NFSv4: Use RCU to protect delegations

Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

diff --git a/fs/nfs/delegation.c b/fs/nfs/delegation.c
index 93a9f4b..56f4f6a 100644 (file)
--- a/fs/nfs/delegation.c
+++ b/fs/nfs/delegation.c
@@ -27,6 +27,13 @@ static void nfs_free_delegation(struct nfs_delegation *delegation)
        kfree(delegation);
 }
 
+static void nfs_free_delegation_callback(struct rcu_head *head)
+{
+       struct nfs_delegation *delegation = container_of(head, struct nfs_delegation, rcu);
+
+       nfs_free_delegation(delegation);
+}
+
 static int nfs_delegation_claim_locks(struct nfs_open_context *ctx, struct nfs4_state *state)
 {
        struct inode *inode = state->inode;
@@ -133,10 +140,10 @@ int nfs_inode_set_delegation(struct inode *inode, struct rpc_cred *cred, struct
        delegation->inode = inode;
 
        spin_lock(&clp->cl_lock);
-       if (nfsi->delegation == NULL) {
-               list_add(&delegation->super_list, &clp->cl_delegations);
-               nfsi->delegation = delegation;
+       if (rcu_dereference(nfsi->delegation) == NULL) {
+               list_add_rcu(&delegation->super_list, &clp->cl_delegations);
                nfsi->delegation_state = delegation->type;
+               rcu_assign_pointer(nfsi->delegation, delegation);
                delegation = NULL;
        } else {
                if (memcmp(&delegation->stateid, &nfsi->delegation->stateid,
@@ -157,7 +164,7 @@ static int nfs_do_return_delegation(struct inode *inode, struct nfs_delegation *
        int res = 0;
 
        res = nfs4_proc_delegreturn(inode, delegation->cred, &delegation->stateid);
-       nfs_free_delegation(delegation);
+       call_rcu(&delegation->rcu, nfs_free_delegation_callback);
        return res;
 }
 
@@ -191,16 +198,16 @@ static int __nfs_inode_return_delegation(struct inode *inode, struct nfs_delegat
 
 static struct nfs_delegation *nfs_detach_delegation_locked(struct nfs_inode *nfsi, const nfs4_stateid *stateid)
 {
-       struct nfs_delegation *delegation = nfsi->delegation;
+       struct nfs_delegation *delegation = rcu_dereference(nfsi->delegation);
 
        if (delegation == NULL)
                goto nomatch;
        if (stateid != NULL && memcmp(delegation->stateid.data, stateid->data,
                                sizeof(delegation->stateid.data)) != 0)
                goto nomatch;
-       list_del_init(&delegation->super_list);
-       nfsi->delegation = NULL;
+       list_del_rcu(&delegation->super_list);
        nfsi->delegation_state = 0;
+       rcu_assign_pointer(nfsi->delegation, NULL);
        return delegation;
 nomatch:
        return NULL;
@@ -213,7 +220,7 @@ int nfs_inode_return_delegation(struct inode *inode)
        struct nfs_delegation *delegation;
        int err = 0;
 
-       if (nfsi->delegation_state != 0) {
+       if (rcu_dereference(nfsi->delegation) != NULL) {
                spin_lock(&clp->cl_lock);
                delegation = nfs_detach_delegation_locked(nfsi, NULL);
                spin_unlock(&clp->cl_lock);
@@ -235,20 +242,23 @@ void nfs_return_all_delegations(struct super_block *sb)
        if (clp == NULL)
                return;
 restart:
-       spin_lock(&clp->cl_lock);
-       list_for_each_entry(delegation, &clp->cl_delegations, super_list) {
+       rcu_read_lock();
+       list_for_each_entry_rcu(delegation, &clp->cl_delegations, super_list) {
                if (delegation->inode->i_sb != sb)
                        continue;
                inode = igrab(delegation->inode);
                if (inode == NULL)
                        continue;
-               nfs_detach_delegation_locked(NFS_I(inode), NULL);
+               spin_lock(&clp->cl_lock);
+               delegation = nfs_detach_delegation_locked(NFS_I(inode), NULL);
                spin_unlock(&clp->cl_lock);
-               __nfs_inode_return_delegation(inode, delegation);
+               rcu_read_unlock();
+               if (delegation != NULL)
+                       __nfs_inode_return_delegation(inode, delegation);
                iput(inode);
                goto restart;
        }
-       spin_unlock(&clp->cl_lock);
+       rcu_read_unlock();
 }
 
