On Mon, Aug 15, 2022 at 12:32:25PM +0800, kernel test robot wrote:
>
>
> Greeting,
>
> FYI, we noticed a -9.0% regression of will-it-scale.per_thread_ops due to commit:
>
>
> commit: faf99b563558f74188b7ca34faae1c1da49a7261 ("fs: add __remove_file_privs() with flags parameter")
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
This seems overall pretty odd tbh at least it's not immediately obvious
how that specific commit would've caused this. But fwiw, I think there's
one issue in this change which we originally overlooked which might
explain this.
Before faf99b563558 ("fs: add __remove_file_privs() with flags
parameter") inode_has_no_xattr() was called when
dentry_needs_remove_privs() returned 0.
int error = 0
[...]
kill = dentry_needs_remove_privs(dentry);
if (kill < 0)
return kill;
if (kill)
error = __remove_privs(file_mnt_user_ns(file), dentry, kill);
if (!error)
inode_has_no_xattr(inode);
but now we do:
kill = dentry_needs_remove_privs(dentry);
if (kill <= 0)
return kill;
which means we don't call inode_has_no_xattr(). I don't think that we
did this intentionally. inode_has_no_xattr() just sets S_NOSEC which
means next time we call into __file_remove_privs() we can return earlier
instead of hitting dentry_needs_remove_privs() again:
if (IS_NOSEC(inode) || !S_ISREG(inode->i_mode))
return 0;
So I think that needs to be fixed?
Christian
