NFSv4.1: Cleanup move session slot management to fs/nfs/nfs4session.c

NFSv4.1 session management is getting complex enough to deserve
a separate file.

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

9 files changed, 477 insertions, 427 deletions

diff --git a/fs/nfs/Makefile b/fs/nfs/Makefile
index b7db60897f91..cce2c057bd2d 100644
--- a/fs/nfs/Makefile
+++ b/fs/nfs/Makefile
@@ -24,7 +24,7 @@ nfsv4-y := nfs4proc.o nfs4xdr.o nfs4state.o nfs4renewd.o nfs4super.o nfs4file.o
           delegation.o idmap.o callback.o callback_xdr.o callback_proc.o \
           nfs4namespace.o nfs4getroot.o nfs4client.o
 nfsv4-$(CONFIG_SYSCTL)  += nfs4sysctl.o
-nfsv4-$(CONFIG_NFS_V4_1)        += pnfs.o pnfs_dev.o
+nfsv4-$(CONFIG_NFS_V4_1)        += nfs4session.o pnfs.o pnfs_dev.o
 
 obj-$(CONFIG_PNFS_FILE_LAYOUT) += nfs_layout_nfsv41_files.o
 nfs_layout_nfsv41_files-y := nfs4filelayout.o nfs4filelayoutdev.o
diff --git a/fs/nfs/callback_proc.c b/fs/nfs/callback_proc.c
index f99faad78c72..c89b26bc9759 100644
--- a/fs/nfs/callback_proc.c
+++ b/fs/nfs/callback_proc.c
@@ -14,6 +14,7 @@
 #include "delegation.h"
 #include "internal.h"
 #include "pnfs.h"
+#include "nfs4session.h"
 
 #ifdef NFS_DEBUG
 #define NFSDBG_FACILITY NFSDBG_CALLBACK
diff --git a/fs/nfs/internal.h b/fs/nfs/internal.h
index 05521cadac2e..8965a998b306 100644
--- a/fs/nfs/internal.h
+++ b/fs/nfs/internal.h
@@ -276,8 +276,6 @@ extern const u32 nfs41_maxwrite_overhead;
 extern struct rpc_procinfo nfs4_procedures[];
 #endif
 
-extern int nfs4_init_ds_session(struct nfs_client *, unsigned long);
-
 /* proc.c */
 void nfs_close_context(struct nfs_open_context *ctx, int is_sync);
 extern struct nfs_client *nfs_init_client(struct nfs_client *clp,
diff --git a/fs/nfs/nfs4_fs.h b/fs/nfs/nfs4_fs.h
index 2f6a9f9d9299..cd3e3096b60a 100644
--- a/fs/nfs/nfs4_fs.h
+++ b/fs/nfs/nfs4_fs.h
@@ -249,19 +249,13 @@ extern int nfs4_setup_sequence(const struct nfs_server *server,
 extern int nfs41_setup_sequence(struct nfs4_session *session,
                 struct nfs4_sequence_args *args, struct nfs4_sequence_res *res,
                 struct rpc_task *task);
-extern void nfs4_destroy_session(struct nfs4_session *session);
-extern struct nfs4_session *nfs4_alloc_session(struct nfs_client *clp);
 extern int nfs4_proc_create_session(struct nfs_client *, struct rpc_cred *);
 extern int nfs4_proc_destroy_session(struct nfs4_session *, struct rpc_cred *);
-extern int nfs4_init_session(struct nfs_server *server);
 extern int nfs4_proc_get_lease_time(struct nfs_client *clp,
                 struct nfs_fsinfo *fsinfo);
 extern int nfs4_proc_layoutcommit(struct nfs4_layoutcommit_data *data,
                                   bool sync);
 
-extern void nfs41_set_target_slotid(struct nfs4_slot_table *tbl,
-                u32 target_highest_slotid);
-
 static inline bool
 is_ds_only_client(struct nfs_client *clp)
 {
@@ -287,11 +281,6 @@ static inline int nfs4_setup_sequence(const struct nfs_server *server,
         return 0;
 }
 
-static inline int nfs4_init_session(struct nfs_server *server)
-{
-        return 0;
-}
-
 static inline bool
 is_ds_only_client(struct nfs_client *clp)
 {
diff --git a/fs/nfs/nfs4client.c b/fs/nfs/nfs4client.c
index 72717e67b34e..acc347268124 100644
--- a/fs/nfs/nfs4client.c
+++ b/fs/nfs/nfs4client.c
@@ -12,6 +12,7 @@
 #include "internal.h"
 #include "callback.h"
 #include "delegation.h"
+#include "nfs4session.h"
 #include "pnfs.h"
 #include "netns.h"
 
diff --git a/fs/nfs/nfs4filelayoutdev.c b/fs/nfs/nfs4filelayoutdev.c
index 93e2530d7098..b720064bcd7f 100644
--- a/fs/nfs/nfs4filelayoutdev.c
+++ b/fs/nfs/nfs4filelayoutdev.c
@@ -33,6 +33,7 @@
 #include <linux/module.h>
 
