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From: Linus Torvalds <torvalds@linux-foundation.org>
To: Will Deacon <will@kernel.org>
Cc: 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>,
	"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
	Vinayak Menon <vinmenon@codeaurora.org>,
	Hugh Dickins <hughd@google.com>,
	Android Kernel Team <kernel-team@android.com>
Subject: Re: [RFC PATCH 4/8] mm: Separate fault info out of 'struct vm_fault'
Date: Thu, 14 Jan 2021 11:09:01 -0800	[thread overview]
Message-ID: <CAHk-=wjdJmL22+zk3_rWAfEJJCf=oDxiJ530qk-WNk_Ji0qhxw@mail.gmail.com> (raw)
In-Reply-To: <20210114190021.GB13135@willie-the-truck>

On Thu, Jan 14, 2021 at 11:00 AM Will Deacon <will@kernel.org> wrote:
>
> I tried that initially, but I found that I had to make all of the
> members const to get it to work, at which point the anonymous struct
> wasn't really adding anything. Did I just botch the syntax?

I'm not sure what you tried. But this stupid test-case sure works for me:

    struct hello {
        const struct {
                unsigned long address;
        };
        unsigned int flags;
    };

    extern int fn(struct hello *);

    int test(void)
    {
        struct hello a = {
                .address = 1,
        };
        a.flags = 0;
        return fn(&a);
    }

and because "address" is in that unnamed constant struct, you can only
set it within that initializer, and cannot do

        a.address = 0;

without an error (the way you _can_ do "a.flags = 0").

I don't see naming the struct making a difference - apart from forcing
that big rename patch, of course.

But maybe we're talking about different issues?

            Linus

WARNING: multiple messages have this Message-ID

From: Linus Torvalds <torvalds@linux-foundation.org>
To: Will Deacon <will@kernel.org>
Cc: 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>,
	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>,
	Android Kernel Team <kernel-team@android.com>,
	Linux ARM <linux-arm-kernel@lists.infradead.org>
Subject: Re: [RFC PATCH 4/8] mm: Separate fault info out of 'struct vm_fault'
Date: Thu, 14 Jan 2021 11:09:01 -0800	[thread overview]
Message-ID: <CAHk-=wjdJmL22+zk3_rWAfEJJCf=oDxiJ530qk-WNk_Ji0qhxw@mail.gmail.com> (raw)
In-Reply-To: <20210114190021.GB13135@willie-the-truck>

On Thu, Jan 14, 2021 at 11:00 AM Will Deacon <will@kernel.org> wrote:
>
> I tried that initially, but I found that I had to make all of the
> members const to get it to work, at which point the anonymous struct
> wasn't really adding anything. Did I just botch the syntax?

I'm not sure what you tried. But this stupid test-case sure works for me:

    struct hello {
        const struct {
                unsigned long address;
        };
        unsigned int flags;
    };

    extern int fn(struct hello *);

    int test(void)
    {
        struct hello a = {
                .address = 1,
        };
        a.flags = 0;
        return fn(&a);
    }

and because "address" is in that unnamed constant struct, you can only
set it within that initializer, and cannot do

        a.address = 0;

without an error (the way you _can_ do "a.flags = 0").

I don't see naming the struct making a difference - apart from forcing
that big rename patch, of course.

But maybe we're talking about different issues?

            Linus

_______________________________________________
linux-arm-kernel mailing list
linux-arm-kernel@lists.infradead.org
http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

  reply	other threads:[~2021-01-14 19:10 UTC|newest]

Thread overview: 52+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-01-14 17:59 [PATCH v3 0/8] Create 'old' ptes for faultaround mappings on arm64 with hardware access flag Will Deacon
2021-01-14 17:59 ` Will Deacon
2021-01-14 17:59 ` [PATCH v3 1/8] mm: Cleanup faultaround and finish_fault() codepaths Will Deacon
2021-01-14 17:59   ` Will Deacon
2021-02-09 20:24   ` Guenter Roeck
2021-02-09 20:24     ` Guenter Roeck
2021-02-10 11:44     ` Will Deacon
2021-02-10 11:44       ` Will Deacon
2021-02-10 14:57       ` Guenter Roeck
2021-02-10 14:57         ` Guenter Roeck
2021-01-14 17:59 ` [PATCH v3 2/8] mm: Allow architectures to request 'old' entries when prefaulting Will Deacon
2021-01-14 17:59   ` Will Deacon
2021-01-14 17:59 ` [PATCH v3 3/8] arm64: mm: Implement arch_wants_old_prefaulted_pte() Will Deacon
2021-01-14 17:59   ` Will Deacon
2021-01-14 17:59 ` [RFC PATCH 4/8] mm: Separate fault info out of 'struct vm_fault' Will Deacon
2021-01-14 18:16   ` Linus Torvalds
2021-01-14 18:16     ` Linus Torvalds
2021-01-14 18:16     ` Linus Torvalds
2021-01-14 19:00     ` Will Deacon
2021-01-14 19:00       ` Will Deacon
2021-01-14 19:09       ` Linus Torvalds [this message]
2021-01-14 19:09         ` Linus Torvalds
2021-01-14 19:09         ` Linus Torvalds
2021-01-14 19:41         ` Will Deacon
2021-01-14 19:41           ` Will Deacon
2021-01-14 20:09           ` Nick Desaulniers
2021-01-14 20:09             ` Nick Desaulniers
2021-01-14 20:09             ` Nick Desaulniers
2021-01-14 21:11           ` Linus Torvalds
2021-01-14 21:11             ` Linus Torvalds
2021-01-14 21:11             ` Linus Torvalds
2021-01-15  9:23             ` Will Deacon
2021-01-15  9:23               ` Will Deacon
2021-01-15 21:32               ` Linus Torvalds
2021-01-15 21:32                 ` Linus Torvalds
2021-01-15 21:32                 ` Linus Torvalds
2021-01-20  0:00                 ` Nick Desaulniers
2021-01-20  0:00                   ` Nick Desaulniers
2021-01-20  0:00                   ` Nick Desaulniers
2021-01-14 17:59 ` [RFC PATCH 5/8] mm: Pass 'address' to map to do_set_pte() and drop FAULT_FLAG_PREFAULT Will Deacon
2021-01-14 17:59   ` Will Deacon
2021-01-14 18:17   ` Linus Torvalds
2021-01-14 18:17     ` Linus Torvalds
2021-01-14 18:17     ` Linus Torvalds
2021-01-15 10:24     ` Will Deacon
2021-01-15 10:24       ` Will Deacon
2021-01-14 17:59 ` [RFC PATCH 6/8] mm: Avoid modifying vmf.info.address in __collapse_huge_page_swapin() Will Deacon
2021-01-14 17:59   ` Will Deacon
2021-01-14 17:59 ` [RFC PATCH 7/8] mm: Use static initialisers for 'info' field of 'struct vm_fault' Will Deacon
2021-01-14 17:59   ` Will Deacon
2021-01-14 17:59 ` [RFC PATCH 8/8] mm: Mark 'info' field of 'struct vm_fault' as 'const' Will Deacon
2021-01-14 17:59   ` Will Deacon

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