Maybe I am reading the lifetimes wrong but is there
any chance the code can just do something like the diff below?
AKA have a special version of kern_umount that does the call_rcu?
Looking at rcu_reclaim_tiny I think this use of mnt_rcu is valid.
AKA reusing the rcu_head in the rcu callback.
diff --git a/fs/namespace.c b/fs/namespace.c
index 40b994a29e90..7d7aaef1592e 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -4395,6 +4395,22 @@ void kern_unmount(struct vfsmount *mnt)
}
EXPORT_SYMBOL(kern_unmount);
+static void rcu_mntput(struct rcu_head *head)
+{
+ struct mount *mnt = container_of(head, struct mount, mnt_rcu);
+ mntput(&mnt->mnt);
+}
+
+void kern_rcu_unmount(struct vfsmount *mnt)
+{
+ /* release long term mount so mount point can be released */
+ if (!IS_ERR_OR_NULL(mnt)) {
+ struct mount *m = real_mount(mnt);
+ m->mnt_ns = NULL;
+ call_rcu(&m->mnt_rcu, rcu_mntput);
+ }
+}
+
void kern_unmount_array(struct vfsmount *mnt[], unsigned int num)
{
unsigned int i;
diff --git a/ipc/mqueue.c b/ipc/mqueue.c
index 5becca9be867..e54742f82e7d 100644
--- a/ipc/mqueue.c
+++ b/ipc/mqueue.c
@@ -1700,7 +1700,7 @@ void mq_clear_sbinfo(struct ipc_namespace *ns)
void mq_put_mnt(struct ipc_namespace *ns)
{
- kern_unmount(ns->mq_mnt);
+ kern_rcu_unmount(ns->mq_mnt);
}
static int __init init_mqueue_fs(void)
Eric
