From patchwork Sun Oct 18 17:13:33 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Douglas Gilbert X-Patchwork-Id: 11843331 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=ham 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 95EE0C433E7 for ; Sun, 18 Oct 2020 17:13:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5F85F2063A for ; Sun, 18 Oct 2020 17:13:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1725776AbgJRRNt (ORCPT ); Sun, 18 Oct 2020 13:13:49 -0400 Received: from smtp.infotech.no ([82.134.31.41]:52020 "EHLO smtp.infotech.no" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726689AbgJRRNt (ORCPT ); Sun, 18 Oct 2020 13:13:49 -0400 Received: from localhost (localhost [127.0.0.1]) by smtp.infotech.no (Postfix) with ESMTP id 849A220425B; Sun, 18 Oct 2020 19:13:46 +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 P5SUJaaRNZ+X; Sun, 18 Oct 2020 19:13:43 +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 8AB1520424C; Sun, 18 Oct 2020 19:13:41 +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, bostroesser@gmail.com Subject: [PATCH v2 1/4] sgl_alloc_order: remove 4 GiB limit, sgl_free() warning Date: Sun, 18 Oct 2020 13:13:33 -0400 Message-Id: <20201018171336.63839-2-dgilbert@interlog.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20201018171336.63839-1-dgilbert@interlog.com> References: <20201018171336.63839-1-dgilbert@interlog.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org This patch removes a check done by sgl_alloc_order() before it starts any allocations. The comment before the removed code says: "Check for integer overflow" arguably gives a false sense of security. The right hand side of the expression in the condition is resolved as u32 so cannot exceed UINT32_MAX (4 GiB) which means 'length' cannot exceed that amount. If that was the intention then the comment above it could be dropped and the condition rewritten more clearly as: if (length > UINT32_MAX) <>; The author's intention is to use sgl_alloc_order() to replace vmalloc(unsigned long) for a large allocation (debug ramdisk). vmalloc has no limit at 4 GiB so its seems unreasonable that: sgl_alloc_order(unsigned long long length, ....) does. sgl_s made with sgl_alloc_order(chainable=false) have equally sized segments placed in a scatter gather array. That allows O(1) navigation around a big sgl using some simple integer maths. Having previously sent a patch to fix a memory leak in sg_alloc_order() take the opportunity to put a one line comment above sgl_free()'s declaration that it is not suitable when order > 0 . The mis-use of sgl_free() when order > 0 was the reason for the memory leak. The other users of sgl_alloc_order() in the kernel where checked and found to handle free-ing properly. Signed-off-by: Douglas Gilbert --- include/linux/scatterlist.h | 1 + lib/scatterlist.c | 3 --- 2 files changed, 1 insertion(+), 3 deletions(-) diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h index 45cf7b69d852..80178afc2a4a 100644 --- a/include/linux/scatterlist.h +++ b/include/linux/scatterlist.h @@ -302,6 +302,7 @@ struct scatterlist *sgl_alloc(unsigned long long length, gfp_t gfp, unsigned int *nent_p); void sgl_free_n_order(struct scatterlist *sgl, int nents, int order); void sgl_free_order(struct scatterlist *sgl, int order); +/* Only use sgl_free() when order is 0 */ void sgl_free(struct scatterlist *sgl); #endif /* CONFIG_SGL_ALLOC */ diff --git a/lib/scatterlist.c b/lib/scatterlist.c index c448642e0f78..d5770e7f1030 100644 --- a/lib/scatterlist.c +++ b/lib/scatterlist.c @@ -493,9 +493,6 @@ struct scatterlist *sgl_alloc_order(unsigned long long length, u32 elem_len; nent = round_up(length, PAGE_SIZE << order) >> (PAGE_SHIFT + order); - /* Check for integer overflow */ - if (length > (nent << (PAGE_SHIFT + order))) - return NULL; nalloc = nent; if (chainable) { /* Check for integer overflow */ From patchwork Sun Oct 18 17:13:34 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Douglas Gilbert X-Patchwork-Id: 11843339 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=-12.