 #include "internal.h"
+#include "nfs4session.h"
 #include "nfs4filelayout.h"
 
 #define NFSDBG_FACILITY         NFSDBG_PNFS_LD
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index d75e2a2576eb..a0c35ab12a6b 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -52,7 +52,6 @@
 #include <linux/mount.h>
 #include <linux/module.h>
 #include <linux/nfs_idmap.h>
-#include <linux/sunrpc/bc_xprt.h>
 #include <linux/xattr.h>
 #include <linux/utsname.h>
 #include <linux/freezer.h>
@@ -64,6 +63,8 @@
 #include "callback.h"
 #include "pnfs.h"
 #include "netns.h"
+#include "nfs4session.h"
+
 
 #define NFSDBG_FACILITY         NFSDBG_PROC
 
@@ -378,64 +379,6 @@ static void renew_lease(const struct nfs_server *server, unsigned long timestamp
 
 #if defined(CONFIG_NFS_V4_1)
 
-/*
- * nfs4_shrink_slot_table - free retired slots from the slot table
- */
-static void nfs4_shrink_slot_table(struct nfs4_slot_table  *tbl, u32 newsize)
-{
-        struct nfs4_slot **p;
-        if (newsize >= tbl->max_slots)
-                return;
-
-        p = &tbl->slots;
-        while (newsize--)
-                p = &(*p)->next;
-        while (*p) {
-                struct nfs4_slot *slot = *p;
-
-                *p = slot->next;
-                kfree(slot);
-                tbl->max_slots--;
-        }
-}
-
-/*
- * nfs4_free_slot - free a slot and efficiently update slot table.
- *
- * freeing a slot is trivially done by clearing its respective bit
- * in the bitmap.
- * If the freed slotid equals highest_used_slotid we want to update it
- * so that the server would be able to size down the slot table if needed,
- * otherwise we know that the highest_used_slotid is still in use.
- * When updating highest_used_slotid there may be "holes" in the bitmap
- * so we need to scan down from highest_used_slotid to 0 looking for the now
- * highest slotid in use.
- * If none found, highest_used_slotid is set to NFS4_NO_SLOT.
- *
- * Must be called while holding tbl->slot_tbl_lock
- */
-static void
-nfs4_free_slot(struct nfs4_slot_table *tbl, struct nfs4_slot *slot)
-{
-        u32 slotid = slot->slot_nr;
-
-        /* clear used bit in bitmap */
-        __clear_bit(slotid, tbl->used_slots);
-
-        /* update highest_used_slotid when it is freed */
-        if (slotid == tbl->highest_used_slotid) {
-                u32 new_max = find_last_bit(tbl->used_slots, slotid);
-                if (new_max < slotid)
-                        tbl->highest_used_slotid = new_max;
-                else {
-                        tbl->highest_used_slotid = NFS4_NO_SLOT;
-                        nfs4_session_drain_complete(tbl->session, tbl);
-                }
-        }
-        dprintk("%s: slotid %u highest_used_slotid %d\n", __func__,
-                slotid, tbl->highest_used_slotid);
-}
-
 bool nfs4_set_task_privileged(struct rpc_task *task, void *dummy)
 {
         rpc_task_set_priority(task, RPC_PRIORITY_PRIVILEGED);
@@ -465,56 +408,6 @@ static void nfs41_sequence_free_slot(struct nfs4_sequence_res *res)
         res->sr_slot = NULL;
 }
 
