memrlimit: cgroup mm owner callback changes to add task info

This patch adds an additional field to the mm_owner callbacks. This field
is required to get to the mm that changed. Hold mmap_sem in write mode
before calling the mm_owner_changed callback

[hugh@veritas.com: fix mmap_sem deadlock]
Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Cc: Sudhir Kumar <skumar@linux.vnet.ibm.com>
Cc: YAMAMOTO Takashi <yamamoto@valinux.co.jp>
Cc: Paul Menage <menage@google.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Pavel Emelianov <xemul@openvz.org>
Cc: Balbir Singh <balbir@linux.vnet.ibm.com>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Hugh Dickins <hugh@veritas.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index c98dd7cb7076f44484a68643995f10fd1bbc2ff8..30934e4bfaab7b9e3197e0d7410579c0737bf2c7 100644 (file)
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -326,7 +326,8 @@ struct cgroup_subsys {
         */
        void (*mm_owner_changed)(struct cgroup_subsys *ss,
                                        struct cgroup *old,
-                                       struct cgroup *new);
+                                       struct cgroup *new,
+                                       struct task_struct *p);
        int subsys_id;
        int active;
        int disabled;

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index a0123d75ec9a7624f897bc2984ca4009b61abfbc..8c6e1c17e6d37faae0870c2d9ff5635c1e192037 100644 (file)
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -2735,6 +2735,8 @@ void cgroup_fork_callbacks(struct task_struct *child)
  * Called on every change to mm->owner. mm_init_owner() does not
  * invoke this routine, since it assigns the mm->owner the first time
  * and does not change it.
+ *
+ * The callbacks are invoked with mmap_sem held in read mode.
  */
 void cgroup_mm_owner_callbacks(struct task_struct *old, struct task_struct *new)
 {
@@ -2750,7 +2752,7 @@ void cgroup_mm_owner_callbacks(struct task_struct *old, struct task_struct *new)
                        if (oldcgrp == newcgrp)
                                continue;
                        if (ss->mm_owner_changed)
-                               ss->mm_owner_changed(ss, oldcgrp, newcgrp);
+                               ss->mm_owner_changed(ss, oldcgrp, newcgrp, new);
                }
        }
 }

diff --git a/kernel/exit.c b/kernel/exit.c
index 85a83c831856c193570e40a3b7d3e03ef8862d1c..0ef4673e351bddd4e738f88941511efa02f062fa 100644 (file)
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -640,24 +640,23 @@ retry:
 assign_new_owner:
        BUG_ON(c == p);
        get_task_struct(c);
+       read_unlock(&tasklist_lock);
+       down_write(&mm->mmap_sem);
        /*
         * The task_lock protects c->mm from changing.
         * We always want mm->owner->mm == mm
         */
        task_lock(c);
-       /*
-        * Delay read_unlock() till we have the task_lock()
-        * to ensure that c does not slip away underneath us
-        */
-       read_unlock(&tasklist_lock);
        if (c->mm != mm) {
                task_unlock(c);
+               up_write(&mm->mmap_sem);
                put_task_struct(c);
                goto retry;
        }
        cgroup_mm_owner_callbacks(mm->owner, c);
        mm->owner = c;
        task_unlock(c);
+       up_write(&mm->mmap_sem);
        put_task_struct(c);
 }
 #endif /* CONFIG_MM_OWNER */