 static int nfs_do_expire_all_delegations(void *ptr)
@@ -259,23 +269,26 @@ static int nfs_do_expire_all_delegations(void *ptr)
 
        allow_signal(SIGKILL);
 restart:
-       spin_lock(&clp->cl_lock);
        if (test_bit(NFS4CLNT_STATE_RECOVER, &clp->cl_state) != 0)
                goto out;
        if (test_bit(NFS4CLNT_LEASE_EXPIRED, &clp->cl_state) == 0)
                goto out;
-       list_for_each_entry(delegation, &clp->cl_delegations, super_list) {
+       rcu_read_lock();
+       list_for_each_entry_rcu(delegation, &clp->cl_delegations, super_list) {
                inode = igrab(delegation->inode);
                if (inode == NULL)
                        continue;
-               nfs_detach_delegation_locked(NFS_I(inode), NULL);
+               spin_lock(&clp->cl_lock);
+               delegation = nfs_detach_delegation_locked(NFS_I(inode), NULL);
                spin_unlock(&clp->cl_lock);
-               __nfs_inode_return_delegation(inode, delegation);
+               rcu_read_unlock();
+               if (delegation)
+                       __nfs_inode_return_delegation(inode, delegation);
                iput(inode);
                goto restart;
        }
+       rcu_read_unlock();
 out:
-       spin_unlock(&clp->cl_lock);
        nfs_put_client(clp);
        module_put_and_exit(0);
 }
@@ -306,18 +319,21 @@ void nfs_handle_cb_pathdown(struct nfs_client *clp)
        if (clp == NULL)
                return;
 restart:
-       spin_lock(&clp->cl_lock);
-       list_for_each_entry(delegation, &clp->cl_delegations, super_list) {
+       rcu_read_lock();
+       list_for_each_entry_rcu(delegation, &clp->cl_delegations, super_list) {
                inode = igrab(delegation->inode);
                if (inode == NULL)
                        continue;
-               nfs_detach_delegation_locked(NFS_I(inode), NULL);
+               spin_lock(&clp->cl_lock);
+               delegation = nfs_detach_delegation_locked(NFS_I(inode), NULL);
                spin_unlock(&clp->cl_lock);
-               __nfs_inode_return_delegation(inode, delegation);
+               rcu_read_unlock();
+               if (delegation != NULL)
+                       __nfs_inode_return_delegation(inode, delegation);
                iput(inode);
                goto restart;
        }
-       spin_unlock(&clp->cl_lock);
+       rcu_read_unlock();
 }
 
 struct recall_threadargs {
@@ -391,14 +407,14 @@ struct inode *nfs_delegation_find_inode(struct nfs_client *clp, const struct nfs
 {
        struct nfs_delegation *delegation;
        struct inode *res = NULL;
-       spin_lock(&clp->cl_lock);
-       list_for_each_entry(delegation, &clp->cl_delegations, super_list) {
+       rcu_read_lock();
+       list_for_each_entry_rcu(delegation, &clp->cl_delegations, super_list) {
                if (nfs_compare_fh(fhandle, &NFS_I(delegation->inode)->fh) == 0) {
                        res = igrab(delegation->inode);
                        break;
                }
        }
-       spin_unlock(&clp->cl_lock);
+       rcu_read_unlock();
        return res;
 }
 
@@ -408,10 +424,10 @@ struct inode *nfs_delegation_find_inode(struct nfs_client *clp, const struct nfs
 void nfs_delegation_mark_reclaim(struct nfs_client *clp)
 {
        struct nfs_delegation *delegation;
-       spin_lock(&clp->cl_lock);
-       list_for_each_entry(delegation, &clp->cl_delegations, super_list)
+       rcu_read_lock();
+       list_for_each_entry_rcu(delegation, &clp->cl_delegations, super_list)
                delegation->flags |= NFS_DELEGATION_NEED_RECLAIM;
-       spin_unlock(&clp->cl_lock);
+       rcu_read_unlock();
 }
 
