Re: [PATCH v4 0/3] fs: allow statmount to fetch the fs_subtype and sb_source

[Karel Zak]

On Tue, Nov 12, 2024 at 02:39:21PM GMT, Christian Brauner wrote:
> On Mon, 11 Nov 2024 10:09:54 -0500, Jeff Layton wrote:
> > Meta has some internal logging that scrapes /proc/self/mountinfo today.
> > I'd like to convert it to use listmount()/statmount(), so we can do a
> > better job of monitoring with containers. We're missing some fields
> > though. This patchset adds them.
> > 
> > 
> 
> Applied to the vfs.misc branch of the vfs/vfs.git tree.
> Patches in the vfs.misc branch should appear in linux-next soon.

Jeff, thank you for this!

I have already implemented support for statmount() and listmount() in
libmount (PR: https://github.com/util-linux/util-linux/pull/3092). The
only remaining issue was the mount source and incomplete file system
type.

Currently, the library does not use these syscalls when mounting (it
still uses /proc/#/mountinfo). However, there is already a library API
to fetch mount information from the kernel using listmount+statmount,
and it can be accessed from the command line using:

   findmnt --kernel=listmount

Next on the wish list is a notification (a file descriptor that can be
used in epoll) that returns a 64-bit ID when there is a change in the
mount node. This will enable us to enhance systemd so that it does not
have to read the entire mount table after every change.


    Karel

-- 
 Karel Zak  <kzak@xxxxxxxxxx>
 http://karelzak.blogspot.com