IMA: explicit IMA i_flag to remove global lock on inode_delete

Currently for every removed inode IMA must take a global lock and search
the IMA rbtree looking for an associated integrity structure.  Instead
we explicitly mark an inode when we add an integrity structure so we
only have to take the global lock and do the removal if it exists.

Signed-off-by: Eric Paris <eparis@redhat.com>
Acked-by: Mimi Zohar <zohar@linux.vnet.ibm.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/security/integrity/ima/ima_iint.c b/security/integrity/ima/ima_iint.c
index 969a1c1..c442e47 100644
--- a/security/integrity/ima/ima_iint.c
+++ b/security/integrity/ima/ima_iint.c
@@ -59,6 +59,9 @@
 {
 	struct ima_iint_cache *iint;
 
+	if (!IS_IMA(inode))
+		return NULL;
+
 	spin_lock(&ima_iint_lock);
 	iint = __ima_iint_find(inode);
 	spin_unlock(&ima_iint_lock);
@@ -91,6 +94,7 @@
 	new_iint->inode = inode;
 	new_node = &new_iint->rb_node;
 
+	mutex_lock(&inode->i_mutex); /* i_flags */
 	spin_lock(&ima_iint_lock);
 
 	p = &ima_iint_tree.rb_node;
@@ -107,14 +111,17 @@
 			goto out_err;
 	}
 
+	inode->i_flags |= S_IMA;
 	rb_link_node(new_node, parent, p);
 	rb_insert_color(new_node, &ima_iint_tree);
 
 	spin_unlock(&ima_iint_lock);
+	mutex_unlock(&inode->i_mutex); /* i_flags */
 
 	return 0;
 out_err:
 	spin_unlock(&ima_iint_lock);
+	mutex_unlock(&inode->i_mutex); /* i_flags */
 	iint_free(new_iint);
 
 	return rc;
@@ -135,15 +142,14 @@
 
 	inode->i_readcount = 0;
 
+	if (!IS_IMA(inode))
+		return;
+
 	spin_lock(&ima_iint_lock);
 	iint = __ima_iint_find(inode);
-	if (iint)
-		rb_erase(&iint->rb_node, &ima_iint_tree);
+	rb_erase(&iint->rb_node, &ima_iint_tree);
 	spin_unlock(&ima_iint_lock);
 
-	if (!iint)
-		return;
-
 	iint_free(iint);
 }