From patchwork Tue Apr 13 05:17:15 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Axel Rasmussen X-Patchwork-Id: 12199287 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=-26.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_GIT,USER_IN_DEF_DKIM_WL 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 136C9C4360C for ; Tue, 13 Apr 2021 05:17:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EBB5B613AB for ; Tue, 13 Apr 2021 05:17:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344522AbhDMFSB (ORCPT ); Tue, 13 Apr 2021 01:18:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:50858 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S244255AbhDMFRu (ORCPT ); Tue, 13 Apr 2021 01:17:50 -0400 Received: from mail-yb1-xb49.google.com (mail-yb1-xb49.google.com [IPv6:2607:f8b0:4864:20::b49]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5F61CC061342 for ; Mon, 12 Apr 2021 22:17:31 -0700 (PDT) Received: by mail-yb1-xb49.google.com with SMTP id g7so15055242ybm.13 for ; Mon, 12 Apr 2021 22:17:31 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:in-reply-to:message-id:mime-version:references:subject:from:to :cc; bh=70Kcx1xrATHIJtpEaJi28zNN7Ahs80HU8g90CQ0Hm2k=; b=p6FuHDvYVTK5bDUeP68j1uSS/Re+ZZUG7I7RWQWNy6fgIqGdc+oiUSwx57YKj6p7re ukIoNy2FmOnHeYhwuvPP8W/RrN+g1A+ayDY0f5qnvnavNp+tqlMVmtbZA1fQNp7LK1Pw N2hCk+3pzS2Sn5O+urQ4M67oxJibQDR6BCYzrlMGTEW+IDKAZ0bpME5oHd3cT5Y5hmZk CaH3MsXqRs1EdRECZS1ryXjb//rQxRekMYPW34tsZ7X26sNR4XrY0bp9zW9AS/OPl7RB UHYDLhpBa67Ig+Jx+Cc4l7srWH/InyARcOwfrwuktxMppWCeHPLiCI3t6ijnPmTS6Ksm rq/Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=70Kcx1xrATHIJtpEaJi28zNN7Ahs80HU8g90CQ0Hm2k=; b=KCzABq7NMx7SQ1L81iitvFuhVF4X6tLFNLx2RvMJFF7qk/JNhhJaGKPEgCORTAFFTM KQs6OKH7AyL+pijnXxp5xZGN89Bcv/HUKJ6/gvgAr5hi6jgA0pQwt0HWLdI8jBBxOARB XnlfmzwrJh/ig1iW4VDFseMb1bgOpE05WNg27257JLMP5Uq+7t0H9uG3eZP/YQ3x+Moc dRGT8v/VvoHqIB+HY4YI2X5GcBhBqkL2H5pYpUFSn3DaspS0hj3QRvqfYGVjzQVVmY9s i83VvxnCQKotucrbqYs8upygkBz9CtpXxVEWSYP7YcxAR+PJLdhE3WSpN0sDbm1aw7j2 8zQQ== X-Gm-Message-State: AOAM530qp+y2K1hiXUTqIuNtkrnJITG9CHjscZxllhaprA5RkfFKmy0l 3pEBHiSaW3FJOOcTwgr84q+IzxdT+o4Rnfnns+zg X-Google-Smtp-Source: ABdhPJx3TQQai0X1de1IO+PrirTFU2uw3gtn/o605SZAaB8Oe1cnqX7iNxp+GKo6pSNFTt/+d73yxdn9vQ9lo8anYfqo X-Received: from ajr0.svl.corp.google.com ([2620:15c:2cd:203:d508:eee5:2d57:3e32]) (user=axelrasmussen job=sendgmr) by 2002:a5b:44e:: with SMTP id s14mr44730257ybp.11.1618291050652; Mon, 12 Apr 2021 22:17:30 -0700 (PDT) Date: Mon, 12 Apr 2021 22:17:15 -0700 In-Reply-To: <20210413051721.2896915-1-axelrasmussen@google.com> Message-Id: <20210413051721.2896915-4-axelrasmussen@google.com> Mime-Version: 1.0 References: <20210413051721.2896915-1-axelrasmussen@google.com> X-Mailer: git-send-email 2.31.1.295.g9ea45b61b8-goog Subject: [PATCH v2 3/9] userfaultfd/shmem: support minor fault registration for shmem From: Axel Rasmussen To: Alexander Viro , Andrea Arcangeli , Andrew Morton , Hugh Dickins , Jerome Glisse , Joe Perches , Lokesh Gidra , Mike Kravetz , Mike Rapoport , Peter Xu , Shaohua Li , Shuah Khan , Stephen Rothwell , Wang Qing Cc: linux-api@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-kselftest@vger.kernel.org, linux-mm@kvack.org, Axel Rasmussen , Brian Geffon , "Dr . David Alan Gilbert" , Mina Almasry , Oliver Upton Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org This patch allows shmem-backed VMAs to be registered for minor faults. Minor faults are appropriately relayed to userspace in the fault path, for VMAs with the relevant flag. This commit doesn't hook up the UFFDIO_CONTINUE ioctl for shmem-backed minor faults, though, so userspace doesn't yet have a way to