Here we need to close proc self fd only, as it's not
a service fd, and it can occupy real task fd number.
Closing of PROC_PID_FD_OFF is useless action here,
because it's already occupy a service fd number.

So, we skip this excess syscall, and leave PROC_PID_FD_OFF
open.

v4: New
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

Place stdin in fdstore. Kill SELF_STDIN_OFF.

v4: New
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

Next patch will move SELF_STDIN_OFF sfd to fdstore.
This patch moves fdstore_init() before tty_prep_fds().

v4: New
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

Create a zombie with specific pgid and check that
pgid remains the same after restore.

This test hangs criu restore without any of two previous patches:
1)without "restore: Call prepare_fds() in restore_one_zombie()"
  in 100% cases;

2)without "restore: Split restore_one_helper() and wait exiting
  zombie children" fail is racy, but you can add something like

criu/cr-restore.c:
## -1130,6 +1130,8 @@ static int restore_one_zombie(CoreEntry *core)

        if (task_entries != NULL) {
                restore_finish_stage(task_entries, CR_STATE_RESTORE);
+               if (current->parent->pid->state == TASK_ALIVE)
+                       sleep(2);
                zombie_prepare_signals();
        }

and it will fail with almost 100% probability.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

Cleanup fork() definition and make a generic function
for all archs. It may be useful, when you want to add
more clone flags to fork(), or if you want to pass more,
than one argument to child function (glibc's clone
alows only one).
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

Zombie is also can be choosen as a parent for task helper like
any other task.

If the task helper exits between restore_finish_stage(CR_STATE_RESTORE)
and zombie_prepare_signals()->SIG_UNBLOCK, the standard criu SIGCHLD
handler is called, and the restore fails:

(00.057762)     41: Error (criu/cr-restore.c:1557): 40 exited, status=0
(00.057815) Error (criu/cr-restore.c:2465): Restoring FAILED.

This patch makes restore_one_zombie() behave as restore_one_helper()
and to wait children exits before allowing SIGCHLD. This makes us
safe against races with exiting children.

See next patch for test details.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

Zombie may be choosen as parent for task helper
during solving pgid dependences. In this situation,
it becomes to share fdt with the helper and it has
to call prepare_fds() to decrement fdt->nr.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

Make it possible to use this function by tests.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

CTL_TTY_OFF and reserve_service_fd() are unused now,
so purge them from the code.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

There are two problems. The first is CTL_TTY_OFF occupies
one of the biggest available fds in the system. It's a number
near service_fd_rlim_cur. Next patches want to allocate
service fds lower, than service_fd_rlim_cur, and they want
to know max used fd from file fles after the image reading.

But since one of fds is already set very big (CTL_TTY_OFF)
on a stage of collection fles, the only availabe service
fds are near service_fd_rlim_cur. It's vicious circle,
and the only way is to change ctl tty fd allocation way.

The second problem is ctl tty is ugly out of generic file
engine fixup (see open_fd()). This is made because ctl tty
is the only slave fle, which needs additional actions
(see tty_restore_ctl_terminal()). Another file types just
receive their slave fle, and do not do anything else.

This patch moves ctl tty to generic engine and solves all
the above problems. To do that, we implement new CTL_TTY
file type, which open method waits till slave tty is received
and then calls tty_restore_ctl_terminal() for that. It fits
to generic engine well, and allocates fd via find_unused_fd(),
and do not polute file table by big fd numbers.

Next patch will kill currently unneed CTL_TTY leftovers
and will remove CTL_TTY_OFF service fd from criu.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

Move the function and reduce its arguments number.
This is cleanup needed to keep all tty code together.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

Just mark the fle as "fake" and the engine will do all the work.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

service_fd_id is id of a specific task, while other tasks
in shared fd table group may have bigger id numbers.
In this case given unused fd intersects with service fds
of such tasks. This leads to undefined behaviour. Fix that.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

This patch speeds up creation of child process by disabling
iteration over open files for the most cases. Really, we don't
need that now, as previous patches make parent files do not leak:

mnt namespace fds are stored in fdstore, pid proc files
are closed directly.

So, now we can skip closing old files for the most cases,
except some CLONE_FILES cases: we need that only if parent
have CLONE_FILES in its flags (and for root_item).
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

When task is in pid namespace, getpid() can't be used
to identify it. So, use vpid instead of that.

Also, move log_init_by_pid() above pid check.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

Child does not know about parent's pid proc fd,
and it can't close it by fd. Next patch will do
close_old_files() optional, and it will base on
the fact there is no leftover fds. So, close pid
proc directly.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

This allows to decrese number of file descriptors,
which are passed to children, and that is need to
close in close_old_files().

Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>:
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

No functional changes.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

The both branches need this, so move it up.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

mntns_get_root_fd() may be called by a task from
!root_user_ns, and it fails if so.

Put root fd to fdstore to allow use it every task.

v3: New
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

CR_PROC_FD_OFF is need for accessing to foreign tasks
fds, and will be used in the future.

TRANSPORT_FD_OFF is for uniformity.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

I need named socket to communicate with pid_ns helpers
(see next patches) and receive answer from them
(it's impossible to send answer to unnamed socket).
As we already have transport socket, we'll reuse it
for the above goal too.

