NFSv4.1: keep seq_res.sr_slot as pointer rather than an index

Having to explicitly initialize sr_slotid to NFS4_MAX_SLOT_TABLE
resulted in numerous bugs.  Keeping the current slot as a pointer
to the slot table is more straight forward and robust as it's
implicitly set up to NULL wherever the seq_res member is initialized
to zeroes.

Signed-off-by: Benny Halevy <bhalevy@panasas.com>
Signed-off-by: Trond Myklebust <Trond.Myklebust@netapp.com>

1 files changed, 21 insertions, 31 deletions

diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index 72aa7067b85d..aee1bcc1fcc9 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -334,10 +334,12 @@ static void renew_lease(const struct nfs_server *server, unsigned long timestamp
  * Must be called while holding tbl->slot_tbl_lock
  */
 static void
-nfs4_free_slot(struct nfs4_slot_table *tbl, u8 free_slotid)
+nfs4_free_slot(struct nfs4_slot_table *tbl, struct nfs4_slot *free_slot)
 {
+        int free_slotid = free_slot - tbl->slots;
         int slotid = free_slotid;
 
+        BUG_ON(slotid < 0 || slotid >= NFS4_MAX_SLOT_TABLE);
         /* clear used bit in bitmap */
         __clear_bit(slotid, tbl->used_slots);
 
@@ -379,7 +381,7 @@ static void nfs41_sequence_free_slot(struct nfs4_sequence_res *res)
         struct nfs4_slot_table *tbl;
 
         tbl = &res->sr_session->fc_slot_table;
-        if (res->sr_slotid == NFS4_MAX_SLOT_TABLE) {
+        if (!res->sr_slot) {
                 /* just wake up the next guy waiting since
                  * we may have not consumed a slot after all */
                 dprintk("%s: No slot\n", __func__);
@@ -387,17 +389,15 @@ static void nfs41_sequence_free_slot(struct nfs4_sequence_res *res)
         }
 
         spin_lock(&tbl->slot_tbl_lock);
-        nfs4_free_slot(tbl, res->sr_slotid);
+        nfs4_free_slot(tbl, res->sr_slot);
         nfs41_check_drain_session_complete(res->sr_session);
         spin_unlock(&tbl->slot_tbl_lock);
-        res->sr_slotid = NFS4_MAX_SLOT_TABLE;
+        res->sr_slot = NULL;
 }
 
 static int nfs41_sequence_done(struct rpc_task *task, struct nfs4_sequence_res *res)
 {
         unsigned long timestamp;
-        struct nfs4_slot_table *tbl;
-        struct nfs4_slot *slot;
         struct nfs_client *clp;
 
         /*
@@ -410,17 +410,14 @@ static int nfs41_sequence_done(struct rpc_task *task, struct nfs4_sequence_res *
                 res->sr_status = NFS_OK;
 
         /* -ERESTARTSYS can result in skipping nfs41_sequence_setup */
-        if (res->sr_slotid == NFS4_MAX_SLOT_TABLE)
+        if (!res->sr_slot)
                 goto out;
 
-        tbl = &res->sr_session->fc_slot_table;
-        slot = tbl->slots + res->sr_slotid;
-
         /* Check the SEQUENCE operation status */
         switch (res->sr_status) {
         case 0:
                 /* Update the slot's sequence and clientid lease timer */
-                ++slot->seq_nr;
+                ++res->sr_slot->seq_nr;
                 timestamp = res->sr_renewal_time;
                 clp = res->sr_session->clp;
                 do_renew_lease(clp, timestamp);
@@ -433,12 +430,14 @@ static int nfs41_sequence_done(struct rpc_task *task, struct nfs4_sequence_res *
                  * returned NFS4ERR_DELAY as per Section 2.10.6.2
                  * of RFC5661.
                  */
-                dprintk("%s: slot=%d seq=%d: Operation in progress\n",
-                                __func__, res->sr_slotid, slot->seq_nr);
+                dprintk("%s: slot=%ld seq=%d: Operation in progress\n",
+                        __func__,
+                        res->sr_slot - res->sr_session->fc_slot_table.slots,
+                        res->sr_slot->seq_nr);
                 goto out_retry;
         default:
                 /* Just update the slot sequence no. */
-                ++slot->seq_nr;
+                ++res->sr_slot->seq_nr;
         }
 out:
         /* The session may be reset by one of the error handlers. */
@@ -505,10 +504,9 @@ static int nfs41_setup_sequence(struct nfs4_session *session,
 
         dprintk("--> %s\n", __func__);
         /* slot already allocated? */
-        if (res->sr_slotid != NFS4_MAX_SLOT_TABLE)
+        if (res->sr_slot != NULL)
                 return 0;
 
-        res->sr_slotid = NFS4_MAX_SLOT_TABLE;
         tbl = &session->fc_slot_table;
 
         spin_lock(&tbl->slot_tbl_lock);
@@ -550,7 +548,7 @@ static int nfs41_setup_sequence(struct nfs4_session *session,
         dprintk("<-- %s slotid=%d seqid=%d\n", __func__, slotid, slot->seq_nr);
 
         res->sr_session = session;
-        res->sr_slotid = slotid;
+        res->sr_slot = slot;
         res->sr_renewal_time = jiffies;
         res->sr_status_flags = 0;
         /*
@@ -576,8 +574,9 @@ int nfs4_setup_sequence(const struct nfs_server *server,
                 goto out;
         }
 
