NFSv4: Fix a race between open() and close()

 We must not remove the nfs4_state structure from the inode open lists
 before we are in sequence lock.

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

1 files changed, 30 insertions, 28 deletions

diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
index 2d5a6a2b9dec..959374d833a7 100644
--- a/fs/nfs/nfs4state.c
+++ b/fs/nfs/nfs4state.c
@@ -366,6 +366,23 @@ nfs4_alloc_open_state(void)
         return state;
 }
 
+void
+nfs4_state_set_mode_locked(struct nfs4_state *state, mode_t mode)
+{
+        if (state->state == mode)
+                return;
+        /* NB! List reordering - see the reclaim code for why.  */
+        if ((mode & FMODE_WRITE) != (state->state & FMODE_WRITE)) {
+                if (mode & FMODE_WRITE)
+                        list_move(&state->open_states, &state->owner->so_states);
+                else
+                        list_move_tail(&state->open_states, &state->owner->so_states);
+        }
+        if (mode == 0)
+                list_del_init(&state->inode_states);
+        state->state = mode;
+}
+
 static struct nfs4_state *
 __nfs4_find_state(struct inode *inode, struct rpc_cred *cred, mode_t mode)
 {
@@ -376,10 +393,6 @@ __nfs4_find_state(struct inode *inode, struct rpc_cred *cred, mode_t mode)
         list_for_each_entry(state, &nfsi->open_states, inode_states) {
                 if (state->owner->so_cred != cred)
                         continue;
-                if ((mode & FMODE_READ) != 0 && state->nreaders == 0)
-                        continue;
-                if ((mode & FMODE_WRITE) != 0 && state->nwriters == 0)
-                        continue;
                 if ((state->state & mode) != mode)
                         continue;
                 atomic_inc(&state->count);
@@ -400,7 +413,7 @@ __nfs4_find_state_byowner(struct inode *inode, struct nfs4_state_owner *owner)
 
         list_for_each_entry(state, &nfsi->open_states, inode_states) {
                 /* Is this in the process of being freed? */
-                if (state->nreaders == 0 && state->nwriters == 0)
+                if (state->state == 0)
                         continue;
                 if (state->owner == owner) {
                         atomic_inc(&state->count);
@@ -481,7 +494,6 @@ void nfs4_put_open_state(struct nfs4_state *state)
         spin_unlock(&inode->i_lock);
         spin_unlock(&owner->so_lock);
         iput(inode);
-        BUG_ON (state->state != 0);
         nfs4_free_open_state(state);
         nfs4_put_state_owner(owner);
 }
@@ -493,7 +505,7 @@ void nfs4_close_state(struct nfs4_state *state, mode_t mode)
 {
         struct inode *inode = state->inode;
         struct nfs4_state_owner *owner = state->owner;
-        int newstate;
+        int oldstate, newstate = 0;
 
         atomic_inc(&owner->so_count);
         /* Protect against nfs4_find_state() */
@@ -503,30 +515,20 @@ void nfs4_close_state(struct nfs4_state *state, mode_t mode)
                 state->nreaders--;
         if (mode & FMODE_WRITE)
                 state->nwriters--;
-        if (state->nwriters == 0) {
-                if (state->nreaders == 0)
-                        list_del_init(&state->inode_states);
-                /* See reclaim code */
-                list_move_tail(&state->open_states, &owner->so_states);
+        oldstate = newstate = state->state;
+        if (state->nreaders == 0)
+                newstate &= ~FMODE_READ;
+        if (state->nwriters == 0)
+                newstate &= ~FMODE_WRITE;
+        if (test_bit(NFS_DELEGATED_STATE, &state->flags)) {
+                nfs4_state_set_mode_locked(state, newstate);
+                oldstate = newstate;
         }
         spin_unlock(&inode->i_lock);
         spin_unlock(&owner->so_lock);
-        newstate = 0;
-        if (state->state != 0) {
-                if (state->nreaders)
-                        newstate |= FMODE_READ;
-                if (state->nwriters)
-                        newstate |= FMODE_WRITE;
-                if (state->state == newstate)
-                        goto out;
-                if (test_bit(NFS_DELEGATED_STATE, &state->flags)) {
-                        state->state = newstate;
-                        goto out;
-                }
-                if (nfs4_do_close(inode, state, newstate) == 0)
-                        return;
-        }
-out:
+
+        if (oldstate != newstate && nfs4_do_close(inode, state) == 0)
+                return;
         nfs4_put_open_state(state);
         nfs4_put_state_owner(owner);
 }