NFSv4: Fix up another delegation related race
When we can update_open_stateid(), we need to be certain that we don't
race with a delegation return. While we could do this by grabbing the
nfs_client->cl_lock, a dedicated spin lock in the delegation structure
will scale better.
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 83e700a..254cbff 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -388,9 +388,8 @@
write_sequnlock(&state->seqlock);
}
-static void update_open_stateid(struct nfs4_state *state, nfs4_stateid *open_stateid, nfs4_stateid *deleg_stateid, int open_flags)
+static void __update_open_stateid(struct nfs4_state *state, nfs4_stateid *open_stateid, const nfs4_stateid *deleg_stateid, int open_flags)
{
- open_flags &= (FMODE_READ|FMODE_WRITE);
/*
* Protect the call to nfs4_state_set_mode_locked and
* serialise the stateid update
@@ -408,6 +407,45 @@
spin_unlock(&state->owner->so_lock);
}
+static int update_open_stateid(struct nfs4_state *state, nfs4_stateid *open_stateid, nfs4_stateid *delegation, int open_flags)
+{
+ struct nfs_inode *nfsi = NFS_I(state->inode);
+ struct nfs_delegation *deleg_cur;
+ int ret = 0;
+
+ open_flags &= (FMODE_READ|FMODE_WRITE);
+
+ rcu_read_lock();
+ deleg_cur = rcu_dereference(nfsi->delegation);
+ if (deleg_cur == NULL)
+ goto no_delegation;
+
+ spin_lock(&deleg_cur->lock);
+ if (nfsi->delegation != deleg_cur ||
+ (deleg_cur->type & open_flags) != open_flags)
+ goto no_delegation_unlock;
+
+ if (delegation == NULL)
+ delegation = &deleg_cur->stateid;
+ else if (memcmp(deleg_cur->stateid.data, delegation->data, NFS4_STATEID_SIZE) != 0)
+ goto no_delegation_unlock;
+
+ __update_open_stateid(state, open_stateid, &deleg_cur->stateid, open_flags);
+ ret = 1;
+no_delegation_unlock:
+ spin_unlock(&deleg_cur->lock);
+no_delegation:
+ rcu_read_unlock();
+
+ if (!ret && open_stateid != NULL) {
+ __update_open_stateid(state, open_stateid, NULL, open_flags);
+ ret = 1;
+ }
+
+ return ret;
+}
+
+
static void nfs4_return_incompatible_delegation(struct inode *inode, mode_t open_flags)
{
struct nfs_delegation *delegation;
@@ -431,23 +469,23 @@
nfs4_stateid stateid;
int ret = -EAGAIN;
- rcu_read_lock();
- delegation = rcu_dereference(nfsi->delegation);
for (;;) {
if (can_open_cached(state, open_mode)) {
spin_lock(&state->owner->so_lock);
if (can_open_cached(state, open_mode)) {
update_open_stateflags(state, open_mode);
spin_unlock(&state->owner->so_lock);
- rcu_read_unlock();
goto out_return_state;
}
spin_unlock(&state->owner->so_lock);
}
- if (delegation == NULL)
+ rcu_read_lock();
+ delegation = rcu_dereference(nfsi->delegation);
+ if (delegation == NULL ||
+ !can_open_delegated(delegation, open_mode)) {
+ rcu_read_unlock();
break;
- if (!can_open_delegated(delegation, open_mode))
- break;
+ }
/* Save the delegation */
memcpy(stateid.data, delegation->stateid.data, sizeof(stateid.data));
rcu_read_unlock();
@@ -455,19 +493,11 @@
if (ret != 0)
goto out;
ret = -EAGAIN;
- rcu_read_lock();
- delegation = rcu_dereference(nfsi->delegation);
- /* If no delegation, try a cached open */
- if (delegation == NULL)
- continue;
- /* Is the delegation still valid? */
- if (memcmp(stateid.data, delegation->stateid.data, sizeof(stateid.data)) != 0)
- continue;
- rcu_read_unlock();
- update_open_stateid(state, NULL, &stateid, open_mode);
- goto out_return_state;
+
+ /* Try to update the stateid using the delegation */
+ if (update_open_stateid(state, NULL, &stateid, open_mode))
+ goto out_return_state;
}
- rcu_read_unlock();
out:
return ERR_PTR(ret);
out_return_state:
@@ -480,7 +510,6 @@
struct inode *inode;
struct nfs4_state *state = NULL;
struct nfs_delegation *delegation;
- nfs4_stateid *deleg_stateid = NULL;
int ret;
if (!data->rpc_done) {
@@ -516,12 +545,9 @@
data->owner->so_cred,
&data->o_res);
}
- rcu_read_lock();
- delegation = rcu_dereference(NFS_I(inode)->delegation);
- if (delegation != NULL)
- deleg_stateid = &delegation->stateid;
- update_open_stateid(state, &data->o_res.stateid, deleg_stateid, data->o_arg.open_flags);
- rcu_read_unlock();
+
+ update_open_stateid(state, &data->o_res.stateid, NULL,
+ data->o_arg.open_flags);
iput(inode);
out:
return state;