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=-11.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 C7E0EC432BE for ; Tue, 3 Aug 2021 19:18:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B1E4D60F56 for ; Tue, 3 Aug 2021 19:18:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239636AbhHCTSn (ORCPT ); Tue, 3 Aug 2021 15:18:43 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:51696 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239622AbhHCTSm (ORCPT ); Tue, 3 Aug 2021 15:18:42 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1628018310; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=DFWNnmq4Fr86FBlSANVnWR2moKkcBcoaXFNT4Ed8iZI=; b=GUGv0mS3pNi1zkLJK9e7s+5n1E73K26ZxFODYss2YvqTvZHa+7NKApvYaD0cmOxWM605Bn tvUUmFAJnYo17xufh9ElV0tEeZ+kUKGACVCW7cCz7nqx6FDovmdYDxO2PPjFwwmSc4O6k+ eAaYL9jZXn917E9ERK8QgkIcMU0nRLk= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-102-F09b58fmOROfEYdP18qfSQ-1; Tue, 03 Aug 2021 15:18:29 -0400 X-MC-Unique: F09b58fmOROfEYdP18qfSQ-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id C48F83E741; Tue, 3 Aug 2021 19:18:27 +0000 (UTC) Received: from max.com (unknown [10.40.193.155]) by smtp.corp.redhat.com (Postfix) with ESMTP id EC59860C0F; Tue, 3 Aug 2021 19:18:20 +0000 (UTC) From: Andreas Gruenbacher To: Linus Torvalds , Alexander Viro , Christoph Hellwig , "Darrick J. Wong" , Paul Mackerras Cc: Jan Kara , Matthew Wilcox , cluster-devel@redhat.com, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, ocfs2-devel@oss.oracle.com, Andreas Gruenbacher , kvm-ppc@vger.kernel.org Subject: [PATCH v5 00/12] gfs2: Fix mmap + page fault deadlocks Date: Tue, 3 Aug 2021 21:18:06 +0200 Message-Id: <20210803191818.993968-1-agruenba@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi all, here's another update on top of v5.14-rc4. There seems to be a bug in get_user_pages_fast when called with FOLL_FAST_ONLY; please see below. Changes: * Change fault_in_pages_{readable,writeable} to return the number of bytes that should be accessible instead of failing outright when part of the requested region cannot be faulted in. Change iov_iter_fault_in_readable to those same semantics. * Add fault_in_iov_iter_writeable for safely faulting in pages for writing without modifying the pages. With this patch queue, fstest generic/208 (aio-dio-invalidate-failure.c) endlessly spins in gfs2_file_direct_write. It looks as if there's a bug in get_user_pages_fast when called with FOLL_FAST_ONLY: (1) The test case performs an aio write into a 32 MB buffer. (2) The buffer is initially not in memory, so when iomap_dio_rw() -> ... -> bio_iov_iter_get_pages() is called with the iter->noio flag set, we get to get_user_pages_fast() with FOLL_FAST_ONLY set. get_user_pages_fast() returns 0, which causes bio_iov_iter_get_pages to return -EFAULT. (3) Then gfs2_file_direct_write faults in the entire buffer with fault_in_iov_iter_readable(), which succeeds. (4) With the buffer in memory, we retry the iomap_dio_rw() -> ... -> bio_iov_iter_get_pages() -> ... -> get_user_pages_fast(). This should succeed now, but get_user_pages_fast() still returns 0. (5) Thus we end up in step (3) again. The buffered writes generic/208 performs are unrelated to this hang. Apart from the generic/208 hang, gfs2 still needs a better strategy for faulting in more reasonable chunks of memory at a time and for resuming requests after faulting in pages. We've got some of the pieces in place for safely allowing that, but more work remains to be done. For immediate consideration by Al Viro: iov_iter: Fix iov_iter_get_pages{,_alloc} page fault return value For immediate consideration by Paul Mackerras: powerpc/kvm: Fix kvm_use_magic_page Thanks, Andreas Andreas Gruenbacher (12): iov_iter: Fix iov_iter_get_pages{,_alloc} page fault return value powerpc/kvm: Fix kvm_use_magic_page Turn fault_in_pages_{readable,writeable} into fault_in_{readable,writeable} Turn iov_iter_fault_in_readable into fault_in_iov_iter_readable iov_iter: Introduce fault_in_iov_iter_writeable gfs2: Add wrapper for iomap_file_buffered_write gfs2: Fix mmap + page fault deadlocks for buffered I/O iomap: Fix iomap_dio_rw return value for user copies iomap: Support restarting direct I/O requests after user copy failures iomap: Add done_before argument to iomap_dio_rw iov_iter: Introduce noio flag to disable page faults gfs2: Fix mmap + page fault deadlocks for direct I/O arch/powerpc/kernel/kvm.c | 3 +- arch/powerpc/kernel/signal_32.c | 4 +- arch/powerpc/kernel/signal_64.c | 2 +- arch/x86/kernel/fpu/signal.c | 8 +- drivers/gpu/drm/armada/armada_gem.c | 7 +- fs/btrfs/file.c | 8 +- fs/btrfs/ioctl.c | 7 +- fs/ext4/file.c | 5 +- fs/f2fs/file.c | 6 +- fs/fuse/file.c | 2 +- fs/gfs2/file.c | 95 ++++++++++++++++++++--- fs/iomap/buffered-io.c | 2 +- fs/iomap/direct-io.c | 28 +++++-- fs/ntfs/file.c | 2 +- fs/xfs/xfs_file.c | 6 +- fs/zonefs/super.c | 4 +- include/linux/iomap.h | 11 ++- include/linux/pagemap.h | 58 +------------- include/linux/uio.h | 4 +- lib/iov_iter.c | 107 ++++++++++++++++++++------ mm/filemap.c | 4 +- mm/gup.c | 113 ++++++++++++++++++++++++++++ 22 files changed, 360 insertions(+), 126 deletions(-) -- 2.26.3