We had some recent queries internally asking how to use the new
statmount() and listmount() interfaces. I was doing some other work in
this area, so I whipped up this tool.

My hope is that this will represent something of a "rosetta stone" for
how to translate between mountinfo and statmount(), and an example for
other people looking to use the new interfaces.

It may also be possible to use this as the basis for a listmount() and
statmount() testcase. We can call this program, and compare its output
to the mountinfo file.

The second patch adds security mount options to the existing mnt_opts in
the statmount() interface, which I think is the final missing piece
here. The alternative to doing that would be to add a new string field
for that, but I'm not sure that's worthwhile.

Signed-off-by: Jeff Layton <jlayton@kernel.org>
---
Changes in v2:
- fixed off-by-one bug in listmount last_mnt_id handling
- patch to add the security mount options to statmount()
- Link to v1: https://lore.kernel.org/r/20241112-statmount-v1-1-d98090c4c8be@kernel.org

---
Jeff Layton (2):
      samples: add a mountinfo program to demonstrate statmount()/listmount()
      fs: prepend statmount.mnt_opts string with security_sb_mnt_opts()

 fs/namespace.c          |   4 +
 samples/vfs/.gitignore  |   1 +
 samples/vfs/Makefile    |   2 +-
 samples/vfs/mountinfo.c | 271 ++++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 277 insertions(+), 1 deletion(-)
---
base-commit: 4be4eaeb1a60a7d52e66123f2f52f2da017c9881
change-id: 20241112-statmount-77808bc02302

Best regards,
-- 
Jeff Layton <jlayton@kernel.org>

On Fri, 15 Nov 2024 10:35:51 -0500, Jeff Layton wrote:
> We had some recent queries internally asking how to use the new
> statmount() and listmount() interfaces. I was doing some other work in
> this area, so I whipped up this tool.
> 
> My hope is that this will represent something of a "rosetta stone" for
> how to translate between mountinfo and statmount(), and an example for
> other people looking to use the new interfaces.
> 
> [...]

Applied to the vfs-6.14.misc branch of the vfs/vfs.git tree.
Patches in the vfs-6.14.misc branch should appear in linux-next soon.

Please report any outstanding bugs that were missed during review in a
new review to the original patch series allowing us to drop it.

It's encouraged to provide Acked-bys and Reviewed-bys even though the
patch has now been applied. If possible patch trailers will be updated.

Note that commit hashes shown below are subject to change due to rebase,
trailer updates or similar. If in doubt, please check the listed branch.

tree:   https://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs.git
branch: vfs-6.14.misc

[1/2] samples: add a mountinfo program to demonstrate statmount()/listmount()
      https://git.kernel.org/vfs/vfs/c/ec07dced06b6
[2/2] fs: prepend statmount.mnt_opts string with security_sb_mnt_opts()
      https://git.kernel.org/vfs/vfs/c/d2269a2bfe4a