On 27/6/24 04:47, Matthew Wilcox wrote:
On Wed, Jun 26, 2024 at 04:07:49PM -0400, Lucas Karpinski wrote:
+++ b/fs/namespace.c
@@ -78,6 +78,7 @@ static struct kmem_cache *mnt_cache __ro_after_init;
static DECLARE_RWSEM(namespace_sem);
static HLIST_HEAD(unmounted); /* protected by namespace_sem */
static LIST_HEAD(ex_mountpoints); /* protected by namespace_sem */
+static bool lazy_unlock = false; /* protected by namespace_sem */
That's a pretty ugly way of doing it. How about this?
Ha!
That was my original thought but I also didn't much like changing all
the callers.
I don't really like the proliferation of these small helper functions
either but if everyone
is happy to do this I think it's a great idea.
Ian
+++ b/fs/namespace.c
@@ -1553,7 +1553,7 @@ int may_umount(struct vfsmount *mnt)
EXPORT_SYMBOL(may_umount);
-static void namespace_unlock(void)
+static void __namespace_unlock(bool lazy)
{
struct hlist_head head;
struct hlist_node *p;
@@ -1570,7 +1570,8 @@ static void namespace_unlock(void)
if (likely(hlist_empty(&head)))
return;
- synchronize_rcu_expedited();
+ if (!lazy)
+ synchronize_rcu_expedited();
hlist_for_each_entry_safe(m, p, &head, mnt_umount) {
hlist_del(&m->mnt_umount);
@@ -1578,6 +1579,11 @@ static void namespace_unlock(void)
}
}
+static inline void namespace_unlock(void)
+{
+ __namespace_unlock(false);
+}
+
static inline void namespace_lock(void)
{
down_write(&namespace_sem);
@@ -1798,7 +1804,7 @@ static int do_umount(struct mount *mnt, int flags)
}
out:
unlock_mount_hash();
- namespace_unlock();
+ __namespace_unlock(flags & MNT_DETACH);
return retval;
}
(other variants on this theme might be to pass the flags to
__namespace_unlock() and check MNT_DETACH there)
