From patchwork Wed May 15 19:27:09 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Vivek Goyal X-Patchwork-Id: 10945211 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id C72AA933 for ; Wed, 15 May 2019 19:30:12 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id B759028555 for ; Wed, 15 May 2019 19:30:12 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id ABCB8285ED; Wed, 15 May 2019 19:30:12 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-7.9 required=2.0 tests=BAYES_00,MAILING_LIST_MULTI, RCVD_IN_DNSWL_HI autolearn=unavailable version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 2FFE128555 for ; Wed, 15 May 2019 19:30:12 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728202AbfEOT3i (ORCPT ); Wed, 15 May 2019 15:29:38 -0400 Received: from mx1.redhat.com ([209.132.183.28]:35010 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727591AbfEOT1e (ORCPT ); Wed, 15 May 2019 15:27:34 -0400 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id E1BDAC09AD12; Wed, 15 May 2019 19:27:33 +0000 (UTC) Received: from horse.redhat.com (unknown [10.18.25.29]) by smtp.corp.redhat.com (Postfix) with ESMTP id BCF9760C2A; Wed, 15 May 2019 19:27:33 +0000 (UTC) Received: by horse.redhat.com (Postfix, from userid 10451) id 0694C22548C; Wed, 15 May 2019 15:27:30 -0400 (EDT) From: Vivek Goyal To: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, linux-nvdimm@lists.01.org Cc: vgoyal@redhat.com, miklos@szeredi.hu, stefanha@redhat.com, dgilbert@redhat.com, swhiteho@redhat.com Subject: [PATCH v2 24/30] fuse, dax: Take ->i_mmap_sem lock during dax page fault Date: Wed, 15 May 2019 15:27:09 -0400 Message-Id: <20190515192715.18000-25-vgoyal@redhat.com> In-Reply-To: <20190515192715.18000-1-vgoyal@redhat.com> References: <20190515192715.18000-1-vgoyal@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.32]); Wed, 15 May 2019 19:27:33 +0000 (UTC) Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP We need some kind of locking mechanism here. Normal file systems like ext4 and xfs seems to take their own semaphore to protect agains truncate while fault is going on. We have additional requirement to protect against fuse dax memory range reclaim. When a range has been selected for reclaim, we need to make sure no other read/write/fault can try to access that memory range while reclaim is in progress. Once reclaim is complete, lock will be released and read/write/fault will trigger allocation of fresh dax range. Taking inode_lock() is not an option in fault path as lockdep complains about circular dependencies. So define a new fuse_inode->i_mmap_sem. Signed-off-by: Vivek Goyal --- fs/fuse/dir.c | 2 ++ fs/fuse/file.c | 17 +++++++++++++---- fs/fuse/fuse_i.h | 7 +++++++ fs/fuse/inode.c | 1 + 4 files changed, 23 insertions(+), 4 deletions(-) diff --git a/fs/fuse/dir.c b/fs/fuse/dir.c index fd8636e67ae9..84c0b638affb 100644 --- a/fs/fuse/dir.c +++ b/fs/fuse/dir.c @@ -1559,8 +1559,10 @@ int fuse_do_setattr(struct dentry *dentry, struct iattr *attr, */ if ((is_truncate || !is_wb) && S_ISREG(inode->i_mode) && oldsize != outarg.attr.size) { + down_write(&fi->i_mmap_sem); truncate_pagecache(inode, outarg.attr.size); invalidate_inode_pages2(inode->i_mapping); + up_write(&fi->i_mmap_sem); } clear_bit(FUSE_I_SIZE_UNSTABLE, &fi->state); diff --git a/fs/fuse/file.c b/fs/fuse/file.c index 2777355bc245..e536a04aaa06 100644 --- a/fs/fuse/file.c +++ b/fs/fuse/file.c @@ -2638,13 +2638,20 @@ static int __fuse_dax_fault(struct vm_fault *vmf, enum page_entry_size pe_size, if (write) sb_start_pagefault(sb); - /* TODO inode semaphore to protect faults vs truncate */ - + /* + * We need to serialize against not only truncate but also against + * fuse dax memory range reclaim. While a range is being reclaimed, + * we do not want any read/write/mmap to make progress and try + * to populate page cache or access memory we are trying to free. + */ + down_read(&get_fuse_inode(inode)->i_mmap_sem); ret = dax_iomap_fault(vmf, pe_size, &pfn, NULL, &fuse_iomap_ops); if (ret & VM_FAULT_NEEDDSYNC) ret = dax_finish_sync_fault(vmf, pe_size, pfn); + up_read(&get_fuse_inode(inode)->i_mmap_sem); + if (write) sb_end_pagefault(sb); @@ -3593,9 +3600,11 @@ static long fuse_file_fallocate(struct file *file, int mode, loff_t offset, file_update_time(file); } - if (mode & FALLOC_FL_PUNCH_HOLE) + if (mode & FALLOC_FL_PUNCH_HOLE) { + down_write(&fi->i_mmap_sem); truncate_pagecache_range(inode, offset, offset + length - 1); - + up_write(&fi->i_mmap_sem); + } fuse_invalidate_attr(inode); out: diff --git a/fs/fuse/fuse_i.h b/fs/fuse/fuse_i.h index f1ae549eff98..a234cf30538d 100644 --- a/fs/fuse/fuse_i.h +++ b/fs/fuse/fuse_i.h @@ -212,6 +212,13 @@ struct fuse_inode { */ struct rw_semaphore i_dmap_sem; + /** + * Can't take inode lock in fault path (leads to circular dependency). + * So take this in fuse dax fault path to make sure truncate and + * punch hole etc. can't make progress in parallel. + */ + struct rw_semaphore i_mmap_sem; + /** Sorted rb tree of struct fuse_dax_mapping elements */ struct rb_root_cached dmap_tree; unsigned long nr_dmaps; diff --git a/fs/fuse/inode.c b/fs/fuse/inode.c index ad66a353554b..713c5f32ab35 100644 --- a/fs/fuse/inode.c +++ b/fs/fuse/inode.c @@ -85,6 +85,7 @@ static struct inode *fuse_alloc_inode(struct super_block *sb) fi->state = 0; fi->nr_dmaps = 0; mutex_init(&fi->mutex); + init_rwsem(&fi->i_mmap_sem); init_rwsem(&fi->i_dmap_sem); spin_lock_init(&fi->lock); fi->forget = fuse_alloc_forget();