Re: [RFC 2/2] initramfs with digital signature protection

From: Kasatkin, Dmitry
Date: Fri Feb 08 2013 - 11:24:54 EST


On Fri, Feb 8, 2013 at 5:49 PM, H. Peter Anvin <hpa@xxxxxxxxx> wrote:
> Yes, but you can't umount rootfs.

But that was not a rootfs, but tmpfs/ramfs mounted to /root folder.

>
> "Kasatkin, Dmitry" <dmitry.kasatkin@xxxxxxxxx> wrote:
>
>>On Wed, Feb 6, 2013 at 6:41 PM, H. Peter Anvin <hpa@xxxxxxxxx> wrote:
>>> The cleanup is not a umount, it is actually a tree walk unlinking the
>>contents.
>>>
>>
>>Please see that umounting ramfs releases the memory.
>>There was no forced cleanup.
>>"cp" copied about 2GB of content.
>>After umounting we got 2GB back to free RAM...
>>
>>kds@kds:~$ sudo mount -t ramfs testramfs /test
>>kds@kds:~$ sudo cp -r /usr/ /test
>>kds@kds:~$ du -sm /test
>>2154 /test
>>kds@kds:~$ free
>> total used free shared
>>buffers cached
>>Mem: 8058600 7855780 202820 0 24768
>>4819136
>>-/+ buffers/cache: 3011876 5046724
>>Swap: 0 0 0
>>kds@kds:~$ sudo umount /test
>>kds@kds:~$ free
>> total used free shared
>>buffers cached
>>Mem: 8058600 5644864 2413736 0 25268
>>2623956
>>-/+ buffers/cache: 2995640 5062960
>>Swap: 0 0 0
>>
>>The same happens also with tmpfs.
>>
>>- Dmitry
>>
>>> "Kasatkin, Dmitry" <dmitry.kasatkin@xxxxxxxxx> wrote:
>>>
>>>>On Wed, Feb 6, 2013 at 7:04 AM, H. Peter Anvin <hpa@xxxxxxxxx> wrote:
>>>>> On 02/05/2013 02:09 PM, Kasatkin, Dmitry wrote:
>>>>>>
>>>>>>
>>>>>> It should not be like that. Actually when pre-init exits, cleanup
>>>>code
>>>>>> umount tmpfs, which in turn cleanups the RAM.
>>>>>>
>>>>>
>>>>> It doesn't quite... the rootfs is permanent. This is also only one
>>>>usage
>>>>> mode: there are quite a few Linux systems running directly out of
>>>>initramfs.
>>>>>
>>>>
>>>>rootfs is not permanent when it is ramfs. It is cleaned up on switch
>>>>root.
>>>>It is easy to find out that it is empty by mounting : mount -t ramfs
>>>>rootfs /mnt/
>>>>
>>>>In the case of running from normal storage, of course, there is
>>>>ridicules remove the content.
>>>>
>>>>- Dmitry
>>>>
>>>>
>>>>> -hpa
>>>>>
>>>>>
>>>>> --
>>>>> H. Peter Anvin, Intel Open Source Technology Center
>>>>> I work for Intel. I don't speak on their behalf.
>>>>>
>>>
>>> --
>>> Sent from my mobile phone. Please excuse brevity and lack of
>>formatting.
>
> --
> Sent from my mobile phone. Please excuse brevity and lack of formatting.
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