orangefs: reorganize setattr functions to track attribute changes

orangefs: reorganize setattr functions to track attribute changes

OrangeFS accepts a mask indicating which attributes were changed.  The
kernel must not set any bits except those that were actually changed.
The kernel must set the uid/gid of the request to the actual uid/gid
responsible for the change.

Code path for notify_change initiated setattrs is

orangefs_setattr(dentry, iattr)
-> __orangefs_setattr(inode, iattr)

In kernel changes are initiated by calling __orangefs_setattr.

Code path for writeback is

orangefs_write_inode
-> orangefs_inode_setattr

attr_valid and attr_uid and attr_gid change together under i_lock.
I_DIRTY changes separately.

__orangefs_setattr
	lock
	if needs to be cleaned first, unlock and retry
	set attr_valid
	copy data in
	unlock
	mark_inode_dirty

orangefs_inode_setattr
	lock
	copy attributes out
	unlock
	clear getattr_time
	# __writeback_single_inode clears dirty

orangefs_inode_getattr
	# possible to get here with attr_valid set and not dirty
	lock
	if getattr_time ok or attr_valid set, unlock and return
	unlock
	do server operation
	# another thread may getattr or setattr, so check for that
	lock
	if getattr_time ok or attr_valid, unlock and return
	else, copy in
	update getattr_time
	unlock

Signed-off-by: Martin Brandenburg <martin@omnibond.com>
Signed-off-by: Mike Marshall <hubcap@omnibond.com>