ipc,namespace: batch free ipc_namespace structures
Instead of waiting for an RCU grace period between each ipc_namespace
structure that is being freed, wait an RCU grace period for every batch
of ipc_namespace structures.
Thanks to Al Viro for the suggestion of the helper function.
This speeds up the run time of the test case that allocates ipc_namespaces
in a loop from 6 minutes, to a little over 1 second:
real 0m1.192s
user 0m0.038s
sys 0m1.152s
Signed-off-by: Rik van Riel <riel@surriel.com>
Reported-by: Chris Mason <clm@meta.com>
Tested-by: Giuseppe Scrivano <gscrivan@redhat.com>
Suggested-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
diff --git a/fs/namespace.c b/fs/namespace.c
index ab467ee..1ad4e5a 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1397,6 +1397,17 @@ struct vfsmount *mntget(struct vfsmount *mnt)
}
EXPORT_SYMBOL(mntget);
+/*
+ * Make a mount point inaccessible to new lookups.
+ * Because there may still be current users, the caller MUST WAIT
+ * for an RCU grace period before destroying the mount point.
+ */
+void mnt_make_shortterm(struct vfsmount *mnt)
+{
+ if (mnt)
+ real_mount(mnt)->mnt_ns = NULL;
+}
+
/**
* path_is_mountpoint() - Check if path is a mount in the current namespace.
* @path: path to check
@@ -4573,8 +4584,8 @@ EXPORT_SYMBOL_GPL(kern_mount);
void kern_unmount(struct vfsmount *mnt)
{
/* release long term mount so mount point can be released */
- if (!IS_ERR_OR_NULL(mnt)) {
- real_mount(mnt)->mnt_ns = NULL;
+ if (!IS_ERR(mnt)) {
+ mnt_make_shortterm(mnt);
synchronize_rcu(); /* yecchhh... */
mntput(mnt);
}
@@ -4586,8 +4597,7 @@ void kern_unmount_array(struct vfsmount *mnt[], unsigned int num)
unsigned int i;
for (i = 0; i < num; i++)
- if (mnt[i])
- real_mount(mnt[i])->mnt_ns = NULL;
+ mnt_make_shortterm(mnt[i]);
synchronize_rcu_expedited();
for (i = 0; i < num; i++)
mntput(mnt[i]);
