From patchwork Fri Oct 16 04:52:55 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Douglas Gilbert X-Patchwork-Id: 11840857 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 8FF1314B2 for ; Fri, 16 Oct 2020 04:53:08 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 767302073A for ; Fri, 16 Oct 2020 04:53:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726827AbgJPExG (ORCPT ); Fri, 16 Oct 2020 00:53:06 -0400 Received: from smtp.infotech.no ([82.134.31.41]:44911 "EHLO smtp.infotech.no" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726305AbgJPExG (ORCPT ); Fri, 16 Oct 2020 00:53:06 -0400 Received: from localhost (localhost [127.0.0.1]) by smtp.infotech.no (Postfix) with ESMTP id 2808C20425A; Fri, 16 Oct 2020 06:53:04 +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 sWB5rYVlcu-3; Fri, 16 Oct 2020 06:53:02 +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 70512204238; Fri, 16 Oct 2020 06:53:01 +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 1/4] sgl_alloc_order: remove 4 GiB limit, sgl_free() warning Date: Fri, 16 Oct 2020 00:52:55 -0400 Message-Id: <20201016045258.16246-2-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 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 Fri Oct 16 04:52:56 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Douglas Gilbert X-Patchwork-Id: 11840863 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 90D5514B2 for ; Fri, 16 Oct 2020 04:53:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 7B72D20897 for ; Fri, 16 Oct 2020 04:53:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388294AbgJPExI (ORCPT ); Fri, 16 Oct 2020 00:53:08 -0400 Received: from smtp.infotech.no ([82.134.31.41]:44921 "EHLO smtp.infotech.no" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726710AbgJPExI (ORCPT ); Fri, 16 Oct 2020 00:53:08 -0400 Received: from localhost (localhost [127.0.0.1]) by smtp.infotech.no (Postfix) with ESMTP id 2219920425C; Fri, 16 Oct 2020 06:53:06 +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 8+pwfKrTq32T; Fri, 16 Oct 2020 06:53:04 +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 CF86120423B; Fri, 16 Oct 2020 06:53:02 +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 2/4] scatterlist: add sgl_copy_sgl() function Date: Fri, 16 Oct 2020 00:52:56 -0400 Message-Id: <20201016045258.16246-3-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 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 | 86 +++++++++++++++++++++++++++++++++++++ 2 files changed, 90 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..1ec2c909c8d4 100644 --- a/lib/scatterlist.c +++ b/lib/scatterlist.c @@ -974,3 +974,89 @@ 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 copying + * @s_sgl: Source sgl + * @s_nents: Number of SG entries in source sgl + * @s_skip: Number of bytes to skip in source before copying + * @n_bytes: The 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 the end of d_sgl or s_sgl is reached. + * + * 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. + * + * 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 d_off, s_off, len, d_len, s_len; + size_t offset = 0; + struct sg_mapping_iter d_iter; + struct sg_mapping_iter s_iter; + + if (n_bytes == 0) + return 0; + sg_miter_start(&d_iter, d_sgl, d_nents, SG_MITER_ATOMIC | SG_MITER_TO_SG); + sg_miter_start(&s_iter, s_sgl, s_nents, SG_MITER_ATOMIC | SG_MITER_FROM_SG); + if (!sg_miter_skip(&d_iter, d_skip)) + goto fini; + if (!sg_miter_skip(&s_iter, s_skip)) + goto fini; + + for (d_off = 0, s_off = 0; true ; ) { + /* Assume d_iter.length and s_iter.length can never be 0 */ + if (d_off == 0) { + if (!sg_miter_next(&d_iter)) + break; + d_len = d_iter.length; + } else { + d_len = d_iter.length - d_off; + } + if (s_off == 0) { + if (!sg_miter_next(&s_iter)) + break; + s_len = s_iter.length; + } else { + s_len = s_iter.length - s_off; + } + len = min3(d_len, s_len, n_bytes - offset); + + memcpy(d_iter.addr + d_off, s_iter.addr + s_off, len); + offset += len; + if (offset >= n_bytes) + break; + if (d_len == s_len) { + d_off = 0; + s_off = 0; + } else if (d_len < s_len) { + d_off = 0; + s_off += len; + } else { + d_off += len; + s_off = 0; + } + } +fini: + sg_miter_stop(&d_iter); + sg_miter_stop(&s_iter); + return offset; +} +EXPORT_SYMBOL(sgl_copy_sgl); + From patchwork Fri Oct 16 04:52:57 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Douglas Gilbert X-Patchwork-Id: 11840875 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id A7B8714B4 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 916AA20874 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 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); From patchwork Fri Oct 16 04:52:58 2020 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Douglas Gilbert X-Patchwork-Id: 11840869 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 1FF151984 for ; Fri, 16 Oct 2020 04:53:22 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0AF532073A for ; Fri, 16 Oct 2020 04:53:21 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2388665AbgJPExU (ORCPT ); Fri, 16 Oct 2020 00:53:20 -0400 Received: from smtp.infotech.no ([82.134.31.41]:44940 "EHLO smtp.infotech.no" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2388345AbgJPExK (ORCPT ); Fri, 16 Oct 2020 00:53:10 -0400 Received: from localhost (localhost [127.0.0.1]) by smtp.infotech.no (Postfix) with ESMTP id B2F60204238; Fri, 16 Oct 2020 06:53:08 +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 l6GpIUqz6pps; Fri, 16 Oct 2020 06:53:07 +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 9A707204259; Fri, 16 Oct 2020 06:53:05 +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 4/4] scatterlist: add sgl_memset() Date: Fri, 16 Oct 2020 00:52:58 -0400 Message-Id: <20201016045258.16246-5-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 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. Signed-off-by: Douglas Gilbert --- include/linux/scatterlist.h | 3 +++ lib/scatterlist.c | 39 +++++++++++++++++++++++++++++++++++-- 2 files changed, 40 insertions(+), 2 deletions(-) diff --git a/include/linux/scatterlist.h b/include/linux/scatterlist.h index ae260dc5fedb..e50dc9a6d887 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); +void 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 344725990b9d..3ca66f0c949f 100644 --- a/lib/scatterlist.c +++ b/lib/scatterlist.c @@ -1083,8 +1083,8 @@ EXPORT_SYMBOL(sgl_copy_sgl); * **/ 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) + 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; @@ -1140,3 +1140,38 @@ 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' 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 number of bytes to modify + * + * Notes: + * Writes val n_bytes times or until sgl is exhausted. + * + **/ +void 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; + unsigned int sg_flags = SG_MITER_ATOMIC | SG_MITER_TO_SG; + + if (n_bytes == 0) + return; + sg_miter_start(&miter, sgl, nents, sg_flags); + 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; + } +fini: + sg_miter_stop(&miter); +}