From nobody Thu Apr 2 06:27:04 2026 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DB9B13B3BE0 for ; Sat, 28 Feb 2026 18:28:17 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=170.10.129.124 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772303299; cv=none; b=iePrjNQ1EKmm/rfHAQ6uWNNhIo64ZlIucsxCpS1G3V9BmKuKUpgINkbupUWb3s+sulbUUMygkoKcrRxx/FizUMoUxvFWaGGUtnIMC8dJPQpdz8Otft9mdQqy/xLvpr/ajDRavm/cXgTRpOqohcXya26s853W0du+d1muDEAuoH4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1772303299; c=relaxed/simple; bh=6gz20nsM24m2S/dck8ZmFQ35FSYPIPpH8Q92e6D/gI8=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=Fi2hkuo+ujz46UtBCUcPu09mDAdPU4OAhnHyIJknyTEEsobzzuJJHr7kkJDVtX8dsvqRIGSOaaDmwR+gQCn+TC3w10GphnC8LmtoUoYXtgPl3ncGs9iQTq6AN7irpMBXHt5/IVCOlSxs2hsTEsANqlI7UNuFr5iyVsxfsvA8pRY= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com; spf=pass smtp.mailfrom=redhat.com; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b=fndDdVxB; arc=none smtp.client-ip=170.10.129.124 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=redhat.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=redhat.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="fndDdVxB" DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1772303296; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=IoIBsfhbhKEi7ETTfW3xNVUCfo/hcm8J/JCFyb6okZw=; b=fndDdVxBi5UzqOmEUqwIAvCEFD9zi35PnkP260jQVj1CPu8mhCpGRywCpe99FEwQG6C7YY KLUWNQ4fks7rkyki9j91QW4DgY5elMaX7bc8ixGzbxtMhmzKADwiA1w1PIM1V0K/3cJYmA HqxcWnT4P7Vr9vNXagTYManeUCLVGt8= Received: from mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-427-GF4WwlKAM_uhwhWHQGt9Dg-1; Sat, 28 Feb 2026 13:28:15 -0500 X-MC-Unique: GF4WwlKAM_uhwhWHQGt9Dg-1 X-Mimecast-MFC-AGG-ID: GF4WwlKAM_uhwhWHQGt9Dg_1772303294 Received: from mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.111]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-05.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id C5F3C195608A; Sat, 28 Feb 2026 18:28:13 +0000 (UTC) Received: from llong-thinkpadp16vgen1.westford.csb (unknown [10.2.16.6]) by mx-prod-int-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTP id B32781800286; Sat, 28 Feb 2026 18:28:10 +0000 (UTC) From: Waiman Long To: Paul Moore , Eric Paris , Christian Brauner , Al Viro , Jan Kara Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, audit@vger.kernel.org, Richard Guy Briggs , Ricardo Robaina , Waiman Long Subject: [PATCH v4 2/2] audit: Use the new {get,put}_fs_pwd_pool() APIs to get/put pwd references Date: Sat, 28 Feb 2026 13:27:57 -0500 Message-ID: <20260228182757.90528-3-longman@redhat.com> In-Reply-To: <20260228182757.90528-1-longman@redhat.com> References: <20260228182757.90528-1-longman@redhat.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.111 Content-Type: text/plain; charset="utf-8" When the audit subsystem is enabled, it can do a lot of get_fs_pwd() calls to get references to fs->pwd and then releasing those references back with path_put() later. That may cause a lot of spinlock contention on a single pwd's dentry lock because of the constant changes to the reference count when there are many processes on the same working directory actively doing open/close system calls. This can cause noticeable performance regresssion when compared with the case where the audit subsystem is turned off especially on systems with a lot of CPUs which is becoming more common these days. To avoid this kind of performance regression, use the new get_fs_pwd_pool() and put_fs_pwd_pool() APIs to acquire and release a fs->pwd reference. This should greatly reduce the number of path_get() and path_put() calls that are needed. After installing a test kernel with auditing enabled and counters added to track the get_fs_pwd_pool() and put_fs_pwd_pool() calls on a 2-socket 96-core test system and running a parallel kernel build, the counter values for this particular test run were shown below. fs_get_path=3D307,903 fs_get_pool=3D56,583,192 fs_put_path=3D6,209 fs_put_pool=3D56,885,147 Of the about 57M calls to get_fs_pwd_pool() and put_fs_pwd_pool(), the majority of them are just updating the pwd_refs counters. Only less than 1% of those calls require an actual path_get() and path_put() calls. The difference between fs_get_path and fs_put_path represents the extra pwd references that were still stored in various active task->fs's when the counter values were retrieved. It can be seen that the number of path_get() and path_put() calls are reduced by quite a lot. Signed-off-by: Waiman Long Acked-by: Paul Moore Reviewed-by: Richard Guy Briggs --- kernel/auditsc.c | 7 +++++-- 1 file changed, 5 insertions(+), 2 deletions(-) diff --git a/kernel/auditsc.c b/kernel/auditsc.c index f6af6a8f68c4..26ba61eabfb0 100644 --- a/kernel/auditsc.c +++ b/kernel/auditsc.c @@ -931,6 +931,9 @@ static inline void audit_free_names(struct audit_contex= t *context) { struct audit_names *n, *next; =20 + if (!context->name_count) + return; /* audit_alloc_name() has not been called */ + list_for_each_entry_safe(n, next, &context->names_list, list) { list_del(&n->list); if (n->name) @@ -939,7 +942,7 @@ static inline void audit_free_names(struct audit_contex= t *context) kfree(n); } context->name_count =3D 0; - path_put(&context->pwd); + put_fs_pwd_pool(current->fs, &context->pwd); context->pwd.dentry =3D NULL; context->pwd.mnt =3D NULL; } @@ -2165,7 +2168,7 @@ static struct audit_names *audit_alloc_name(struct au= dit_context *context, =20 context->name_count++; if (!context->pwd.dentry) - get_fs_pwd(current->fs, &context->pwd); + get_fs_pwd_pool(current->fs, &context->pwd); return aname; } =20 --=20 2.53.0