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[37.188.135.150]) by smtp.gmail.com with ESMTPSA id t126sm10715412wmb.27.2020.03.25.11.40.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 25 Mar 2020 11:40:15 -0700 (PDT) Date: Wed, 25 Mar 2020 19:40:15 +0100 From: Michal Hocko To: Matthew Wilcox Cc: Alexander Potapenko , 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 , "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: <20200325184015.GJ19542@dhcp22.suse.cz> References: <20200325161249.55095-1-glider@google.com> <20200325161249.55095-4-glider@google.com> <20200325161952.GF19542@dhcp22.suse.cz> <20200325174916.GC22483@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200325174916.GC22483@bombadil.infradead.org> 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 10:49:16, Matthew Wilcox wrote: > On Wed, Mar 25, 2020 at 06:40:29PM +0100, 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? > > I would suggest using bits in the section labelled: > > /* Unserialized, strictly 'current' */ > > since this doesn't need to be accessed from any other task. Michal, > can we move PF_MEMALLOC_NOIO and NOFS to that area too? I wouldn't object. The only reason for using PF_$FOO is historical. It was XFS which started to use pf flag for NOSF AFAIR. I haven't checked recently but xfs still used to use its own api in the past. -- Michal Hocko SUSE Labs