task_struct cleanup: move binfmt field to mm_struct

Because the binfmt is not different between threads in the same process,
it can be moved from task_struct to mm_struct.  And binfmt moudle is
handled per mm_struct instead of task_struct.

Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
Acked-by: Oleg Nesterov <oleg@redhat.com>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Acked-by: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 7 insertions, 8 deletions

diff --git a/kernel/exit.c b/kernel/exit.c
index 6c75ff83a8f..5859f598c95 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -976,8 +976,6 @@ NORET_TYPE void do_exit(long code)
                 disassociate_ctty(1);
 
         module_put(task_thread_info(tsk)->exec_domain->module);
-        if (tsk->binfmt)
-                module_put(tsk->binfmt->module);
 
         proc_exit_connector(tsk);
 
diff --git a/kernel/fork.c b/kernel/fork.c
index e49f181ba1c..266c6af6ef1 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -518,6 +518,8 @@ void mmput(struct mm_struct *mm)
                         spin_unlock(&mmlist_lock);
                 }
                 put_swap_token(mm);
+                if (mm->binfmt)
+                        module_put(mm->binfmt->module);
                 mmdrop(mm);
         }
 }
@@ -643,9 +645,14 @@ struct mm_struct *dup_mm(struct task_struct *tsk)
         mm->hiwater_rss = get_mm_rss(mm);
         mm->hiwater_vm = mm->total_vm;
 
+        if (mm->binfmt && !try_module_get(mm->binfmt->module))
+                goto free_pt;
+
         return mm;
 
 free_pt:
+        /* don't put binfmt in mmput, we haven't got module yet */
+        mm->binfmt = NULL;
         mmput(mm);
 
 fail_nomem:
@@ -1037,9 +1044,6 @@ static struct task_struct *copy_process(unsigned long clone_flags,
         if (!try_module_get(task_thread_info(p)->exec_domain->module))
                 goto bad_fork_cleanup_count;
 
-        if (p->binfmt && !try_module_get(p->binfmt->module))
-                goto bad_fork_cleanup_put_domain;
-
         p->did_exec = 0;
         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
         copy_flags(clone_flags, p);
@@ -1327,9 +1331,6 @@ bad_fork_cleanup_cgroup:
 #endif
         cgroup_exit(p, cgroup_callbacks_done);
         delayacct_tsk_free(p);
-        if (p->binfmt)
-                module_put(p->binfmt->module);
-bad_fork_cleanup_put_domain:
         module_put(task_thread_info(p)->exec_domain->module);
 bad_fork_cleanup_count:
         atomic_dec(&p->cred->user->processes);