NFSv4: Don't call OPEN if we already have an open stateid for a file

If we already have a stateid with the correct open mode for a given file,
then we can reuse that stateid instead of re-issuing an OPEN call without
violating the close-to-open caching semantics.

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

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index ea332e8..1de0766 100644 (file)
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -324,6 +324,24 @@ static int nfs4_wait_for_completion_rpc_task(struct rpc_task *task)
        return ret;
 }
 
+static int can_open_cached(struct nfs4_state *state, int mode)
+{
+       int ret = 0;
+       switch (mode & (FMODE_READ|FMODE_WRITE|O_EXCL)) {
+               case FMODE_READ:
+                       ret |= test_bit(NFS_O_RDONLY_STATE, &state->flags) != 0;
+                       ret |= test_bit(NFS_O_RDWR_STATE, &state->flags) != 0;
+                       break;
+               case FMODE_WRITE:
+                       ret |= test_bit(NFS_O_WRONLY_STATE, &state->flags) != 0;
+                       ret |= test_bit(NFS_O_RDWR_STATE, &state->flags) != 0;
+                       break;
+               case FMODE_READ|FMODE_WRITE:
+                       ret |= test_bit(NFS_O_RDWR_STATE, &state->flags) != 0;
+       }
+       return ret;
+}
+
 static int can_open_delegated(struct nfs_delegation *delegation, mode_t open_flags)
 {
        if ((delegation->type & open_flags) != open_flags)
@@ -407,7 +425,7 @@ static void nfs4_return_incompatible_delegation(struct inode *inode, mode_t open
        nfs_inode_return_delegation(inode);
 }
 
-static struct nfs4_state *nfs4_try_open_delegated(struct nfs4_opendata *opendata)
+static struct nfs4_state *nfs4_try_open_cached(struct nfs4_opendata *opendata)
 {
        struct nfs4_state *state = opendata->state;
        struct nfs_inode *nfsi = NFS_I(state->inode);
@@ -418,9 +436,19 @@ static struct nfs4_state *nfs4_try_open_delegated(struct nfs4_opendata *opendata
 
        rcu_read_lock();
        delegation = rcu_dereference(nfsi->delegation);
-       if (delegation == NULL)
-               goto out_unlock;
        for (;;) {
+               if (can_open_cached(state, open_mode)) {
+                       spin_lock(&state->owner->so_lock);
+                       if (can_open_cached(state, open_mode)) {
+                               update_open_stateflags(state, open_mode);
+                               spin_unlock(&state->owner->so_lock);
+                               rcu_read_unlock();
+                               goto out_return_state;
+                       }
+                       spin_unlock(&state->owner->so_lock);
+               }
+               if (delegation == NULL)
+                       break;
                if (!can_open_delegated(delegation, open_mode))
                        break;
                /* Save the delegation */
@@ -434,8 +462,9 @@ static struct nfs4_state *nfs4_try_open_delegated(struct nfs4_opendata *opendata
                ret = -EAGAIN;
                rcu_read_lock();
                delegation = rcu_dereference(nfsi->delegation);
+               /* If no delegation, try a cached open */
                if (delegation == NULL)
-                       break;
+                       continue;
                /* Is the delegation still valid? */
                if (memcmp(stateid.data, delegation->stateid.data, sizeof(stateid.data)) != 0)
                        continue;
@@ -443,7 +472,6 @@ static struct nfs4_state *nfs4_try_open_delegated(struct nfs4_opendata *opendata
                update_open_stateid(state, NULL, &stateid, open_mode);
                goto out_return_state;
        }
-out_unlock:
        rcu_read_unlock();
 out:
        return ERR_PTR(ret);
@@ -461,7 +489,7 @@ static struct nfs4_state *nfs4_opendata_to_nfs4_state(struct nfs4_opendata *data
        int ret;
 
        if (!data->rpc_done) {
-               state = nfs4_try_open_delegated(data);
+               state = nfs4_try_open_cached(data);
                goto out;
        }
 
@@ -775,13 +803,14 @@ static void nfs4_open_prepare(struct rpc_task *task, void *calldata)
        if (data->state != NULL) {
                struct nfs_delegation *delegation;
 
+               if (can_open_cached(data->state, data->o_arg.open_flags & (FMODE_READ|FMODE_WRITE|O_EXCL)))
+                       goto out_no_action;
                rcu_read_lock();
                delegation = rcu_dereference(NFS_I(data->state->inode)->delegation);
                if (delegation != NULL &&
                   (delegation->flags & NFS_DELEGATION_NEED_RECLAIM) == 0) {
                        rcu_read_unlock();
-                       task->tk_action = NULL;
-                       return;
+                       goto out_no_action;
                }
                rcu_read_unlock();
        }
@@ -792,6 +821,10 @@ static void nfs4_open_prepare(struct rpc_task *task, void *calldata)
                msg.rpc_proc = &nfs4_procedures[NFSPROC4_CLNT_OPEN_NOATTR];
        data->timestamp = jiffies;
        rpc_call_setup(task, &msg, 0);
+       return;
+out_no_action:
+       task->tk_action = NULL;
+
 }
 
 static void nfs4_open_done(struct rpc_task *task, void *calldata)