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Date: Sat, 26 Dec 2020 13:16:09 -0800 From: Linus Torvalds <torvalds@...ux-foundation.org> To: Hugh Dickins <hughd@...gle.com> Cc: "Kirill A. Shutemov" <kirill@...temov.name>, Matthew Wilcox <willy@...radead.org>, "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>, Will Deacon <will@...nel.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Linux-MM <linux-mm@...ck.org>, Linux ARM <linux-arm-kernel@...ts.infradead.org>, Catalin Marinas <catalin.marinas@....com>, Jan Kara <jack@...e.cz>, Minchan Kim <minchan@...nel.org>, Andrew Morton <akpm@...ux-foundation.org>, Vinayak Menon <vinmenon@...eaurora.org>, Android Kernel Team <kernel-team@...roid.com> Subject: Re: [PATCH 1/2] mm: Allow architectures to request 'old' entries when prefaulting On Sat, Dec 26, 2020 at 1:04 PM Hugh Dickins <hughd@...gle.com> wrote: > > > Hold on. I guess this one will suffer from the same bug as the previous. > I was about to report back, after satisfactory overnight testing of that > version - provided that one big little bug is fixed: > > --- a/mm/filemap.c > +++ b/mm/filemap.c > @@ -2919,7 +2919,7 @@ static bool filemap_map_pmd(struct vm_fa > > if (pmd_none(*vmf->pmd) && > PageTransHuge(page) && > - do_set_pmd(vmf, page)) { > + do_set_pmd(vmf, page) == 0) { > unlock_page(page); > return true; > } I missed that entirely, because when just reading the patch it looks fine and I didn't look at what do_set_pmd() function returns outside the patch. And maybe it would be better to write it as if (pmd_none(*vmf->pmd) && PageTransHuge(page)) { vm_fault_t ret = do_set_pmd(vmf, page); if (!ret) { ... instead to make it a bit more explicit about how that return value is a vm_fault_t there... And see my other email about how I suspect there is still a leak in that patch for the previous test-case. Linus
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