Re: RFC: adding an "fs" directory under /sys

[viro@parcelfarce.linux.theplanet.co.uk]

On Sat, Apr 17, 2004 at 10:55:09PM +0100, Christoph Hellwig wrote:
> On Sat, Apr 17, 2004 at 02:51:48PM -0700, Lever, Charles wrote:
> > so, i take it you would prefer me to add a kobject to the
> > nfs_server struct for my purposes, rather than use the
> > unused kobject that is *already* embedded in the
> > super_block?

keyword being "unused".  It has no business being there in the first
place and yes, it should be removed.  And no, the way you are using it
is not safe - it creates a user-triggerable oops if you ever get an
NFS filesystem unmounted.
 
> I think Al wants you to understand what you're trying to do first.
> Please read up about the kobject lifetime rules first, if you can make
> the nfs_server lifetime work with kobjects expectation go for it, but
> don't think it's easy.

Precisely.  Add to that the lifetime rules for module itself and you are
in for fun.

Linus, could you apply the patch below - the field in question is
	a) unused
	b) damn next to impossible to use correctly, due to struct super_block
lifetime and locking rules.

diff -urN RC6-rc1-bk1/include/linux/fs.h RC6-rc1-bk1-current/include/linux/fs.h
--- RC6-rc1-bk1/include/linux/fs.h	Fri Apr 16 12:39:19 2004
+++ RC6-rc1-bk1-current/include/linux/fs.h	Sat Apr 17 18:09:34 2004
@@ -751,7 +751,6 @@
 
 	char s_id[32];				/* Informational name */
 
-	struct kobject           kobj;          /* anchor for sysfs */
 	void 			*s_fs_info;	/* Filesystem private info */
 
 	/*