From: Linus Torvalds <torvalds@linux-foundation.org>
To: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: Hugh Dickins <hughd@google.com>,
Matthew Wilcox <willy@infradead.org>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
Will Deacon <will@kernel.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linux-MM <linux-mm@kvack.org>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Jan Kara <jack@suse.cz>, Minchan Kim <minchan@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Vinayak Menon <vinmenon@codeaurora.org>,
Android Kernel Team <kernel-team@android.com>
Subject: Re: [PATCH 1/2] mm: Allow architectures to request 'old' entries when prefaulting
Date: Mon, 28 Dec 2020 13:58:40 -0800 [thread overview]
Message-ID: <CAHk-=whwJcJubrP8ELH=UvEHX146_Jdmfn992W55KJgPvUx_Uw@mail.gmail.com> (raw)
In-Reply-To: <CAHk-=wg4bzJ9ugrOp7DBoMjNpHechm4QWb0-HC3A_pN564RU5A@mail.gmail.com>
On Mon, Dec 28, 2020 at 10:47 AM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> I personally think it's wrong to update vmf->pte at all. We should
> just have a local 'ptep' pointer that we update as we walk along. But
> that requires another change to the calling convention, namely to
> "do_set_pte()".
Actually, I think we should not use do_set_pte() at all.
About half of do_set_pte() is about the FAULT_FLAG_WRITE case, which
the fault-around code never has set (and would be wrong if it did).
So I think do_set_pte() should be made local to mm/memory.c, and the
filemap_map_pages() code should do it's own simplified version that
just does the non-writable case, and that just gets passed the address
and the pte pointer.
At that point, there would no longer be any need to update the
address/pte fields in the vmf struct, and in fact I think it could be
made a "const" pointer in this cal chain.
This is all just from looking at the code, I haven't tried to write a
patch to do this, so I might be missing some case.
Linus
WARNING: multiple messages have this Message-ID (diff)
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>,
Hugh Dickins <hughd@google.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>,
Linux ARM <linux-arm-kernel@lists.infradead.org>,
Andrew Morton <akpm@linux-foundation.org>,
Will Deacon <will@kernel.org>,
"Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
Subject: Re: [PATCH 1/2] mm: Allow architectures to request 'old' entries when prefaulting
Date: Mon, 28 Dec 2020 13:58:40 -0800 [thread overview]
Message-ID: <CAHk-=whwJcJubrP8ELH=UvEHX146_Jdmfn992W55KJgPvUx_Uw@mail.gmail.com> (raw)
In-Reply-To: <CAHk-=wg4bzJ9ugrOp7DBoMjNpHechm4QWb0-HC3A_pN564RU5A@mail.gmail.com>
On Mon, Dec 28, 2020 at 10:47 AM Linus Torvalds
<torvalds@linux-foundation.org> wrote:
>
> I personally think it's wrong to update vmf->pte at all. We should
> just have a local 'ptep' pointer that we update as we walk along. But
> that requires another change to the calling convention, namely to
> "do_set_pte()".
Actually, I think we should not use do_set_pte() at all.
About half of do_set_pte() is about the FAULT_FLAG_WRITE case, which
the fault-around code never has set (and would be wrong if it did).
So I think do_set_pte() should be made local to mm/memory.c, and the
filemap_map_pages() code should do it's own simplified version that
just does the non-writable case, and that just gets passed the address
and the pte pointer.
At that point, there would no longer be any need to update the
address/pte fields in the vmf struct, and in fact I think it could be
made a "const" pointer in this cal chain.
This is all just from looking at the code, I haven't tried to write a
patch to do this, so I might be missing some case.
Linus
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next prev parent reply other threads:[~2020-12-28 22:59 UTC|newest]
Thread overview: 138+ 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 ` Will Deacon
2020-12-09 16:39 ` [PATCH 1/2] mm: Allow architectures to request 'old' entries when prefaulting Will Deacon
2020-12-09 16:39 ` Will Deacon
2020-12-09 17:58 ` Linus Torvalds
2020-12-09 17:58 ` Linus Torvalds
2020-12-09 17:58 ` Linus Torvalds
2020-12-09 18:40 ` Will Deacon
2020-12-09 18:40 ` Will Deacon
2020-12-09 19:04 ` Linus Torvalds
2020-12-09 19:04 ` Linus Torvalds
2020-12-09 19:04 ` Linus Torvalds
2020-12-09 20:32 ` Matthew Wilcox
2020-12-09 20:32 ` Matthew Wilcox
