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From: Suren Baghdasaryan <surenb@google.com>
To: David Hildenbrand <david@redhat.com>
Cc: "Michal Hocko" <mhocko@suse.com>,
	"Kees Cook" <keescook@chromium.org>,
	"Pavel Machek" <pavel@ucw.cz>,
	"Rasmus Villemoes" <linux@rasmusvillemoes.dk>,
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Subject: Re: [PATCH v10 3/3] mm: add anonymous vma name refcounting
Date: Tue, 12 Oct 2021 10:01:05 -0700	[thread overview]
Message-ID: <CAJuCfpGTCM_Rf3GEyzpR5UOTfgGKTY0_rvAbGdtjbyabFhrRAw@mail.gmail.com> (raw)
In-Reply-To: <26f9db1e-69e9-1a54-6d49-45c0c180067c@redhat.com>

On Tue, Oct 12, 2021 at 12:44 AM David Hildenbrand <david@redhat.com> wrote:
>
> > I'm still evaluating the proposal to use memfds but I'm not sure if
> > the issue that David Hildenbrand mentioned about additional memory
> > consumed in pagecache (which has to be addressed) is the only one we
> > will encounter with this approach. If anyone knows of any potential
> > issues with using memfds as named anonymous memory, I would really
> > appreciate your feedback before I go too far in that direction.
>
> [MAP_PRIVATE memfd only behave that way with 4k, not with huge pages, so
> I think it just has to be fixed. It doesn't make any sense to allocate a
> page for the pagecache ("populate the file") when accessing via a
> private mapping that's supposed to leave the file untouched]
>
> My gut feeling is if you really need a string as identifier, then try
> going with memfds. Yes, we might hit some road blocks to be sorted out,
> but it just logically makes sense to me: Files have names. These names
> exist before mapping and after mapping. They "name" the content.

I'm investigating this direction. I don't have much background with
memfds, so I'll need to digest the code first.

>
> Maybe it's just me, but the whole interface, setting the name via a
> prctl after the mapping was already instantiated doesn't really spark
> joy at my end. That's not a strong pushback, but if we can avoid it
> using something that's already there, that would be very much preferred.

Actually that's one of my worries about using memfds. There might be
cases when we need to name a vma after it was mapped. memfd_create()
would not allow us to do that AFAIKT. But I need to check all usages
to say if that's really an issue.
Thanks!

>
> --
> Thanks,
>
> David / dhildenb
>
> --
> To unsubscribe from this group and stop receiving emails from it, send an email to kernel-team+unsubscribe@android.com.
>

  reply	other threads:[~2021-10-12 17:01 UTC|newest]

