linux-kernel - Re: [PATCH v4 2/2] mm/vmalloc.c: Modify struct vmap

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CAD7_sbEoGRUOJdcHnfUTzP7GfUhCdhfo8uBpUFZ9HGwS36VkSg@mail.gmail.com>
Date:   Fri, 12 Jul 2019 23:09:00 +0800
From:   Pengfei Li <lpf.vector@...il.com>
To:     Matthew Wilcox <willy@...radead.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Uladzislau Rezki <urezki@...il.com>, rpenyaev@...e.de,
        peterz@...radead.org, guro@...com, rick.p.edgecombe@...el.com,
        rppt@...ux.ibm.com, aryabinin@...tuozzo.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 2/2] mm/vmalloc.c: Modify struct vmap_area to reduce
 its size

On Fri, Jul 12, 2019 at 9:49 PM Matthew Wilcox <willy@...radead.org> wrote:
>
> On Fri, Jul 12, 2019 at 08:02:13PM +0800, Pengfei Li wrote:
>
> I don't think you need struct union struct union.  Because llist_node
> is just a pointer, you can get the same savings with just:
>
>         union {
>                 struct llist_node purge_list;
>                 struct vm_struct *vm;
>                 unsigned long subtree_max_size;
>         };
>

Thanks for your comments.

As you said, I did this in v3.
https://patchwork.kernel.org/patch/11031507/

The reason why I use struct union struct in v4 is that I want to
express "in the tree" and "in the purge list" are two completely
isolated cases.

struct vmap_area {
        union {
                struct {        /* Case A: In the tree */
                        ...
                };

                struct {        /* Case B: In the purge list */
                        ...
                };
        };
};

The "rb_node" and "list" should also not be used when va is in
the purge list

what do you think of this idea?