mm, hugetlb: add thread name and pid to SHM_HUGETLB mlock rlimit warning

Add the thread name and pid of the application that is allocating shm
segments with MAP_HUGETLB without being a part of
/proc/sys/vm/hugetlb_shm_group or having CAP_IPC_LOCK.

This identifies the application so it may be fixed by avoiding using the
deprecated exception (see Documentation/feature-removal-schedule.txt).
Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Dave Jones <davej@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

fs/hugetlbfs/inode.c

@@ -953,7 +953,11 @@ struct file *hugetlb_file_setup(const char *name, size_t size,
 	if (creat_flags == HUGETLB_SHMFS_INODE && !can_do_hugetlb_shm()) {
 		*user = current_user();
 		if (user_shm_lock(size, *user)) {
-			printk_once(KERN_WARNING "Using mlock ulimits for SHM_HUGETLB is deprecated\n");
+			task_lock(current);
+			printk_once(KERN_WARNING
+				"%s (%d): Using mlock ulimits for SHM_HUGETLB is deprecated\n",
+				current->comm, current->pid);
+			task_unlock(current);
 		} else {
 			*user = NULL;
 			return ERR_PTR(-EPERM);