From patchwork Fri Aug 4 13:13:10 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Howells X-Patchwork-Id: 13341827 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id B363BC001DB for ; Fri, 4 Aug 2023 13:14:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229725AbjHDNO0 (ORCPT ); Fri, 4 Aug 2023 09:14:26 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:55996 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229665AbjHDNOX (ORCPT ); Fri, 4 Aug 2023 09:14:23 -0400 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8FF0946A8 for ; Fri, 4 Aug 2023 06:13:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1691154815; 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=dHYA2IrNpONr95AjtpQxWSgfxf0e6O6AgQhvb/6sHd0=; b=i5NZeLNl4fCZCLmvtU1UexP34HLubgqIJGitTRHwCClErfpx1PP0V8nG4I9thXsdbIW/7X hG6YjPrK4PW3PKGPYmQPCOvMHOr85tmtYYX1nSUsCatYRbLcSi8jC9zlVbCWiFwmr3Ne29 9YgnrmLpihJ7ncIlfdKGMDzKHG5bevg= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-317-SckMlT4pN9uRr4YSQHtsZw-1; Fri, 04 Aug 2023 09:13:34 -0400 X-MC-Unique: SckMlT4pN9uRr4YSQHtsZw-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id DC7F28022EF; Fri, 4 Aug 2023 13:13:33 +0000 (UTC) Received: from warthog.procyon.org.uk (unknown [10.42.28.131]) by smtp.corp.redhat.com (Postfix) with ESMTP id BC457492CA6; Fri, 4 Aug 2023 13:13:32 +0000 (UTC) From: David Howells To: Ilya Dryomov , Xiubo Li Cc: David Howells , Jeff Layton , Dongsheng Yang , ceph-devel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [RFC PATCH 01/18] iov_iter: Add function to see if buffer is all zeros Date: Fri, 4 Aug 2023 14:13:10 +0100 Message-ID: <20230804131327.2574082-2-dhowells@redhat.com> In-Reply-To: <20230804131327.2574082-1-dhowells@redhat.com> References: <20230804131327.2574082-1-dhowells@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.9 Precedence: bulk List-ID: X-Mailing-List: ceph-devel@vger.kernel.org Add a function to scan a buffer and indicate if all of the bytes contained therein are zero. Signed-off-by: David Howells --- include/linux/uio.h | 1 + lib/iov_iter.c | 22 ++++++++++++++++++++++ 2 files changed, 23 insertions(+) diff --git a/include/linux/uio.h b/include/linux/uio.h index ff81e5ccaef2..49de7b8a8890 100644 --- a/include/linux/uio.h +++ b/include/linux/uio.h @@ -264,6 +264,7 @@ static inline bool iov_iter_is_copy_mc(const struct iov_iter *i) #endif size_t iov_iter_zero(size_t bytes, struct iov_iter *); +bool iov_iter_is_zero(const struct iov_iter *i, size_t count); bool iov_iter_is_aligned(const struct iov_iter *i, unsigned addr_mask, unsigned len_mask); unsigned long iov_iter_alignment(const struct iov_iter *i); diff --git a/lib/iov_iter.c b/lib/iov_iter.c index b667b1e2f688..ec9e3e1a11a9 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -566,6 +566,28 @@ size_t iov_iter_zero(size_t bytes, struct iov_iter *i) } EXPORT_SYMBOL(iov_iter_zero); +/** + * iov_iter_is_zero - Return true if the buffer is entirely zeroed + * @i: The iterator describing the buffer + * @count: Amount of buffer to scan + * + * Scans the specified amount of the supplied buffer and returns true if only + * zero bytes are found therein and false otherwise. + */ +bool iov_iter_is_zero(const struct iov_iter *i, size_t count) +{ + struct iov_iter j = *i, *pj = &j; + void *p; + + iterate_and_advance(pj, count, base, len, count, + ({ p = memchr_inv(base, 0, len); p ? p - base : len; }), + ({ p = memchr_inv(base, 0, len); p ? p - base : len; }) + ) + + return !count; +} +EXPORT_SYMBOL(iov_iter_is_zero); + size_t copy_page_from_iter_atomic(struct page *page, unsigned offset, size_t bytes, struct iov_iter *i) {