From: Alan Jenkins <alan.christopher.jenkins@gmail.com>
To: David Howells <dhowells@redhat.com>, viro@zeniv.linux.org.uk
Cc: 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]
Date: Fri, 19 Oct 2018 18:35:50 +0100 [thread overview]
Message-ID: <97872123-70be-2833-ea7a-a463ce204b53@gmail.com> (raw)
In-Reply-To: <6518.1539956277@warthog.procyon.org.uk>
On 19/10/2018 14:37, David Howells wrote:
> Alan Jenkins <alan.christopher.jenkins@gmail.com> 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;
>
I guess this tries to fix the second of the two sequences I mentioned -
mount+unmount, then close the FD. It doesn't seem to work.
# open_tree_clone 3</mnt 3 sh
# cd /proc/self/fd/3
# mount --move . /mnt
[ 41.747831] mnt_flags=1020 umount=0
# cd /
# umount /mnt
umount: /mnt: target is busy
^ a newly introduced bug? I do not remember having this problem before.
# umount -l /mnt
# exec 3<&- # close FD 3
[ 95.984094] watchdog: BUG: soft lockup - CPU#1 stuck for 22s! [sh:1423]
...
[ 96.000032] RIP: 0010:pin_kill+0x128/0x140
And the first sequence I mentioned - close the FD, then mount+unmount -
seems to be unchanged.
# open_tree_clone 3</mnt 3 sh
# cd /proc/self/fd/3
# exec 3<&- # close FD 3
# mount --move . /mnt
[ 76.175127] mnt_flags=8000020 umount=1
# cd /
# umount /mnt
watchdog: BUG: soft lockup - CPU#0 stuck for 23s! [umount:1472]
...
RIP: 0010:pin_kill+0x128/0x140
The close-then-mount test seemed to be solved by the diff you suggested
earlier.
diff --git a/fs/namespace.c b/fs/namespace.c
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2469,7 +2469,7 @@ static int do_move_mount(struct path *old_path, struct path *new_path)
if (old->mnt_ns && !attached)
goto out1;
- if (old->mnt.mnt_flags & MNT_LOCKED)
+ if (old->mnt.mnt_flags & (MNT_LOCKED | MNT_UMOUNT))
goto out1;
if (old_path->dentry != old_path->mnt->mnt_root)
If we can do that, then is it possible to solve mount-unmount-close the
same way?
@@ -1763,7 +1763,7 @@ void dissolve_on_fput(struct vfsmount *mnt)
{
namespace_lock();
lock_mount_hash();
- if (!real_mount(mnt)->mnt_ns) {
+ if (!real_mount(mnt)->mnt_ns && !(mnt->mnt_flags & MNT_UMOUNT)) {
mntget(mnt);
umount_tree(real_mount(mnt), UMOUNT_CONNECTED);
}
Regards
Alan
next prev parent reply other threads:[~2018-10-19 17:35 UTC|newest]
Thread overview: 98+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-09-21 16:30 [PATCH 00/34] VFS: Introduce filesystem context [ver #12] David Howells
2018-09-21 16:30 ` [PATCH 01/34] vfs: syscall: Add open_tree(2) to reference or clone a mount " David Howells
2018-10-21 16:41 ` Eric W. Biederman
2018-09-21 16:30 ` [PATCH 02/34] vfs: syscall: Add move_mount(2) to move mounts around " David Howells
2018-09-21 16:30 ` [PATCH 03/34] teach move_mount(2) to work with OPEN_TREE_CLONE " David Howells
2018-10-05 18:24 ` Alan Jenkins
2018-10-07 10:48 ` Alan Jenkins
2018-10-07 19:20 ` Alan Jenkins
2018-10-10 12:36 ` David Howells
2018-10-12 14:22 ` Alan Jenkins
2018-10-12 14:54 ` David Howells
2018-10-12 14:57 ` Alan Jenkins
2018-10-11 9:17 ` David Howells
2018-10-11 11:48 ` Alan Jenkins
2018-10-11 13:10 ` David Howells
2018-10-11 12:14 ` David Howells
2018-10-11 12:23 ` Alan Jenkins
2018-10-11 15:33 ` David Howells
2018-10-11 18:38 ` Eric W. Biederman
2018-10-11 20:17 ` David Howells
2018-10-13 6:06 ` Al Viro
2018-10-17 17:45 ` Alan Jenkins
2018-10-18 20:09 ` David Howells
2018-10-18 20:58 ` David Howells
2018-10-19 11:57 ` David Howells
2018-10-19 13:37 ` David Howells
2018-10-19 17:35 ` Alan Jenkins [this message]
2018-10-19 21:35 ` David Howells
2018-10-19 21:40 ` David Howells
2018-10-19 22:36 ` David Howells
2018-10-20 5:25 ` Al Viro
2018-10-20 11:06 ` Alan Jenkins
2018-10-20 11:48 ` Al Viro
2018-10-20 12:26 ` Al Viro
2018-10-21 0:40 ` David Howells
2018-10-10 11:56 ` David Howells
2018-10-10 12:31 ` David Howells
2018-10-10 12:39 ` Alan Jenkins
2018-10-10 12:50 ` David Howells
2018-10-10 13:02 ` David Howells
2018-10-10 13:06 ` Alan Jenkins
