quota: unify quota init condition in setattr

Quota must being initialized if size or uid/git changes requested.
But initialization performed in two different places:
in case of i_size file system is responsible for dquot init
, but in case of uid/gid init will be called internally in
dquot_transfer().
This ambiguity makes code harder to understand.
Let's move this logic to one common helper function.

Signed-off-by: Dmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: Jan Kara <jack@suse.cz>
diff --git a/fs/ufs/truncate.c b/fs/ufs/truncate.c
index ee8db3e..f294c44 100644
--- a/fs/ufs/truncate.c
+++ b/fs/ufs/truncate.c
@@ -518,18 +518,18 @@
 	if (error)
 		return error;
 
+	if (is_quota_modification(inode, attr))
+		dquot_initialize(inode);
+
 	if ((ia_valid & ATTR_UID && attr->ia_uid != inode->i_uid) ||
 	    (ia_valid & ATTR_GID && attr->ia_gid != inode->i_gid)) {
 		error = dquot_transfer(inode, attr);
 		if (error)
 			return error;
 	}
-	if (ia_valid & ATTR_SIZE &&
-	    attr->ia_size != i_size_read(inode)) {
+	if (ia_valid & ATTR_SIZE && attr->ia_size != inode->i_size) {
 		loff_t old_i_size = inode->i_size;
 
-		dquot_initialize(inode);
-
 		error = vmtruncate(inode, attr->ia_size);
 		if (error)
 			return error;