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[37.188.135.150]) by smtp.gmail.com with ESMTPSA id p22sm9984548wmg.37.2020.03.25.11.38.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 25 Mar 2020 11:38:33 -0700 (PDT) Date: Wed, 25 Mar 2020 19:38:32 +0100 From: Michal Hocko To: Alexander Potapenko Cc: Vegard Nossum , Andrew Morton , Dmitry Vyukov , Marco Elver , Andrey Konovalov , Linux Memory Management List , Al Viro , Andreas Dilger , Andrey Ryabinin , Andy Lutomirski , Ard Biesheuvel , Arnd Bergmann , Christoph Hellwig , Christoph Hellwig , "Darrick J. Wong" , David Miller , Dmitry Torokhov , Eric Biggers , Eric Dumazet , Eric Van Hensbergen , Greg Kroah-Hartman , Harry Wentland , Herbert Xu , Ilya Leoshkevich , Ingo Molnar , Jason Wang , Jens Axboe , Marek Szyprowski , Mark Rutland , "Martin K . Petersen" , Martin Schwidefsky , Matthew Wilcox , "Michael S. Tsirkin" , Michal Simek , Petr Mladek , Qian Cai , Randy Dunlap , Robin Murphy , Sergey Senozhatsky , Steven Rostedt , Takashi Iwai , Theodore Ts'o , Thomas Gleixner , Vasily Gorbik , Wolfram Sang Subject: Re: [PATCH v5 03/38] kmsan: gfp: introduce __GFP_NO_KMSAN_SHADOW Message-ID: <20200325183832.GI19542@dhcp22.suse.cz> References: <20200325161249.55095-1-glider@google.com> <20200325161249.55095-4-glider@google.com> <20200325161952.GF19542@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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: On Wed 25-03-20 18:40:29, Alexander Potapenko wrote: > On Wed, Mar 25, 2020 at 6:26 PM Alexander Potapenko wrote: > > > > On Wed, Mar 25, 2020 at 5:19 PM Michal Hocko wrote: > > > > > > On Wed 25-03-20 17:12:14, glider@google.com wrote: > > > > This flag is to be used by KMSAN runtime to mark that newly created > > > > memory pages don't need KMSAN metadata backing them. > > > > > > I really dislike an idea of the gfp flag. If you need some form of > > > exclusion for kmsan allocations then follow the pattern of memalloc_no{fs,io}_{save,restore} > > > History tells us that single usecase gfp flags are too tempting to abuse > > > and using incorrectly. > > > > Great idea, will do! > > Guess PF_ flags isn't a scarce resource? > > Actually, no, we are out of bits in current->flags already. > I could introduce a separate flag into struct task, but that won't > work in interrupt contexts - how do you solve that problem for FS/IO > allocations? NOFS/NOIO is not a problem for IRQ context because we never do reclaim from that context. I was also not aware that there are users from the IRQ context. I thought this would be an internal KMSAN stuff. What would be the IRQ context you call this from? Anyway, if you cannot go with the task_struct then a per-cpu value should work, right? -- Michal Hocko SUSE Labs