Now that mem_cgroup_pre_destroy callback doesn't fail finally we can
safely move on and forbit all the callbacks to fail. The last missing
piece is moving cgroup_call_pre_destroy after cgroup_clear_css_refs so
that css_tryget fails so no new charges for the memcg can happen.
The callbacks are also called from within cgroup_lock to guarantee that
no new tasks show up. We could theoretically call them outside of the
lock but then we have to move after CGRP_REMOVED flag is set.
Signed-off-by: Michal Hocko <mho...@suse.cz>
---
kernel/cgroup.c | 30 +++++++++---------------------
1 file changed, 9 insertions(+), 21 deletions(-)
diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index b7d9606..00729c1 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -855,7 +855,7 @@ static struct inode *cgroup_new_inode(umode_t mode, struct
super_block *sb)
* Call subsys's pre_destroy handler.
* This is called before css refcnt check.
*/
-static int cgroup_call_pre_destroy(struct cgroup *cgrp)
+static void cgroup_call_pre_destroy(struct cgroup *cgrp)
{
struct cgroup_subsys *ss;
int ret = 0;
@@ -864,15 +864,8 @@ static int cgroup_call_pre_destroy(struct cgroup *cgrp)
if (!ss->pre_destroy)
continue;
- ret = ss->pre_destroy(cgrp);
- if (ret) {
- /* ->pre_destroy() failure is being deprecated */
- WARN_ON_ONCE(!ss->__DEPRECATED_clear_css_refs);
- break;
- }
+ BUG_ON(ss->pre_destroy(cgrp));
}
-
- return ret;
}
static void cgroup_diput(struct dentry *dentry, struct inode *inode)
@@ -4161,7 +4154,6 @@ again:
mutex_unlock(&cgroup_mutex);
return -EBUSY;
}
- mutex_unlock(&cgroup_mutex);
/*
* In general, subsystem has no css->refcnt after pre_destroy(). But
@@ -4174,17 +4166,6 @@ again:
*/
set_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
- /*
- * Call pre_destroy handlers of subsys. Notify subsystems
- * that rmdir() request comes.
- */
- ret = cgroup_call_pre_destroy(cgrp);
- if (ret) {
- clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
- return ret;
- }
-
- mutex_lock(&cgroup_mutex);
parent = cgrp->parent;
if (atomic_read(&cgrp->count) || !list_empty(&cgrp->children)) {
clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
@@ -4206,6 +4187,13 @@ again:
return -EINTR;
goto again;
}
+
+ /*
+ * Call pre_destroy handlers of subsys. Notify subsystems
+ * that rmdir() request comes.
+ */
+ cgroup_call_pre_destroy(cgrp);
+
/* NO css_tryget() can success after here. */
finish_wait(&cgroup_rmdir_waitq, &wait);
clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags);
--
1.7.10.4
--
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