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Thu, 29 Aug 2024 10:24:49 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id +SV3GXFM0GbbBAAAD6G6ig (envelope-from ); Thu, 29 Aug 2024 10:24:49 +0000 Message-ID: <2663352f-ecef-4e5b-bee5-e31d2b286c63@suse.cz> Date: Thu, 29 Aug 2024 12:24:49 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 0/4] mm: clarify nofail memory allocation Content-Language: en-US To: Barry Song <21cnbao@gmail.com> Cc: Linus Torvalds , David Hildenbrand , Michal Hocko , Yafang Shao , akpm@linux-foundation.org, linux-mm@kvack.org, 42.hyeyoo@gmail.com, cl@linux.com, hailong.liu@oppo.com, hch@infradead.org, iamjoonsoo.kim@lge.com, penberg@kernel.org, rientjes@google.com, roman.gushchin@linux.dev, urezki@gmail.com, v-songbaohua@oppo.com, virtualization@lists.linux.dev, "linux-hardening@vger.kernel.org" References: <59e90825-4efa-4384-8286-06c0235304dc@redhat.com> From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; 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charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspam-User: X-Stat-Signature: mqjby1ahqyhxjj9n4doxm55z3rjshksn X-Rspamd-Queue-Id: 3BE684001E X-Rspamd-Server: rspam11 X-HE-Tag: 1724927090-826071 X-HE-Meta: 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 XCPvL1aR X9C3/yCLuQpst/keLenw31StntYOlg0SlgXt8ImGsv+jbXGMKhZBbPWFqm21vuM77MPJsEGq6Otf0Rsu4cHcj/dqIngGLU2idEI74IH9qSFN+UUmz8Cd9ThSurv7XxU2QS5FtehfUQz5BTOHAI4ZLnt+gHHvXZ6P7A0JUNlslWthrRN4uYJIZeuvsVtdLO2ksw2ZdLPzg29nX2dyW9PuFRAz1R3FnjdKtstHvB1lhGYtsJRD5M1Prt6OFIarRsIPulxukYXkMBBVyjXsdufpJb6HGasYDhQ/dhT7E5VgT+rXbV6QF/4c7PW6nS4w72YkojAp1O2IygsJ/U0hdrXKzbh+8BU7Li8JTMuezlfP2/wznj7zyKpOE07GnsZ03hV7JjBTJUksT/nxJTkfnVq10ZwRVs3f0gUawrf4vaqicpUxt2hI= 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 8/27/24 09:50, Barry Song wrote: > On Tue, Aug 27, 2024 at 7:38 PM Vlastimil Babka wrote: >> >> >> Ugh, wasn't aware, well spotted. So it means there at least shouldn't be >> existing users of __GFP_NOFAIL with order > 1 :) >> >> But also the check is in the hotpath, even before trying the pcplists, so we >> could move it to __alloc_pages_slowpath() while extending it? > > Agreed. I don't think it is reasonable to check the order and flags in > two different places especially rmqueue() has already had > gfp_flags & __GFP_NOFAIL operation and order > 1 > overhead. > > We can at least extend the current check to make some improvement > though I still believe Michal's suggestion of implementing OOPS_ON is a > better approach to pursue, as it doesn't crash the entire system > while ensuring the problematic process is terminated. Linus made clear it's not a mm concern. If e.g. hardening people want to pursuit that instead, they can. BTW I think BUG_ON already works like this, if possible only the calling process is terminated. panic happens in case of being in a irq context, or due to panic_on_oops. Which the security people are setting to 1 anyway and OOPS_ON would have to observe it too. So AFAICS the only difference from BUG_ON would be not panic in the irq context, if panic_on_oops isn't set. (as for "no mm locks held" I think it's already satisfied at the points we check for __GFP_NOFAIL).