Merge branch 'bugfixes' of git://git.linux-nfs.org/projects/trondmy/nfs-2.6

* 'bugfixes' of git://git.linux-nfs.org/projects/trondmy/nfs-2.6:
  NFS: Fix RCU issues in the NFSv4 delegation code
  NFSv4: Fix the locking in nfs_inode_reclaim_delegation()

1 files changed, 51 insertions, 35 deletions

diff --git a/fs/nfs/delegation.c b/fs/nfs/delegation.c
index 15671245c6ee..ea61d26e7871 100644
--- a/fs/nfs/delegation.c
+++ b/fs/nfs/delegation.c
@@ -24,6 +24,8 @@
 
 static void nfs_do_free_delegation(struct nfs_delegation *delegation)
 {
+        if (delegation->cred)
+                put_rpccred(delegation->cred);
         kfree(delegation);
 }
 
@@ -36,13 +38,7 @@ static void nfs_free_delegation_callback(struct rcu_head *head)
 
 static void nfs_free_delegation(struct nfs_delegation *delegation)
 {
-        struct rpc_cred *cred;
-
-        cred = rcu_dereference(delegation->cred);
-        rcu_assign_pointer(delegation->cred, NULL);
         call_rcu(&delegation->rcu, nfs_free_delegation_callback);
-        if (cred)
-                put_rpccred(cred);
 }
 
 void nfs_mark_delegation_referenced(struct nfs_delegation *delegation)
@@ -129,21 +125,35 @@ again:
  */
 void nfs_inode_reclaim_delegation(struct inode *inode, struct rpc_cred *cred, struct nfs_openres *res)
 {
-        struct nfs_delegation *delegation = NFS_I(inode)->delegation;
-        struct rpc_cred *oldcred;
+        struct nfs_delegation *delegation;
+        struct rpc_cred *oldcred = NULL;
 
-        if (delegation == NULL)
-                return;
-        memcpy(delegation->stateid.data, res->delegation.data,
-                        sizeof(delegation->stateid.data));
-        delegation->type = res->delegation_type;
-        delegation->maxsize = res->maxsize;
-        oldcred = delegation->cred;
-        delegation->cred = get_rpccred(cred);
-        clear_bit(NFS_DELEGATION_NEED_RECLAIM, &delegation->flags);
-        NFS_I(inode)->delegation_state = delegation->type;
-        smp_wmb();
-        put_rpccred(oldcred);
+        rcu_read_lock();
+        delegation = rcu_dereference(NFS_I(inode)->delegation);
+        if (delegation != NULL) {
+                spin_lock(&delegation->lock);
+                if (delegation->inode != NULL) {
+                        memcpy(delegation->stateid.data, res->delegation.data,
+                               sizeof(delegation->stateid.data));
+                        delegation->type = res->delegation_type;
+                        delegation->maxsize = res->maxsize;
+                        oldcred = delegation->cred;
+                        delegation->cred = get_rpccred(cred);
+                        clear_bit(NFS_DELEGATION_NEED_RECLAIM,
+                                  &delegation->flags);
+                        NFS_I(inode)->delegation_state = delegation->type;
+                        spin_unlock(&delegation->lock);
+                        put_rpccred(oldcred);
+                        rcu_read_unlock();
+                } else {
+                        /* We appear to have raced with a delegation return. */
+                        spin_unlock(&delegation->lock);
+                        rcu_read_unlock();
+                        nfs_inode_set_delegation(inode, cred, res);
+                }
+        } else {
+                rcu_read_unlock();
+        }
 }
 
 static int nfs_do_return_delegation(struct inode *inode, struct nfs_delegation *delegation, int issync)
@@ -166,9 +176,13 @@ static struct inode *nfs_delegation_grab_inode(struct nfs_delegation *delegation
         return inode;
 }
 
-static struct nfs_delegation *nfs_detach_delegation_locked(struct nfs_inode *nfsi, const nfs4_stateid *stateid)
+static struct nfs_delegation *nfs_detach_delegation_locked(struct nfs_inode *nfsi,
+                                                           const nfs4_stateid *stateid,
+                                                           struct nfs_client *clp)
 {
-        struct nfs_delegation *delegation = rcu_dereference(nfsi->delegation);
+        struct nfs_delegation *delegation =
+                rcu_dereference_protected(nfsi->delegation,
+                                          lockdep_is_held(&clp->cl_lock));
 
         if (delegation == NULL)
                 goto nomatch;
@@ -195,7 +209,7 @@ int nfs_inode_set_delegation(struct inode *inode, struct rpc_cred *cred, struct
 {
         struct nfs_client *clp = NFS_SERVER(inode)->nfs_client;
         struct nfs_inode *nfsi = NFS_I(inode);
-        struct nfs_delegation *delegation;
+        struct nfs_delegation *delegation, *old_delegation;
         struct nfs_delegation *freeme = NULL;
         int status = 0;
 
