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=-19.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,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 B420AC11F6D for ; Mon, 12 Jul 2021 08:15:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AD058613E4 for ; Mon, 12 Jul 2021 08:15:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1356865AbhGLIQt (ORCPT ); Mon, 12 Jul 2021 04:16:49 -0400 Received: from mail.kernel.org ([198.145.29.99]:53862 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240902AbhGLHct (ORCPT ); Mon, 12 Jul 2021 03:32:49 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 87E2C61008; Mon, 12 Jul 2021 07:29:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1626074984; bh=j/hfKJTTAEp2JofBV0iu1l3g7CIKwhamTP8twTxnDQI=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=CMZYNkY7Ybj528mMAV2zJZ40bcyzL5zdNLYX0JAio+Mpqrkmy4/XelCMmMRss8XW3 DmU6/ANEtBAeD34DNg/PsvshQUAVegpDxI9DMO7McvoeEkeb0lbuEteNbsceGQXODt rEP9iRFTk68Weu6mXblB59TXbS0syxp+zAhCB3j0= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Al Viro Subject: [PATCH 5.13 037/800] teach copy_page_to_iter() to handle compound pages Date: Mon, 12 Jul 2021 08:01:00 +0200 Message-Id: <20210712060918.498753221@linuxfoundation.org> X-Mailer: git-send-email 2.32.0 In-Reply-To: <20210712060912.995381202@linuxfoundation.org> References: <20210712060912.995381202@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Al Viro commit 08aa64796016cb47b2ef3d0924653b4d944b0d65 upstream. In situation when copy_page_to_iter() got a compound page the current code would only work on systems with no CONFIG_HIGHMEM. It *is* the majority of real-world setups, or we would've drown in bug reports by now. Still needs fixing. Current variant works for solitary page; rename that to __copy_page_to_iter() and turn the handling of compound pages into a loop over subpages. Cc: stable@vger.kernel.org Signed-off-by: Al Viro Signed-off-by: Greg Kroah-Hartman --- lib/iov_iter.c | 28 +++++++++++++++++++++++++--- 1 file changed, 25 insertions(+), 3 deletions(-) --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -957,11 +957,9 @@ static inline bool page_copy_sane(struct return false; } -size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes, +static size_t __copy_page_to_iter(struct page *page, size_t offset, size_t bytes, struct iov_iter *i) { - if (unlikely(!page_copy_sane(page, offset, bytes))) - return 0; if (i->type & (ITER_BVEC | ITER_KVEC | ITER_XARRAY)) { void *kaddr = kmap_atomic(page); size_t wanted = copy_to_iter(kaddr + offset, bytes, i); @@ -977,6 +975,30 @@ size_t copy_page_to_iter(struct page *pa else return copy_page_to_iter_pipe(page, offset, bytes, i); } + +size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes, + struct iov_iter *i) +{ + size_t res = 0; + if (unlikely(!page_copy_sane(page, offset, bytes))) + return 0; + page += offset / PAGE_SIZE; // first subpage + offset %= PAGE_SIZE; + while (1) { + size_t n = __copy_page_to_iter(page, offset, + min(bytes, (size_t)PAGE_SIZE - offset), i); + res += n; + bytes -= n; + if (!bytes || !n) + break; + offset += n; + if (offset == PAGE_SIZE) { + page++; + offset = 0; + } + } + return res; +} EXPORT_SYMBOL(copy_page_to_iter); size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes,