iLOsYE1NeOC/XffoaNm 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, Aug 26, 2024 at 06:51:55PM +0200, Michal Hocko wrote: > 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. There aren't any other users of PF_MEMALLOC_NOWARN and it definitely seems like something you want at a callsite rather than blanket for every allocation below this point. We don't seem to have many PF_ flags left, so let's not keep it around if there's no immediate plans for it.