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[37.188.135.150]) by smtp.gmail.com with ESMTPSA id j6sm33264825wrb.4.2020.03.25.09.19.54 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 25 Mar 2020 09:19:55 -0700 (PDT) Date: Wed, 25 Mar 2020 17:19:52 +0100 From: Michal Hocko To: glider@google.com Cc: Vegard Nossum , Andrew Morton , Dmitry Vyukov , Marco Elver , Andrey Konovalov , linux-mm@kvack.org, viro@zeniv.linux.org.uk, adilger.kernel@dilger.ca, aryabinin@virtuozzo.com, luto@kernel.org, ard.biesheuvel@linaro.org, arnd@arndb.de, hch@infradead.org, hch@lst.de, darrick.wong@oracle.com, davem@davemloft.net, dmitry.torokhov@gmail.com, ebiggers@google.com, edumazet@google.com, ericvh@gmail.com, gregkh@linuxfoundation.org, harry.wentland@amd.com, herbert@gondor.apana.org.au, iii@linux.ibm.com, mingo@elte.hu, jasowang@redhat.com, axboe@kernel.dk, m.szyprowski@samsung.com, mark.rutland@arm.com, martin.petersen@oracle.com, schwidefsky@de.ibm.com, willy@infradead.org, mst@redhat.com, monstr@monstr.eu, pmladek@suse.com, cai@lca.pw, rdunlap@infradead.org, robin.murphy@arm.com, sergey.senozhatsky@gmail.com, rostedt@goodmis.org, tiwai@suse.com, tytso@mit.edu, tglx@linutronix.de, gor@linux.ibm.com, wsa@the-dreams.de Subject: Re: [PATCH v5 03/38] kmsan: gfp: introduce __GFP_NO_KMSAN_SHADOW Message-ID: <20200325161952.GF19542@dhcp22.suse.cz> References: <20200325161249.55095-1-glider@google.com> <20200325161249.55095-4-glider@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200325161249.55095-4-glider@google.com> 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 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. > Signed-off-by: Alexander Potapenko > To: Alexander Potapenko > Cc: Vegard Nossum > Cc: Andrew Morton > Cc: Michal Hocko > Cc: Dmitry Vyukov > Cc: Marco Elver > Cc: Andrey Konovalov > Cc: linux-mm@kvack.org > > --- > We can't decide what to do here: > - do we need to conditionally define ___GFP_NO_KMSAN_SHADOW depending on > CONFIG_KMSAN like LOCKDEP does? > - if KMSAN is defined, and LOCKDEP is not, do we want to "compactify" the GFP > bits? > > Change-Id: If5d0352fd5711ad103328e2c185eb885e826423a > --- > include/linux/gfp.h | 4 +++- > 1 file changed, 3 insertions(+), 1 deletion(-) > > diff --git a/include/linux/gfp.h b/include/linux/gfp.h > index be2754841369e..e1ab42b5e9ce2 100644 > --- a/include/linux/gfp.h > +++ b/include/linux/gfp.h > @@ -44,6 +44,7 @@ struct vm_area_struct; > #else > #define ___GFP_NOLOCKDEP 0 > #endif > +#define ___GFP_NO_KMSAN_SHADOW 0x1000000u > /* If the above are modified, __GFP_BITS_SHIFT may need updating */ > > /* > @@ -212,12 +213,13 @@ struct vm_area_struct; > #define __GFP_NOWARN ((__force gfp_t)___GFP_NOWARN) > #define __GFP_COMP ((__force gfp_t)___GFP_COMP) > #define __GFP_ZERO ((__force gfp_t)___GFP_ZERO) > +#define __GFP_NO_KMSAN_SHADOW ((__force gfp_t)___GFP_NO_KMSAN_SHADOW) > > /* Disable lockdep for GFP context tracking */ > #define __GFP_NOLOCKDEP ((__force gfp_t)___GFP_NOLOCKDEP) > > /* Room for N __GFP_FOO bits */ > -#define __GFP_BITS_SHIFT (23 + IS_ENABLED(CONFIG_LOCKDEP)) > +#define __GFP_BITS_SHIFT (25) > #define __GFP_BITS_MASK ((__force gfp_t)((1 << __GFP_BITS_SHIFT) - 1)) > > /** > -- > 2.25.1.696.g5e7596f4ac-goog > -- Michal Hocko SUSE Labs