@@ -213,10 +227,12 @@ int nfs_inode_set_delegation(struct inode *inode, struct rpc_cred *cred, struct
         spin_lock_init(&delegation->lock);
 
         spin_lock(&clp->cl_lock);
-        if (rcu_dereference(nfsi->delegation) != NULL) {
-                if (memcmp(&delegation->stateid, &nfsi->delegation->stateid,
-                                        sizeof(delegation->stateid)) == 0 &&
-                                delegation->type == nfsi->delegation->type) {
+        old_delegation = rcu_dereference_protected(nfsi->delegation,
+                                                   lockdep_is_held(&clp->cl_lock));
+        if (old_delegation != NULL) {
+                if (memcmp(&delegation->stateid, &old_delegation->stateid,
+                                        sizeof(old_delegation->stateid)) == 0 &&
+                                delegation->type == old_delegation->type) {
                         goto out;
                 }
                 /*
@@ -226,12 +242,12 @@ int nfs_inode_set_delegation(struct inode *inode, struct rpc_cred *cred, struct
                 dfprintk(FILE, "%s: server %s handed out "
                                 "a duplicate delegation!\n",
                                 __func__, clp->cl_hostname);
-                if (delegation->type <= nfsi->delegation->type) {
+                if (delegation->type <= old_delegation->type) {
                         freeme = delegation;
                         delegation = NULL;
                         goto out;
                 }
-                freeme = nfs_detach_delegation_locked(nfsi, NULL);
+                freeme = nfs_detach_delegation_locked(nfsi, NULL, clp);
         }
         list_add_rcu(&delegation->super_list, &clp->cl_delegations);
         nfsi->delegation_state = delegation->type;
@@ -301,7 +317,7 @@ restart:
                 if (inode == NULL)
                         continue;
                 spin_lock(&clp->cl_lock);
-                delegation = nfs_detach_delegation_locked(NFS_I(inode), NULL);
+                delegation = nfs_detach_delegation_locked(NFS_I(inode), NULL, clp);
                 spin_unlock(&clp->cl_lock);
                 rcu_read_unlock();
                 if (delegation != NULL) {
@@ -330,9 +346,9 @@ void nfs_inode_return_delegation_noreclaim(struct inode *inode)
         struct nfs_inode *nfsi = NFS_I(inode);
         struct nfs_delegation *delegation;
 
-        if (rcu_dereference(nfsi->delegation) != NULL) {
+        if (rcu_access_pointer(nfsi->delegation) != NULL) {
                 spin_lock(&clp->cl_lock);
-                delegation = nfs_detach_delegation_locked(nfsi, NULL);
+                delegation = nfs_detach_delegation_locked(nfsi, NULL, clp);
                 spin_unlock(&clp->cl_lock);
                 if (delegation != NULL)
                         nfs_do_return_delegation(inode, delegation, 0);
@@ -346,9 +362,9 @@ int nfs_inode_return_delegation(struct inode *inode)
         struct nfs_delegation *delegation;
         int err = 0;
 
-        if (rcu_dereference(nfsi->delegation) != NULL) {
+        if (rcu_access_pointer(nfsi->delegation) != NULL) {
                 spin_lock(&clp->cl_lock);
-                delegation = nfs_detach_delegation_locked(nfsi, NULL);
+                delegation = nfs_detach_delegation_locked(nfsi, NULL, clp);
                 spin_unlock(&clp->cl_lock);
                 if (delegation != NULL) {
                         nfs_msync_inode(inode);
@@ -526,7 +542,7 @@ restart:
                 if (inode == NULL)
                         continue;
                 spin_lock(&clp->cl_lock);
-                delegation = nfs_detach_delegation_locked(NFS_I(inode), NULL);
+                delegation = nfs_detach_delegation_locked(NFS_I(inode), NULL, clp);
                 spin_unlock(&clp->cl_lock);
                 rcu_read_unlock();
                 if (delegation != NULL)