Thread overview: 87+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-10-01 20:56 [PATCH v10 1/3] mm: rearrange madvise code to allow for reuse Suren Baghdasaryan
2021-10-01 20:56 ` Suren Baghdasaryan
2021-10-01 20:56 ` [PATCH v10 2/3] mm: add a field to store names for private anonymous memory Suren Baghdasaryan
2021-10-01 20:56   ` Suren Baghdasaryan
2021-10-01 23:08   ` Andrew Morton
2021-10-02  0:52     ` Suren Baghdasaryan
2021-10-04 16:21       ` Suren Baghdasaryan
2021-10-07  2:39         ` Andrew Morton
2021-10-07  2:50           ` Suren Baghdasaryan
2021-10-01 23:11   ` kernel test robot
2021-10-02  1:59     ` Suren Baghdasaryan
2021-10-01 23:27   ` kernel test robot
2021-10-01 20:56 ` [PATCH v10 3/3] mm: add anonymous vma name refcounting Suren Baghdasaryan
2021-10-01 20:56   ` Suren Baghdasaryan
2021-10-05 18:42   ` Pavel Machek
2021-10-05 19:14     ` Suren Baghdasaryan
2021-10-05 19:21       ` Kees Cook
2021-10-05 20:04       ` Pavel Machek
2021-10-05 20:43         ` Suren Baghdasaryan
2021-10-06  6:57           ` John Hubbard
2021-10-06  8:27             ` Michal Hocko
2021-10-06  9:27               ` David Hildenbrand
2021-10-06 15:01                 ` Suren Baghdasaryan
2021-10-06 15:07                   ` David Hildenbrand
2021-10-06 15:20                     ` Suren Baghdasaryan
2021-10-07  2:29                       ` Andrew Morton
2021-10-07  2:46                         ` Suren Baghdasaryan
2021-10-07  2:53                           ` Andrew Morton
2021-10-07  3:01                             ` Suren Baghdasaryan
2021-10-07  7:27                               ` David Hildenbrand
2021-10-07  7:33                       ` David Hildenbrand
2021-10-07 15:42                         ` Suren Baghdasaryan
2021-10-06 17:58                   ` Pavel Machek
2021-10-06 18:18                     ` Suren Baghdasaryan
2021-10-07  8:10                       ` Michal Hocko
2021-10-07  8:41                         ` Pavel Machek
2021-10-07  8:47                         ` Rasmus Villemoes
2021-10-07 10:15                           ` Pavel Machek
2021-10-07 16:04                             ` Suren Baghdasaryan
2021-10-07 16:40                               ` Michal Hocko
2021-10-07 16:58                                 ` Suren Baghdasaryan
2021-10-07 17:31                                   ` Michal Hocko
2021-10-07 17:50                                     ` Suren Baghdasaryan
2021-10-07 18:12                                       ` Kees Cook
2021-10-07 18:50                                         ` Suren Baghdasaryan
2021-10-07 19:02                                           ` John Hubbard
2021-10-07 21:32                                             ` Suren Baghdasaryan
2021-10-08  1:04                                               ` Liam Howlett
2021-10-08  7:25                                             ` Rasmus Villemoes
2021-10-08  7:43                                               ` David Hildenbrand
2021-10-08 21:13                                                 ` Kees Cook
2021-10-08  6:34                                         ` Michal Hocko
2021-10-08 14:14                                           ` Dave Hansen
2021-10-08 14:57                                             ` Michal Hocko
2021-10-08 16:10                                               ` Suren Baghdasaryan
2021-10-08 20:58                                           ` Kees Cook
2021-10-11  8:36                                             ` Michal Hocko
2021-10-12  1:18                                               ` Suren Baghdasaryan
2021-10-12  1:20                                                 ` Suren Baghdasaryan
2021-10-12  3:00                                                   ` Johannes Weiner
2021-10-12  5:36                                                     ` Suren Baghdasaryan
2021-10-12 18:26                                                       ` Johannes Weiner
2021-10-12 18:52                                                         ` Suren Baghdasaryan
2021-10-12 20:41                                                           ` Johannes Weiner
2021-10-12 20:59                                                             ` Suren Baghdasaryan
2021-10-12  7:36                                                   ` Michal Hocko
2021-10-12 16:50                                                     ` Suren Baghdasaryan
2021-10-12  7:43                                                 ` David Hildenbrand
2021-10-12 17:01                                                   ` Suren Baghdasaryan [this message]
2021-10-14 20:16                                                     ` Suren Baghdasaryan
2021-10-15  8:03                                                       ` David Hildenbrand
2021-10-15 16:30                                                         ` Suren Baghdasaryan
2021-10-15 16:39                                                           ` David Hildenbrand
2021-10-15 18:33                                                             ` Suren Baghdasaryan
2021-10-15 17:45                                                           ` Kees Cook
2021-10-07  7:59                   ` Michal Hocko
2021-10-07 15:45                     ` Suren Baghdasaryan
2021-10-07 16:37                       ` Michal Hocko
2021-10-07 16:43                         ` Suren Baghdasaryan
2021-10-07 17:25                           ` Michal Hocko
2021-10-07 17:30                             ` Suren Baghdasaryan
2021-10-04  7:03 ` [PATCH v10 1/3] mm: rearrange madvise code to allow for reuse Rolf Eike Beer
2021-10-04  7:03   ` Rolf Eike Beer
2021-10-04 16:18   ` Suren Baghdasaryan
2021-10-05 21:00     ` Liam Howlett
2021-10-05 21:30       ` Suren Baghdasaryan
2021-10-06 17:33         ` Liam Howlett

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