From: Linus Torvalds <torvalds@linux-foundation.org>
To: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Android Kernel Team <kernel-team@android.com>,
Jan Kara <jack@suse.cz>, Minchan Kim <minchan@kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Matthew Wilcox <willy@infradead.org>,
Linux-MM <linux-mm@kvack.org>,
Vinayak Menon <vinmenon@codeaurora.org>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
Will Deacon <will@kernel.org>,
Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH 1/2] mm: Allow architectures to request 'old' entries when prefaulting
Date: Sat, 19 Dec 2020 12:34:17 -0800 [thread overview]
Message-ID: <CAHk-=wifcVaxaTn_RbZ=idfYFazTPwm8t5cB1rY6xEBjbcfO5g@mail.gmail.com> (raw)
In-Reply-To: <20201219124103.w6isern3ywc7xbur@box>
On Sat, Dec 19, 2020 at 4:41 AM Kirill A. Shutemov <kirill@shutemov.name> wrote:
>
> @@ -2884,19 +2966,18 @@ void filemap_map_pages(struct vm_fault *vmf,
> if (vmf->pte)
> vmf->pte += xas.xa_index - last_pgoff;
> last_pgoff = xas.xa_index;
> - if (alloc_set_pte(vmf, page))
> - goto unlock;
> + if (pte_none(*vmf->pte))
> + do_set_pte(vmf, page);
> + /* no need to invalidate: a not-present page won't be cached */
> + update_mmu_cache(vma, vmf->address, vmf->pte);
> unlock_page(head);
> - goto next;
> + continue;
This can't be right.
Look at what happens if "pte_none()" is not true.. It won't install
the new pte, but it also won't drop the ref to the page.
So I think it needs to be
- if (alloc_set_pte(vmf, page))
+ if (!pte_none(*vmf->pte))
goto unlock;
+ do_set_pte(vmf, page);
instead, so that the "if somebody else already filled the page table"
case gets handled right.
Hmm?
Linus
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next prev parent reply other threads:[~2020-12-19 20:35 UTC|newest]
Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-12-09 16:39 [PATCH 0/2] Create 'old' ptes for faultaround mappings on arm64 with hardware access flag Will Deacon
2020-12-09 16:39 ` [PATCH 1/2] mm: Allow architectures to request 'old' entries when prefaulting Will Deacon
2020-12-09 17:58 ` Linus Torvalds
2020-12-09 18:40 ` Will Deacon
2020-12-09 19:04 ` Linus Torvalds
2020-12-09 20:32 ` Matthew Wilcox
2020-12-09 21:04 ` Linus Torvalds
2020-12-10 15:08 ` Kirill A. Shutemov
2020-12-10 17:23 ` Linus Torvalds
2020-12-14 16:07 ` Kirill A. Shutemov
2020-12-14 17:54 ` Linus Torvalds
2020-12-14 18:56 ` Matthew Wilcox
2020-12-16 17:07 ` Kirill A. Shutemov
2020-12-16 18:41 ` Linus Torvalds
2020-12-17 10:54 ` Kirill A. Shutemov
2020-12-17 18:22 ` Linus Torvalds
2020-12-18 11:04 ` Kirill A. Shutemov
2020-12-18 18:56 ` Linus Torvalds
2020-12-19 12:41 ` Kirill A. Shutemov
2020-12-19 20:08 ` Linus Torvalds
2020-12-19 20:34 ` Linus Torvalds [this message]
2020-12-22 10:00 ` Kirill A. Shutemov
2020-12-24 4:04 ` Hugh Dickins
2020-12-25 11:31 ` Kirill A. Shutemov
2020-12-26 17:57 ` Linus Torvalds
2020-12-26 20:43 ` Kirill A. Shutemov
2020-12-26 21:03 ` Hugh Dickins
2020-12-26 21:16 ` Linus Torvalds
2020-12-26 22:40 ` Kirill A. Shutemov
2020-12-27 0:45 ` Hugh Dickins
2020-12-27 2:38 ` Hugh Dickins
2020-12-27 19:38 ` Linus Torvalds
2020-12-27 20:32 ` Damian Tometzki
2020-12-27 22:35 ` Hugh Dickins
2020-12-27 23:12 ` Linus Torvalds
2020-12-27 23:40 ` Linus Torvalds
2020-12-27 23:55 ` Kirill A. Shutemov
2020-12-27 23:48 ` Kirill A. Shutemov
2020-12-28 1:54 ` Linus Torvalds
2020-12-28 6:43 ` Hugh Dickins
2020-12-28 12:53 ` Kirill A. Shutemov
2020-12-28 18:47 ` Linus Torvalds
2020-12-28 21:58 ` Linus Torvalds
2020-12-29 13:28 ` Kirill A. Shutemov
2020-12-29 15:19 ` Matthew Wilcox
2020-12-29 20:52 ` Linus Torvalds
2020-12-28 22:05 ` Kirill A. Shutemov
2020-12-28 22:12 ` Kirill A. Shutemov
2020-12-29 4:35 ` Hugh Dickins
2020-12-28 23:28 ` Linus Torvalds
2020-12-26 21:07 ` Linus Torvalds
2020-12-26 21:41 ` Matthew Wilcox
2020-12-09 16:39 ` [PATCH 2/2] arm64: mm: Implement arch_wants_old_faultaround_pte() Will Deacon
2020-12-09 18:35 ` Catalin Marinas
2020-12-09 18:46 ` Will Deacon
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