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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>
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0cb2659b81
commit
343104308a
@ -140,13 +140,17 @@ static struct nfs_delegation *nfs_detach_delegation_locked(struct nfs_inode *nfs
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if (delegation == NULL)
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goto nomatch;
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spin_lock(&delegation->lock);
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if (stateid != NULL && memcmp(delegation->stateid.data, stateid->data,
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sizeof(delegation->stateid.data)) != 0)
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goto nomatch;
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goto nomatch_unlock;
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list_del_rcu(&delegation->super_list);
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nfsi->delegation_state = 0;
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rcu_assign_pointer(nfsi->delegation, NULL);
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spin_unlock(&delegation->lock);
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return delegation;
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nomatch_unlock:
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spin_unlock(&delegation->lock);
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nomatch:
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return NULL;
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}
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@ -172,6 +176,7 @@ int nfs_inode_set_delegation(struct inode *inode, struct rpc_cred *cred, struct
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delegation->change_attr = nfsi->change_attr;
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delegation->cred = get_rpccred(cred);
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delegation->inode = inode;
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spin_lock_init(&delegation->lock);
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spin_lock(&clp->cl_lock);
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if (rcu_dereference(nfsi->delegation) != NULL) {
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@ -22,6 +22,7 @@ struct nfs_delegation {
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long flags;
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loff_t maxsize;
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__u64 change_attr;
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spinlock_t lock;
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struct rcu_head rcu;
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};
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@ -388,9 +388,8 @@ static void nfs_set_open_stateid(struct nfs4_state *state, nfs4_stateid *stateid
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write_sequnlock(&state->seqlock);
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}
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static void update_open_stateid(struct nfs4_state *state, nfs4_stateid *open_stateid, nfs4_stateid *deleg_stateid, int open_flags)
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static void __update_open_stateid(struct nfs4_state *state, nfs4_stateid *open_stateid, const nfs4_stateid *deleg_stateid, int open_flags)
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{
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open_flags &= (FMODE_READ|FMODE_WRITE);
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/*
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* Protect the call to nfs4_state_set_mode_locked and
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* serialise the stateid update
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@ -408,6 +407,45 @@ static void update_open_stateid(struct nfs4_state *state, nfs4_stateid *open_sta
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spin_unlock(&state->owner->so_lock);
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}
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static int update_open_stateid(struct nfs4_state *state, nfs4_stateid *open_stateid, nfs4_stateid *delegation, int open_flags)
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{
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struct nfs_inode *nfsi = NFS_I(state->inode);
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struct nfs_delegation *deleg_cur;
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int ret = 0;
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open_flags &= (FMODE_READ|FMODE_WRITE);
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rcu_read_lock();
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deleg_cur = rcu_dereference(nfsi->delegation);
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if (deleg_cur == NULL)
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goto no_delegation;
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spin_lock(&deleg_cur->lock);
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if (nfsi->delegation != deleg_cur ||
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(deleg_cur->type & open_flags) != open_flags)
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goto no_delegation_unlock;
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if (delegation == NULL)
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delegation = &deleg_cur->stateid;
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else if (memcmp(deleg_cur->stateid.data, delegation->data, NFS4_STATEID_SIZE) != 0)
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goto no_delegation_unlock;
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__update_open_stateid(state, open_stateid, &deleg_cur->stateid, open_flags);
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ret = 1;
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no_delegation_unlock:
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spin_unlock(&deleg_cur->lock);
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no_delegation:
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rcu_read_unlock();
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if (!ret && open_stateid != NULL) {
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__update_open_stateid(state, open_stateid, NULL, open_flags);
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ret = 1;
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}
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return ret;
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}
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static void nfs4_return_incompatible_delegation(struct inode *inode, mode_t open_flags)
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{
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struct nfs_delegation *delegation;
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@ -431,23 +469,23 @@ static struct nfs4_state *nfs4_try_open_cached(struct nfs4_opendata *opendata)
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nfs4_stateid stateid;
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int ret = -EAGAIN;
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rcu_read_lock();
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delegation = rcu_dereference(nfsi->delegation);
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for (;;) {
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if (can_open_cached(state, open_mode)) {
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spin_lock(&state->owner->so_lock);
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if (can_open_cached(state, open_mode)) {
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update_open_stateflags(state, open_mode);
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spin_unlock(&state->owner->so_lock);
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rcu_read_unlock();
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goto out_return_state;
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}
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spin_unlock(&state->owner->so_lock);
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}
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if (delegation == NULL)
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break;
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if (!can_open_delegated(delegation, open_mode))
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rcu_read_lock();
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delegation = rcu_dereference(nfsi->delegation);
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if (delegation == NULL ||
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!can_open_delegated(delegation, open_mode)) {
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rcu_read_unlock();
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break;
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}
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/* Save the delegation */
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memcpy(stateid.data, delegation->stateid.data, sizeof(stateid.data));
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rcu_read_unlock();
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@ -455,19 +493,11 @@ static struct nfs4_state *nfs4_try_open_cached(struct nfs4_opendata *opendata)
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if (ret != 0)
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goto out;
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ret = -EAGAIN;
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rcu_read_lock();
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delegation = rcu_dereference(nfsi->delegation);
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/* If no delegation, try a cached open */
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if (delegation == NULL)
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continue;
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/* Is the delegation still valid? */
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if (memcmp(stateid.data, delegation->stateid.data, sizeof(stateid.data)) != 0)
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continue;
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rcu_read_unlock();
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update_open_stateid(state, NULL, &stateid, open_mode);
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/* Try to update the stateid using the delegation */
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if (update_open_stateid(state, NULL, &stateid, open_mode))
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goto out_return_state;
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}
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rcu_read_unlock();
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out:
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return ERR_PTR(ret);
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out_return_state:
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@ -480,7 +510,6 @@ static struct nfs4_state *nfs4_opendata_to_nfs4_state(struct nfs4_opendata *data
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struct inode *inode;
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struct nfs4_state *state = NULL;
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struct nfs_delegation *delegation;
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nfs4_stateid *deleg_stateid = NULL;
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int ret;
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if (!data->rpc_done) {
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@ -516,12 +545,9 @@ static struct nfs4_state *nfs4_opendata_to_nfs4_state(struct nfs4_opendata *data
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data->owner->so_cred,
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&data->o_res);
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}
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rcu_read_lock();
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delegation = rcu_dereference(NFS_I(inode)->delegation);
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if (delegation != NULL)
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deleg_stateid = &delegation->stateid;
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update_open_stateid(state, &data->o_res.stateid, deleg_stateid, data->o_arg.open_flags);
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rcu_read_unlock();
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update_open_stateid(state, &data->o_res.stateid, NULL,
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data->o_arg.open_flags);
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iput(inode);
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out:
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return state;
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