resolve such faults. Signed-off-by: Axel Rasmussen Acked-by: Peter Xu --- fs/userfaultfd.c | 6 +++--- include/uapi/linux/userfaultfd.h | 7 ++++++- mm/memory.c | 8 +++++--- mm/shmem.c | 10 +++++++++- 4 files changed, 23 insertions(+), 8 deletions(-) diff --git a/fs/userfaultfd.c b/fs/userfaultfd.c index 14f92285d04f..9f3b8684cf3c 100644 --- a/fs/userfaultfd.c +++ b/fs/userfaultfd.c @@ -1267,8 +1267,7 @@ static inline bool vma_can_userfault(struct vm_area_struct *vma, } if (vm_flags & VM_UFFD_MINOR) { - /* FIXME: Add minor fault interception for shmem. */ - if (!is_vm_hugetlb_page(vma)) + if (!(is_vm_hugetlb_page(vma) || vma_is_shmem(vma))) return false; } @@ -1941,7 +1940,8 @@ static int userfaultfd_api(struct userfaultfd_ctx *ctx, /* report all available features and ioctls to userland */ uffdio_api.features = UFFD_API_FEATURES; #ifndef CONFIG_HAVE_ARCH_USERFAULTFD_MINOR - uffdio_api.features &= ~UFFD_FEATURE_MINOR_HUGETLBFS; + uffdio_api.features &= + ~(UFFD_FEATURE_MINOR_HUGETLBFS | UFFD_FEATURE_MINOR_SHMEM); #endif uffdio_api.ioctls = UFFD_API_IOCTLS; ret = -EFAULT; diff --git a/include/uapi/linux/userfaultfd.h b/include/uapi/linux/userfaultfd.h index bafbeb1a2624..159a74e9564f 100644 --- a/include/uapi/linux/userfaultfd.h +++ b/include/uapi/linux/userfaultfd.h @@ -31,7 +31,8 @@ UFFD_FEATURE_MISSING_SHMEM | \ UFFD_FEATURE_SIGBUS | \ UFFD_FEATURE_THREAD_ID | \ - UFFD_FEATURE_MINOR_HUGETLBFS) + UFFD_FEATURE_MINOR_HUGETLBFS | \ + UFFD_FEATURE_MINOR_SHMEM) #define UFFD_API_IOCTLS \ ((__u64)1 << _UFFDIO_REGISTER | \ (__u64)1 << _UFFDIO_UNREGISTER | \ @@ -185,6 +186,9 @@ struct uffdio_api { * UFFD_FEATURE_MINOR_HUGETLBFS indicates that minor faults * can be intercepted (via REGISTER_MODE_MINOR) for * hugetlbfs-backed pages. + * + * UFFD_FEATURE_MINOR_SHMEM indicates the same support as + * UFFD_FEATURE_MINOR_HUGETLBFS, but for shmem-backed pages instead. */ #define UFFD_FEATURE_PAGEFAULT_FLAG_WP (1<<0) #define UFFD_FEATURE_EVENT_FORK (1<<1) @@ -196,6 +200,7 @@ struct uffdio_api { #define UFFD_FEATURE_SIGBUS (1<<7) #define UFFD_FEATURE_THREAD_ID (1<<8) #define UFFD_FEATURE_MINOR_HUGETLBFS (1<<9) +#define UFFD_FEATURE_MINOR_SHMEM (1<<10) __u64 features; __u64 ioctls; diff --git a/mm/memory.c b/mm/memory.c index 4e358601c5d6..cc71a445c76c 100644 --- a/mm/memory.c +++ b/mm/memory.c @@ -3972,9 +3972,11 @@ static vm_fault_t do_read_fault(struct vm_fault *vmf) * something). */ if (vma->vm_ops->map_pages && fault_around_bytes >> PAGE_SHIFT > 1) { - ret = do_fault_around(vmf); - if (ret) - return ret; + if (likely(!userfaultfd_minor(vmf->vma))) { + ret = do_fault_around(vmf); + if (ret) + return ret; + } } ret = __do_fault(vmf); diff --git a/mm/shmem.c b/mm/shmem.c index b72c55aa07fc..3f48cb5e8404 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -1785,7 +1785,7 @@ static int shmem_swapin_page(struct inode *inode, pgoff_t index, * vm. If we swap it in we mark it dirty since we also free the swap * entry since a page cannot live in both the swap and page cache. * - * vmf and fault_type are only supplied by shmem_fault: + * vma, vmf, and fault_type are only supplied by shmem_fault: * otherwise they are NULL. */ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index, @@ -1820,6 +1820,14 @@ static int shmem_getpage_gfp(struct inode *inode, pgoff_t index, page = pagecache_get_page(mapping, index, FGP_ENTRY | FGP_HEAD | FGP_LOCK, 0); + + if (page && vma && userfaultfd_minor(vma)) { + unlock_page(page); + put_page(page); + *fault_type = handle_userfault(vmf, VM_UFFD_MINOR); + return 0; + } + if (xa_is_value(page)) { error = shmem_swapin_page(inode, index, &page, sgp, gfp, vma, fault_type);