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authorGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-01-14 02:43:11 +0400
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2014-01-14 02:43:11 +0400
commit87da149343c8c93f6984c0f4b9da7651709624f7 (patch)
tree47e2f102a0dd40ae822a8b7c470da07f3a1b9081
parent0890147fe09ff7e8275a162b1ab76ab5e3158c6d (diff)
downloadlinux-87da149343c8c93f6984c0f4b9da7651709624f7.tar.xz
Revert "kernfs: replace kernfs_node->u.completion with kernfs_root->deactivate_waitq"
This reverts commit ea1c472dfeada211a0100daa7976e8e8e779b858. Tejun writes: I'm sorry but can you please revert the whole series? get_active() waiting while a node is deactivated has potential to lead to deadlock and that deactivate/reactivate interface is something fundamentally flawed and that cgroup will have to work with the remove_self() like everybody else. IOW, I think the first posting was correct. Cc: Tejun Heo <tj@kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
-rw-r--r--fs/kernfs/dir.c27
-rw-r--r--include/linux/kernfs.h4
2 files changed, 18 insertions, 13 deletions
diff --git a/fs/kernfs/dir.c b/fs/kernfs/dir.c
index ed62de6cdf8f..510b5062ef30 100644
--- a/fs/kernfs/dir.c
+++ b/fs/kernfs/dir.c
@@ -8,7 +8,6 @@
* This file is released under the GPLv2.
*/
-#include <linux/sched.h>
#include <linux/fs.h>
#include <linux/namei.h>
#include <linux/idr.h>
@@ -152,7 +151,6 @@ struct kernfs_node *kernfs_get_active(struct kernfs_node *kn)
*/
void kernfs_put_active(struct kernfs_node *kn)
{
- struct kernfs_root *root = kernfs_root(kn);
int v;
if (unlikely(!kn))
@@ -164,7 +162,11 @@ void kernfs_put_active(struct kernfs_node *kn)
if (likely(v != KN_DEACTIVATED_BIAS))
return;
- wake_up_all(&root->deactivate_waitq);
+ /*
+ * atomic_dec_return() is a mb(), we'll always see the updated
+ * kn->u.completion.
+ */
+ complete(kn->u.completion);
}
/**
@@ -175,22 +177,26 @@ void kernfs_put_active(struct kernfs_node *kn)
*/
static void kernfs_deactivate(struct kernfs_node *kn)
{
- struct kernfs_root *root = kernfs_root(kn);
+ DECLARE_COMPLETION_ONSTACK(wait);
+ int v;
BUG_ON(!(kn->flags & KERNFS_REMOVED));
if (!(kernfs_type(kn) & KERNFS_ACTIVE_REF))
return;
- rwsem_acquire(&kn->dep_map, 0, 0, _RET_IP_);
+ kn->u.completion = (void *)&wait;
- atomic_add(KN_DEACTIVATED_BIAS, &kn->active);
+ rwsem_acquire(&kn->dep_map, 0, 0, _RET_IP_);
+ /* atomic_add_return() is a mb(), put_active() will always see
+ * the updated kn->u.completion.
+ */
+ v = atomic_add_return(KN_DEACTIVATED_BIAS, &kn->active);
- if (atomic_read(&kn->active) != KN_DEACTIVATED_BIAS)
+ if (v != KN_DEACTIVATED_BIAS) {
lock_contended(&kn->dep_map, _RET_IP_);
-
- wait_event(root->deactivate_waitq,
- atomic_read(&kn->active) == KN_DEACTIVATED_BIAS);
+ wait_for_completion(&wait);
+ }
lock_acquired(&kn->dep_map, _RET_IP_);
rwsem_release(&kn->dep_map, 1, _RET_IP_);
@@ -607,7 +613,6 @@ struct kernfs_root *kernfs_create_root(struct kernfs_dir_ops *kdops, void *priv)
root->dir_ops = kdops;
root->kn = kn;
- init_waitqueue_head(&root->deactivate_waitq);
return root;
}
diff --git a/include/linux/kernfs.h b/include/linux/kernfs.h
index 232f1a632383..d2c439db4efa 100644
--- a/include/linux/kernfs.h
+++ b/include/linux/kernfs.h
@@ -15,7 +15,7 @@
#include <linux/lockdep.h>
#include <linux/rbtree.h>
#include <linux/atomic.h>
-#include <linux/wait.h>
+#include <linux/completion.h>
struct file;
struct iattr;
@@ -91,6 +91,7 @@ struct kernfs_node {
struct rb_node rb;
union {
+ struct completion *completion;
struct kernfs_node *removed_list;
} u;
@@ -131,7 +132,6 @@ struct kernfs_root {
/* private fields, do not use outside kernfs proper */
struct ida ino_ida;
struct kernfs_dir_ops *dir_ops;
- wait_queue_head_t deactivate_waitq;
};
struct kernfs_open_file {