net: mount sysfs in a new mount name-space

The current scheme is racy. It use open_detache_mount in a current
name-space. If a mount namespace is created by someone else between
mount and umount(detach) in open_detache_mount, the mount will be
propagated in the new mntns, then it is detached in a current ns and
rmdir fails, because it's still mounted in athother mntns.

This patch creates a new mount namespace for mounting sysfs.

Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
mm: don't add a guard page if a prev vma grows-down too

The kernel logic is described in v2.6.36-rc1-161-g7798330:
"If we've split the stack vma, only the lowest one has the guard page."

https://bugzilla.openvz.org/show_bug.cgi?id=2715
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
mm: map grow-down VMA-s with guard pages

In /proc/pid/maps grow-down VMA-s are shown without guard pages, but
sometime these "guard" pages can contain usefull data. For example if
a real guard page has been remmaped by another VMA. Let's call such
pages as fake guard pages.

So when a grow-down VMA is mmaped on restore, it should be mapped with
one more guard page to restore content of the fake guard page.

https://bugzilla.openvz.org/show_bug.cgi?id=2715
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
zdtm: check that two continuous grow-down VMA-s are restored correctly

It's a special case, because if we've split the stack vma,
only the lowest one has the guard page.

Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
zdtm: add grow_down test cases for regular execution

Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
zdtm: check grow-down vma-s in cow01

Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
mount: link dependent mounts (v3)

All shared mounts from one group are connected to circular list.
All slave are added into the proper master list.

v2: change variable name and fix a bug about adding shared mounts in a
circular list.
v3: handle errors of collect_shared

Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
mount: save group and master in image file (v2)

They are required for restoring shared and slave mounts

v2: use the same names of variables in image and in code
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
mounts: if a mount can't be mounted, it is queued in postpone list (v4)

Try to restore mounts while a postpone list isn't empty and check
that each iteration has some progress, otherwice it will fails for
preventing infinite loops

v2: rework logic about postpone list
    add more comments

v3: one more attempt to make it more readable
v4: Here is a master class from Pavel how to write self-documented code.

Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
mounts: find mounts, which are propagated from a current one (v2)

A few sentences, which are required for understanging this patch

2a) A shared mount can be replicated to as many mountpoints and all the
replicas continue to be exactly same.
2b) A slave mount is like a shared mount except that mount and umount
events only propagate towards it.
2c) A private mount does not forward or receive propagation.

All rules is there Documentation/filesystems/sharedsubtree.txt

If it's a first mount in a group, all group members should be
bind-mounted from this one.

Each mount propagates to all members of parent's group. The group can
contains a few slaves.

Mounts, which have propagated to slaves, are unmounted, because we can't
be sure, that they propagated in real life. For example:

mount --bind --make-slave /share /slave1
mount --bind --make-slave /share /slave2
mount /share/test
umount /slave2/test
mount --make-share /slave1/test
mount --bind --make-share /slave1/test /slave2/test

41 40 0:33 / /share rw,relatime shared:28 - tmpfs xxx rw
42 40 0:33 / /slave1 rw,relatime master:28 - tmpfs xxx rw
43 40 0:33 / /slave2 rw,relatime master:28 - tmpfs xxx rw
44 41 0:34 / /share/test rw,relatime shared:29 - tmpfs xxx rw
46 42 0:34 / /slave1/test rw,relatime shared:30 master:29 - tmpfs xxx rw
45 43 0:34 / /slave2/test rw,relatime shared:30 master:29 - tmpfs xxx rw

/slave1/test and /slave2/test depend on each other and minimum one of them
doesn't propagate from /share/test

v2: use false and true for bool

Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
mount: restore shared, slave, private properties.

Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
mounts: handle shared and slave mounts (v3)

The idea is simple. If a mount can't be mounted now, we will try to
mount it later.

v2: don't wait slaves, they are unmounted anyway
v3: add a comment in do_bind_mount to explain restoring of shared groups
Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
mounts: handle non-root bind-mounts

A non-root mount is bind-mounted from a proper root mount.

Non-root mount without root mount is not supported yet

Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
mount: prevent dumping mounts, if they can't be restored (v2)

Currently we check that all shared mounts have identical set of
children and that Each non-root mount has a proper root mount.

v2: check that nobody is overmounted
    check a tree before trying to restore it.

Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
zdtm: expand the mountpoints test

* check shared and slave mounts
* check bind-mounts

Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
test: generate a random tree of mounts

Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
cr-restore.c: fixed compilation errors on ARM

Use decode_pointer() to convert a virtual address into a native pointer.

Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
zdtm: fix a race condition during concurrent execution of tests

When tests are executed concurrently all of them use
the same root, so libraries must be copied atomically.

Without this patch we can get errors like this:
cp: cannot create regular file ‘/tmp/criu-root.m45u5Y/lib64/ld-linux-x86-64.so.2’: File exists

Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
pie: don't use pr_perror in pie code

pr_perror uses errno, which is set by glibc wrappers.
In pi return codes of syscalls should be printed

Signed-off-by: Andrey Vagin <avagin@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
rst: Formalize the shared resource restore order

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>