Re: Adding subroot information to /proc/mounts, or obtaining that through other means

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



Al Viro wrote:
> On Wed, Jun 20, 2007 at 01:57:33PM -0700, H. Peter Anvin wrote:
>> ... or, alternatively, add a subfield to the first field (which would
>> entail escaping whatever separator we choose):
>>
>> /dev/md6 /export ext3 rw,data=ordered 0 0
>> /dev/md6:/users/foo /home/foo ext3 rw,data=ordered 0 0
>> /dev/md6:/users/bar /home/bar ext3 rw,data=ordered 0 0
> 
> Hell, no.  The first field is in principle impossible to parse unless
> you know the fs type.
> 
> How about making a new file with sane format?  From the very
> beginning.  E.g. mountpoint + ID + relative path + type + options,
> where ID uniquely identifies superblock (e.g. numeric st_dev)
> and backing device (if any) is sitting among the options...

The more I'm thinking about this, I think it's simplest to just add
fields to the right of the existing /proc/*/mounts.  Yes, the format is
ugly, and it will end up being uglier still, but it's also ugly to have
a bunch of different chunks of information formatted in different ways.

So, the existing fields are:

mnt_devname mnt_path filesystem_type options 0 0

... and we'd want to add ...

mnt_id propagation_info sb_dev path_to_fs_root

As previously stated, in order to avoid having to expose kernel
addresses to userspace, I suggest we simply add a counter field to
struct vfsmount and use that for mnt_id.

I'm not all that up on what is needed for propagation_info.  I presume
we want to be able to deduce the full mount lattice.  One particularly
important thing in my mind is to be able to distinguish overmounted
filesystems (which I think is possible in the current setup only by
ordering -- the filesystem on top I believe will end up last in
/proc/mounts, but I don't know if there actually is anything that
enforces that.)

	-hpa
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/

[Index of Archives]     [Kernel Newbies]     [Netfilter]     [Bugtraq]     [Photo]     [Stuff]     [Gimp]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Video 4 Linux]     [Linux for the blind]     [Linux Resources]
  Powered by Linux