Commit:     4fca88c87b7969c698912e2de9b1b31088c777cb
Parent:     d2ceb9b7ddedbb2e8e590bc6ce33c854043016f9
Author:     KAMEZAWA Hiroyuki <[EMAIL PROTECTED]>
AuthorDate: Thu Feb 7 00:14:27 2008 -0800
Committer:  Linus Torvalds <[EMAIL PROTECTED]>
CommitDate: Thu Feb 7 08:42:20 2008 -0800

    memory cgroup enhancements: add- pre_destroy() handler
    Add a handler "pre_destroy" to cgroup_subsys.  It is called before
    cgroup_rmdir() checks all subsys's refcnt.
    I think this is useful for subsys which have some extra refs even if there
    are no tasks in cgroup.  By adding pre_destroy(), the kernel keeps the rule
    "destroy() against subsystem is called only when refcnt=0." and allows css
    ref to be used by other objects than tasks.
    Signed-off-by: KAMEZAWA Hiroyuki <[EMAIL PROTECTED]>
    Cc: "Eric W. Biederman" <[EMAIL PROTECTED]>
    Cc: Balbir Singh <[EMAIL PROTECTED]>
    Cc: David Rientjes <[EMAIL PROTECTED]>
    Cc: Herbert Poetzl <[EMAIL PROTECTED]>
    Cc: Kirill Korotaev <[EMAIL PROTECTED]>
    Cc: Nick Piggin <[EMAIL PROTECTED]>
    Cc: Paul Menage <[EMAIL PROTECTED]>
    Cc: Pavel Emelianov <[EMAIL PROTECTED]>
    Cc: Peter Zijlstra <[EMAIL PROTECTED]>
    Cc: Vaidyanathan Srinivasan <[EMAIL PROTECTED]>
    Signed-off-by: Andrew Morton <[EMAIL PROTECTED]>
    Signed-off-by: Linus Torvalds <[EMAIL PROTECTED]>
 include/linux/cgroup.h |    1 +
 kernel/cgroup.c        |   22 ++++++++++++++++++++++
 2 files changed, 23 insertions(+), 0 deletions(-)

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 8747932..d8e9222 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -233,6 +233,7 @@ int cgroup_is_descendant(const struct cgroup *cont);
 struct cgroup_subsys {
        struct cgroup_subsys_state *(*create)(struct cgroup_subsys *ss,
                                                  struct cgroup *cont);
+       void (*pre_destroy)(struct cgroup_subsys *ss, struct cgroup *cont);
        void (*destroy)(struct cgroup_subsys *ss, struct cgroup *cont);
        int (*can_attach)(struct cgroup_subsys *ss,
                          struct cgroup *cont, struct task_struct *tsk);
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index 4d67a39..4e8b16a 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -586,6 +586,21 @@ static struct inode *cgroup_new_inode(mode_t mode, struct 
super_block *sb)
        return inode;
+ * Call subsys's pre_destroy handler.
+ * This is called before css refcnt check.
+ */
+static void cgroup_call_pre_destroy(struct cgroup *cgrp)
+       struct cgroup_subsys *ss;
+       for_each_subsys(cgrp->root, ss)
+               if (ss->pre_destroy && cgrp->subsys[ss->subsys_id])
+                       ss->pre_destroy(ss, cgrp);
+       return;
 static void cgroup_diput(struct dentry *dentry, struct inode *inode)
        /* is dentry a directory ? if so, kfree() associated cgroup */
@@ -2160,6 +2175,13 @@ static int cgroup_rmdir(struct inode *unused_dir, struct 
dentry *dentry)
        parent = cgrp->parent;
        root = cgrp->root;
        sb = root->sb;
+       /*
+        * Call pre_destroy handlers of subsys
+        */
+       cgroup_call_pre_destroy(cgrp);
+       /*
+        * Notify subsyses that rmdir() request comes.
+        */
        if (cgroup_has_css_refs(cgrp)) {
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