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>

3 files changed, 49 insertions, 47 deletions

diff --git a/fs/nfs/nfs4_fs.h b/fs/nfs/nfs4_fs.h
index 78a53f5a9f18..53969022d239 100644
--- a/fs/nfs/nfs4_fs.h
+++ b/fs/nfs/nfs4_fs.h
@@ -214,7 +214,7 @@ extern int nfs4_proc_setclientid(struct nfs4_client *, u32, unsigned short);
 extern int nfs4_proc_setclientid_confirm(struct nfs4_client *);
 extern int nfs4_proc_async_renew(struct nfs4_client *);
 extern int nfs4_proc_renew(struct nfs4_client *);
-extern int nfs4_do_close(struct inode *inode, struct nfs4_state *state, mode_t mode);
+extern int nfs4_do_close(struct inode *inode, struct nfs4_state *state);
 extern struct dentry *nfs4_atomic_open(struct inode *, struct dentry *, struct nameidata *);
 extern int nfs4_open_revalidate(struct inode *, struct dentry *, int, struct nameidata *);
 
@@ -248,6 +248,7 @@ extern struct nfs4_state * nfs4_get_open_state(struct inode *, struct nfs4_state
 extern void nfs4_put_open_state(struct nfs4_state *);
 extern void nfs4_close_state(struct nfs4_state *, mode_t);
 extern struct nfs4_state *nfs4_find_state(struct inode *, struct rpc_cred *, mode_t mode);
+extern void nfs4_state_set_mode_locked(struct nfs4_state *, mode_t);
 extern void nfs4_schedule_state_recovery(struct nfs4_client *);
 extern void nfs4_put_lock_state(struct nfs4_lock_state *lsp);
 extern int nfs4_set_lock_state(struct nfs4_state *state, struct file_lock *fl);
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 933e13b383f8..02fddd0e27e8 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -217,13 +217,12 @@ static void update_open_stateid(struct nfs4_state *state, nfs4_stateid *stateid,
         /* Protect against nfs4_find_state() */
         spin_lock(&state->owner->so_lock);
         spin_lock(&inode->i_lock);
-        state->state |= open_flags;
-        /* NB! List reordering - see the reclaim code for why.  */
-        if ((open_flags & FMODE_WRITE) && 0 == state->nwriters++)
-                list_move(&state->open_states, &state->owner->so_states);
+        memcpy(&state->stateid, stateid, sizeof(state->stateid));
+        if ((open_flags & FMODE_WRITE))
+                state->nwriters++;
         if (open_flags & FMODE_READ)
                 state->nreaders++;
-        memcpy(&state->stateid, stateid, sizeof(state->stateid));
+        nfs4_state_set_mode_locked(state, state->state | open_flags);
         spin_unlock(&inode->i_lock);
         spin_unlock(&state->owner->so_lock);
 }
@@ -896,7 +895,6 @@ static void nfs4_close_done(struct rpc_task *task)
                         break;
                 case -NFS4ERR_STALE_STATEID:
                 case -NFS4ERR_EXPIRED:
-                        state->state = calldata->arg.open_flags;
                         nfs4_schedule_state_recovery(server->nfs4_state);
                         break;
                 default:
@@ -906,7 +904,6 @@ static void nfs4_close_done(struct rpc_task *task)
                         }
         }
         nfs_refresh_inode(calldata->inode, calldata->res.fattr);
-        state->state = calldata->arg.open_flags;
         nfs4_free_closedata(calldata);
 }
 
@@ -920,24 +917,26 @@ static void nfs4_close_begin(struct rpc_task *task)
                 .rpc_resp = &calldata->res,
                 .rpc_cred = state->owner->so_cred,
         };
-        int mode = 0;
+        int mode = 0, old_mode;
         int status;
 
         status = nfs_wait_on_sequence(calldata->arg.seqid, task);
         if (status != 0)
                 return;
-        /* Don't reorder reads */
-        smp_rmb();
         /* Recalculate the new open mode in case someone reopened the file
          * while we were waiting in line to be scheduled.
          */
-        if (state->nreaders != 0)
-                mode |= FMODE_READ;
-        if (state->nwriters != 0)
-                mode |= FMODE_WRITE;
-        if (test_bit(NFS_DELEGATED_STATE, &state->flags))
-                state->state = mode;
-        if (mode == state->state) {
+        spin_lock(&state->owner->so_lock);
+        spin_lock(&calldata->inode->i_lock);
+        mode = old_mode = state->state;
+        if (state->nreaders == 0)
+                mode &= ~FMODE_READ;
+        if (state->nwriters == 0)
+                mode &= ~FMODE_WRITE;
+        nfs4_state_set_mode_locked(state, mode);
+        spin_unlock(&calldata->inode->i_lock);
+        spin_unlock(&state->owner->so_lock);
+        if (mode == old_mode || test_bit(NFS_DELEGATED_STATE, &state->flags)) {
                 nfs4_free_closedata(calldata);
                 task->tk_exit = NULL;
                 rpc_exit(task, 0);
@@ -961,7 +960,7 @@ static void nfs4_close_begin(struct rpc_task *task)
  *
  * NOTE: Caller must be holding the sp->so_owner semaphore!
  */
-int nfs4_do_close(struct inode *inode, struct nfs4_state *state, mode_t mode) 
+int nfs4_do_close(struct inode *inode, struct nfs4_state *state) 
 {
         struct nfs_server *server = NFS_SERVER(inode);
         struct nfs4_closedata *calldata;
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);
 }