proc 2/2: remove struct proc_dir_entry::owner

Setting ->owner as done currently (pde->owner = THIS_MODULE) is racy
as correctly noted at bug #12454. Someone can lookup entry with NULL
->owner, thus not pinning enything, and release it later resulting
in module refcount underflow.

We can keep ->owner and supply it at registration time like ->proc_fops
and ->data.

But this leaves ->owner as easy-manipulative field (just one C assignment)
and somebody will forget to unpin previous/pin current module when
switching ->owner. ->proc_fops is declared as "const" which should give
some thoughts.

->read_proc/->write_proc were just fixed to not require ->owner for
protection.

rmmod'ed directories will be empty and return "." and ".." -- no harm.
And directories with tricky enough readdir and lookup shouldn't be modular.
We definitely don't want such modular code.

Removing ->owner will also make PDE smaller.

So, let's nuke it.

Kudos to Jeff Layton for reminding about this, let's say, oversight.

http://bugzilla.kernel.org/show_bug.cgi?id=12454

Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>

fs/reiserfs/procfs.c

@@ -492,7 +492,6 @@ int reiserfs_proc_info_init(struct super_block *sb)
 	spin_lock_init(&__PINFO(sb).lock);
 	REISERFS_SB(sb)->procdir = proc_mkdir(b, proc_info_root);
 	if (REISERFS_SB(sb)->procdir) {
-		REISERFS_SB(sb)->procdir->owner = THIS_MODULE;
 		REISERFS_SB(sb)->procdir->data = sb;
 		add_file(sb, "version", show_version);
 		add_file(sb, "super", show_super);
@@ -556,9 +555,7 @@ int reiserfs_proc_info_global_init(void)
 {
 	if (proc_info_root == NULL) {
 		proc_info_root = proc_mkdir(proc_info_root_name, NULL);
-		if (proc_info_root) {
-			proc_info_root->owner = THIS_MODULE;
-		} else {
+		if (!proc_info_root) {
 			reiserfs_warning(NULL, "cannot create /proc/%s",
 					 proc_info_root_name);
 			return 1;