-        dprintk("--> %s clp %p session %p sr_slotid %d\n",
-                __func__, session->clp, session, res->sr_slotid);
+        dprintk("--> %s clp %p session %p sr_slot %ld\n",
+                __func__, session->clp, session, res->sr_slot ?
+                        res->sr_slot - session->fc_slot_table.slots : -1);
 
         ret = nfs41_setup_sequence(session, args, res, cache_reply,
                                    task);
@@ -650,7 +649,7 @@ static int nfs4_call_sync_sequence(struct nfs_server *server,
                 .callback_data = &data
         };
 
-        res->sr_slotid = NFS4_MAX_SLOT_TABLE;
+        res->sr_slot = NULL;
         if (privileged)
                 task_setup.callback_ops = &nfs41_call_priv_sync_ops;
         task = rpc_run_task(&task_setup);
@@ -735,7 +734,6 @@ static void nfs4_init_opendata_res(struct nfs4_opendata *p)
         p->o_res.server = p->o_arg.server;
         nfs_fattr_init(&p->f_attr);
         nfs_fattr_init(&p->dir_attr);
-        p->o_res.seq_res.sr_slotid = NFS4_MAX_SLOT_TABLE;
 }
 
 static struct nfs4_opendata *nfs4_opendata_alloc(struct path *path,
@@ -1975,7 +1973,6 @@ int nfs4_do_close(struct path *path, struct nfs4_state *state, gfp_t gfp_mask, i
         calldata->res.fattr = &calldata->fattr;
         calldata->res.seqid = calldata->arg.seqid;
         calldata->res.server = server;
-        calldata->res.seq_res.sr_slotid = NFS4_MAX_SLOT_TABLE;
         path_get(path);
         calldata->path = *path;
 
@@ -2550,7 +2547,7 @@ static void nfs4_proc_unlink_setup(struct rpc_message *msg, struct inode *dir)
 
         args->bitmask = server->cache_consistency_bitmask;
         res->server = server;
-        res->seq_res.sr_slotid = NFS4_MAX_SLOT_TABLE;
+        res->seq_res.sr_slot = NULL;
         msg->rpc_proc = &nfs4_procedures[NFSPROC4_CLNT_REMOVE];
 }
 
@@ -2576,7 +2573,6 @@ static void nfs4_proc_rename_setup(struct rpc_message *msg, struct inode *dir)
         msg->rpc_proc = &nfs4_procedures[NFSPROC4_CLNT_RENAME];
         arg->bitmask = server->attr_bitmask;
         res->server = server;
-        res->seq_res.sr_slotid = NFS4_MAX_SLOT_TABLE;
 }
 
 static int nfs4_proc_rename_done(struct rpc_task *task, struct inode *old_dir,
@@ -3646,7 +3642,6 @@ static int _nfs4_proc_delegreturn(struct inode *inode, struct rpc_cred *cred, co
         memcpy(&data->stateid, stateid, sizeof(data->stateid));
         data->res.fattr = &data->fattr;
         data->res.server = server;
-        data->res.seq_res.sr_slotid = NFS4_MAX_SLOT_TABLE;
         nfs_fattr_init(data->res.fattr);
         data->timestamp = jiffies;
         data->rpc_status = 0;
@@ -3799,7 +3794,6 @@ static struct nfs4_unlockdata *nfs4_alloc_unlockdata(struct file_lock *fl,
         p->arg.fl = &p->fl;
         p->arg.seqid = seqid;
         p->res.seqid = seqid;
-        p->res.seq_res.sr_slotid = NFS4_MAX_SLOT_TABLE;
         p->arg.stateid = &lsp->ls_stateid;
         p->lsp = lsp;
         atomic_inc(&lsp->ls_count);
@@ -3979,7 +3973,6 @@ static struct nfs4_lockdata *nfs4_alloc_lockdata(struct file_lock *fl,
         p->arg.lock_owner.clientid = server->nfs_client->cl_clientid;
         p->arg.lock_owner.id = lsp->ls_id.id;
         p->res.lock_seqid = p->arg.lock_seqid;
-        p->res.seq_res.sr_slotid = NFS4_MAX_SLOT_TABLE;
         p->lsp = lsp;
         p->server = server;
         atomic_inc(&lsp->ls_count);
@@ -4612,7 +4605,6 @@ int nfs4_proc_get_lease_time(struct nfs_client *clp, struct nfs_fsinfo *fsinfo)
         };
         int status;
 
-        res.lr_seq_res.sr_slotid = NFS4_MAX_SLOT_TABLE;
         dprintk("--> %s\n", __func__);
         task = rpc_run_task(&task_setup);
 
@@ -5105,12 +5097,11 @@ static struct rpc_task *_nfs41_proc_sequence(struct nfs_client *clp, struct rpc_
 
         if (!atomic_inc_not_zero(&clp->cl_count))
                 return ERR_PTR(-EIO);
-        calldata = kmalloc(sizeof(*calldata), GFP_NOFS);
+        calldata = kzalloc(sizeof(*calldata), GFP_NOFS);
         if (calldata == NULL) {
                 nfs_put_client(clp);
                 return ERR_PTR(-ENOMEM);
         }
-        calldata->res.sr_slotid = NFS4_MAX_SLOT_TABLE;
         msg.rpc_argp = &calldata->args;
         msg.rpc_resp = &calldata->res;
         calldata->clp = clp;
@@ -5242,7 +5233,6 @@ static int nfs41_proc_reclaim_complete(struct nfs_client *clp)
                 goto out;
         calldata->clp = clp;
         calldata->arg.one_fs = 0;
-        calldata->res.seq_res.sr_slotid = NFS4_MAX_SLOT_TABLE;
 
         msg.rpc_argp = &calldata->arg;
         msg.rpc_resp = &calldata->res;