This patch makes transport sockets be created before
creation of children tasks. Also, now they are created
not only for alive tasks (so we need additional
manipulations for TASK_HELPERS, e.g., to call prepare_fdt()).

v5: Return CLONE_FILES clone() argument during task helpers
creation. Also get rid of fdt_mutex as CLONE_FILES processes
does not close old files after clone, and we don't have
intertersections between them. Also, socket() system call
can't return a fd in service fds range, which was the main
reason to have this mutex.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

Next patches will create transport sockets in task helpers.
As helpers are forked using CLONE_FILES, they must resolve
shared fds to create their own service fds. This patch allows
that.

I've digged in the code, and there is no a reason, we need
pid_rst_prio() during choosing of fdt restorer. So, this
case may be safely deleted, which guarantees, that in case
of TASK_HELPER, the restorer of fdt will be parent, i.e.,
no one TASK_HELPER will be restorer of fdt.

v5: New
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

This is refactoring, which will be used in next patches.
BUG_ON() just to mention that parent must be set before
call of this function.

v5: New
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

We close it in sigreturn_restore() for unification with other
service fds, so kill the second close() from here.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

This minimize chances to hit problem where files
used for page transfer are trying to use same number
reserved for service fd.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

Will need it to unlimit the files allocation
for service fd reserving and later for parasite code run
(which is implemented in vz7 instance and soon will be
ported into vanilla).
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

It has only one user, so unexport it.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

Add a fake fd type for autofs. This allows functions
like find_file_desc() work as expected, without
having two different file_desc with the same type
and same id.

Also, later, it will allow to delete autofs_create_fle()
and to use generic helper.
Signed-off-by: Kirill Tkhai <ktkhai@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

Unchanged test provided by Andrew.
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>
Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

In case we have mounts:

1 /mnt/
2 /mnt/a with parent 1
3 /mnt/a/b with parent 1
4 /mnt/a with parent 2

We determine 2 as needing remap with does_mnt_overmount() and remap it.
Next we mount 4 on top of 2. Next in fixup_remap_mounts() we want to
move 2 back to it's parent 1, but instead move 4 there. So in these case
children-overmounts need to be remapped too.
Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

Remaps in mnt_remap_list should follow same descending order which was
setup in mnt_resort_siblings(), so don't reorder them.

For instance if we have sibling mounts with mountpoints:
1) /dir1/dir2/dir3
2) /dir1/dir2
3) /dir1
Here (2) is sibling-overmount for (1). Mount (3) is sibling-overmount
for both (1) and (2). So when we move overmounts back in
fixup_remap_mounts() we should first move (2) and only then (3).
Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

We should add new entry _before_ first entry with less depth to sort in
descending order.

e.g: entries in list have depths [7,5,3], adding new entry m with depth
4 we would break list_for_each_entry loop on p with depth 3, before
patch we would get [7,5,3,4] after list_add, which is wrong.

Also we can relax "<=" check to "<" to avoid unnecessary reordering.
Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

dump of VZ7 ct fails, if we have overmounted tmpfs inside:

[root@silo ~]# prlctl enter su-test-2
entered into CT
CT-829e7b28 /# mkdir /mnt/overmntedtmp
CT-829e7b28 /# mount -t tmpfs tmpfs /mnt/overmntedtmp/
CT-829e7b28 /# mount -t tmpfs tmpfs /mnt
CT-829e7b28 /# logout

[root@silo ~]# prlctl suspend su-test-2
Suspending the CT...
Failed to suspend the CT: PRL_ERR_VZCTL_OPERATION_FAILED (Details: Will skip in-flight TCP connections
(01.657913) Error (criu/mount.c:1202): mnt: Can't open ./mnt/overmntedtmp: No such file or directory
(01.662528) Error (criu/util.c:709): exited, status=1
(01.664329) Error (criu/util.c:709): exited, status=1
(01.664694) Error (criu/cr-dump.c:2005): Dumping FAILED.
Failed to checkpoint the Container
All dump files and logs were saved to /vz/private/829e7b28-f204-4bce-b09f-d203b99befd4/dump/Dump.fail
Checkpointing failed
)

Criu wants to dump the contents of /mnt/overmntedtmp/ mount but it is
unavailable. So we copy the mount namespace in such a case and unmount
overmounts to access what we want to dump.

Actual usecase here is dumping CT with active mariadb and ssh
connection. Together they happen to create such overmount. As by default
systemd creates a separate mount namespace for mysql and also mounts
tmpfs to /run/user in it, and when ssh(root) is connected - systemd also
mounts tmpfs in container root mount namespace to /run/user/0 for user
files. As /run is slave mount /run/user/0 also propagates to mysql's
mount namespace and initially becomes overmounted by /run/user.

https://jira.sw.ru/browse/PSBM-57362

remove __maybe_unused for mnt_is_overmounted and umount_overmounts

changes in v2:
1) Use clone not fork, share resources with parent same as in
call_in_child_process.
2) Do not enter userns (create helper) for non-overmounted mounts. Thus
return back setns/resorens logic.
3) Helper opens fd for parent directly due to CLONE_FILES, remove futex.
4) Check helper exit status properly.
5) Add get_clean_fd helper.
6) Add better comments.

changes in v3:
1) Pass fd from helper through args instead of ret code, fix ret code
checking.
2) Add \n to pr_err in open_mountpoint

changes in v5:
Make comments even better.
Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

also remove __maybe_unused for __umount_children_overmounts

note: leave it __maybe_unused yet
Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

note: leave it __maybe_unused yet
Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

note: leave it __maybe_unused yet
Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>

It was droped during one of rebases.
Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>