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,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 E6154C43457 for ; Sun, 18 Oct 2020 17:14:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id BE22B2063A for ; Sun, 18 Oct 2020 17:14:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726831AbgJRROD (ORCPT ); Sun, 18 Oct 2020 13:14:03 -0400 Received: from smtp.infotech.no ([82.134.31.41]:52039 "EHLO smtp.infotech.no" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726725AbgJRRNu (ORCPT ); Sun, 18 Oct 2020 13:13:50 -0400 Received: from localhost (localhost [127.0.0.1]) by smtp.infotech.no (Postfix) with ESMTP id 6545520425C; Sun, 18 Oct 2020 19:13:48 +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 jD2poka938Cf; Sun, 18 Oct 2020 19:13:46 +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 9678D204258; Sun, 18 Oct 2020 19:13:43 +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, bostroesser@gmail.com Subject: [PATCH v2 2/4] scatterlist: add sgl_copy_sgl() function Date: Sun, 18 Oct 2020 13:13:34 -0400 Message-Id: <20201018171336.63839-3-dgilbert@interlog.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20201018171336.63839-1-dgilbert@interlog.com> References: <20201018171336.63839-1-dgilbert@interlog.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Both the SCSI and NVMe subsystems receive user data from the block layer in scatterlist_s (aka scatter gather lists (sgl) which are often arrays). If drivers in those subsystems represent storage (e.g. a ramdisk) or cache "hot" user data then they may also choose to use scatterlist_s. Currently there are no sgl to sgl operations in the kernel. Start with a copy. Signed-off-by: Douglas Gilbert --- include/linux/scatterlist.h | 4 ++ lib/scatterlist.c | 74 +++++++++++++++++++++++++++++++++++++ 2 files changed, 78 insertions(+) diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h index 80178afc2a4a..6649414c0749 100644 --- a/include/linux/scatterlist.h +++ b/include/linux/scatterlist.h @@ -321,6 +321,10 @@ size_t sg_pcopy_to_buffer(struct scatterlist *sgl, unsigned int nents, size_t sg_zero_buffer(struct scatterlist *sgl, unsigned int nents, size_t buflen, off_t skip); +size_t sgl_copy_sgl(struct scatterlist *d_sgl, unsigned int d_nents, off_t d_skip, + struct scatterlist *s_sgl, unsigned int s_nents, off_t s_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 d5770e7f1030..a0a86059c10e 100644 --- a/lib/scatterlist.c +++ b/lib/scatterlist.c @@ -974,3 +974,77 @@ size_t sg_zero_buffer(struct scatterlist *sgl, unsigned int nents, return offset; } 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 starting + * @s_sgl: Source sgl + * @s_nents: Number of SG entries in source sgl + * @s_skip: Number of bytes to skip in source before starting + * @n_bytes: The (maximum) number of bytes to copy + * + * Returns the number of copied bytes. + * + * Notes: + * Destination arguments appear before the source arguments, as with memcpy(). + * + * Stops copying if either d_sgl, s_sgl or n_bytes is exhausted. + * + * Since memcpy() is used, overlapping copies (where d_sgl and s_sgl belong + * to the same sgl and the copy regions overlap) are not supported. + * + * Large copies are broken into copy segments whose sizes may vary. Those + * copy segment sizes are chosen by the min3() statement in the code below. + * Since SG_MITER_ATOMIC is used for both sides, each copy segment is started + * with kmap_atomic() [in sg_miter_next()] and completed with kunmap_atomic() + * [in sg_miter_stop()]. This means pre-emption is inhibited for relatively + * short periods even in very large copies. + * + * If d_skip is large, potentially spanning multiple d_nents then some + * integer arithmetic to adjust d_sgl may improve performance. For example + * if d_sgl is built using