Re: [PATCH 00/18] VFS: Filesystem information [ver #21]

From: David Howells
Date: Wed Aug 05 2020 - 15:26:16 EST

James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx> wrote:

> It sort of petered out into a long winding thread about why not use
> sysfs instead, which really doesn't look like a good idea to me.

It seemed to turn into a set of procfs symlinks that pointed at a bunch of
sysfs stuff - or possibly some special filesystem.

> Could I make a suggestion about how this should be done in a way that
> doesn't actually require the fsinfo syscall at all: it could just be
> done with fsconfig.

I'd prefer to keep it separate. The interface for fsconfig() is intended to
move stuff into the kernel, not out of it. Better to add a parallel syscall
to go the other way (kind of like we have setxattr/getxattr, sendmsg/recvmsg).

Further, fsinfo() can refer directly to a file/fd/mount/whatever, but
fsconfig() doesn't do that. You have to use fspick() to get a context before
you can use fsconfig(). Now, that's fine if you want to gather several pieces
of information from a particular object, but it's not so good if you want to
get one piece of information from each of several objects.

> ... make it table configured...

I did, kind of (though I didn't call it that). Al rewrote the code to get rid
of it.