[arch-releng] [PATCH] Mount tmpfs filesystems with mode=0755

[Gerardo Exequiel Pozzi]

  On 07/08/2010 08:49 PM, Gerardo Exequiel Pozzi wrote:
>  On 07/08/2010 04:51 AM, Thomas Bächler wrote:
>> Am 06.07.2010 20:02, schrieb Gerardo Exequiel Pozzi:
>>> the other fix a directory that is unreacheable outside initramfs (is 
>>> not needed but fixed anyway).
>> There's something I've been meaning to do for a while, but my time is
>> very short recently. I'm telling you this, because I have the feeling if
>> I do, there'll be a patch for it tomorrow :)
> hehe :P
>> I don't want to leave dangling mounts in initramfs that are invisible
>> from the system. This would involve the following:
>>
>> 1) Don't bind /bootmnt into the root, but mount --move it there.
>> 2) Don't bind _mnt_bind file systems into the root, but also mount
>> --move (or mount them there directly)
> Yes
>> 3) After mounting, mount --move all aufs branches into a directory in
>> the root.
>>
>> This way, nothing will be left in rootfs and invisible for us. I don't
>> know a good name for a directory, so I'll stick to /bootmnt. A layout
>> could be like:
>> /bootmnt/
>> /bootmnt/image (move the image here)
>> /bootmnt/isomounts
>> /bootmnt/isomounts/loop0 (move /mnt/loop0 here)
>> /bootmnt/isomounts/loop1
>> etc. What do you think?
>>
> If I understand corretly, please fix me if I am wrong, but.the problem 
> is that mounts will be overlapped(*) with aufs mount stack, so at 
> least one mountpoint must be unreacheable, this is where sqfs images 
> are mounted /tmpfs (and /tmpfs.sqfs if copytoram is used).
> (*) http://bugs.archlinux.org/task/17182
> "Aufs rejects the branch which is an ancestor or a descendant of 
> another branch. It is called overlapped. When the branch is 
> loopback-mounted directory, aufs also checks the source fs-image file 
> of loopback device. If the source file is a descendant of another 
> branch, it will be rejected too" 
> http://aufs.sourceforge.net/aufs2/man.html
>
> ------------------------------------------------------------------------------------------------------------ 
>
> Currently this is what commands are executed on normal boot (mkdir 
> steps skipped)
>
> 1) mount -t tmpfs -o size=75%,mode=0755 tmpfs /tmpfs
> 2) mount -r -t udf /dev/disk/by-label/ARCH_201007 /bootmnt
> 3) mount -t aufs -o dirs=/tmpfs=rw none /new_root
> 4) mount -r -t squashfs /bootmnt/overlay.sqfs /tmpfs/mnt/overlay
> 5) mount -t aufs -o remount,append:/tmpfs/mnt/overlay=ro none /new_root
> 6) mount -r -t squashfs /bootmnt/root-image.sqfs /tmpfs/mnt/root-image
> 7) mount -t aufs -o remount,append:/tmpfs/mnt/root-image=ro none 
> /new_root
> 8) mount -o bind /bootmnt /new_root/bootmnt
>
> What thing that may be improved here is:
> * steps 4 and 6 instead of mounting on /tmpfs/mnt/imagename mount 
> under /mnt/imagename
>    currently an ls /new_root/mnt will display empty dirs "overlay" and 
> "root-image".
>    Now looks like a bit recursive.
> * execute 3) then 2) so medium will me mounted directly to 
> /new_root/bootmnt
>
NO!, bind mount /bootmnt to /new_root/bootmnt should be keep... 
otherwise on "shutdown", resourse or device busy message.
the same applies when copytoram

My hardcode archiso experiment: http://gist.github.com/468957 (I using 
using initscript.git + my pending patch for rc.shutdown from 
http://bugs.archlinux.org/task/19783)

> Doing that dirs that will be unreachable are:
> /tmpfs that is needed for aufs writeable branch, maybe can be renamed 
> to better named than tmpfs something like /rw_branch
> /mnt/X where sqfs are mounted
>
> ------------------------------------------------------------------------------------------------------------ 
>
> when copytoram=y (steps for mkdir and cp to /tmpfs.sqfs skipped)
>
> 1) mount -t tmpfs -o size=75%,mode=0755 tmpfs /tmpfs
> 2) mount -r -t udf /dev/disk/by-label/ARCH_201007 /bootmnt
> 3) mount -t aufs -o dirs=/tmpfs=rw none /new_root
> 4) mount -t tmpfs -o size=75%,mode=0755 tmpfs /tmpfs.sqfs
> 5) mount -r -t squashfs /tmpfs.sqfs/overlay.sqfs /tmpfs/mnt/overlay
> 6) mount -t aufs -o remount,append:/tmpfs/mnt/overlay=ro none /new_root
> 7) mount -r -t squashfs /tmpfs.sqfs/overlay.sqfs /tmpfs/mnt/overlay
> 8) mount -t aufs -o remount,append:/tmpfs/mnt/overlay=ro none /new_root
> 9) umount /bootmnt
>
> Same commands except that sqfs images are mounted from /tmpfs.sqfs 
> directory on ram instead from /bootmnt (the boot medium)
>
> - Same improvements here
> - Same dirs unreachable plus /tmpfs.sqfs
> ------------------------------------------------------------------------------------------------------------ 
>
>
>
> _mnt_bind function can be replaced with _mnt_move or removed, since 
> all things can be appended as aufs branch.
>












-- 
Gerardo Exequiel Pozzi
\cos^2\alpha + \sin^2\alpha = 1