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/include/linux/quotaops.h b/include/linux/quotaops.h
index 82c70c4..8a78187 100644
--- a/include/linux/quotaops.h
+++ b/include/linux/quotaops.h
@@ -14,6 +14,14 @@
 	return &sb->s_dquot;
 }
 
+/* i_mutex must being held */
+static inline bool is_quota_modification(struct inode *inode, struct iattr *ia)
+{
+	return (ia->ia_valid & ATTR_SIZE && ia->ia_size != inode->i_size) ||
+		(ia->ia_valid & ATTR_UID && ia->ia_uid != inode->i_uid) ||
+		(ia->ia_valid & ATTR_GID && ia->ia_gid != inode->i_gid);
+}
+
 #if defined(CONFIG_QUOTA)
 
 /*