Commit c8a3dfe7 authored by Ricardo Robaina's avatar Ricardo Robaina Committed by Paul Moore
Browse files

audit: merge loops in __audit_inode_child() 



Whenever there's audit context, __audit_inode_child() gets called
numerous times, which can lead to high latency in scenarios that
create too many sysfs/debugfs entries at once, for instance, upon
device_add_disk() invocation.

   # uname -r
   6.18.0-rc2+

   # auditctl -a always,exit -F path=/tmp -k foo
   # time insmod loop max_loop=1000
   real 0m46.676s
   user 0m0.000s
   sys 0m46.405s

   # perf record -a insmod loop max_loop=1000
   # perf report --stdio |grep __audit_inode_child
   32.73%  insmod [kernel.kallsyms] [k] __audit_inode_child

__audit_inode_child() searches for both the parent and the child
in two different loops that iterate over the same list. This
process can be optimized by merging these into a single loop,
without changing the function behavior or affecting the code's
readability.

This patch merges the two loops that walk through the list
context->names_list into a single loop. This optimization resulted
in around 51% performance enhancement for the benchmark.

   # uname -r
   6.18.0-rc2-enhancedv3+

   # auditctl -a always,exit -F path=/tmp -k foo
   # time insmod loop max_loop=1000
   real 0m22.899s
   user 0m0.001s
   sys 0m22.652s

Signed-off-by: default avatarRicardo Robaina <rrobaina@redhat.com>
Signed-off-by: default avatarPaul Moore <paul@paul-moore.com>
parent 77563f3d

kernel/auditsc.c

+19 −24
Original line number Diff line number Diff line
@@ -2416,40 +2416,35 @@ void __audit_inode_child(struct inode *parent, 
	if (inode)

		handle_one(inode);



	/* look for a parent entry first */

	list_for_each_entry(n, &context->names_list, list) {

		if (!n->name ||

		    (n->type != AUDIT_TYPE_PARENT &&

		     n->type != AUDIT_TYPE_UNKNOWN))

		/* can only match entries that have a name */

		if (!n->name)

			continue;



		if (n->ino == parent->i_ino && n->dev == parent->i_sb->s_dev &&

		    !audit_compare_dname_path(dname,

					      n->name->name, n->name_len)) {

			if (n->type == AUDIT_TYPE_UNKNOWN)

		/* look for a parent entry first */

		if (!found_parent &&

		    (n->type == AUDIT_TYPE_PARENT || n->type == AUDIT_TYPE_UNKNOWN) &&

		    (n->ino == parent->i_ino && n->dev == parent->i_sb->s_dev &&

		     !audit_compare_dname_path(dname, n->name->name, n->name_len))) {

			n->type = AUDIT_TYPE_PARENT;

			found_parent = n;

			if (found_child)

				break;

			continue;

		}

	}



	cond_resched();



		/* is there a matching child entry? */

	list_for_each_entry(n, &context->names_list, list) {

		/* can only match entries that have a name */

		if (!n->name ||

		    (n->type != type && n->type != AUDIT_TYPE_UNKNOWN))

			continue;



		if (!strcmp(dname->name, n->name->name) ||

		if (!found_child &&

		    (n->type == type || n->type == AUDIT_TYPE_UNKNOWN) &&

		    (!strcmp(dname->name, n->name->name) ||

		     !audit_compare_dname_path(dname, n->name->name,

						found_parent ?

						found_parent->name_len :

						AUDIT_NAME_FULL)) {

						AUDIT_NAME_FULL))) {

			if (n->type == AUDIT_TYPE_UNKNOWN)

				n->type = type;

			found_child = n;

			if (found_parent)

				break;

		}

	}