2018-10-21 16:57 ` Eric W. Biederman
2018-10-23 11:19 ` Alan Jenkins
2018-10-23 16:22 ` Al Viro
2018-09-21 16:30 ` [PATCH 04/34] vfs: Suppress MS_* flag defs within the kernel unless explicitly enabled " David Howells
2018-09-21 16:30 ` [PATCH 05/34] vfs: Introduce the basic header for the new mount API's filesystem context " David Howells
2018-09-21 16:30 ` [PATCH 06/34] vfs: Introduce logging functions " David Howells
2018-09-21 16:31 ` [PATCH 07/34] vfs: Add configuration parser helpers " David Howells
2019-03-14 7:46 ` Geert Uytterhoeven
2019-03-14 10:27 ` David Howells
2019-03-14 10:49 ` Geert Uytterhoeven
2018-09-21 16:31 ` [PATCH 08/34] vfs: Add LSM hooks for the new mount API " David Howells
2018-09-21 16:31 ` [PATCH 09/34] vfs: Put security flags into the fs_context struct " David Howells
2018-09-21 16:31 ` [PATCH 10/34] selinux: Implement the new mount API LSM hooks " David Howells
2018-09-21 16:31 ` [PATCH 11/34] smack: Implement filesystem context security " David Howells
2018-09-21 16:31 ` [PATCH 12/34] apparmor: Implement security hooks for the new mount API " David Howells
2018-09-21 16:31 ` [PATCH 13/34] tomoyo: " David Howells
2018-09-21 16:32 ` [PATCH 14/34] vfs: Separate changing mount flags full remount " David Howells
2018-09-21 16:32 ` [PATCH 15/34] vfs: Implement a filesystem superblock creation/configuration context " David Howells
2018-09-21 16:32 ` [PATCH 16/34] vfs: Remove unused code after filesystem context changes " David Howells
2018-09-21 16:32 ` [PATCH 17/34] procfs: Move proc_fill_super() to fs/proc/root.c " David Howells
2018-09-21 16:32 ` [PATCH 18/34] proc: Add fs_context support to procfs " David Howells
2018-09-21 16:32 ` [PATCH 19/34] ipc: Convert mqueue fs to fs_context " David Howells
2018-09-21 16:32 ` [PATCH 20/34] cpuset: Use " David Howells
2018-09-21 16:33 ` [PATCH 21/34] kernfs, sysfs, cgroup, intel_rdt: Support " David Howells
2018-11-19 4:23 ` Andrei Vagin
2018-12-06 17:08 ` Andrei Vagin
2018-09-21 16:33 ` [PATCH 22/34] hugetlbfs: Convert to " David Howells
2018-09-21 16:33 ` [PATCH 23/34] vfs: Remove kern_mount_data() " David Howells
2018-09-21 16:33 ` [PATCH 24/34] vfs: Provide documentation for new mount API " David Howells
2018-09-21 16:33 ` [PATCH 25/34] Make anon_inodes unconditional " David Howells
2018-09-21 16:33 ` [PATCH 26/34] vfs: syscall: Add fsopen() to prepare for superblock creation " David Howells
2018-09-21 16:33 ` [PATCH 27/34] vfs: Implement logging through fs_context " David Howells
2018-09-21 16:33 ` [PATCH 28/34] vfs: Add some logging to the core users of the fs_context log " David Howells
2018-09-21 16:34 ` [PATCH 29/34] vfs: syscall: Add fsconfig() for configuring and managing a context " David Howells
2018-09-21 16:34 ` [PATCH 30/34] vfs: syscall: Add fsmount() to create a mount for a superblock " David Howells
2018-09-21 16:34 ` [PATCH 31/34] vfs: syscall: Add fspick() to select a superblock for reconfiguration " David Howells
2018-10-12 14:49 ` Alan Jenkins
2018-10-13 6:11 ` Al Viro
2018-10-13 9:45 ` Alan Jenkins
2018-10-13 23:04 ` Andy Lutomirski
2018-10-17 13:15 ` David Howells
2018-10-17 13:20 ` David Howells
2018-10-17 14:31 ` Alan Jenkins
2018-10-17 14:35 ` Eric W. Biederman
2018-10-17 14:55 ` Alan Jenkins
2018-10-17 15:24 ` David Howells
2018-10-17 15:38 ` Eric W. Biederman
2018-10-17 15:45 ` David Howells
2018-10-17 17:41 ` Alan Jenkins
2018-10-17 21:20 ` David Howells
2018-10-17 22:13 ` Alan Jenkins
2018-09-21 16:34 ` [PATCH 32/34] afs: Add fs_context support " David Howells
2018-09-21 16:34 ` [PATCH 33/34] afs: Use fs_context to pass parameters over automount " David Howells
2018-09-21 16:34 ` [PATCH 34/34] vfs: Add a sample program for the new mount API " David Howells
2018-12-17 14:12 ` Anders Roxell
2018-12-20 16:36 ` David Howells
2018-10-04 18:37 ` [PATCH 00/34] VFS: Introduce filesystem context " Eric W. Biederman
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