sgl_alloc_order(chainable=false) then the sgl + * will be an array with equally sized segments facilitating that + * arithmetic. The suggestion applies to s_skip, s_sgl and s_nents as well. + * + **/ +size_t sgl_copy_sgl(struct scatterlist *d_sgl, unsigned int d_nents, off_t d_skip, + struct scatterlist *s_sgl, unsigned int s_nents, off_t s_skip, + size_t n_bytes) +{ + size_t len; + size_t offset = 0; + struct sg_mapping_iter d_iter, s_iter; + + if (n_bytes == 0) + return 0; + sg_miter_start(&s_iter, s_sgl, s_nents, SG_MITER_ATOMIC | SG_MITER_FROM_SG); + sg_miter_start(&d_iter, d_sgl, d_nents, SG_MITER_ATOMIC | SG_MITER_TO_SG); + if (!sg_miter_skip(&s_iter, s_skip)) + goto fini; + if (!sg_miter_skip(&d_iter, d_skip)) + goto fini; + + while (offset < n_bytes) { + if (!sg_miter_next(&s_iter)) + break; + if (!sg_miter_next(&d_iter)) + break; + len = min3(d_iter.length, s_iter.length, n_bytes - offset); + + memcpy(d_iter.addr, s_iter.addr, len); + offset += len; + /* LIFO order (stop d_iter before s_iter) needed with SG_MITER_ATOMIC */ + d_iter.consumed = len; + sg_miter_stop(&d_iter); + s_iter.consumed = len; + sg_miter_stop(&s_iter); + } +fini: + sg_miter_stop(&d_iter); + sg_miter_stop(&s_iter); + return offset; +} +EXPORT_SYMBOL(sgl_copy_sgl); + From patchwork Sun Oct 18 17:13:35 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Douglas Gilbert X-Patchwork-Id: 11843333 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=-12.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham 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 43C66C433DF for ; Sun, 18 Oct 2020 17:13:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0DCEF2222B for ; Sun, 18 Oct 2020 17:13:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727378AbgJRRNw (ORCPT ); Sun, 18 Oct 2020 13:13:52 -0400 Received: from smtp.infotech.no ([82.134.31.41]:52047 "EHLO smtp.infotech.no" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726689AbgJRRNw (ORCPT ); Sun, 18 Oct 2020 13:13:52 -0400 Received: from localhost (localhost [127.0.0.1]) by smtp.infotech.no (Postfix) with ESMTP id 809E5204258; Sun, 18 Oct 2020 19:13:49 +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 wIqqiOebVjCm; Sun, 18 Oct 2020 19:13:47 +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 D435C20425A; Sun, 18 Oct 2020 19:13:45 +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, bostroesser@gmail.com Subject: [PATCH v2 3/4] scatterlist: add sgl_compare_sgl() function Date: Sun, 18 Oct 2020 13:13:35 -0400 Message-Id: <20201018171336.63839-4-dgilbert@interlog.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20201018171336.63839-1-dgilbert@interlog.com> References: <20201018171336.63839-1-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. 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 | 60 +++++++++++++++++++++++++++++++++++++ 2 files changed, 64 insertions(+) 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 a0a86059c10e..d910776a4c96 100644 --- a/lib/scatterlist.c +++ b/lib/scatterlist.c @@ -1048,3 +1048,63 @@ 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 (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_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 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 (equ && 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); + 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: + sg_miter_stop(&y_iter); + sg_miter_stop(&x_iter); + return equ; +} +EXPORT_SYMBOL(sgl_compare_sgl); From patchwork Sun Oct 18 17:13:36 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Douglas Gilbert X-Patchwork-Id: 11843337 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=-12.