From: John Hubbard <jhubbard@nvidia.com>
To: Suren Baghdasaryan <surenb@google.com>,
Kees Cook <keescook@chromium.org>
Cc: "Michal Hocko" <mhocko@suse.com>, "Pavel Machek" <pavel@ucw.cz>,
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Subject: Re: [PATCH v10 3/3] mm: add anonymous vma name refcounting
Date: Thu, 7 Oct 2021 12:02:55 -0700 [thread overview]
Message-ID: <caa830de-ea66-267d-bafa-369a6175251e@nvidia.com> (raw)
In-Reply-To: <CAJuCfpFT7qcLM0ygjbzgCj1ScPDkZvv0hcvHkc40s9wgoTov7A@mail.gmail.com>
On 10/7/21 11:50, Suren Baghdasaryan wrote:
...
>>>>>>>>>> I believe Pavel meant something as simple as
>>>>>>>>>> $ YOUR_FILE=$YOUR_IDS_DIR/my_string_name
>>>>>>>>>> $ touch $YOUR_FILE
>>>>>>>>>> $ stat -c %i $YOUR_FILE
>>>>>>>
>>>>>>> Ah, ok, now I understand the proposal. Thanks for the clarification!
>>>>>>> So, this would use filesystem as a directory for inode->name mappings.
>>>>>>> One rough edge for me is that the consumer would still need to parse
>>>>>>> /proc/$pid/maps and convert [anon:inode] into [anon:name] instead of
>>>>>>> just dumping the content for the user. Would it be acceptable if we
>>>>>>> require the ID provided by prctl() to always be a valid inode and
>>>>>>> show_map_vma() would do the inode-to-filename conversion when
>>>>>>> generating maps/smaps files? I know that inode->dentry is not
>>>>>>> one-to-one mapping but we can simply output the first dentry name.
>>>>>>> WDYT?
>>>>>>
>>>>>> No. You do not want to dictate any particular way of the mapping. The
>>>>>> above is just one way to do that without developing any actual mapping
>>>>>> yourself. You just use a filesystem for that. Kernel doesn't and
>>>>>> shouldn't understand the meaning of those numbers. It has no business in
>>>>>> that.
>>>>>>
>>>>>> In a way this would be pushing policy into the kernel.
>>>>>
>>>>> I can see your point. Any other ideas on how to prevent tools from
>>>>> doing this id-to-name conversion themselves?
>>>>
>>>> I really fail to understand why you really want to prevent them from that.
>>>> Really, the whole thing is just a cookie that kernel maintains for memory
>>>> mappings so that two parties can understand what the meaning of that
>>>> mapping is from a higher level. They both have to agree on the naming
>>>> but the kernel shouldn't dictate any specific convention because the
>>>> kernel _doesn't_ _care_. These things are not really anything actionable
>>>> for the kernel. It is just a metadata.
>>>
>>> The desire is for one of these two parties to be a human who can get
>>> the data and use it as is without additional conversions.
>>> /proc/$pid/maps could report FD numbers instead of pathnames, which
>>> could be converted to pathnames in userspace. However we do not do
>>> that because pathnames are more convenient for humans to identify a
>>> specific resource. Same logic applies here IMHO.
>>
>> Yes, please. It really seems like the folks that are interested in this
>> feature want strings. (I certainly do.) For those not interested in the
>> feature, it sounds like a CONFIG to keep it away would be sufficient.
>> Can we just move forward with that?
>
> Would love to if others are ok with this.
>
If this doesn't get accepted, then another way forward would to continue
the ideas above to their logical conclusion, and create a new file system:
vma-fs. Like debug-fs and other special file systems, similar policy and
motivation. Also protected by a CONFIG option.
Actually this seems at least as natural as the procfs approach, especially
given the nature of these strings, which feel more like dir+file names, than
simple strings.
thanks,
--
John Hubbard
NVIDIA
next prev parent reply other threads:[~2021-10-07 19:03 UTC|newest]
Thread overview: 80+ 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 ` [PATCH v10 2/3] mm: add a field to store names for private anonymous memory 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 20:56 ` [PATCH v10 3/3] mm: add anonymous vma name refcounting 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 [this message]
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
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 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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