On Thu, 2024-10-17 at 17:09 +0000, Trond Myklebust wrote:

On Thu, 2024-10-17 at 13:05 -0400, Jeff Layton wrote:

quoted

On Thu, 2024-10-17 at 11:15 -0400, Paul Moore wrote:

quoted

On Thu, Oct 17, 2024 at 10:58 AM Christoph Hellwig
[off-list ref] wrote:

quoted

On Thu, Oct 17, 2024 at 10:54:12AM -0400, Paul Moore wrote:

quoted

Okay, good to know, but I was hoping that there we could come
up with
an explicit list of filesystems that maintain their own private
inode
numbers outside of inode-i_ino.

Anything using iget5_locked is a good start.  Add to that file
systems
implementing their own inode cache (at least xfs and bcachefs).

Also good to know, thanks.  However, at this point the lack of a
clear
answer is making me wonder a bit more about inode numbers in the
view
of VFS developers; do you folks care about inode numbers?  I'm not
asking to start an argument, it's a genuine question so I can get a
better understanding about the durability and sustainability of
inode->i_no.  If all of you (the VFS folks) aren't concerned about
inode numbers, I suspect we are going to have similar issues in the
future and we (the LSM folks) likely need to move away from
reporting
inode numbers as they aren't reliably maintained by the VFS layer.

Like Christoph said, the kernel doesn't care much about inode
numbers.

People care about them though, and sometimes we have things in the
kernel that report them in some fashion (tracepoints, procfiles,
audit
events, etc.). Having those match what the userland stat() st_ino
field
tells you is ideal, and for the most part that's the way it works.

The main exception is when people use 32-bit interfaces (somewhat
rare
these days), or they have a 32-bit kernel with a filesystem that has
a
64-bit inode number space (NFS being one of those). The NFS client
has
basically hacked around this for years by tracking its own fileid
field
in its inode. That's really a waste though. That could be converted
over to use i_ino instead if it were always wide enough.

It'd be better to stop with these sort of hacks and just fix this the
right way once and for all, by making i_ino 64 bits everywhere.

Nope.

That won't fix glibc, which is the main problem NFS has to work around.

True, but that's really a separate problem.

It also doesn't inform how we track inode numbers inside the kernel.
Inode numbers have been 64 bits for years on "real" filesystems. If we
were designing this today, i_ino would be a u64, and we'd only hash
that down to 32 bits when necessary.
-- 
Jeff Layton [off-list ref]