From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Eric W. Biederman" Subject: [PATCH review 13/19] mnt: Honor MNT_LOCKED when detaching mounts Date: Thu, 2 Apr 2015 20:56:17 -0500 Message-ID: <1428026183-14879-13-git-send-email-ebiederm@xmission.com> References: <87a8yqou41.fsf_-_@x220.int.ebiederm.org> Cc: , "Serge E. Hallyn" , Andy Lutomirski , Richard Weinberger , Andrey Vagin , Al Viro , Jann Horn , Willy Tarreau , Omar Sandoval To: Linux Containers Return-path: Received: from out03.mta.xmission.com ([166.70.13.233]:51483 "EHLO out03.mta.xmission.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751308AbbDCCBp (ORCPT ); Thu, 2 Apr 2015 22:01:45 -0400 In-Reply-To: <87a8yqou41.fsf_-_@x220.int.ebiederm.org> Sender: linux-fsdevel-owner@vger.kernel.org List-ID: Modify umount(MNT_DETACH) to keep mounts in the hash table that are locked to their parent mounts, when the parent is lazily unmounted. In mntput_no_expire detach the children from the hash table, depending on mnt_pin_kill in cleanup_mnt to decrement the mnt_count of the children. In __detach_mounts if there are any mounts that have been unmounted but still are on the list of mounts of a mountpoint, remove their children from the mount hash table and those children to the unmounted list so they won't linger potentially indefinitely waiting for their final mntput, now that the mounts serve no purpose. Cc: stable@vger.kernel.org Signed-off-by: "Eric W. Biederman" --- fs/namespace.c | 29 ++++++++++++++++++++++++++--- fs/pnode.h | 2 ++ 2 files changed, 28 insertions(+), 3 deletions(-) diff --git a/fs/namespace.c b/fs/namespace.c index 010d5bebcb7e..1894d1878dbc 100644 --- a/fs/namespace.c +++ b/fs/namespace.c @@ -1099,6 +1099,13 @@ static void mntput_no_expire(struct mount *mnt) rcu_read_unlock(); list_del(&mnt->mnt_instance); + + if (unlikely(!list_empty(&mnt->mnt_mounts))) { + struct mount *p, *tmp; + list_for_each_entry_safe(p, tmp, &mnt->mnt_mounts, mnt_child) { + umount_mnt(p); + } + } unlock_mount_hash(); if (likely(!(mnt->mnt.mnt_flags & MNT_INTERNAL))) { @@ -1370,6 +1377,7 @@ static void umount_tree(struct mount *mnt, enum umount_tree_flags how) propagate_umount(&tmp_list); while (!list_empty(&tmp_list)) { + bool disconnect; p = list_first_entry(&tmp_list, struct mount, mnt_list); list_del_init(&p->mnt_expire); list_del_init(&p->mnt_list); @@ -1378,10 +1386,18 @@ static void umount_tree(struct mount *mnt, enum umount_tree_flags how) if (how & UMOUNT_SYNC) p->mnt.mnt_flags |= MNT_SYNC_UMOUNT; - pin_insert_group(&p->mnt_umount, &p->mnt_parent->mnt, &unmounted); + disconnect = !IS_MNT_LOCKED_AND_LAZY(p); + + pin_insert_group(&p->mnt_umount, &p->mnt_parent->mnt, + disconnect ? &unmounted : NULL); if (mnt_has_parent(p)) { mnt_add_count(p->mnt_parent, -1); - umount_mnt(p); + if (!disconnect) { + /* Don't forget about p */ + list_add_tail(&p->mnt_child, &p->mnt_parent->mnt_mounts); + } else { + umount_mnt(p); + } } change_mnt_propagation(p, MS_PRIVATE); } @@ -1506,7 +1522,14 @@ void __detach_mounts(struct dentry *dentry) lock_mount_hash(); while (!hlist_empty(&mp->m_list)) { mnt = hlist_entry(mp->m_list.first, struct mount, mnt_mp_list); - umount_tree(mnt, 0); + if (mnt->mnt.mnt_flags & MNT_UMOUNT) { + struct mount *p, *tmp; + list_for_each_entry_safe(p, tmp, &mnt->mnt_mounts, mnt_child) { + hlist_add_head(&p->mnt_umount.s_list, &unmounted); + umount_mnt(p); + } + } + else umount_tree(mnt, 0); } unlock_mount_hash(); put_mountpoint(mp); diff --git a/fs/pnode.h b/fs/pnode.h index 0fcdbe7ca648..7114ce6e6b9e 100644 --- a/fs/pnode.h +++ b/fs/pnode.h @@ -20,6 +20,8 @@ #define SET_MNT_MARK(m) ((m)->mnt.mnt_flags |= MNT_MARKED) #define CLEAR_MNT_MARK(m) ((m)->mnt.mnt_flags &= ~MNT_MARKED) #define IS_MNT_LOCKED(m) ((m)->mnt.mnt_flags & MNT_LOCKED) +#define IS_MNT_LOCKED_AND_LAZY(m) \ + (((m)->mnt.mnt_flags & (MNT_LOCKED|MNT_SYNC_UMOUNT)) == MNT_LOCKED) #define CL_EXPIRE 0x01 #define CL_SLAVE 0x02 -- 2.2.1