From patchwork Tue Feb 1 03:49:14 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Douglas Gilbert X-Patchwork-Id: 12731380 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 D4F15C433FE for ; Tue, 1 Feb 2022 03:57:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232796AbiBAD5i (ORCPT ); Mon, 31 Jan 2022 22:57:38 -0500 Received: from smtp.infotech.no ([82.134.31.41]:32861 "EHLO smtp.infotech.no" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232719AbiBAD5h (ORCPT ); Mon, 31 Jan 2022 22:57:37 -0500 Received: from localhost (localhost [127.0.0.1]) by smtp.infotech.no (Postfix) with ESMTP id 25AB32041AF; Tue, 1 Feb 2022 04:49:27 +0100 (CET) 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 UQU7f0mfQ1O7; Tue, 1 Feb 2022 04:49:25 +0100 (CET) Received: from xtwo70.bingwo.ca (host-45-78-195-155.dyn.295.ca [45.78.195.155]) by smtp.infotech.no (Postfix) with ESMTPA id 7D2942041BB; Tue, 1 Feb 2022 04:49:21 +0100 (CET) From: Douglas Gilbert To: linux-scsi@vger.kernel.org, linux-block@vger.kernel.org Cc: martin.petersen@oracle.com, jejb@linux.vnet.ibm.com, hare@suse.de, bvanassche@acm.org, Bodo Stroesser , David Disseldorp Subject: [PATCH v7 3/4] scatterlist: add sgl_equal_sgl() function Date: Mon, 31 Jan 2022 22:49:14 -0500 Message-Id: <20220201034915.183117-4-dgilbert@interlog.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20220201034915.183117-1-dgilbert@interlog.com> References: <20220201034915.183117-1-dgilbert@interlog.com> MIME-Version: 1.0 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 for equality. This new function is designed to partially implement NVMe's Compare command and the SCSI VERIFY(BYTCHK=1) command. Like memcmp() this function begins scanning at the start (of each sgl) and returns false on the first miscompare and stops comparing. The sgl_equal_sgl_idx() function additionally yields the index (i.e. byte position) of the first miscompare. The additional parameter, miscompare_idx, is a pointer. If it is non-NULL and a miscompare is detected (i.e. the function returns false) then the byte index of the first miscompare is written to *miscompare_idx. Knowing the location of the first miscompare is needed to implement properly the SCSI COMPARE AND WRITE command. Reviewed-by: Bodo Stroesser Reviewed-by: David Disseldorp Signed-off-by: Douglas Gilbert --- include/linux/scatterlist.h | 8 +++ lib/scatterlist.c | 110 ++++++++++++++++++++++++++++++++++++ 2 files changed, 118 insertions(+) diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h index 1291ff63fe83..a96874a8b791 100644 --- a/include/linux/scatterlist.h +++ b/include/linux/scatterlist.h @@ -380,6 +380,14 @@ 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_equal_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 sgl_equal_sgl_idx(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, size_t *miscompare_idx); + /* * 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 d4d56eece250..1fb14b2e320a 100644 --- a/lib/scatterlist.c +++ b/lib/scatterlist.c @@ -1161,3 +1161,113 @@ size_t sgl_copy_sgl(struct scatterlist *d_sgl, unsigned int d_nents, off_t d_ski return offset; } EXPORT_SYMBOL(sgl_copy_sgl); + +/** + * sgl_equal_sgl_idx - check if x and y (both sgl_s) compare equal, report + * index for first unequal bytes + * @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 (maximum) number of bytes to compare + * @miscompare_idx: if return is false, index of first miscompare written + * to this pointer (if non-NULL). Value will be < n_bytes + * + * 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). If return + * is false and miscompare_idx is non-NULL, then index of first miscompared + * byte written to *miscompare_idx. + * + * 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. + * + * The notes in sgl_copy_sgl() about large sgl_s _applies here as well. + * + **/ +bool sgl_equal_sgl_idx(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, size_t *miscompare_idx) +{ + bool equ = true; + size_t len; + size_t offset = 0; + struct sg_mapping_iter x_iter, y_iter; + + if (n_bytes == 0) + return true; + sg_miter_start(&x_iter, x_sgl, x_nents, SG_MITER_ATOMIC | SG_MITER_FROM_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; + + while (offset < n_bytes) { + if (!sg_miter_next(&x_iter)) + break; + if (!sg_miter_next(&y_iter)) + break; + len = min3(x_iter.length, y_iter.length, n_bytes - offset); + + equ = !memcmp(x_iter.addr, y_iter.addr, len); + if (!equ) + goto fini; + offset += len; + /* LIFO order is important when SG_MITER_ATOMIC is used */ + y_iter.consumed = len; + sg_miter_stop(&y_iter); + x_iter.consumed = len; + sg_miter_stop(&x_iter); + } +fini: + if (miscompare_idx && !equ) { + u8 *xp = x_iter.addr; + u8 *yp = y_iter.addr; + u8 *x_endp; + + for (x_endp = xp + len ; xp < x_endp; ++xp, ++yp) { + if (*xp != *yp) + break; + } + *miscompare_idx = offset + len - (x_endp - xp); + } + sg_miter_stop(&y_iter); + sg_miter_stop(&x_iter); + return equ; +} +EXPORT_SYMBOL(sgl_equal_sgl_idx); + +/** + * sgl_equal_sgl - check if x and y (both sgl_s) compare equal + * @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 (maximum) 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. + * + * The notes in sgl_copy_sgl() about large sgl_s _applies here as well. + * + **/ +bool sgl_equal_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) +{ + return sgl_equal_sgl_idx(x_sgl, x_nents, x_skip, y_sgl, y_nents, y_skip, n_bytes, NULL); +} +EXPORT_SYMBOL(sgl_equal_sgl);