3 files changed, 108 insertions, 43 deletions

diff --git a/fs/nfs/delegation.c b/fs/nfs/delegation.c
index 81c5eec3cf38..2542cdaa1116 100644
--- a/fs/nfs/delegation.c
+++ b/fs/nfs/delegation.c
@@ -55,7 +55,8 @@ int nfs4_have_delegation(struct inode *inode, fmode_t flags)
         flags &= FMODE_READ|FMODE_WRITE;
         rcu_read_lock();
         delegation = rcu_dereference(NFS_I(inode)->delegation);
-        if (delegation != NULL && (delegation->type & flags) == flags) {
+        if (delegation != NULL && (delegation->type & flags) == flags &&
+            !test_bit(NFS_DELEGATION_RETURNING, &delegation->flags)) {
                 nfs_mark_delegation_referenced(delegation);
                 ret = 1;
         }
@@ -94,7 +95,9 @@ static int nfs_delegation_claim_opens(struct inode *inode, const nfs4_stateid *s
 {
         struct nfs_inode *nfsi = NFS_I(inode);
         struct nfs_open_context *ctx;
+        struct nfs4_state_owner *sp;
         struct nfs4_state *state;
+        unsigned int seq;
         int err;
 
 again:
@@ -109,9 +112,13 @@ again:
                         continue;
                 get_nfs_open_context(ctx);
                 spin_unlock(&inode->i_lock);
+                sp = state->owner;
+                seq = raw_seqcount_begin(&sp->so_reclaim_seqcount);
                 err = nfs4_open_delegation_recall(ctx, state, stateid);
-                if (err >= 0)
+                if (!err)
                         err = nfs_delegation_claim_locks(ctx, state);
+                if (!err && read_seqcount_retry(&sp->so_reclaim_seqcount, seq))
+                        err = -EAGAIN;
                 put_nfs_open_context(ctx);
                 if (err != 0)
                         return err;
@@ -182,39 +189,91 @@ static struct inode *nfs_delegation_grab_inode(struct nfs_delegation *delegation
 }
 
 static struct nfs_delegation *
+nfs_start_delegation_return_locked(struct nfs_inode *nfsi)
+{
+        struct nfs_delegation *ret = NULL;
+        struct nfs_delegation *delegation = rcu_dereference(nfsi->delegation);
+
+        if (delegation == NULL)
+                goto out;
+        spin_lock(&delegation->lock);
+        if (!test_and_set_bit(NFS_DELEGATION_RETURNING, &delegation->flags))
+                ret = delegation;
+        spin_unlock(&delegation->lock);
+out:
+        return ret;
+}
+
+static struct nfs_delegation *
+nfs_start_delegation_return(struct nfs_inode *nfsi)
+{
+        struct nfs_delegation *delegation;
+
+        rcu_read_lock();
+        delegation = nfs_start_delegation_return_locked(nfsi);
+        rcu_read_unlock();
+        return delegation;
+}
+
+static void
+nfs_abort_delegation_return(struct nfs_delegation *delegation,
+                struct nfs_client *clp)
+{
+
+        spin_lock(&delegation->lock);
+        clear_bit(NFS_DELEGATION_RETURNING, &delegation->flags);
+        set_bit(NFS_DELEGATION_RETURN, &delegation->flags);
+        spin_unlock(&delegation->lock);
+        set_bit(NFS4CLNT_DELEGRETURN, &clp->cl_state);
+}
+
+static struct nfs_delegation *
 nfs_detach_delegation_locked(struct nfs_inode *nfsi,
-                             struct nfs_server *server)
+                struct nfs_delegation *delegation,
+                struct nfs_client *clp)
 {
-        struct nfs_delegation *delegation =
+        struct nfs_delegation *deleg_cur =
                 rcu_dereference_protected(nfsi->delegation,
-                                lockdep_is_held(&server->nfs_client->cl_lock));
+                                lockdep_is_held(&clp->cl_lock));
 
-        if (delegation == NULL)
-                goto nomatch;
+        if (deleg_cur == NULL || delegation != deleg_cur)
+                return NULL;
 
         spin_lock(&delegation->lock);
+        set_bit(NFS_DELEGATION_RETURNING, &delegation->flags);
         list_del_rcu(&delegation->super_list);
         delegation->inode = NULL;
         nfsi->delegation_state = 0;
         rcu_assign_pointer(nfsi->delegation, NULL);
         spin_unlock(&delegation->lock);
         return delegation;
-nomatch:
-        return NULL;
 }
 
 static struct nfs_delegation *nfs_detach_delegation(struct nfs_inode *nfsi,
-                                                    struct nfs_server *server)
+                struct nfs_delegation *delegation,
+                struct nfs_server *server)
 {
         struct nfs_client *clp = server->nfs_client;
-        struct nfs_delegation *delegation;
 
         spin_lock(&clp->cl_lock);
-        delegation = nfs_detach_delegation_locked(nfsi, server);
+        delegation = nfs_detach_delegation_locked(nfsi, delegation, clp);
         spin_unlock(&clp->cl_lock);
         return delegation;
 }
 
+static struct nfs_delegation *
+nfs_inode_detach_delegation(struct inode *inode)
+{
+        struct nfs_inode *nfsi = NFS_I(inode);
+        struct nfs_server *server = NFS_SERVER(inode);
+        struct nfs_delegation *delegation;
+
+        delegation = nfs_start_delegation_return(nfsi);
+        if (delegation == NULL)
+                return NULL;
+        return nfs_detach_delegation(nfsi, delegation, server);
+}
+
 /**
  * nfs_inode_set_delegation - set up a delegation on an inode
  * @inode: inode to which delegation applies
@@ -268,7 +327,10 @@ int nfs_inode_set_delegation(struct inode *inode, struct rpc_cred *cred, struct
                         delegation = NULL;
                         goto out;
                 }
-                freeme = nfs_detach_delegation_locked(nfsi, server);
+                freeme = nfs_detach_delegation_locked(nfsi, 
+                                old_delegation, clp);
+                if (freeme == NULL)
+                        goto out;
         }
         list_add_rcu(&delegation->super_list, &server->delegations);
         nfsi->delegation_state = delegation->type;
@@ -292,19 +354,29 @@ out:
 /*
  * Basic procedure for returning a delegation to the server
  */
-static int __nfs_inode_return_delegation(struct inode *inode, struct nfs_delegation *delegation, int issync)
+static int nfs_end_delegation_return(struct inode *inode, struct nfs_delegation *delegation, int issync)
 {
+        struct nfs_client *clp = NFS_SERVER(inode)->nfs_client;
         struct nfs_inode *nfsi = NFS_I(inode);
         int err;
 
-        /*
-         * Guard against new delegated open/lock/unlock calls and against
-         * state recovery
-         */
-        down_write(&nfsi->rwsem);
-        err = nfs_delegation_claim_opens(inode, &delegation->stateid);
-        up_write(&nfsi->rwsem);
-        if (err)
+        if (delegation == NULL)
+                return 0;
+        do {
+                err = nfs_delegation_claim_opens(inode, &delegation->stateid);
+                if (!issync || err != -EAGAIN)
+                        break;
+                /*
+                 * Guard against state recovery