On Mon, 20 May 2024 at 12:01, Linus Torvalds
<torvalds@xxxxxxxxxxxxxxxxxxxx> wrote:
>
> So how about just a patch like this? It doesn't do anything
> *internally* to the inodes, but it fixes up what we expose to user
> level to make it look like lsof expects.
Note that the historical dname for those pidfs files was
"anon_inode:[pidfd]", and that patch still kept the inode number in
there, so now it's "anon_inode:[pidfd-XYZ]", but I think lsof is still
happy with that.
Somebody should check.
I also wrote some kind of tentative commit log for this:
fs/pidfs: make 'lsof' happy with our inode changes
pidfs started using much saner inodes in commit b28ddcc32d8f ("pidfs:
convert to path_from_stashed() helper"), but that exposed the fact that
lsof had some knowledge of just how odd our old anon_inode usage was.
For example, legacy anon_inodes hadn't even initialized the inode type
in the inode mode, so everything had a type of zero.
So sane tools like 'stat' would report these files as "weird file", but
'lsof' instead used that (together with the name of the link in proc) to
notice that it's an anonymous inode, and used it to detect pidfd files.
Let's keep our internal new sane inode model, but mask the file type
bits at 'stat()' time in the getattr() function we already have, and by
making the dentry name match what lsof expects too.
This keeps our internal models sane, but should make user space see the
same old odd behavior.
Reported-by: Jiri Slaby <jirislaby@xxxxxxxxxx>
Link: https://lore.kernel.org/all/a15b1050-4b52-4740-a122-a4d055c17f11@xxxxxxxxxx/
Link: https://github.com/lsof-org/lsof/issues/317
Cc: Christian Brauner <brauner@xxxxxxxxxx>
Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Seth Forshee <sforshee@xxxxxxxxxx>
Cc: Tycho Andersen <tycho@tycho.pizza>
Signed-off-by: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
but I haven't actually committed it to my main tree, since I'd hope to
get Ack's for it (and testing).
Or does somebody have any other ideas? I think that patch is fairly
clean, even if the *reason* for the patch is odd as heck.
Linus
