On Oct 22, 2025 Ricardo Robaina <[email protected]> wrote:
>
> 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
> 6.17.0-rc3+
>
> # auditctl -a always,exit -F path=/tmp -k foo
> # time insmod loop max_loop=1000
> real 0m42.753s
> user 0m0.000s
> sys 0m42.494s
>
> # perf record -a insmod loop max_loop=1000
> # perf report --stdio |grep __audit_inode_child
> 37.95% 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 54% performance enhancement for the benchmark.
>
> # uname -r
> 6.17.0-rc3+-enhanced
>
> # auditctl -a always,exit -F path=/tmp -k foo
> # time insmod loop max_loop=1000
> real 0m19.388s
> user 0m0.000s
> sys 0m19.149s
>
> Signed-off-by: Ricardo Robaina <[email protected]>
> ---
> kernel/auditsc.c | 39 +++++++++++++++++----------------------
> 1 file changed, 17 insertions(+), 22 deletions(-)
>
> diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> index d1966144bdfe..8cebc016d9eb 100644
> --- a/kernel/auditsc.c
> +++ b/kernel/auditsc.c
> @@ -2416,41 +2416,36 @@ 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)) {
> + /* look for a parent entry first */
> + if (!found_parent &&
> + (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)
> n->type = AUDIT_TYPE_PARENT;
As mentioned in my feedback on your v1 patch, we can probably set
n->type equal to AUDIT_TYPE_PARENT without checking n->type first
as it we want this set to AUDIT_TYPE_PARENT regardless.
Please either fix this, or explain why it needs to be the way that it
is in your v2 patch.
> found_parent = n;
> - break;
> - }
> - }
> -
> - 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))
> + if (found_child)
> + break;
> continue;
> + }
>
> - if (!strcmp(dname->name, n->name->name) ||
> - !audit_compare_dname_path(dname, n->name->name,
> + /* is there a matching child entry? */
> + 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;
> - break;
> + if (found_parent)
> + break;
> }
> }
>
> --
> 2.51.0
--
paul-moore.com