2020-12-09 21:04 ` Linus Torvalds
2020-12-09 21:04 ` Linus Torvalds
2020-12-09 21:04 ` Linus Torvalds
2020-12-10 15:08 ` Kirill A. Shutemov
2020-12-10 15:08 ` Kirill A. Shutemov
2020-12-10 17:23 ` Linus Torvalds
2020-12-10 17:23 ` Linus Torvalds
2020-12-10 17:23 ` Linus Torvalds
2020-12-14 16:07 ` Kirill A. Shutemov
2020-12-14 16:07 ` Kirill A. Shutemov
2020-12-14 17:54 ` Linus Torvalds
2020-12-14 17:54 ` Linus Torvalds
2020-12-14 17:54 ` Linus Torvalds
2020-12-14 18:56 ` Matthew Wilcox
2020-12-14 18:56 ` Matthew Wilcox
2020-12-16 17:07 ` Kirill A. Shutemov
2020-12-16 17:07 ` Kirill A. Shutemov
2020-12-16 18:41 ` Linus Torvalds
2020-12-16 18:41 ` Linus Torvalds
2020-12-16 18:41 ` Linus Torvalds
2020-12-17 10:54 ` Kirill A. Shutemov
2020-12-17 10:54 ` Kirill A. Shutemov
2020-12-17 18:22 ` Linus Torvalds
2020-12-17 18:22 ` Linus Torvalds
2020-12-17 18:22 ` Linus Torvalds
2020-12-18 11:04 ` Kirill A. Shutemov
2020-12-18 11:04 ` Kirill A. Shutemov
2020-12-18 18:56 ` Linus Torvalds
2020-12-18 18:56 ` Linus Torvalds
2020-12-18 18:56 ` Linus Torvalds
2020-12-19 12:41 ` Kirill A. Shutemov
2020-12-19 12:41 ` Kirill A. Shutemov
2020-12-19 20:08 ` Linus Torvalds
2020-12-19 20:08 ` Linus Torvalds
2020-12-19 20:08 ` Linus Torvalds
2020-12-19 20:34 ` Linus Torvalds
2020-12-19 20:34 ` Linus Torvalds
2020-12-19 20:34 ` Linus Torvalds
2020-12-22 10:00 ` Kirill A. Shutemov
2020-12-22 10:00 ` Kirill A. Shutemov
2020-12-24 4:04 ` Hugh Dickins
2020-12-24 4:04 ` Hugh Dickins
2020-12-24 4:04 ` Hugh Dickins
2020-12-25 11:31 ` Kirill A. Shutemov
2020-12-25 11:31 ` Kirill A. Shutemov
2020-12-26 17:57 ` Linus Torvalds
2020-12-26 17:57 ` Linus Torvalds
2020-12-26 17:57 ` Linus Torvalds
2020-12-26 20:43 ` Kirill A. Shutemov
2020-12-26 20:43 ` Kirill A. Shutemov
2020-12-26 21:03 ` Hugh Dickins
2020-12-26 21:03 ` Hugh Dickins
2020-12-26 21:03 ` Hugh Dickins
2020-12-26 21:16 ` Linus Torvalds
2020-12-26 21:16 ` Linus Torvalds
2020-12-26 21:16 ` Linus Torvalds
2020-12-26 22:40 ` Kirill A. Shutemov
2020-12-26 22:40 ` Kirill A. Shutemov
2020-12-27 0:45 ` Hugh Dickins
2020-12-27 0:45 ` Hugh Dickins
2020-12-27 0:45 ` Hugh Dickins
2020-12-27 2:38 ` Hugh Dickins
2020-12-27 2:38 ` Hugh Dickins
2020-12-27 2:38 ` Hugh Dickins
2020-12-27 19:38 ` Linus Torvalds
2020-12-27 19:38 ` Linus Torvalds
2020-12-27 19:38 ` Linus Torvalds
2020-12-27 20:32 ` Damian Tometzki
2020-12-27 20:32 ` Damian Tometzki
2020-12-27 22:35 ` Hugh Dickins
2020-12-27 22:35 ` Hugh Dickins
2020-12-27 22:35 ` Hugh Dickins
2020-12-27 23:12 ` Linus Torvalds
2020-12-27 23:12 ` Linus Torvalds
2020-12-27 23:12 ` Linus Torvalds
2020-12-27 23:40 ` Linus Torvalds
2020-12-27 23:40 ` Linus Torvalds
2020-12-27 23:40 ` Linus Torvalds
2020-12-27 23:55 ` Kirill A. Shutemov
2020-12-27 23:55 ` Kirill A. Shutemov
2020-12-27 23:48 ` Kirill A. Shutemov
2020-12-27 23:48 ` Kirill A. Shutemov
2020-12-28 1:54 ` Linus Torvalds
2020-12-28 1:54 ` Linus Torvalds
2020-12-28 1:54 ` Linus Torvalds
2020-12-28 6:43 ` Hugh Dickins
2020-12-28 6:43 ` Hugh Dickins
2020-12-28 6:43 ` Hugh Dickins
2020-12-28 12:53 ` Kirill A. Shutemov
2020-12-28 12:53 ` Kirill A. Shutemov
2020-12-28 18:47 ` Linus Torvalds
2020-12-28 18:47 ` Linus Torvalds
2020-12-28 18:47 ` Linus Torvalds
2020-12-28 21:58 ` Linus Torvalds [this message]
2020-12-28 21:58 ` Linus Torvalds
2020-12-28 21:58 ` Linus Torvalds
2020-12-29 13:28 ` Kirill A. Shutemov
2020-12-29 13:28 ` Kirill A. Shutemov
2020-12-29 15:19 ` Matthew Wilcox
2020-12-29 15:19 ` Matthew Wilcox
2020-12-29 20:52 ` Linus Torvalds
2020-12-29 20:52 ` Linus Torvalds
2020-12-29 20:52 ` Linus Torvalds
2020-12-28 22:05 ` Kirill A. Shutemov
2020-12-28 22:05 ` Kirill A. Shutemov
2020-12-28 22:12 ` Kirill A. Shutemov
2020-12-28 22:12 ` Kirill A. Shutemov
2020-12-29 4:35 ` Hugh Dickins
2020-12-29 4:35 ` Hugh Dickins
2020-12-29 4:35 ` Hugh Dickins
2020-12-28 23:28 ` Linus Torvalds
2020-12-28 23:28 ` Linus Torvalds
2020-12-28 23:28 ` Linus Torvalds
2020-12-26 21:07 ` Linus Torvalds
2020-12-26 21:07 ` Linus Torvalds
2020-12-26 21:07 ` Linus Torvalds
2020-12-26 21:41 ` Matthew Wilcox
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 16:39 ` Will Deacon
2020-12-09 18:35 ` Catalin Marinas
2020-12-09 18:35 ` Catalin Marinas
2020-12-09 18:46 ` Will Deacon
2020-12-09 18:46 ` Will Deacon
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