From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-12.7 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_GIT autolearn=unavailable autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D1B69C433E7 for ; Fri, 16 Oct 2020 04:53:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 929C92087D for ; Fri, 16 Oct 2020 04:53:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388843AbgJPExU (ORCPT ); Fri, 16 Oct 2020 00:53:20 -0400 Received: from smtp.infotech.no ([82.134.31.41]:44935 "EHLO smtp.infotech.no" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388247AbgJPExJ (ORCPT ); Fri, 16 Oct 2020 00:53:09 -0400 Received: from localhost (localhost [127.0.0.1]) by smtp.infotech.no (Postfix) with ESMTP id DAF72204191; Fri, 16 Oct 2020 06:53:07 +0200 (CEST) X-Virus-Scanned: by amavisd-new-2.6.6 (20110518) (Debian) at infotech.no Received: from smtp.infotech.no ([127.0.0.1]) by localhost (smtp.infotech.no [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id g1Jfl04mXnez; Fri, 16 Oct 2020 06:53:06 +0200 (CEST) Received: from xtwo70.bingwo.ca (host-104-157-204-209.dyn.295.ca [104.157.204.209]) by smtp.infotech.no (Postfix) with ESMTPA id 39303204238; Fri, 16 Oct 2020 06:53:04 +0200 (CEST) From: Douglas Gilbert To: linux-scsi@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Cc: martin.petersen@oracle.com, axboe@kernel.dk, bvanassche@acm.org Subject: [PATCH 3/4] scatterlist: add sgl_compare_sgl() function Date: Fri, 16 Oct 2020 00:52:57 -0400 Message-Id: <20201016045258.16246-4-dgilbert@interlog.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20201016045258.16246-1-dgilbert@interlog.com> References: <20201016045258.16246-1-dgilbert@interlog.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org After enabling copies between scatter gather lists (sgl_s), another storage related operation is to compare two sgl_s. This new function is modelled on NVMe's Compare command and the SCSI VERIFY(BYTCHK=1) command. Like memcmp() this function returns false on the first miscompare and stop comparing. Signed-off-by: Douglas Gilbert --- include/linux/scatterlist.h | 4 ++ lib/scatterlist.c | 84 ++++++++++++++++++++++++++++++++++++- 2 files changed, 86 insertions(+), 2 deletions(-) diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h index 6649414c0749..ae260dc5fedb 100644 --- a/include/linux/scatterlist.h +++ b/include/linux/scatterlist.h @@ -325,6 +325,10 @@ size_t sgl_copy_sgl(struct scatterlist *d_sgl, unsigned int d_nents, off_t d_ski struct scatterlist *s_sgl, unsigned int s_nents, off_t s_skip, size_t n_bytes); +bool sgl_compare_sgl(struct scatterlist *x_sgl, unsigned int x_nents, off_t x_skip, + struct scatterlist *y_sgl, unsigned int y_nents, off_t y_skip, + size_t n_bytes); + /* * Maximum number of entries that will be allocated in one piece, if * a list larger than this is required then chaining will be utilized. diff --git a/lib/scatterlist.c b/lib/scatterlist.c index 1ec2c909c8d4..344725990b9d 100644 --- a/lib/scatterlist.c +++ b/lib/scatterlist.c @@ -979,10 +979,10 @@ EXPORT_SYMBOL(sg_zero_buffer); * sgl_copy_sgl - Copy over a destination sgl from a source sgl * @d_sgl: Destination sgl * @d_nents: Number of SG entries in destination sgl - * @d_skip: Number of bytes to skip in destination before copying + * @d_skip: Number of bytes to skip in destination before starting * @s_sgl: Source sgl * @s_nents: Number of SG entries in source sgl - * @s_skip: Number of bytes to skip in source before copying + * @s_skip: Number of bytes to skip in source before starting * @n_bytes: The number of bytes to copy * * Returns the number of copied bytes. @@ -1060,3 +1060,83 @@ size_t sgl_copy_sgl(struct scatterlist *d_sgl, unsigned int d_nents, off_t d_ski } EXPORT_SYMBOL(sgl_copy_sgl); +/** + * sgl_compare_sgl - Compare x and y (both sgl_s) + * @x_sgl: x (left) sgl + * @x_nents: Number of SG entries in x (left) sgl + * @x_skip: Number of bytes to skip in x (left) before starting + * @y_sgl: y (right) sgl + * @y_nents: Number of SG entries in y (right) sgl + * @y_skip: Number of bytes to skip in y (right) before starting + * @n_bytes: The number of bytes to compare + * + * Returns true if x and y compare equal before x, y or n_bytes is exhausted. + * Otherwise on a miscompare, returns false (and stops comparing). + * + * Notes: + * x and y are symmetrical: they can be swapped and the result is the same. + * + * Implementation is based on memcmp(). x and y segments may overlap. + * + * Same comment from sgl_copy_sgl() about large _skip arguments applies here + * as well. + * + **/ +bool sgl_compare_sgl(struct scatterlist *x_sgl, unsigned int x_nents, off_t x_skip, + struct scatterlist *y_sgl, unsigned int y_nents, off_t y_skip, + size_t n_bytes) +{ + bool equ = true; + size_t x_off, y_off, len, x_len, y_len; + size_t offset = 0; + struct sg_mapping_iter x_iter; + struct sg_mapping_iter y_iter; + + if (n_bytes == 0) + return true; + sg_miter_start(&x_iter, x_sgl, x_nents, SG_MITER_ATOMIC | SG_MITER_TO_SG); + sg_miter_start(&y_iter, y_sgl, y_nents, SG_MITER_ATOMIC | SG_MITER_FROM_SG); + if (!sg_miter_skip(&x_iter, x_skip)) + goto fini; + if (!sg_miter_skip(&y_iter, y_skip)) + goto fini; + + for (x_off = 0, y_off = 0; true ; ) { + /* Assume x_iter.length and y_iter.length can never be 0 */ + if (x_off == 0) { + if (!sg_miter_next(&x_iter)) + break; + x_len = x_iter.length; + } else { + x_len = x_iter.length - x_off; + } + if (y_off == 0) { + if (!sg_miter_next(&y_iter)) + break; + y_len = y_iter.length; + } else { + y_len = y_iter.length - y_off; + } + len = min3(x_len, y_len, n_bytes - offset); + + equ = memcmp(x_iter.addr + x_off, y_iter.addr + y_off, len) == 0; + offset += len; + if (!equ || offset >= n_bytes) + break; + if (x_len == y_len) { + x_off = 0; + y_off = 0; + } else if (x_len < y_len) { + x_off = 0; + y_off += len; + } else { + x_off += len; + y_off = 0; + } + } +fini: + sg_miter_stop(&x_iter); + sg_miter_stop(&y_iter); + return equ; +} +EXPORT_SYMBOL(sgl_compare_sgl); -- 2.25.1