From patchwork Wed Mar 22 14:55:27 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Lorenzo Stoakes X-Patchwork-Id: 13184194 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 3E22CC761A6 for ; Wed, 22 Mar 2023 14:56:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229973AbjCVO4X (ORCPT ); Wed, 22 Mar 2023 10:56:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59766 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230516AbjCVOz5 (ORCPT ); Wed, 22 Mar 2023 10:55:57 -0400 Received: from mail-wm1-x336.google.com (mail-wm1-x336.google.com [IPv6:2a00:1450:4864:20::336]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 43E03F74D; Wed, 22 Mar 2023 07:55:38 -0700 (PDT) Received: by mail-wm1-x336.google.com with SMTP id l15-20020a05600c4f0f00b003ed58a9a15eso11680979wmq.5; Wed, 22 Mar 2023 07:55:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; t=1679496937; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=ziv2ovcgc/3NOuBG0+YWYfMhKDq2ZBtAkLCMMX3QtWE=; b=OAV5bOCAXt/brQqvvLh3Ler2AJ9GHlTfIBj1zt+bsAVk1mAGgHj8zeXzy1CFUIp59c g0j4bfCzrA7HOPI24EkKttjDSOoekv+lp+Ux319tiQlEiMRhczQCWjFgd+nzWyQKlYOT 4G+WxPHSgXXiBWEEVZp2ZsT7q1mu6rQC7V+PJJFavEAzMrHcGzFz/V0d2Ten7uIdDb2o Rh+kJe2IOaU5+vJojOU8XbVJBIgq4JPoY7Lw2AfMgj7MaAlx776xF93KeEnSwUv6Plzp l1moQKfShHAfPpJjJMHywcku9UjCVzyket6xtX2PJvJCiWX1uH1VH3plioVFy68wB7v2 TPhg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1679496937; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=ziv2ovcgc/3NOuBG0+YWYfMhKDq2ZBtAkLCMMX3QtWE=; b=edOQ4JU/au7L5Vu1swcyW3dr5AD8MRb0SUT0/xDHsfEk/Y+/G3qQU0UPGSpur23UVX 6yF8Wo2VK9eWsZhWYPwcSCDt5sTahTzPK1cfF5CQhxpSlkACxO8a2eCB6uePkV2ttVtV DiC5ej+hMVlhG7scaDumBQ+rNMKz9nLJkUZf3RhUmGPisYbkm6ncisA1fpzgxVsca7IP kG3HK73LZT++SlO6CF3mtmk1g0E9P6XsziKB5UjOoa4NAaTiTYzwTtzcxfDVoYCQt/Cy Tb2O14EistXZx8pAZHixIpq0eFVlhHr3bGd32RX/2AQwc/vgr73rNoIv8p83PSZFunzq jdGg== X-Gm-Message-State: AO0yUKXm2L6nvQVH1gp3Zm9rdDzuwtAK2tOPuIYtwWanQcsew47VDHh7 zUgiFuKqimeAcvuh2gpl5lA= X-Google-Smtp-Source: AK7set9doYzaEsFJwhlnO7ROmhc0QBK17nVojzEcg2JEds9E8AVQb6TMCOYkJXMHKA13gZcDAvM6xw== X-Received: by 2002:a05:600c:2048:b0:3ed:cf2a:3fe8 with SMTP id p8-20020a05600c204800b003edcf2a3fe8mr5815815wmg.8.1679496936720; Wed, 22 Mar 2023 07:55:36 -0700 (PDT) Received: from lucifer.home ([2a00:23c5:dc8c:8701:1663:9a35:5a7b:1d76]) by smtp.googlemail.com with ESMTPSA id n23-20020a7bcbd7000000b003ed243222adsm16812246wmi.42.2023.03.22.07.55.35 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 22 Mar 2023 07:55:35 -0700 (PDT) From: Lorenzo Stoakes To: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, Andrew Morton Cc: Baoquan He , Uladzislau Rezki , Matthew Wilcox , David Hildenbrand , Liu Shixin , Jiri Olsa , Jens Axboe , Alexander Viro , Lorenzo Stoakes Subject: [PATCH v6 3/4] iov_iter: add copy_page_to_iter_nofault() Date: Wed, 22 Mar 2023 14:55:27 +0000 Message-Id: <19734729defb0f498a76bdec1bef3ac48a3af3e8.1679496827.git.lstoakes@gmail.com> X-Mailer: git-send-email 2.39.2 In-Reply-To: References: MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Provide a means to copy a page to user space from an iterator, aborting if a page fault would occur. This supports compound pages, but may be passed a tail page with an offset extending further into the compound page, so we cannot pass a folio. This allows for this function to be called from atomic context and _try_ to user pages if they are faulted in, aborting if not. The function does not use _copy_to_iter() in order to not specify might_fault(), this is similar to copy_page_from_iter_atomic(). This is being added in order that an iteratable form of vread() can be implemented while holding spinlocks. Signed-off-by: Lorenzo Stoakes --- include/linux/uio.h | 2 ++ lib/iov_iter.c | 48 +++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 50 insertions(+) diff --git a/include/linux/uio.h b/include/linux/uio.h index 27e3fd942960..29eb18bb6feb 100644 --- a/include/linux/uio.h +++ b/include/linux/uio.h @@ -173,6 +173,8 @@ static inline size_t copy_folio_to_iter(struct folio *folio, size_t offset, { return copy_page_to_iter(&folio->page, offset, bytes, i); } +size_t copy_page_to_iter_nofault(struct page *page, unsigned offset, + size_t bytes, struct iov_iter *i); static __always_inline __must_check size_t copy_to_iter(const void *addr, size_t bytes, struct iov_iter *i) diff --git a/lib/iov_iter.c b/lib/iov_iter.c index 274014e4eafe..34dd6bdf2fba 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -172,6 +172,18 @@ static int copyout(void __user *to, const void *from, size_t n) return n; } +static int copyout_nofault(void __user *to, const void *from, size_t n) +{ + long res; + + if (should_fail_usercopy()) + return n; + + res = copy_to_user_nofault(to, from, n); + + return res < 0 ? n : res; +} + static int copyin(void *to, const void __user *from, size_t n) { size_t res = n; @@ -734,6 +746,42 @@ size_t copy_page_to_iter(struct page *page, size_t offset, size_t bytes, } EXPORT_SYMBOL(copy_page_to_iter); +size_t copy_page_to_iter_nofault(struct page *page, unsigned offset, size_t bytes, + struct iov_iter *i) +{ + size_t res = 0; + + if (!page_copy_sane(page, offset, bytes)) + return 0; + if (WARN_ON_ONCE(i->data_source)) + return 0; + if (unlikely(iov_iter_is_pipe(i))) + return copy_page_to_iter_pipe(page, offset, bytes, i); + page += offset / PAGE_SIZE; // first subpage + offset %= PAGE_SIZE; + while (1) { + void *kaddr = kmap_local_page(page); + size_t n = min(bytes, (size_t)PAGE_SIZE - offset); + + iterate_and_advance(i, n, base, len, off, + copyout_nofault(base, kaddr + offset + off, len), + memcpy(base, kaddr + offset + off, len) + ) + kunmap_local(kaddr); + 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_nofault); + size_t copy_page_from_iter(struct page *page, size_t offset, size_t bytes, struct iov_iter *i) {