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Shutemov" To: Wei Yang Cc: Wei Yang , akpm@linux-foundation.org, kirill.shutemov@linux.intel.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/2] mm/page_vma_mapped: use PMD_SIZE instead of calculating it Message-ID: <20191203094730.7oh4j5juh3jsx5dk@box> References: <20191128010321.21730-1-richardw.yang@linux.intel.com> <20191128083255.ab5rwj7gvktwunik@box.shutemov.name> <20191128212226.sfrhfs5m3q7m6tly@master> <20191202080315.oqtm3q7cyfkl5rma@box.shutemov.name> <20191202222151.xx4g3ry7mrcselh5@master> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191202222151.xx4g3ry7mrcselh5@master> User-Agent: NeoMutt/20180716 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 Mon, Dec 02, 2019 at 10:21:51PM +0000, Wei Yang wrote: > On Mon, Dec 02, 2019 at 11:03:15AM +0300, Kirill A. Shutemov wrote: > >On Thu, Nov 28, 2019 at 09:22:26PM +0000, Wei Yang wrote: > >> On Thu, Nov 28, 2019 at 11:32:55AM +0300, Kirill A. Shutemov wrote: > >> >On Thu, Nov 28, 2019 at 09:03:20AM +0800, Wei Yang wrote: > >> >> At this point, we are sure page is PageTransHuge, which means > >> >> hpage_nr_pages is HPAGE_PMD_NR. > >> >> > >> >> This is safe to use PMD_SIZE instead of calculating it. > >> >> > >> >> Signed-off-by: Wei Yang > >> >> --- > >> >> mm/page_vma_mapped.c | 2 +- > >> >> 1 file changed, 1 insertion(+), 1 deletion(-) > >> >> > >> >> diff --git a/mm/page_vma_mapped.c b/mm/page_vma_mapped.c > >> >> index eff4b4520c8d..76e03650a3ab 100644 > >> >> --- a/mm/page_vma_mapped.c > >> >> +++ b/mm/page_vma_mapped.c > >> >> @@ -223,7 +223,7 @@ bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw) > >> >> if (pvmw->address >= pvmw->vma->vm_end || > >> >> pvmw->address >= > >> >> __vma_address(pvmw->page, pvmw->vma) + > >> >> - hpage_nr_pages(pvmw->page) * PAGE_SIZE) > >> >> + PMD_SIZE) > >> >> return not_found(pvmw); > >> >> /* Did we cross page table boundary? */ > >> >> if (pvmw->address % PMD_SIZE == 0) { > >> > > >> >It is dubious cleanup. Maybe page_size(pvmw->page) instead? It will not > >> >break if we ever get PUD THP pages. > >> > > >> > >> Thanks for your comment. > >> > >> I took a look into the code again and found I may miss something. > >> > >> I found we support PUD THP pages, whilc hpage_nr_pages() just return > >> HPAGE_PMD_NR on PageTransHuge. Why this is not possible to return PUD number? > > > >We only support PUD THP for DAX. Means, we don't have struct page for it. > > > > BTW, may I ask why you suggest to use page_size() if we are sure only PMD THP > page is used here? To be more generic? Yeah. I would rather not touch it at all. -- Kirill A. Shutemov