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[109.81.83.72]) by smtp.gmail.com with ESMTPSA id 4fb4d7f45d1cf-5bebc0812a3sm5401160a12.82.2024.08.19.03.19.30 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 19 Aug 2024 03:19:30 -0700 (PDT) Date: Mon, 19 Aug 2024 12:19:30 +0200 From: Michal Hocko To: David Hildenbrand 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: <20240817062449.21164-1-21cnbao@gmail.com> <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-Stat-Signature: o9556pbgmsekudpfhnic1611nhtsugb8 X-Rspamd-Queue-Id: B2FCA40013 X-Rspamd-Server: rspam11 X-HE-Tag: 1724062772-452982 X-HE-Meta: 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 tYHFWcFU affX3P5T1BS27r+C1jf3s9WZE1Qt/AETVl2Wgpa1TVeJLTye28IoRg47UIzbMsWiTMNL9es4jmvliir3soEsHwv2HuKQkEOY1tgSDFmsj+Q83zz4BGnPiRaPbeSS4ink2/T+gq0EpiqRoEiY/rxM9Rk3eiw4GP6kDEMYBTNmMI2XkI3tg5UAWjAG78QczpuhwKvyOM+XlAk/srt+B0xBUcSvmlxW4v5BmFLYPuc2hl2xlXqSLMf2IwrFZeZuu8g42JN2vRimUut8REOLt6DgSUo5RJ5+aRL+buXqMdgghqA/uQJrjsK36AlR3QWmkPVWw1qRtlaajR547ZR/zIXJ0mjVa5oL7undCPDv01kCNdAwF6/pEDIsvhi+gjKES5PIj4fggfXRSiuV/QTgoTUWiqvadfQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000252, 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 11:44:39, David Hildenbrand wrote: [...] > > if (gfp_mask & __GFP_NOFAIL) { > > /* > > - * All existing users of the __GFP_NOFAIL are blockable, so warn > > - * of any new users that actually require GFP_NOWAIT > > + * All existing users of the __GFP_NOFAIL are blockable > > + * otherwise we introduce a busy loop with inside the page > > + * allocator from non-sleepable contexts > > */ > > - if (WARN_ON_ONCE_GFP(!can_direct_reclaim, gfp_mask)) > > - goto fail; > > + BUG_ON(!can_direct_reclaim); > > No new BUG_ON(), WARN_ON_ONCE() is good enough for something that should be > found during ordinary testing. Do you mean if (WARN_ON_ONCE_GFP(...)) goto retry? Barry has mentioned that option in the changelog. -- Michal Hocko SUSE Labs