Re: procfs files vs symlink

[RVP <rvp%SDF.ORG@localhost>]

On Thu, 13 Jan 2022, Robert Elz wrote:

> This problem isn't in procfs, but in ls, and is hard to fix.
> The general issus is that any directory can change while ls
> is processing it, leading to either incorrect (or even nonsense)
> output, or apparent errors.
>
> procfs is only notable here by being more dynamic than most
> filesystems, and its self/fd subr particularly in that it changes
> as the process opens and closes files

That's it exactly.

>  | Anyway, here's one more patch:
>  |
>  | ---START PATCH---
>  | --- sys/miscfs/procfs/procfs_vnops.c.orig	2022-01-12 20:57:25.944841288 +0000
>  | +++ sys/miscfs/procfs/procfs_vnops.c	2022-01-12 23:07:44.736070587 +0000
>
>
> that cannot be more than papering over one special case.

The patch is for processes to know that stat() will have to be
called for that particular dirent. DT_REG would not be right there.
(I've done this myself: call stat() if dirent.d_type is DT_UNKNOWN;
otherwise, take dirent.d_type as valid and save a syscall.)

A note in dirent.3 that procfs (and some others?) will always return
DT_UNKNOWN would be a good idea, I think.

Thanks,
-RVP