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Date: Mon, 31 Oct 2022 10:36:08 +0100 From: Peter Zijlstra <peterz@...radead.org> To: Linus Torvalds <torvalds@...ux-foundation.org> Cc: Nadav Amit <nadav.amit@...il.com>, Jann Horn <jannh@...gle.com>, John Hubbard <jhubbard@...dia.com>, X86 ML <x86@...nel.org>, Matthew Wilcox <willy@...radead.org>, Andrew Morton <akpm@...ux-foundation.org>, kernel list <linux-kernel@...r.kernel.org>, Linux-MM <linux-mm@...ck.org>, Andrea Arcangeli <aarcange@...hat.com>, "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>, jroedel@...e.de, ubizjak@...il.com, Alistair Popple <apopple@...dia.com> Subject: Re: [PATCH 01/13] mm: Update ptep_get_lockless()s comment On Sun, Oct 30, 2022 at 06:47:23PM -0700, Linus Torvalds wrote: > Also, it's worth noting that zap_pte_range() does this sanity test: > > if (unlikely(page_mapcount(page) < 0)) > print_bad_pte(vma, addr, ptent, page); > > and that is likely worthless now (because it hasn't actually > decremented the mapcount yet). I didn't remove it, because I wasn't > sure which option was best: > > (a) just remove it entirely > > (b) change the "< 0" to "<= 0" > > (c) move it to clean_and_free_pages_and_swap_cache() that actually > does the page_zap_pte_rmap() now. I'm leaning towards (c); simply because the error case is so terrifying I feel we should check for it (and I do have vague memories of us actually hitting something like this in the very distant past).
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