linux-kernel - Re: [PATCH v3 12/24] erofs: introduce tagged pointer

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Message-ID: <CAOQ4uxh04gwbM4yFaVpWHVwmJ4BJo4bZaU8A4_NQh2bO_xCHJg@mail.gmail.com>
Date:   Mon, 22 Jul 2019 07:39:27 +0300
From:   Amir Goldstein <amir73il@...il.com>
To:     Gao Xiang <gaoxiang25@...wei.com>
Cc:     Alexander Viro <viro@...iv.linux.org.uk>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        "Theodore Ts'o" <tytso@....edu>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>,
        devel@...verdev.osuosl.org, LKML <linux-kernel@...r.kernel.org>,
        linux-erofs@...ts.ozlabs.org, Chao Yu <yuchao0@...wei.com>,
        Miao Xie <miaoxie@...wei.com>,
        Li Guifu <bluce.liguifu@...wei.com>,
        Fang Wei <fangwei1@...wei.com>
Subject: Re: [PATCH v3 12/24] erofs: introduce tagged pointer

On Mon, Jul 22, 2019 at 5:54 AM Gao Xiang <gaoxiang25@...wei.com> wrote:
>
> Currently kernel has scattered tagged pointer usages
> hacked by hand in plain code, without a unique and
> portable functionset to highlight the tagged pointer
> itself and wrap these hacked code in order to clean up
> all over meaningless magic masks.
>
> This patch introduces simple generic methods to fold
> tags into a pointer integer. Currently it supports
> the last n bits of the pointer for tags, which can be
> selected by users.
>
> In addition, it will also be used for the upcoming EROFS
> filesystem, which heavily uses tagged pointer pproach
>  to reduce extra memory allocation.
>
> Link: https://en.wikipedia.org/wiki/Tagged_pointer

Well, it won't do much good for other kernel users in fs/erofs/ ;-)

I think now would be a right time to promote this facility to
include/linux as you initially proposed.
I don't recall you got any objections. No ACKs either, but I think
that was the good kind of silence (?)

You might want to post the __fdget conversion patch [1] as a
bonus patch on top of your series.

Thanks,
Amir.

[1] https://lore.kernel.org/linux-fsdevel/1530543233-65279-2-git-send-email-gaoxiang25@huawei.com/