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Received: from willy by casper.infradead.org with local (Exim 4.97.1 #2 (Red Hat Linux)) id 1rl6jr-0000000AFSp-1mzs; Fri, 15 Mar 2024 12:32:43 +0000 Date: Fri, 15 Mar 2024 12:32:43 +0000 From: Matthew Wilcox To: Miaohe Lin Cc: Andrew Morton , linux-mm@kvack.org, Oscar Salvador , David Hildenbrand Subject: Re: [PATCH 1/2] mm: Turn folio_test_hugetlb into a PageType Message-ID: References: <20240314012506.1600378-1-willy@infradead.org> <20240314012506.1600378-2-willy@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: AC696180010 X-Stat-Signature: b5jktp9o4y43o5ph49bhotw8kk58pk4y X-Rspam-User: X-HE-Tag: 1710505969-444710 X-HE-Meta: U2FsdGVkX1/1JijecxaeJp4fq4a7QE8USRAFC8eS9mSY1G5RQ06i2ljFICD6CfYZued9Z0u5pRwsE8oTfSroKIUw3Oxa74oIeJzw1fI0Ia+32SrNEILoQK3aVMM14/Iw5xHbIJlyg2FkMI5mHVqJ+bv2hQ9Px8STskJdZ5p3bIYBXcBv1urU41OqOCmawm6lnLG7j5ni4V5OKdnuMXUEAUApaH7s6wljAl7nR0Qgved+gK1s4p//GARJOKaJS0vc3Wnsuj/75cSWNGXQR+dB5j9syKkjd3HshsEU7eNrJvMTp9V6FUDvgieyV2Pxp81/rEytJnjOfBWHNLm0dbJARbBdLFziLJxir/R28BkHlVuIsba779vI2i3apdrMYQYvwFQOZWYkdGyi7F0IC59hJHp4I5RTdrjwP8dCYSB8iTAFwjABRHgJs9OgDzkHWo+HVHeZhlrHUmzTUjJyjjyLEcc0MFwE6GuZoVzshTgfpgOGSnGboRESpc99NR5q9hzWIy6lk2EVsY7f8r0nOx3tTTyDLF8Ch11Xl/2Szhh57HhjmrByip6JoFE5oDLX6bBQsw5Uhc3mi8MQCmKnYjne17MWb4pCapO6Y0wyHsMpkFdRsuitu3Umm3t/Q8rC5rlHWeJ/6COfsnPd89DddOspYDKEHUlq/SBZu3JpqvzEMnr9CWM2NzniUVIeUQy0Oq4cVAdj6Vo5viGmwKGpVppqo8/n/b5RKuEB2Eo3ZzPvpNZ7Ps6zZC/pmvVcIv9vr0bDO/ziDkRZ4C4rInMhzborFZG6hu3qt1O/0cbw4Y943jWfnua++Ty6gAn6kTcVY8KGLSLO/xtrNcIBz124bR3qQbNRXc5rP17mInBpthYfbDtFtrCeaFHsaGmtZOoUABMP 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, Mar 15, 2024 at 02:19:10PM +0800, Miaohe Lin wrote: > On 2024/3/14 22:33, Matthew Wilcox wrote: > > I actually want to do a bit more here ... > > > > +++ b/mm/debug.c > > @@ -58,15 +58,10 @@ static void __dump_folio(struct folio *folio, struct page *page, > > int mapcount = 0; > > char *type = ""; > > > > - /* > > - * page->_mapcount space in struct page is used by slab pages to > > - * encode own info, and we must avoid calling page_folio() again. > > - */ > > - if (!folio_test_slab(folio)) { > > + if (!page_has_type(page)) { > > mapcount = atomic_read(&page->_mapcount) + 1; > > - if (folio_test_large(folio)) > > - mapcount += folio_entire_mapcount(folio); > > - } > > + if (folio_test_large(folio)) > > + mapcount += folio_entire_mapcount(folio); > > Why folio_test_large is not within the "if (!page_has_type(page))" block? I think a slab page could also be large folio. > Or am I miss something? Slab pages don't use the first tail page so folio_entire_mapcount will be 0 for them. And we don't want the folio_test_large() to be gated by page_has_type() because hugetlb pages (after this patch) will be in the page_has_type() category. So for hugetlb pages, we want to not read page->mapcount (leaving mapcount at zero), but we do want to read the entire_mapcount.