The unique id is 32 bit and consists only of the subid value. This
is _really_ enough. The genid part is just a hint for the tree-search
algirythm to avoid unneeded sys_kcmp calls.
Plus, generate IDs for special files. This will make it easier to
move the regfiles into into separate files (see the respective patch
for details).
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
The subtree node should be linked with common rbtree procedure. Otherwise
the very first subtree insertion results in an infinite loop in the rb
linking and balancing code.
Plus, mark the root as static and add the subroot node initialization check.
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
Hide the structure - it's not required.
[ xemul: Ranem long id into u32 id and adopt to current tree ]
Signed-off-by: Stanislav Kinsbursky <skinsbursky@openvz.org>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>
We switch generic-object-id concept with sys_kcmp approach,
which implies changes of image format a bit (and since it's
early time for project overall, we're allowed to).
In short -- previously every file descriptor had an ID
generated by a kernel and exported via procfs. If the
appropriate file descriptors were the same objects in
kernel memory -- the IDs did match up to bit. It allows
us to figure out which files were actually the identical
ones and should be restored in a special way.
Once sys_kcmp system call was merged into the kernel,
we've got a new opprotunity -- to use this syscall instead.
The syscall basically compares kernel objects and returns
ordered results suitable for objects sorting in a userspace.
For us it means -- we treat every file descriptor as a combination
of 'genid' and 'subid'. While 'genid' serves for fast comparison
between fds, the 'subid' is kind of a second key, which guarantees
uniqueness of genid+subid tuple over all file descritors found
in a process (or group of processes).
To be able to find and dump file descriptors in a single pass we
collect every fd into a global rbtree, where (!) each node might
become a root for a subtree as well.
The main tree carries only non-equal genid. If we find genid which
is already in tree, we need to make sure that it's either indeed
a duplicate or not. For this we use sys_kcmp syscall and if we
find that file descriptors are different -- we simply put new
fd into a subtree.
Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
Acked-by: Pavel Emelyanov <xemul@parallels.com>