 /*
@@ -419,39 +435,35 @@ void nfs_delegation_mark_reclaim(struct nfs_client *clp)
  */
 void nfs_delegation_reap_unclaimed(struct nfs_client *clp)
 {
-       struct nfs_delegation *delegation, *n;
-       LIST_HEAD(head);
-       spin_lock(&clp->cl_lock);
-       list_for_each_entry_safe(delegation, n, &clp->cl_delegations, super_list) {
+       struct nfs_delegation *delegation;
+restart:
+       rcu_read_lock();
+       list_for_each_entry_rcu(delegation, &clp->cl_delegations, super_list) {
                if ((delegation->flags & NFS_DELEGATION_NEED_RECLAIM) == 0)
                        continue;
-               list_move(&delegation->super_list, &head);
-               NFS_I(delegation->inode)->delegation = NULL;
-               NFS_I(delegation->inode)->delegation_state = 0;
-       }
-       spin_unlock(&clp->cl_lock);
-       while(!list_empty(&head)) {
-               delegation = list_entry(head.next, struct nfs_delegation, super_list);
-               list_del(&delegation->super_list);
-               nfs_free_delegation(delegation);
+               spin_lock(&clp->cl_lock);
+               delegation = nfs_detach_delegation_locked(NFS_I(delegation->inode), NULL);
+               spin_unlock(&clp->cl_lock);
+               rcu_read_unlock();
+               if (delegation != NULL)
+                       call_rcu(&delegation->rcu, nfs_free_delegation_callback);
+               goto restart;
        }
+       rcu_read_unlock();
 }
 
 int nfs4_copy_delegation_stateid(nfs4_stateid *dst, struct inode *inode)
 {
-       struct nfs_client *clp = NFS_SERVER(inode)->nfs_client;
        struct nfs_inode *nfsi = NFS_I(inode);
        struct nfs_delegation *delegation;
-       int res = 0;
+       int ret = 0;
 
-       if (nfsi->delegation_state == 0)
-               return 0;
-       spin_lock(&clp->cl_lock);
-       delegation = nfsi->delegation;
+       rcu_read_lock();
+       delegation = rcu_dereference(nfsi->delegation);
        if (delegation != NULL) {
                memcpy(dst->data, delegation->stateid.data, sizeof(dst->data));
-               res = 1;
+               ret = 1;
        }
-       spin_unlock(&clp->cl_lock);
-       return res;
+       rcu_read_unlock();
+       return ret;
 }

diff --git a/fs/nfs/delegation.h b/fs/nfs/delegation.h
index 8f79a31..5874ce7 100644 (file)
--- a/fs/nfs/delegation.h
+++ b/fs/nfs/delegation.h
@@ -22,6 +22,7 @@ struct nfs_delegation {
        long flags;
        loff_t maxsize;
        __u64 change_attr;
+       struct rcu_head rcu;
 };
 
 int nfs_inode_set_delegation(struct inode *inode, struct rpc_cred *cred, struct nfs_openres *res);
@@ -45,11 +46,16 @@ int nfs4_copy_delegation_stateid(nfs4_stateid *dst, struct inode *inode);
 
 static inline int nfs_have_delegation(struct inode *inode, int flags)
 {
+       struct nfs_delegation *delegation;
+       int ret = 0;
+
        flags &= FMODE_READ|FMODE_WRITE;
-       smp_rmb();
-       if ((NFS_I(inode)->delegation_state & flags) == flags)
-               return 1;
-       return 0;
+       rcu_read_lock();
+       delegation = rcu_dereference(NFS_I(inode)->delegation);
+       if (delegation != NULL && (delegation->type & flags) == flags)
+               ret = 1;
+       rcu_read_unlock();
+       return ret;
 }
 
 #else