From patchwork Wed Feb 2 20:30:33 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Waiman Long X-Patchwork-Id: 12733454 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id F344EC433F5 for ; Wed, 2 Feb 2022 20:33:24 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 74F976B02BC; Wed, 2 Feb 2022 15:33:24 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 6FF4B6B02BF; Wed, 2 Feb 2022 15:33:24 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5C6916B02C0; Wed, 2 Feb 2022 15:33:24 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0126.hostedemail.com [216.40.44.126]) by kanga.kvack.org (Postfix) with ESMTP id 4DEC36B02BC for ; Wed, 2 Feb 2022 15:33:24 -0500 (EST) Received: from smtpin15.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id 07BD1182888A4 for ; Wed, 2 Feb 2022 20:33:24 +0000 (UTC) X-FDA: 79098989928.15.F6CA074 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by imf18.hostedemail.com (Postfix) with ESMTP id A28501C0004 for ; Wed, 2 Feb 2022 20:33:23 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1643834003; 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=FSCcYBtevS72h8Rb3ThNAKipb4CG2TPJPslkwwiiaHA=; b=KVfVmSQHkxLBL+kTnPZV01wA7wAPff7Lqb0VAuv9I403lDNjLQtTGRLgA+SU7aO6e1k+nI QQuBGitGik8Qy2vIiy+tO34rrclZ5np5J8CvetNkUi+/4yGLygj/3cpDHSsrWFajKJy6Kk feEp/81ozAAjzJ9J9woeY1NT1TvFlBc= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-363-CsfU89KkOJ6_0-acPHmVUQ-1; Wed, 02 Feb 2022 15:33:22 -0500 X-MC-Unique: CsfU89KkOJ6_0-acPHmVUQ-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id B0445100C661; Wed, 2 Feb 2022 20:33:19 +0000 (UTC) Received: from llong.com (unknown [10.22.34.202]) by smtp.corp.redhat.com (Postfix) with ESMTP id 36C3512E30; Wed, 2 Feb 2022 20:32:44 +0000 (UTC) From: Waiman Long To: Johannes Weiner , Michal Hocko , Vladimir Davydov , Andrew Morton , Petr Mladek , Steven Rostedt , Sergey Senozhatsky , Andy Shevchenko , Rasmus Villemoes Cc: linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org, Ira Weiny , Mike Rapoport , David Rientjes , Roman Gushchin , Rafael Aquini , Waiman Long Subject: [PATCH v4 1/4] lib/vsprintf: Avoid redundant work with 0 size Date: Wed, 2 Feb 2022 15:30:33 -0500 Message-Id: <20220202203036.744010-2-longman@redhat.com> In-Reply-To: <20220131192308.608837-5-longman@redhat.com> References: <20220131192308.608837-5-longman@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: A28501C0004 X-Stat-Signature: 4ch988tzbzhg6octqyn4i57uddifqtjf Authentication-Results: imf18.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=KVfVmSQH; dmarc=pass (policy=none) header.from=redhat.com; spf=none (imf18.hostedemail.com: domain of longman@redhat.com has no SPF policy when checking 170.10.129.124) smtp.mailfrom=longman@redhat.com X-Rspam-User: nil X-HE-Tag: 1643834003-683777 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: For *scnprintf(), vsnprintf() is always called even if the input size is 0. That is a waste of time, so just return 0 in this case. Note that vsnprintf() will never return -1 to indicate an error. So skipping the call to vsnprintf() when size is 0 will have no functional impact at all. Signed-off-by: Waiman Long Acked-by: David Rientjes Reviewed-by: Sergey Senozhatsky Acked-by: Roman Gushchin Reviewed-by: Petr Mladek --- lib/vsprintf.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/lib/vsprintf.c b/lib/vsprintf.c index 3b8129dd374c..d419154b47bb 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -2895,13 +2895,15 @@ int vscnprintf(char *buf, size_t size, const char *fmt, va_list args) { int i; + if (unlikely(!size)) + return 0; + i = vsnprintf(buf, size, fmt, args); if (likely(i < size)) return i; - if (size != 0) - return size - 1; - return 0; + + return size - 1; } EXPORT_SYMBOL(vscnprintf);