From patchwork Thu Jul 21 18:21:31 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Anna Schumaker X-Patchwork-Id: 12925679 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 C3E13C43334 for ; Thu, 21 Jul 2022 18:21:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231642AbiGUSVk (ORCPT ); Thu, 21 Jul 2022 14:21:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42944 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229693AbiGUSVj (ORCPT ); Thu, 21 Jul 2022 14:21:39 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 02E788210E for ; Thu, 21 Jul 2022 11:21:39 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 9451561FC9 for ; Thu, 21 Jul 2022 18:21:38 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9C150C341CB; Thu, 21 Jul 2022 18:21:37 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1658427698; bh=/rdMpVPibNoV+V4UZpxODig15LN1SP1snCf7ckUe3vo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=IADmKO1sP+3j0nJHqiIPRGWS1Hy7WI+gbl+lGcFFlCgC18iMz8jtlmtd36ifz+qts DOTRq88MuRwJQEQJRPGFOsyBgunXlzo9bRbC/7l3DQz9PiekT9BmWgVOmqKFcv9akl 7pDp2c15GWEwGiqJNu679TGnkNM9kR9XKz2OOlLJQFX7VCc9KVZJxV1bLLQkX2szQ5 c91dGxETEl2vgmL65HXZwpDL145FCkwdp5SYl1LtTfoBPhacJ5qZCMXH2U8lbWU0My RrBKRxYVljAoTqdpUDnat/b1XSOmbqZmPWH3CxWH6CjYfsNTvqDzGkzqs6QWeGIdXE dqUEEZmMXxAcw== From: Anna Schumaker To: linux-nfs@vger.kernel.org, trond.myklebust@hammerspace.com Cc: anna@kernel.org Subject: [PATCH v3 1/5] SUNRPC: Introduce xdr_stream_move_subsegment() Date: Thu, 21 Jul 2022 14:21:31 -0400 Message-Id: <20220721182135.1885071-2-anna@kernel.org> X-Mailer: git-send-email 2.37.1 In-Reply-To: <20220721182135.1885071-1-anna@kernel.org> References: <20220721182135.1885071-1-anna@kernel.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-nfs@vger.kernel.org From: Anna Schumaker I do this by creating an xdr subsegment for the range we will be operating over. This lets me shift data to the correct place without potentially overwriting anything already there. Signed-off-by: Anna Schumaker --- include/linux/sunrpc/xdr.h | 2 ++ net/sunrpc/xdr.c | 59 ++++++++++++++++++++++++++++++++++++++ 2 files changed, 61 insertions(+) diff --git a/include/linux/sunrpc/xdr.h b/include/linux/sunrpc/xdr.h index 5860f32e3958..7dcc6c31fe29 100644 --- a/include/linux/sunrpc/xdr.h +++ b/include/linux/sunrpc/xdr.h @@ -262,6 +262,8 @@ extern unsigned int xdr_align_data(struct xdr_stream *, unsigned int offset, uns extern unsigned int xdr_expand_hole(struct xdr_stream *, unsigned int offset, unsigned int length); extern bool xdr_stream_subsegment(struct xdr_stream *xdr, struct xdr_buf *subbuf, unsigned int len); +extern unsigned int xdr_stream_move_subsegment(struct xdr_stream *xdr, unsigned int offset, + unsigned int target, unsigned int length); /** * xdr_set_scratch_buffer - Attach a scratch buffer for decoding data. diff --git a/net/sunrpc/xdr.c b/net/sunrpc/xdr.c index 5d2b3e6979fb..8ba11a754297 100644 --- a/net/sunrpc/xdr.c +++ b/net/sunrpc/xdr.c @@ -775,6 +775,34 @@ static void xdr_buf_pages_shift_left(const struct xdr_buf *buf, xdr_buf_tail_copy_left(buf, 0, len - buf->page_len, shift); } +static void xdr_buf_head_shift_left(const struct xdr_buf *buf, + unsigned int base, unsigned int len, + unsigned int shift) +{ + const struct kvec *head = buf->head; + unsigned int bytes; + + if (!shift || !len) + return; + + if (shift > base) { + bytes = (shift - base); + if (bytes >= len) + return; + base += bytes; + len -= bytes; + } + + if (base < head->iov_len) { + bytes = min_t(unsigned int, len, head->iov_len - base); + memmove(head->iov_base + (base - shift), + head->iov_base + base, bytes); + base += bytes; + len -= bytes; + } + xdr_buf_pages_shift_left(buf, base - head->iov_len, len, shift); +} + /** * xdr_shrink_bufhead * @buf: xdr_buf @@ -1680,6 +1708,37 @@ bool xdr_stream_subsegment(struct xdr_stream *xdr, struct xdr_buf *subbuf, } EXPORT_SYMBOL_GPL(xdr_stream_subsegment); +/** + * xdr_stream_move_subsegment - Move part of a stream to another position + * @xdr: the source xdr_stream + * @offset: the source offset of the segment + * @target: the target offset of the segment + * @length: the number of bytes to move + * + * Moves @length bytes from @offset to @target in the xdr_stream, overwriting + * anything in its space. Returns the number of bytes in the segment. + */ +unsigned int xdr_stream_move_subsegment(struct xdr_stream *xdr, unsigned int offset, + unsigned int target, unsigned int length) +{ + struct xdr_buf buf; + unsigned int shift; + + if (offset < target) { + shift = target - offset; + if (xdr_buf_subsegment(xdr->buf, &buf, offset, shift + length) < 0) + return 0; + xdr_buf_head_shift_right(&buf, 0, length, shift); + } else if (offset > target) { + shift = offset - target; + if (xdr_buf_subsegment(xdr->buf, &buf, target, shift + length) < 0) + return 0; + xdr_buf_head_shift_left(&buf, shift, length, shift); + } + return length; +} +EXPORT_SYMBOL_GPL(xdr_stream_move_subsegment); + /** * xdr_buf_trim - lop at most "len" bytes off the end of "buf" * @buf: buf to be trimmed