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Fri, 23 Jul 2021 01:40:04 -0700 Received: from MTKCAS06.mediatek.inc (172.21.101.30) by mtkmbs01n2.mediatek.inc (172.21.101.79) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Fri, 23 Jul 2021 16:40:02 +0800 Received: from [172.21.77.33] (172.21.77.33) by MTKCAS06.mediatek.inc (172.21.101.73) with Microsoft SMTP Server id 15.0.1497.2 via Frontend Transport; Fri, 23 Jul 2021 16:40:01 +0800 Message-ID: <1627029602.14347.6.camel@mtkswgap22> Subject: Re: [RESEND PATCH v2] mm/sparse: clarify pgdat_to_phys From: Miles Chen To: David Hildenbrand CC: Andrew Morton , Mike Rapoport , Mark Rutland , , , , Date: Fri, 23 Jul 2021 16:40:02 +0800 In-Reply-To: References: <20210723070137.23321-1-miles.chen@mediatek.com> X-Mailer: Evolution 3.2.3-0ubuntu6 MIME-Version: 1.0 X-MTK: N X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20210723_014009_054846_4DFCCED7 X-CRM114-Status: GOOD ( 28.03 ) X-BeenThere: linux-mediatek@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "Linux-mediatek" Errors-To: linux-mediatek-bounces+linux-mediatek=archiver.kernel.org@lists.infradead.org On Fri, 2021-07-23 at 09:10 +0200, David Hildenbrand wrote: > On 23.07.21 09:01, Miles Chen wrote: > > Clarify pgdat_to_phys() by testing if > > pgdat == &contig_page_data when CONFIG_NUMA=n. > > > > contig_page_data is only available when CONFIG_NUMA=n > > so we have to use #ifndef here. > > > > No functional change intended. > > > > Comment from Mark [1]: > > " > > ... and I reckon it'd be clearer and more robust to define > > pgdat_to_phys() in the same ifdefs as contig_page_data so > > that these, stay in-sync. e.g. have: > > > > | #ifdef CONFIG_NUMA > > | #define pgdat_to_phys(x) virt_to_phys(x) > > | #else /* CONFIG_NUMA */ > > | > > | extern struct pglist_data contig_page_data; > > | ... > > | #define pgdat_to_phys(x) __pa_symbol(&contig_page_data) > > | > > | #endif /* CONIFIG_NUMA */ > > " > > > > Comment from Mike [2]: > > " > > I'm not sure a macro is better than a static inline. > > > > Maybe we'd want to warn if pgdat passed to pgtat_to_phys() is not > > &contig_page_data, e.g something like > > > > static inline phys_addr_t pgdat_to_phys(struct pglist_data *pgdat) > > { > > if (!IS_ENABLED(CONFIG_NUMA)) { > > if (pgdat == &contig_page_data) > > return __pa_symbol(&contig_page_data); > > else > > pr_warn("Unexpected pglist_data pointer!\n"); > > } > > > > return __pa(pgdat); > > } > > " > > > > [1] https://urldefense.com/v3/__https://lore.kernel.org/linux-arm-kernel/20210615131902.GB47121@C02TD0UTHF1T.local/__;!!CTRNKA9wMg0ARbw!1bJTnH2gJ6QvsBKTXH8xOiKfHF-xq_1dok3cnETD4e4qjryntFm8K0XjtEmkHAxG6g$ > > [2] https://urldefense.com/v3/__https://lore.kernel.org/patchwork/patch/1452903/*1650759__;Iw!!CTRNKA9wMg0ARbw!1bJTnH2gJ6QvsBKTXH8xOiKfHF-xq_1dok3cnETD4e4qjryntFm8K0XjtEmbGXEkVg$ > > > > Cc: Mike Rapoport > > Cc: Mark Rutland > > Signed-off-by: Miles Chen > > > > --- > > > > Change since v1: > > Thanks for Mike's comment, check if pgdat == &contig_page_data, > > so it is clearer that we only expect contig_page_data when > > CONFIG_NUMA=n. > > --- > > mm/sparse.c | 7 ++++--- > > 1 file changed, 4 insertions(+), 3 deletions(-) > > > > diff --git a/mm/sparse.c b/mm/sparse.c > > index 6326cdf36c4f..f73ff3c124c5 100644 > > --- a/mm/sparse.c > > +++ b/mm/sparse.c > > @@ -348,10 +348,11 @@ size_t mem_section_usage_size(void) > > static inline phys_addr_t pgdat_to_phys(struct pglist_data *pgdat) > > { > > #ifndef CONFIG_NUMA > > - return __pa_symbol(pgdat); > > -#else > > + if (pgdat == &contig_page_data) > > + return __pa_symbol(&contig_page_data); > > + pr_warn("Unexpected pglist_data pointer!\n"); > > Shouldn't this rather be a VM_BUG_ON()? > > Because it looks like something that should barely happen and we might > not want to perform runtime checks on each and every system? thanks for your comment, I will use VM_BUG_ON() to check if pgdat == contig_page_data to avoid the runtime check. > > _______________________________________________ Linux-mediatek mailing list Linux-mediatek@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-mediatek