call_usermodehelper: simplify/fix UMH_NO_WAIT case
Oleg Nesterov [Wed, 26 May 2010 21:43:04 +0000 (14:43 -0700)]
__call_usermodehelper(UMH_NO_WAIT) has 2 problems:

- if kernel_thread() fails, call_usermodehelper_freeinfo()
  is not called.

- for unknown reason UMH_NO_WAIT has UMH_WAIT_PROC logic,
  we spawn yet another thread which waits until the user
  mode application exits.

Change the UMH_NO_WAIT code to use ____call_usermodehelper() instead of
wait_for_helper(), and do call_usermodehelper_freeinfo() unconditionally.
We can rely on CLONE_VFORK, do_fork(CLONE_VFORK) until the child exits or
execs.

With or without this patch UMH_NO_WAIT does not report the error if
kernel_thread() fails, this is correct since the caller doesn't wait for
result.

Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

kernel/kmod.c

index 48daed4..ad9f2ed 100644 (file)
@@ -205,10 +205,7 @@ static int wait_for_helper(void *data)
                        sub_info->retval = ret;
        }
 
-       if (sub_info->wait == UMH_NO_WAIT)
-               call_usermodehelper_freeinfo(sub_info);
-       else
-               complete(sub_info->complete);
+       complete(sub_info->complete);
        return 0;
 }
 
@@ -217,13 +214,13 @@ static void __call_usermodehelper(struct work_struct *work)
 {
        struct subprocess_info *sub_info =
                container_of(work, struct subprocess_info, work);
-       pid_t pid;
        enum umh_wait wait = sub_info->wait;
+       pid_t pid;
 
        /* CLONE_VFORK: wait until the usermode helper has execve'd
         * successfully We need the data structures to stay around
         * until that is done.  */
-       if (wait == UMH_WAIT_PROC || wait == UMH_NO_WAIT)
+       if (wait == UMH_WAIT_PROC)
                pid = kernel_thread(wait_for_helper, sub_info,
                                    CLONE_FS | CLONE_FILES | SIGCHLD);
        else
@@ -232,6 +229,7 @@ static void __call_usermodehelper(struct work_struct *work)
 
        switch (wait) {
        case UMH_NO_WAIT:
+               call_usermodehelper_freeinfo(sub_info);
                break;
 
        case UMH_WAIT_PROC: