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b=FiaKRZyNECXzqsmm518kY4YImut7+RqRY/u83sC0CbO0A2dvgSnZSxhG2D13VF6XT 9b72x5RWt/r/PglfRYS7083GHijxTz45dd0gRECwTHnfrmZiBNbGeogmirECw8klLV +U8gI0Ju59qaUC84ShjO9Dr6m0Z49KKB/sNFaeiI= Date: Sun, 20 Apr 2025 16:29:25 -0700 From: Andrew Morton To: Lance Yang Cc: mingzhe.yang@ly.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, David Hildenbrand , Lance Yang Subject: Re: [RESEND PATCH v2 1/1] mm/rmap: add CONFIG_MM_ID guard for folio_test_large_maybe_mapped_shared() Message-Id: <20250420162925.2c58c018defee9ee192be553@linux-foundation.org> In-Reply-To: <20250418152228.20545-1-lance.yang@linux.dev> References: <20250418152228.20545-1-lance.yang@linux.dev> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: CB0C8100004 X-Stat-Signature: cp4ixueyb5up93mnp75uo1jqcsbyn4bw X-HE-Tag: 1745191767-264237 X-HE-Meta: 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 w8k28dme JyKUI 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, 18 Apr 2025 23:22:28 +0800 Lance Yang wrote: > From: Lance Yang > > To prevent folio_test_large_maybe_mapped_shared() from being used without > CONFIG_MM_ID, we add a compile-time check rather than wrapping it in > '#ifdef', avoiding even more #ifdef in callers that already use > IS_ENABLED(CONFIG_MM_ID). > > Also, we used plenty of IS_ENABLED() on purpose to keep the code free of > '#ifdef' mess. I dunno, this just seems really whacky. > --- a/include/linux/page-flags.h > +++ b/include/linux/page-flags.h > @@ -1232,6 +1232,8 @@ static inline int folio_has_private(const struct folio *folio) > > static inline bool folio_test_large_maybe_mapped_shared(const struct folio *folio) > { > + /* This function should never be called without CONFIG_MM_ID enabled. */ A correcter comment would be "This function should never be compiled without CONFIG_MM_ID enabled". Which lets the cat out of the bag. Why the heck is it being compiled with CONFIG_MM_ID=n?? We have tools to prevent that. Can we just slap "#ifdef CONFIG_MM_ID" around the whole function? It should have no callers, right? If the linker ends up complaining then something went wrong.