Messages in this thread Patch in this message | | | Date | Wed, 9 Sep 2009 23:09:55 -0700 | From | Sukadev Bhattiprolu <> | Subject | [RFC][v6][PATCH 4/9]: Add target_pid parameter to alloc_pidmap() |
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Subject: [RFC][v6][PATCH 4/9]: 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[v3]: - (Eric Biederman): Avoid set_pidmap() function. Added couple of checks for target_pid in alloc_pidmap() itself. 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> --- kernel/pid.c | 24 ++++++++++++++++++------ 1 file changed, 18 insertions(+), 6 deletions(-)
Index: linux-2.6/kernel/pid.c =================================================================== --- linux-2.6.orig/kernel/pid.c 2009-09-09 19:07:20.000000000 -0700 +++ linux-2.6/kernel/pid.c 2009-09-09 19:07:28.000000000 -0700 @@ -146,16 +146,22 @@ static int alloc_pidmap_page(struct pidm return 0; } -static int alloc_pidmap(struct pid_namespace *pid_ns) +static int alloc_pidmap(struct pid_namespace *pid_ns, int target_pid) { int i, offset, max_scan, pid, last = pid_ns->last_pid; int rc = -EAGAIN; int pid_max = pid_ns->pid_max; struct pidmap *map; - pid = last + 1; - if (pid >= pid_max) - pid = RESERVED_PIDS; + if (target_pid) { + pid = target_pid; + if (pid < 0 || pid >= pid_max) + return -EINVAL; + } else { + pid = last + 1; + if (pid >= pid_max) + pid = RESERVED_PIDS; + } offset = pid & BITS_PER_PAGE_MASK; map = &pid_ns->pidmap[pid/BITS_PER_PAGE]; max_scan = (pid_max + BITS_PER_PAGE - 1)/BITS_PER_PAGE - !offset; @@ -168,9 +174,14 @@ static int alloc_pidmap(struct pid_names do { if (!test_and_set_bit(offset, map->page)) { atomic_dec(&map->nr_free); - pid_ns->last_pid = pid; + if (!target_pid) + pid_ns->last_pid = pid; return pid; + } else if (target_pid) { + rc = -EBUSY; + break; } + offset = find_next_offset(map, offset); pid = mk_pid(pid_ns, map, offset); /* @@ -196,6 +207,7 @@ static int alloc_pidmap(struct pid_names } pid = mk_pid(pid_ns, map, offset); } + return rc; } @@ -272,7 +284,7 @@ struct pid *alloc_pid(struct pid_namespa tmp = ns; for (i = ns->level; i >= 0; i--) { - nr = alloc_pidmap(tmp); + nr = alloc_pidmap(tmp, 0); if (nr < 0) goto out_free;
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