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Received: from willy by casper.infradead.org with local (Exim 4.94.2 #2 (Red Hat Linux)) id 1q9Wvu-006kPi-9B; Wed, 14 Jun 2023 20:17:34 +0000 Date: Wed, 14 Jun 2023 21:17:34 +0100 From: Matthew Wilcox To: Andrew Morton Cc: "Vishal Moola (Oracle)" , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 2/5] mmzone: Introduce folio_migratetype() Message-ID: References: <20230614021312.34085-1-vishal.moola@gmail.com> <20230614021312.34085-3-vishal.moola@gmail.com> <20230614131305.2939f29e4372c94a8c6a56a8@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230614131305.2939f29e4372c94a8c6a56a8@linux-foundation.org> X-Rspamd-Queue-Id: 048BE1C0018 X-Rspam-User: X-Rspamd-Server: rspam02 X-Stat-Signature: cy343tah1k7cxcyom1u5187aadnyqumz X-HE-Tag: 1686773857-310199 X-HE-Meta: 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 7NyCpX/A Er9EkPjtnQ27de5UP141HlPSjOCZGV1kenLA7KdKFCheROEH5ZW6KMn6QnVZK3CRr6/oQdCG2NhYHW4NZPnD/VCi8lAekgfXoUaVplfRb//d8maarKxY+XZcZzoQJqtXiqPq4r7x7YSAohRhdXKm8U0LRw6rYYy4GHaatMtau9ELEslVS5TOrrA6LBwfJScdJO7XUtxNQ0KdwRYhzFqpoqYzzbocyIxiHMynKChMtNMm5rj7SN91u7sy8fj1d1c02hTu4rwEQu75NhVuAGkWjL597SA== 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, Jun 14, 2023 at 01:13:05PM -0700, Andrew Morton wrote: > On Tue, 13 Jun 2023 19:13:09 -0700 "Vishal Moola (Oracle)" wrote: > > > Introduce folio_migratetype() as a folio equivalent for > > get_pageblock_migratetype(). This function intends to return the > > migratetype the folio is located in, hence the name choice. > > > > ... > > > > --- a/include/linux/mmzone.h > > +++ b/include/linux/mmzone.h > > @@ -105,6 +105,9 @@ extern int page_group_by_mobility_disabled; > > #define get_pageblock_migratetype(page) \ > > get_pfnblock_flags_mask(page, page_to_pfn(page), MIGRATETYPE_MASK) > > > > +#define folio_migratetype(folio) \ > > + get_pfnblock_flags_mask(&folio->page, folio_pfn(folio), \ > > + MIGRATETYPE_MASK) > > Theoretically this is risky because it evaluates its argument more than > once. Although folio_migratetype(folio++) seems an unlikely thing to do. folio++ is always an unsafe thing to do. folios are not consecutive in memory (unless we know they're order-0). > An inlined C function is always preferable. My quick attempt at that > reveals that the header files are All Messed Up As Usual. The page-equivalent of this also evaluates its arguments more than once, so it doesn't see too risky for now?