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[82.69.66.36]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-47930c76edcsm96140615e9.11.2025.12.05.10.43.43 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 05 Dec 2025 10:43:43 -0800 (PST) Date: Fri, 5 Dec 2025 18:43:42 +0000 From: David Laight To: Lorenzo Stoakes Cc: Andrew Morton , David Hildenbrand , "Liam R . Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , oliver.sang@intel.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] mm: avoid use of BIT() macro for initialising VMA flags Message-ID: <20251205184342.2cfcc73e@pumpkin> In-Reply-To: <20251205175037.1287366-1-lorenzo.stoakes@oracle.com> References: <20251205175037.1287366-1-lorenzo.stoakes@oracle.com> X-Mailer: Claws Mail 4.1.1 (GTK 3.24.38; arm-unknown-linux-gnueabihf) MIME-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Queue-Id: 92A328000A X-Rspamd-Server: rspam10 X-Stat-Signature: g8xfy6e5icks7rknwjms73z9i3uztau3 X-HE-Tag: 1764960225-914273 X-HE-Meta: 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 I5JDY1Qr 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 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: List-Subscribe: List-Unsubscribe: On Fri, 5 Dec 2025 17:50:37 +0000 Lorenzo Stoakes wrote: > Commit 2b6a3f061f11 ("mm: declare VMA flags by bit") significantly changed > how VMA flags are declared, utilising an enum of VMA bit values and > ifdef-fery VM_xxx flag declarations via macro. > > As part of this change, it uses INIT_VM_FLAG() to define VM_xxx flags from > the newly introduced VMA bit numbers. > > However, use of this macro results in apparently unfortunate macro > expansion and resulted in a performance degradation.This appears to be due > to the (__force int), which is required for the sparse typechecking to > work. Does sparse complain if you just add 0? As in: #define INIT_VM_FLAG(name) BIT(VMA_ ## name ## _BIT + 0u) That should change the type without affecting what BIT() expands to. David > > Avoid macro expansion issues by simply using 1UL << bitnum. > > Reported-by: kernel test robot > Closes: https://lore.kernel.org/oe-lkp/202512041634.150c7e4f-lkp@intel.com > Signed-off-by: Lorenzo Stoakes > --- > > Andrew - note I've referenced the linux-next commit number above, could you > replace with the upstream commit hash once your PR is taken? Thanks! > > include/linux/mm.h | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/include/linux/mm.h b/include/linux/mm.h > index a2f38fb68840..c4438b30c140 100644 > --- a/include/linux/mm.h > +++ b/include/linux/mm.h > @@ -395,7 +395,8 @@ enum { > #undef DECLARE_VMA_BIT > #undef DECLARE_VMA_BIT_ALIAS > > -#define INIT_VM_FLAG(name) BIT((__force int) VMA_ ## name ## _BIT) > +#define INIT_VM_FLAG(name) (1UL << (__force int)(VMA_ ## name ## _BIT)) > + > #define VM_READ INIT_VM_FLAG(READ) > #define VM_WRITE INIT_VM_FLAG(WRITE) > #define VM_EXEC INIT_VM_FLAG(EXEC) > -- > 2.52.0 >