btrfs: Introduce BTRFS engine

It is been found that BTRFS uses per subvolume device
numbering scheme  which causes some of our tests to fail
if they are laying on this filesystem.

Here we introduce minimal engine which parses subvolumes
present on mount point.

The interface is two functions

 - btrfs_parse_mountinfo: this one parses subvolume and caches the results
 - is_btrfs_subvol: test if device id is laying on subvolume

In the code we assume that cpu we're running on
is little endian, thus if one day we run on big
ending machine the code must be updated accordingly.

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
proc_parse: Call for btrfs_parse_mountinfo on every mount

This helper will cause BTRFS engine to collect all subvolumes.

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
mount: Add phys_stat_dev_match helper

This helper serves to hide fs specifics (in particular
btrfs) thus the caller won't need the details.

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
sk-unix: Don't fail if socket path lays on btrfs volume

Because socket migh lay on btrfs volume (thus the device
number reported by diag module won't be the same as obtained
from stat(2)) we need to do an additional test and try
to resolve device number with help of btrfs engine.

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
files-reg: Don't fail matching if ghost file is on BTRFS subvolume

In case if ghost file is on BTRFS subvolume we should not fail
but test if there is a match.

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
mount: Prepare fstypes to contain more unsupported FSs

We will need to parse btrfs stuff, but this one is not
in the supported list yet (as it's bound to hardware).

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
Acked-by: Cyrill Gorcunov <gorcunov@openvz.org>
mount: Introduce generic FSs parsing callback

And make use of it in for btrfs.

Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
Acked-by: Cyrill Gorcunov <gorcunov@openvz.org>
service: set success to true before exit

Signed-off-by: Ruslan Kuprieiev <kupruser@gmail.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
btrfs: Don't miss subvol0 on matching

Subvolume 0 has own device number as well, don't miss it
when looking up for match.

Reported-by: Andrew Vagin <avagin@parallels.com>
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Tested-by: Andrew Vagin <avagin@parallels.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
btrfs: Don't fail if we meet non-subvolume mountpoint

If mount point is not a subvolume we need more complex logic
to figure out which subvolumes it might have. It'll be addressed
later, at moment simply don't fail in such case: for worst
scenarion we will fail later in CRIU code when devs are not
matching, in best case if application is not using notify,
sockets or deleted files -- we should continue without errors.

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>