From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com ([209.132.183.28]:60806 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727357AbeJSVoJ (ORCPT ); Fri, 19 Oct 2018 17:44:09 -0400 From: David Howells In-Reply-To: <862e36a2-2a6f-4e26-3228-8cab4b4cf230@gmail.com> References: <862e36a2-2a6f-4e26-3228-8cab4b4cf230@gmail.com> <153754740781.17872.7869536526927736855.stgit@warthog.procyon.org.uk> <153754743491.17872.12115848333103740766.stgit@warthog.procyon.org.uk> To: Alan Jenkins , viro@zeniv.linux.org.uk Cc: dhowells@redhat.com, torvalds@linux-foundation.org, ebiederm@xmission.com, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, mszeredi@redhat.com Subject: Re: [PATCH 03/34] teach move_mount(2) to work with OPEN_TREE_CLONE [ver #12] MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <6517.1539956277.1@warthog.procyon.org.uk> Content-Transfer-Encoding: 8BIT Date: Fri, 19 Oct 2018 14:37:57 +0100 Message-ID: <6518.1539956277@warthog.procyon.org.uk> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: Alan Jenkins wrote: > If I close() the mount FD "mfd", and then do "mount --move . /mnt", my > printk() shows MNT_UMOUNT has been set. ( I guess fchdir() works more like > openat(... , O_PATH) than dup() ). Then unmounting /mnt hangs, as I would > expect from my previous test. Okay, I think the attached should fix it. The issue being that do_move_mount() calls attach_recursive_mnt() with a NULL parent_path, which means that the moved-mount doesn't get its refcount incremented. David --- diff --git a/fs/namespace.c b/fs/namespace.c index 6370bfabec99..ce9fff980549 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -1935,7 +1935,8 @@ int count_mounts(struct mnt_namespace *ns, struct mount *mnt) static int attach_recursive_mnt(struct mount *source_mnt, struct mount *dest_mnt, struct mountpoint *dest_mp, - struct path *parent_path) + struct path *parent_path, + bool moving) { HLIST_HEAD(tree_list); struct mnt_namespace *ns = dest_mnt->mnt_ns; @@ -1976,6 +1977,8 @@ static int attach_recursive_mnt(struct mount *source_mnt, attach_mnt(source_mnt, dest_mnt, dest_mp); touch_mnt_namespace(source_mnt->mnt_ns); } else { + if (moving) + mnt_add_count(source_mnt, 1); mnt_set_mountpoint(dest_mnt, dest_mp, source_mnt); commit_tree(source_mnt); } @@ -2062,7 +2065,7 @@ static int graft_tree(struct mount *mnt, struct mount *p, struct mountpoint *mp) d_is_dir(mnt->mnt.mnt_root)) return -ENOTDIR; - return attach_recursive_mnt(mnt, p, mp, NULL); + return attach_recursive_mnt(mnt, p, mp, NULL, false); } /* @@ -2522,7 +2525,7 @@ static int do_move_mount(struct path *old_path, struct path *new_path) goto out1; err = attach_recursive_mnt(old, real_mount(new_path->mnt), mp, - attached ? &parent_path : NULL); + attached ? &parent_path : NULL, true); if (err) goto out1;