[RFC][v4][PATCH 3/7]: Add target_pid parameter to alloc_pidmap()

Sukadev Bhattiprolu
2009-08-07T06:12:48Z

Subject: [RFC][v4][PATCH 3/7]: Add target_pid parameter to alloc_pidmap()

With support for setting a specific pid number for a process,
alloc_pidmap() will need a 'target_pid' parameter.

Changelog[v2]:
- (Serge Hallyn) Check for 'pid < 0' in set_pidmap().(Code
actually checks for 'pid <= 0' for completeness).

Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.vnet.ibm.com>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Reviewed-by: Oren Laadan <orenl@cs.columbia.edu>
---
kernel/pid.c | 28 ++++++++++++++++++++++++++--
1 files changed, 26 insertions(+), 2 deletions(-)

Index: linux-2.6/kernel/pid.c
===================================================================
--- linux-2.6.orig/kernel/pid.c 2009-08-05 17:02:45.000000000 -0700
+++ linux-2.6/kernel/pid.c 2009-08-05 19:34:37.000000000 -0700
@@ -147,11 +147,35 @@
return 0;
}

-static int alloc_pidmap(struct pid_namespace *pid_ns)
+static int set_pidmap(struct pid_namespace *pid_ns, int pid)
+{
+ int offset;
+ struct pidmap *map;
+
+ if (pid <= 0 || pid >= pid_max)
+ return -EINVAL;
+
+ offset = pid & BITS_PER_PAGE_MASK;
+ map = &pid_ns->pidmap[pid/BITS_PER_PAGE];
+
+ if (alloc_pidmap_page(map))
+ return -ENOMEM;
+
+ if (test_and_set_bit(offset, map->page))
+ return -EBUSY;
+
+ atomic_dec(&map->nr_free);
+ return pid;
+}
+
+static int alloc_pidmap(struct pid_namespace *pid_ns, int target_pid)
{
int i, rc, offset, max_scan, pid, last = pid_ns->last_pid;
struct pidmap *map;

+ if (target_pid)
+ return set_pidmap(pid_ns, target_pid);
+
pid = last + 1;
if (pid >= pid_max)
pid = RESERVED_PIDS;
@@ -270,7 +294,7 @@

tmp = ns;
for (i = ns->level; i >= 0; i--) {
- nr = alloc_pidmap(tmp);
+ nr = alloc_pidmap(tmp, 0);
if (nr < 0)
goto out_free;