2020-04-02 20:32:56

by Trond Myklebust

Subject: [PATCH 1/2] NFS: finish_automount() requires us to hold 2 refs to the mount record

From: Trond Myklebust <[email protected]>

We must not return from nfs_d_automount() without holding 2 references
to the mount record. Doing so, will trigger the BUG() in finish_automount().
Also ensure that we don't try to reschedule the automount timer with
a negative timeout value.

Fixes: 22a1ae9a93fb ("NFS: If nfs_mountpoint_expiry_timeout < 0, do not expire submounts")
Cc: [email protected] # v5.5+
Signed-off-by: Trond Myklebust <[email protected]>
---
fs/nfs/namespace.c | 12 +++++++-----
1 file changed, 7 insertions(+), 5 deletions(-)

diff --git a/fs/nfs/namespace.c b/fs/nfs/namespace.c
index da67820462f2..50b162dd88f5 100644
--- a/fs/nfs/namespace.c
+++ b/fs/nfs/namespace.c
@@ -145,6 +145,7 @@ struct vfsmount *nfs_d_automount(struct path *path)
struct vfsmount *mnt = ERR_PTR(-ENOMEM);
struct nfs_server *server = NFS_SERVER(d_inode(path->dentry));
struct nfs_client *client = server->nfs_client;
+ int timeout = READ_ONCE(nfs_mountpoint_expiry_timeout);
int ret;

if (IS_ROOT(path->dentry))
@@ -190,12 +191,12 @@ struct vfsmount *nfs_d_automount(struct path *path)
if (IS_ERR(mnt))
goto out_fc;

- if (nfs_mountpoint_expiry_timeout < 0)
+ mntget(mnt); /* prevent immediate expiration */
+ if (timeout < 0)
goto out_fc;

- mntget(mnt); /* prevent immediate expiration */
mnt_set_expiry(mnt, &nfs_automount_list);
- schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
+ schedule_delayed_work(&nfs_automount_task, timeout);

out_fc:
put_fs_context(fc);
@@ -233,10 +234,11 @@ const struct inode_operations nfs_referral_inode_operations = {
static void nfs_expire_automounts(struct work_struct *work)
{
struct list_head *list = &nfs_automount_list;
+ int timeout = READ_ONCE(nfs_mountpoint_expiry_timeout);

mark_mounts_for_expiry(list);
- if (!list_empty(list))
- schedule_delayed_work(&nfs_automount_task, nfs_mountpoint_expiry_timeout);
+ if (!list_empty(list) && timeout >= 0)
+ schedule_delayed_work(&nfs_automount_task, timeout);
}

void nfs_release_automount_timer(void)
--
2.25.1

2020-04-02 20:32:57

by Trond Myklebust

Subject: [PATCH 2/2] NFS: Add a module parameter to set nfs_mountpoint_expiry_timeout

From: Trond Myklebust <[email protected]>

Setting nfs_mountpoint_expiry_timeout() to a negative value stops
mountpoint expiration, while setting it to a positive value restarts
the scheduler.

Signed-off-by: Trond Myklebust <[email protected]>
---
fs/nfs/namespace.c | 35 +++++++++++++++++++++++++++++++++++
1 file changed, 35 insertions(+)

diff --git a/fs/nfs/namespace.c b/fs/nfs/namespace.c
index 50b162dd88f5..4c02f0e00620 100644
--- a/fs/nfs/namespace.c
+++ b/fs/nfs/namespace.c
@@ -311,3 +311,38 @@ int nfs_submount(struct fs_context *fc, struct nfs_server *server)
return nfs_do_submount(fc);
}
EXPORT_SYMBOL_GPL(nfs_submount);
+
+static int param_set_nfs_timeout(const char *val, const struct kernel_param *kp)
+{
+ long num;
+ int ret;
+
+ if (!val)
+ return -EINVAL;
+ ret = kstrtol(val, 0, &num);
+ if (ret)
+ return -EINVAL;
+ if (num >= 0) {
+ num *= HZ;
+ if (num > INT_MAX)
+ num = INT_MAX;
+ *((int *)kp->arg) = num;
+ if (!list_empty(&nfs_automount_list))
+ mod_delayed_work(system_wq, &nfs_automount_task, num);
+ } else {
+ *((int *)kp->arg) = -1;
+ cancel_delayed_work(&nfs_automount_task);
+ }
+ return 0;
+}
+
+static const struct kernel_param_ops param_ops_nfs_timeout = {
+ .set = param_set_nfs_timeout,
+ .get = param_get_uint,
+};
+#define param_check_nfs_timeout(name, p) __param_check(name, p, int);
+
+module_param(nfs_mountpoint_expiry_timeout, nfs_timeout, 0644);
+MODULE_PARM_DESC(nfs_mountpoint_expiry_timeout,
+ "Set the NFS automounted mountpoint timeout value."
+ "Negative values turn expiration off.");
--
2.25.1