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[109.81.83.72]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-5bebbde4964sm5610388a12.24.2024.08.19.07.01.21 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 19 Aug 2024 07:01:21 -0700 (PDT) Date: Mon, 19 Aug 2024 16:01:21 +0200 From: Michal Hocko To: Yafang Shao Cc: Barry Song <21cnbao@gmail.com>, 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, torvalds@linux-foundation.org, urezki@gmail.com, v-songbaohua@oppo.com, vbabka@suse.cz, virtualization@lists.linux.dev, Lorenzo Stoakes , Kees Cook , Eugenio =?iso-8859-1?Q?P=E9rez?= , Jason Wang , Maxime Coquelin , "Michael S. Tsirkin" , Xuan Zhuo Subject: Re: [PATCH v3 4/4] mm: prohibit NULL deference exposed for unsupported non-blockable __GFP_NOFAIL Message-ID: References: <20240817062449.21164-5-21cnbao@gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 88E1D8003C X-Stat-Signature: eebfx6m87b9fp4xzzc541tytewm4qj8b X-HE-Tag: 1724076084-799976 X-HE-Meta: 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 OqcahJu2 EuAxHbt6Ev6b0FNgFwu5e+Le9eynPVXaEf0WXv8KHyUmKwtjWxiVaPxat3aVlsgo+7MEqHaf3OfCKWRzMxs4Xm6kQjfzAF7LtUJQNiby7LC31daB90YrT4qmFzHMo9UKlj/p/I2fIs4gleZT68awF7K4ji0RWRyJbwKlumzMN3fgvHWB79EOhbajRcwRym95B3mhCnu1GdQitKVLxw/uTp97E+X3GVZd6mmWJwN9IvkQ6uuZdT2FmGk0ui1gvMujkQHX48l1jQqTJ+Kgf+sDthc9YceYFl/DvYjze0YxVJ8BJxDMVuOHfX5fp/PrvY8b9UlxN6aFhTLfeFqw249pQxTKYtEDyH/BAhOrncu7V9/DCUPtybJ756vFrzPGaqC5t/UUmOeZy2K3Xk1CLY/DsJlQW9w== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000181, 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 19-08-24 20:17:36, Yafang Shao wrote: > My question is why is that ? Why not let it loop around the allocator? Because of 2 reasons. It is much easier to see NOFAIL allocations when they are annotated properly (try to grep for all sorts of endless loops) and also the allocator can make sertain heuristics if it knows that allocation must not fail. -- Michal Hocko SUSE Labs