[Toybox] getmountlist - enhancement

[Rob Landley]

On 04/26/2013 04:45:27 AM, Ashwini Sharma wrote:
> Hi Rob,
> 
>    Can you change the getmountlist to accept the file path from user,  
> as to
> in which file he is interested.
> 
> As of now you bind it to read only /proc/mounts, giving the option  
> will
> make it usable for /etc/fstab or /etc/mtab

I'm not sure this is useful for /etc/fstab, because it doesn't record  
all the getmntent fields (no mnt_opts, mnt_freq, or mnt_passno). And  
half of what it does is collect stat() and statvfs() info on each mount  
point, which isn't useful for fstab because they're not necessarily  
mounted yet.

As for /etc/mtab: it's obsolete as anything but a symlink to  
/proc/self/mounts. What's mounted can vary per-process (the first part  
of containers support, process-local mount namespaces, went into  
Linus's tree around ten years ago), and can be updated from places that  
can't access any given file (if you mount something in a chroot then  
exit, it's not in the host's /etc/mtab but it's still mounted).

The kernel knows what is mounted. A single global /etc/mtab can't get  
it right, except as a symlink to /proc/mounts. So adding code to toybox  
to maintain an /etc/mtab is of no interest to me.

(If you want to argue that the kernel's procfs should be cleaned up and  
pared down, I'm all for it. Especially now that we have union mounts  
and can separate the process directories, /proc/sys, and the rest into  
separate filesystems. But that's a separate project.)

Rob
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