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Subject: Re: [RFC PATCH 4/8] mm/madvise: define madvise behavior in a struct
From:   Nadav Amit <nadav.amit@gmail.com>
In-Reply-To: <20210927121449.kac5g25aejbwvylf@box>
Date:   Mon, 27 Sep 2021 13:36:20 -0700
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Linux-MM <linux-mm@kvack.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Peter Xu <peterx@redhat.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Minchan Kim <minchan@kernel.org>,
        Colin Cross <ccross@google.com>,
        Suren Baghdasarya <surenb@google.com>,
        Mike Rapoport <rppt@linux.vnet.ibm.com>
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Message-Id: <CB2E02DB-0675-4053-B223-06D4BF26641C@gmail.com>
References: <20210926161259.238054-1-namit@vmware.com>
 <20210926161259.238054-5-namit@vmware.com>
 <20210927093103.g3cszw75gfctwtzk@box.shutemov.name>
 <48D4E700-0005-46D4-8EAA-B839D8449C66@gmail.com>
 <20210927121449.kac5g25aejbwvylf@box>
To:     "Kirill A. Shutemov" <kirill@shutemov.name>
Precedence: bulk


> On Sep 27, 2021, at 5:14 AM, Kirill A. Shutemov <kirill@shutemov.name> =
wrote:
>=20
> On Mon, Sep 27, 2021 at 03:31:21AM -0700, Nadav Amit wrote:
>>=20
>>=20
>>> On Sep 27, 2021, at 2:31 AM, Kirill A. Shutemov =
<kirill@shutemov.name> wrote:
>>>=20
>>> On Sun, Sep 26, 2021 at 09:12:55AM -0700, Nadav Amit wrote:
>>>> From: Nadav Amit <namit@vmware.com>
>>>>=20
>>>> The different behaviors of madvise are different in several ways, =
which
>>>> are distributed across several functions. Use the design pattern =
from
>>>> iouring in order to define the actions that are required for each
>>>> behavior.
>>>>=20
>>>> The next patches will get rid of old helper functions that are =
modified
>>>> in this patch and the redundant use of array_index_nospec(). The =
next
>>>> patches will add more actions for each leaf into the new struct.
>>>=20

[ snip ]

>>> MADV_SOFT_OFFLINE+1 smells bad.
>>=20
>> I can set another constant instead and let the compiler shout if =
anything
>> outside the array is initialized.
>=20
> I would rather introduce a function that would return struct =
madvise_info
> for a given behavior. The function would have a switch inside. The =
default:
> may have BUILD_BUG() or something.

Sounds better than my solution. I will do so.=