-/* Update the client's idea of target_highest_slotid */
-static void nfs41_set_target_slotid_locked(struct nfs4_slot_table *tbl,
-                u32 target_highest_slotid)
-{
-        unsigned int max_slotid, i;
-
-        if (tbl->target_highest_slotid == target_highest_slotid)
-                return;
-        tbl->target_highest_slotid = target_highest_slotid;
-        tbl->generation++;
-
-        max_slotid = min(NFS4_MAX_SLOT_TABLE - 1, tbl->target_highest_slotid);
-        for (i = tbl->max_slotid + 1; i <= max_slotid; i++)
-                rpc_wake_up_next(&tbl->slot_tbl_waitq);
-        tbl->max_slotid = max_slotid;
-}
-
-void nfs41_set_target_slotid(struct nfs4_slot_table *tbl,
-                u32 target_highest_slotid)
-{
-        spin_lock(&tbl->slot_tbl_lock);
-        nfs41_set_target_slotid_locked(tbl, target_highest_slotid);
-        spin_unlock(&tbl->slot_tbl_lock);
-}
-
-static void nfs41_set_server_slotid_locked(struct nfs4_slot_table *tbl,
-                u32 highest_slotid)
-{
-        if (tbl->server_highest_slotid == highest_slotid)
-                return;
-        if (tbl->highest_used_slotid > highest_slotid)
-                return;
-        /* Deallocate slots */
-        nfs4_shrink_slot_table(tbl, highest_slotid + 1);
-        tbl->server_highest_slotid = highest_slotid;
-}
-
-static void nfs41_update_target_slotid(struct nfs4_slot_table *tbl,
-                struct nfs4_slot *slot,
-                struct nfs4_sequence_res *res)
-{
-        spin_lock(&tbl->slot_tbl_lock);
-        if (tbl->generation != slot->generation)
-                goto out;
-        nfs41_set_server_slotid_locked(tbl, res->sr_highest_slotid);
-        nfs41_set_target_slotid_locked(tbl, res->sr_target_highest_slotid);
-out:
-        spin_unlock(&tbl->slot_tbl_lock);
-}
-
 static int nfs41_sequence_done(struct rpc_task *task, struct nfs4_sequence_res *res)
 {
         struct nfs4_session *session;
@@ -585,79 +478,6 @@ static int nfs4_sequence_done(struct rpc_task *task,
         return nfs41_sequence_done(task, res);
 }
 
-static struct nfs4_slot *nfs4_new_slot(struct nfs4_slot_table  *tbl,
-                u32 slotid, u32 seq_init, gfp_t gfp_mask)
-{
-        struct nfs4_slot *slot;
-
-        slot = kzalloc(sizeof(*slot), gfp_mask);
-        if (slot) {
-                slot->table = tbl;
-                slot->slot_nr = slotid;
-                slot->seq_nr = seq_init;
-        }
-        return slot;
-}
-
-static struct nfs4_slot *nfs4_find_or_create_slot(struct nfs4_slot_table  *tbl,
-                u32 slotid, u32 seq_init, gfp_t gfp_mask)
-{
-        struct nfs4_slot **p, *slot;
-
-        p = &tbl->slots;
-        for (;;) {
-                if (*p == NULL) {
-                        *p = nfs4_new_slot(tbl, tbl->max_slots,
-                                        seq_init, gfp_mask);
-                        if (*p == NULL)
-                                break;
-                        tbl->max_slots++;
-                }
-                slot = *p;
-                if (slot->slot_nr == slotid)
-                        return slot;
-                p = &slot->next;
-        }
-        return ERR_PTR(-ENOMEM);
-}
-
-/*
- * nfs4_alloc_slot - efficiently look for a free slot
- *
- * nfs4_alloc_slot looks for an unset bit in the used_slots bitmap.
- * If found, we mark the slot as used, update the highest_used_slotid,
- * and respectively set up the sequence operation args.
- *
- * Note: must be called with under the slot_tbl_lock.
- */
-static struct nfs4_slot *nfs4_alloc_slot(struct nfs4_slot_table *tbl)
-{
-        struct nfs4_slot *ret = ERR_PTR(-EBUSY);
-        u32 slotid;
-
-        dprintk("--> %s used_slots=%04lx highest_used=%u max_slots=%u\n",
-                __func__, tbl->used_slots[0], tbl->highest_used_slotid,
-                tbl->max_slotid + 1);
-        slotid = find_first_zero_bit(tbl->used_slots, tbl->max_slotid + 1);
-        if (slotid > tbl->max_slotid)
-                goto out;
-        ret = nfs4_find_or_create_slot(tbl, slotid, 1, GFP_NOWAIT);
-        if (IS_ERR(ret))
-                goto out;
-        __set_bit(slotid, tbl->used_slots);
-        if (slotid > tbl->highest_used_slotid ||
-                        tbl->highest_used_slotid == NFS4_NO_SLOT)
-                tbl->highest_used_slotid = slotid;
-        ret->renewal_time = jiffies;
-        ret->generation = tbl->generation;
-
-out:
-        dprintk("<-- %s used_slots=%04lx highest_used=%d slotid=%d \n",
-                __func__, tbl->used_slots[0], tbl->highest_used_slotid,
-                !IS_ERR(ret) ? ret->slot_nr : -1);
-        return ret;
-}
-
 static void nfs41_init_sequence(struct nfs4_sequence_args *args,
                 struct nfs4_sequence_res *res, int cache_reply)
 {
@@ -5716,143 +5536,6 @@ int nfs4_proc_get_lease_time(struct nfs_client *clp, struct nfs_fsinfo *fsinfo)
         return status;
 }
 
