[PATCH] oom-killer disable for iscsi/lvm2/multipath userland critical sections

iscsi/lvm2/multipath needs guaranteed protection from the oom-killer, so
make the magical value of -17 in /proc/<pid>/oom_adj defeat the oom-killer
altogether.

(akpm: we still need to document oom_adj and friends in
Documentation/filesystems/proc.txt!)
Signed-off-by: NAndrea Arcangeli <andrea@suse.de>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

fs/proc/base.c

@@ -751,7 +751,7 @@ static ssize_t oom_adjust_write(struct file *file, const char __user *buf,
 	if (copy_from_user(buffer, buf, count))
 		return -EFAULT;
 	oom_adjust = simple_strtol(buffer, &end, 0);
-	if (oom_adjust < -16 || oom_adjust > 15)
+	if ((oom_adjust < -16 || oom_adjust > 15) && oom_adjust != OOM_DISABLE)
 		return -EINVAL;
 	if (*end == '\n')
 		end++;

include/linux/mm.h

@@ -857,5 +857,8 @@ int in_gate_area_no_task(unsigned long addr);
 #define in_gate_area(task, addr) ({(void)task; in_gate_area_no_task(addr);})
 #endif	/* __HAVE_ARCH_GATE_AREA */
 
+/* /proc/<pid>/oom_adj set to -17 protects from the oom-killer */
+#define OOM_DISABLE -17
+
 #endif /* __KERNEL__ */
 #endif /* _LINUX_MM_H */

mm/oom_kill.c

@@ -145,7 +145,7 @@ static struct task_struct * select_bad_process(void)
 	do_posix_clock_monotonic_gettime(&uptime);
 	do_each_thread(g, p)
 		/* skip the init task with pid == 1 */
-		if (p->pid > 1) {
+		if (p->pid > 1 && p->oomkilladj != OOM_DISABLE) {
 			unsigned long points;
 
 			/*