NFSv4: Use RCU to protect delegations

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

2 files changed, 73 insertions, 55 deletions

diff --git a/fs/nfs/delegation.c b/fs/nfs/delegation.c
index 93a9f4bd9bd0..56f4f6a99d4e 100644
--- 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 8f79a3135167..5874ce7fdbae 100644
--- 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