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Mon, 26 Jul 2021 21:04:27 +0000 Received: from BY5PR10MB4196.namprd10.prod.outlook.com ([fe80::8d2a:558d:ab4a:9c2a]) by BY5PR10MB4196.namprd10.prod.outlook.com ([fe80::8d2a:558d:ab4a:9c2a%6]) with mapi id 15.20.4352.031; Mon, 26 Jul 2021 21:04:27 +0000 Subject: Re: [PATCH 1/5] mm: introduce PAGEFLAGS_MASK to replace ((1UL << NR_PAGEFLAGS) - 1) To: Muchun Song , akpm@linux-foundation.org, osalvador@suse.de, mhocko@suse.com, song.bao.hua@hisilicon.com, david@redhat.com, chenhuang5@huawei.com, bodeddub@amazon.com, corbet@lwn.net Cc: duanxiongchun@bytedance.com, fam.zheng@bytedance.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, zhengqi.arch@bytedance.com References: <20210714091800.42645-1-songmuchun@bytedance.com> <20210714091800.42645-2-songmuchun@bytedance.com> From: Mike Kravetz Message-ID: Date: Mon, 26 Jul 2021 14:04:23 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.1.1 In-Reply-To: <20210714091800.42645-2-songmuchun@bytedance.com> Content-Type: text/plain; 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dkim=pass header.d=oracle.com header.s=corp-2021-07-09 header.b=zRz0irdJ; dkim=pass header.d=oracle.com header.s=corp-2020-01-29 header.b=TZa0scbb; dkim=pass header.d=oracle.onmicrosoft.com header.s=selector2-oracle-onmicrosoft-com header.b=uONEwmGV; spf=none (imf03.hostedemail.com: domain of mike.kravetz@oracle.com has no SPF policy when checking 205.220.177.32) smtp.mailfrom=mike.kravetz@oracle.com; dmarc=pass (policy=none) header.from=oracle.com X-Stat-Signature: 4oourmp9q6s7sjt8n3uwpf3osti91fny X-HE-Tag: 1627333480-24447 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 7/14/21 2:17 AM, Muchun Song wrote: > Instead of hard-coding ((1UL << NR_PAGEFLAGS) - 1) everywhere, introducing > PAGEFLAGS_MASK to make the code clear to get the page flags. > > Signed-off-by: Muchun Song > --- > include/linux/page-flags.h | 4 +++- > include/trace/events/page_ref.h | 4 ++-- > lib/test_printf.c | 2 +- > lib/vsprintf.c | 2 +- > 4 files changed, 7 insertions(+), 5 deletions(-) > > diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h > index 5922031ffab6..358d3f6fa976 100644 > --- a/include/linux/page-flags.h > +++ b/include/linux/page-flags.h > @@ -178,6 +178,8 @@ enum pageflags { > PG_reported = PG_uptodate, > }; > > +#define PAGEFLAGS_MASK (~((1UL << NR_PAGEFLAGS) - 1)) Can you explain why you chose this definition instead of #define PAGEFLAGS_MASK ((1UL << NR_PAGEFLAGS) - 1) and mostly use ~PAGEFLAGS_MASK below? -- Mike Kravetz > + > #ifndef __GENERATING_BOUNDS_H > > static inline unsigned long _compound_head(const struct page *page) > @@ -859,7 +861,7 @@ static inline void ClearPageSlabPfmemalloc(struct page *page) > * alloc-free cycle to prevent from reusing the page. > */ > #define PAGE_FLAGS_CHECK_AT_PREP \ > - (((1UL << NR_PAGEFLAGS) - 1) & ~__PG_HWPOISON) > + (~(PAGEFLAGS_MASK | __PG_HWPOISON)) > > #define PAGE_FLAGS_PRIVATE \ > (1UL << PG_private | 1UL << PG_private_2) > diff --git a/include/trace/events/page_ref.h b/include/trace/events/page_ref.h > index 5d2ea93956ce..643b1b4e9f27 100644 > --- a/include/trace/events/page_ref.h > +++ b/include/trace/events/page_ref.h > @@ -38,7 +38,7 @@ DECLARE_EVENT_CLASS(page_ref_mod_template, > > TP_printk("pfn=0x%lx flags=%s count=%d mapcount=%d mapping=%p mt=%d val=%d", > __entry->pfn, > - show_page_flags(__entry->flags & ((1UL << NR_PAGEFLAGS) - 1)), > + show_page_flags(__entry->flags & ~PAGEFLAGS_MASK), > __entry->count, > __entry->mapcount, __entry->mapping, __entry->mt, > __entry->val) > @@ -88,7 +88,7 @@ DECLARE_EVENT_CLASS(page_ref_mod_and_test_template, > > TP_printk("pfn=0x%lx flags=%s count=%d mapcount=%d mapping=%p mt=%d val=%d ret=%d", > __entry->pfn, > - show_page_flags(__entry->flags & ((1UL << NR_PAGEFLAGS) - 1)), > + show_page_flags(__entry->flags & ~PAGEFLAGS_MASK), > __entry->count, > __entry->mapcount, __entry->mapping, __entry->mt, > __entry->val, __entry->ret) > diff --git a/lib/test_printf.c b/lib/test_printf.c > index 8ac71aee46af..eadcc6458b10 100644 > --- a/lib/test_printf.c > +++ b/lib/test_printf.c > @@ -614,7 +614,7 @@ page_flags_test(int section, int node, int zone, int last_cpupid, > bool append = false; > int i; > > - flags &= BIT(NR_PAGEFLAGS) - 1; > + flags &= ~PAGEFLAGS_MASK; > if (flags) { > page_flags |= flags; > snprintf(cmp_buf + size, BUF_SIZE - size, "%s", name); > diff --git a/lib/vsprintf.c b/lib/vsprintf.c > index dd006adfe853..ff7c180a2971 100644 > --- a/lib/vsprintf.c > +++ b/lib/vsprintf.c > @@ -2019,7 +2019,7 @@ static const struct page_flags_fields pff[] = { > static > char *format_page_flags(char *buf, char *end, unsigned long flags) > { > - unsigned long main_flags = flags & (BIT(NR_PAGEFLAGS) - 1); > + unsigned long main_flags = flags & ~PAGEFLAGS_MASK; > bool append = false; > int i; > >