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,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 68874C433E7 for ; Sun, 18 Oct 2020 17:14:00 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3B18E2063A for ; Sun, 18 Oct 2020 17:14:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727398AbgJRRNy (ORCPT ); Sun, 18 Oct 2020 13:13:54 -0400 Received: from smtp.infotech.no ([82.134.31.41]:52056 "EHLO smtp.infotech.no" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727377AbgJRRNy (ORCPT ); Sun, 18 Oct 2020 13:13:54 -0400 Received: from localhost (localhost [127.0.0.1]) by smtp.infotech.no (Postfix) with ESMTP id E3C01204255; Sun, 18 Oct 2020 19:13:51 +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 gHPwiAFxcovT; Sun, 18 Oct 2020 19:13:49 +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 1DDB720418E; Sun, 18 Oct 2020 19:13:47 +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, bostroesser@gmail.com Subject: [PATCH v2 4/4] scatterlist: add sgl_memset() Date: Sun, 18 Oct 2020 13:13:36 -0400 Message-Id: <20201018171336.63839-5-dgilbert@interlog.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20201018171336.63839-1-dgilbert@interlog.com> References: <20201018171336.63839-1-dgilbert@interlog.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org The existing sg_zero_buffer() function is a bit restrictive. For example protection information (PI) blocks are usually initialized to 0xff bytes. As its name suggests sgl_memset() is modelled on memset(). One difference is the type of the val argument which is u8 rather than int. Plus it returns the number of bytes (over)written. Signed-off-by: Douglas Gilbert --- include/linux/scatterlist.h | 3 +++ lib/scatterlist.c | 54 ++++++++++++++++++++++++++++++++++--- 2 files changed, 54 insertions(+), 3 deletions(-) diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h index ae260dc5fedb..a40012c8a4e6 100644 --- a/include/linux/scatterlist.h +++ b/include/linux/scatterlist.h @@ -329,6 +329,9 @@ bool sgl_compare_sgl(struct scatterlist *x_sgl, unsigned int x_nents, off_t x_sk struct scatterlist *y_sgl, unsigned int y_nents, off_t y_skip, size_t n_bytes); +size_t sgl_memset(struct scatterlist *sgl, unsigned int nents, off_t skip, + u8 val, 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 d910776a4c96..a704039ab54d 100644 --- a/lib/scatterlist.c +++ b/lib/scatterlist.c @@ -985,7 +985,8 @@ EXPORT_SYMBOL(sg_zero_buffer); * @s_skip: Number of bytes to skip in source before starting * @n_bytes: The (maximum) number of bytes to copy * - * Returns the number of copied bytes. + * Returns: + * The number of copied bytes. * * Notes: * Destination arguments appear before the source arguments, as with memcpy(). @@ -1058,8 +1059,9 @@ EXPORT_SYMBOL(sgl_copy_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). + * 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. @@ -1108,3 +1110,49 @@ bool sgl_compare_sgl(struct scatterlist *x_sgl, unsigned int x_nents, off_t x_sk return equ; } EXPORT_SYMBOL(sgl_compare_sgl); + +/** + * sgl_memset - set byte 'val' up to n_bytes times on SG list + * @sgl: The SG list + * @nents: Number of SG entries in sgl + * @skip: Number of bytes to skip before starting + * @val: byte value to write to sgl + * @n_bytes: The (maximum) number of bytes to modify + * + * Returns: + * The number of bytes written. + * + * Notes: + * Stops writing if either sgl or n_bytes is exhausted. If n_bytes is + * set SIZE_MAX then val will be written to each byte until the end + * of sgl. + * + * The notes in sgl_copy_sgl() about large sgl_s _applies here as well. + * + **/ +size_t sgl_memset(struct scatterlist *sgl, unsigned int nents, off_t skip, + u8 val, size_t n_bytes) +{ + size_t offset = 0; + size_t len; + struct sg_mapping_iter miter; + + if (n_bytes == 0) + return 0; + sg_miter_start(&miter, sgl, nents, SG_MITER_ATOMIC | SG_MITER_TO_SG); + if (!sg_miter_skip(&miter, skip)) + goto fini; + + while ((offset < n_bytes) && sg_miter_next(&miter)) { + len = min(miter.length, n_bytes - offset); + memset(miter.addr, val, len); + offset += len; + miter.consumed = len; + sg_miter_stop(&miter); + } +fini: + sg_miter_stop(&miter); + return offset; +} +EXPORT_SYMBOL(sgl_memset); +