linux-kernel - Re: [PATCH v1] audit: merge loops in __audit_inode

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Message-ID: <CAABTaaB7SxWZUH+VxyOwZWBi6uPERg-qkMosFA=MTst5Rbc6kw@mail.gmail.com>
Date: Fri, 3 Oct 2025 12:49:52 -0300
From: Ricardo Robaina <rrobaina@...hat.com>
To: audit@...r.kernel.org, linux-kernel@...r.kernel.org, paul@...l-moore.com
Cc: eparis@...hat.com
Subject: Re: [PATCH v1] audit: merge loops in __audit_inode_child()

On Thu, Sep 4, 2025 at 1:59 PM Ricardo Robaina <rrobaina@...hat.com> 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 <rrobaina@...hat.com>
> ---
>  kernel/auditsc.c | 40 ++++++++++++++++++----------------------
>  1 file changed, 18 insertions(+), 22 deletions(-)
>
> diff --git a/kernel/auditsc.c b/kernel/auditsc.c
> index eb98cd6fe91f..7abfb68687fb 100644
> --- a/kernel/auditsc.c
> +++ b/kernel/auditsc.c
> @@ -2437,44 +2437,40 @@ 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->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))) {
>                         if (n->type == AUDIT_TYPE_UNKNOWN)
>                                 n->type = AUDIT_TYPE_PARENT;
>                         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))
> -                       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 && found_child)
> +                       break;
>         }
>
> +       cond_resched();
> +
>         if (!found_parent) {
>                 /* create a new, "anonymous" parent record */
>                 n = audit_alloc_name(context, AUDIT_TYPE_PARENT);
> --
> 2.51.0
>
Hi Paul,

I’m curious if you have any thoughts on this one.
Please disregard this email if it’s already in your to-do list. It’s
not my intention to rush you in any way.