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=-17.2 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 autolearn=ham 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 DA965C636C8 for ; Sun, 18 Jul 2021 22:40:17 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C47F760FF4 for ; Sun, 18 Jul 2021 22:40:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233954AbhGRWnO (ORCPT ); Sun, 18 Jul 2021 18:43:14 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:49115 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233832AbhGRWnL (ORCPT ); Sun, 18 Jul 2021 18:43:11 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1626648012; 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: in-reply-to:in-reply-to:references:references; bh=KCnSLNP7riR8LfALdj37STeKckvJ3hnzBxN8+ybrwAA=; b=DORTl0wL2GrDC3cQDxuGaL84Bry578ckGn3rYsNLvL5yhX2KfZmFtvQ4TiNSq55d8swSu0 Tfeppj+JQYTHX5TR+oHnWB575Ip5IqkMHwgvCWcZZgTp+6esTwMc/XXOYC/QYNTQbwX1h9 GaaQ/r6csaEKxF5+hTGX14rHFmXD1T0= 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-422-_lYvoSUYM2qhfapcOfSkeQ-1; Sun, 18 Jul 2021 18:40:10 -0400 X-MC-Unique: _lYvoSUYM2qhfapcOfSkeQ-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 3994F362F8; Sun, 18 Jul 2021 22:40:09 +0000 (UTC) Received: from max.com (unknown [10.40.195.75]) by smtp.corp.redhat.com (Postfix) with ESMTP id 6D5A560C0F; Sun, 18 Jul 2021 22:40:02 +0000 (UTC) From: Andreas Gruenbacher To: Linus Torvalds Cc: Alexander Viro , Jan Kara , Matthew Wilcox , Christoph Hellwig , cluster-devel@redhat.com, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, ocfs2-devel@oss.oracle.com, Andreas Gruenbacher Subject: [PATCH v2 6/6] gfs2: Fix mmap + page fault deadlocks for direct I/O Date: Mon, 19 Jul 2021 00:39:32 +0200 Message-Id: <20210718223932.2703330-7-agruenba@redhat.com> In-Reply-To: <20210718223932.2703330-1-agruenba@redhat.com> References: <20210718223932.2703330-1-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 Direct I/O differs from buffered I/O in that it uses bio_iov_iter_get_pages for grabbing page references and for manually faulting in pages instead of triggering actual page faults. For disabling these manual page faults, it's not enough to call pagefault_disable(); instead, we use the new ITER_FLAG_FAST_ONLY flag for telling iomap_dio_rw to stop faulting pages in for us. Signed-off-by: Andreas Gruenbacher --- fs/gfs2/file.c | 35 ++++++++++++++++++++++++++++++++++- 1 file changed, 34 insertions(+), 1 deletion(-) diff --git a/fs/gfs2/file.c b/fs/gfs2/file.c index 99df7934b4d8..6feb857a8a1c 100644 --- a/fs/gfs2/file.c +++ b/fs/gfs2/file.c @@ -763,21 +763,42 @@ static ssize_t gfs2_file_direct_read(struct kiocb *iocb, struct iov_iter *to, struct file *file = iocb->ki_filp; struct gfs2_inode *ip = GFS2_I(file->f_mapping->host); size_t count = iov_iter_count(to); + size_t written = 0; ssize_t ret; + /* + * In this function, we disable page faults when whe're holding the + * inode glock while doing I/O. If a page fault occurs, we drop the + * inode glock, fault in the pages manually, and then we retry. Other + * than in gfs2_file_read_iter, iomap_dio_rw can trigger implicit as + * well as manual page faults, and we need to disable both kinds + * separately. + */ + if (!count) return 0; /* skip atime */ gfs2_holder_init(ip->i_gl, LM_ST_DEFERRED, 0, gh); +retry: ret = gfs2_glock_nq(gh); if (ret) goto out_uninit; + pagefault_disable(); + to->type |= ITER_FLAG_FAST_ONLY; ret = iomap_dio_rw(iocb, to, &gfs2_iomap_ops, NULL, 0); + to->type &= ~ITER_FLAG_FAST_ONLY; + pagefault_enable(); + gfs2_glock_dq(gh); + if (ret > 0) + written += ret; + if (unlikely(iov_iter_count(to) && (ret > 0 || ret == -EFAULT)) && + fault_in_iov_iter(to)) + goto retry; out_uninit: gfs2_holder_uninit(gh); - return ret; + return written ? written : ret; } static ssize_t gfs2_file_direct_write(struct kiocb *iocb, struct iov_iter *from, @@ -790,6 +811,12 @@ static ssize_t gfs2_file_direct_write(struct kiocb *iocb, struct iov_iter *from, loff_t offset = iocb->ki_pos; ssize_t ret; + /* + * In this function, we disable page faults when whe're holding the + * inode glock while doing I/O. If a page fault occurs, we drop the + * inode glock, fault in the pages manually, and then we retry. + */ + /* * Deferred lock, even if its a write, since we do no allocation on * this path. All we need to change is the atime, and this lock mode @@ -799,6 +826,7 @@ static ssize_t gfs2_file_direct_write(struct kiocb *iocb, struct iov_iter *from, * VFS does. */ gfs2_holder_init(ip->i_gl, LM_ST_DEFERRED, 0, gh); +retry: ret = gfs2_glock_nq(gh); if (ret) goto out_uninit; @@ -807,11 +835,16 @@ static ssize_t gfs2_file_direct_write(struct kiocb *iocb, struct iov_iter *from, if (offset + len > i_size_read(&ip->i_inode)) goto out; + from->type |= ITER_FLAG_FAST_ONLY; ret = iomap_dio_rw(iocb, from, &gfs2_iomap_ops, NULL, 0); + from->type &= ~ITER_FLAG_FAST_ONLY; + if (ret == -ENOTBLK) ret = 0; out: gfs2_glock_dq(gh); + if (unlikely(ret == -EFAULT) && fault_in_iov_iter(from)) + goto retry; out_uninit: gfs2_holder_uninit(gh); return ret; -- 2.26.3