[PATCH] sys_setpgid: simplify pid/ns interaction

From: Oleg Nesterov
Date: Sun Nov 25 2007 - 09:44:17 EST


sys_setpgid() does unneeded conversions from pid_t to "struct pid" and vice
versa. Use "struct pid" more consistently. Saves one find_vpid() and eliminates
the explicit usage of ->nsproxy->pid_ns. Imho, cleanups the code.

Also use the same_thread_group() helper.

Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>

--- PT/kernel/sys.c~ 2007-11-20 17:16:10.000000000 +0300
+++ PT/kernel/sys.c 2007-11-25 17:16:59.000000000 +0300
@@ -916,8 +916,8 @@ asmlinkage long sys_setpgid(pid_t pid, p
{
struct task_struct *p;
struct task_struct *group_leader = current->group_leader;
- int err = -EINVAL;
- struct pid_namespace *ns;
+ struct pid *pgrp;
+ int err;

if (!pid)
pid = task_pid_vnr(group_leader);
@@ -929,12 +929,10 @@ asmlinkage long sys_setpgid(pid_t pid, p
/* From this point forward we keep holding onto the tasklist lock
* so that our parent does not change from under us. -DaveM
*/
- ns = current->nsproxy->pid_ns;
-
write_lock_irq(&tasklist_lock);

err = -ESRCH;
- p = find_task_by_pid_ns(pid, ns);
+ p = find_task_by_vpid(pid);
if (!p)
goto out;

@@ -942,7 +940,7 @@ asmlinkage long sys_setpgid(pid_t pid, p
if (!thread_group_leader(p))
goto out;

- if (p->real_parent->tgid == group_leader->tgid) {
+ if (same_thread_group(p->real_parent, group_leader)) {
err = -EPERM;
if (task_session(p) != task_session(group_leader))
goto out;
@@ -959,10 +957,12 @@ asmlinkage long sys_setpgid(pid_t pid, p
if (p->signal->leader)
goto out;

+ pgrp = task_pid(p);
if (pgid != pid) {
struct task_struct *g;

- g = find_task_by_pid_type_ns(PIDTYPE_PGID, pgid, ns);
+ pgrp = find_vpid(pgid);
+ g = pid_task(pgrp, PIDTYPE_PGID);
if (!g || task_session(g) != task_session(group_leader))
goto out;
}
@@ -971,13 +971,10 @@ asmlinkage long sys_setpgid(pid_t pid, p
if (err)
goto out;

- if (task_pgrp_nr_ns(p, ns) != pgid) {
- struct pid *pid;
-
+ if (task_pgrp(p) != pgrp) {
detach_pid(p, PIDTYPE_PGID);
- pid = find_vpid(pgid);
- attach_pid(p, PIDTYPE_PGID, pid);
- set_task_pgrp(p, pid_nr(pid));
+ attach_pid(p, PIDTYPE_PGID, pgrp);
+ set_task_pgrp(p, pid_nr(pgrp));
}

err = 0;

-
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