-static int nfs4_grow_slot_table(struct nfs4_slot_table *tbl,
-                 u32 max_reqs, u32 ivalue)
-{
-        if (max_reqs <= tbl->max_slots)
-                return 0;
-        if (!IS_ERR(nfs4_find_or_create_slot(tbl, max_reqs - 1, ivalue, GFP_NOFS)))
-                return 0;
-        return -ENOMEM;
-}
-
-static void nfs4_reset_slot_table(struct nfs4_slot_table *tbl,
-                u32 server_highest_slotid,
-                u32 ivalue)
-{
-        struct nfs4_slot **p;
-
-        nfs4_shrink_slot_table(tbl, server_highest_slotid + 1);
-        p = &tbl->slots;
-        while (*p) {
-                (*p)->seq_nr = ivalue;
-                p = &(*p)->next;
-        }
-        tbl->highest_used_slotid = NFS4_NO_SLOT;
-        tbl->target_highest_slotid = server_highest_slotid;
-        tbl->server_highest_slotid = server_highest_slotid;
-        tbl->max_slotid = server_highest_slotid;
-}
-
-/*
- * (re)Initialise a slot table
- */
-static int nfs4_realloc_slot_table(struct nfs4_slot_table *tbl,
-                u32 max_reqs, u32 ivalue)
-{
-        int ret;
-
-        dprintk("--> %s: max_reqs=%u, tbl->max_slots %d\n", __func__,
-                max_reqs, tbl->max_slots);
-
-        if (max_reqs > NFS4_MAX_SLOT_TABLE)
-                max_reqs = NFS4_MAX_SLOT_TABLE;
-
-        ret = nfs4_grow_slot_table(tbl, max_reqs, ivalue);
-        if (ret)
-                goto out;
-
-        spin_lock(&tbl->slot_tbl_lock);
-        nfs4_reset_slot_table(tbl, max_reqs - 1, ivalue);
-        spin_unlock(&tbl->slot_tbl_lock);
-
-        dprintk("%s: tbl=%p slots=%p max_slots=%d\n", __func__,
-                tbl, tbl->slots, tbl->max_slots);
-out:
-        dprintk("<-- %s: return %d\n", __func__, ret);
-        return ret;
-}
-
-/* Destroy the slot table */
-static void nfs4_destroy_slot_tables(struct nfs4_session *session)
-{
-        nfs4_shrink_slot_table(&session->fc_slot_table, 0);
-        nfs4_shrink_slot_table(&session->bc_slot_table, 0);
-}
-
-/*
- * Initialize or reset the forechannel and backchannel tables
- */
-static int nfs4_setup_session_slot_tables(struct nfs4_session *ses)
-{
-        struct nfs4_slot_table *tbl;
-        int status;
-
-        dprintk("--> %s\n", __func__);
-        /* Fore channel */
-        tbl = &ses->fc_slot_table;
-        tbl->session = ses;
-        status = nfs4_realloc_slot_table(tbl, ses->fc_attrs.max_reqs, 1);
-        if (status) /* -ENOMEM */
-                return status;
-        /* Back channel */
-        tbl = &ses->bc_slot_table;
-        tbl->session = ses;
-        status = nfs4_realloc_slot_table(tbl, ses->bc_attrs.max_reqs, 0);
-        if (status && tbl->slots == NULL)
-                /* Fore and back channel share a connection so get
-                 * both slot tables or neither */
-                nfs4_destroy_slot_tables(ses);
-        return status;
-}
-
-struct nfs4_session *nfs4_alloc_session(struct nfs_client *clp)
-{
-        struct nfs4_session *session;
-        struct nfs4_slot_table *tbl;
-
-        session = kzalloc(sizeof(struct nfs4_session), GFP_NOFS);
-        if (!session)
-                return NULL;
-
-        tbl = &session->fc_slot_table;
-        tbl->highest_used_slotid = NFS4_NO_SLOT;
-        spin_lock_init(&tbl->slot_tbl_lock);
-        rpc_init_priority_wait_queue(&tbl->slot_tbl_waitq, "ForeChannel Slot table");
-        init_completion(&tbl->complete);
-
-        tbl = &session->bc_slot_table;
-        tbl->highest_used_slotid = NFS4_NO_SLOT;
-        spin_lock_init(&tbl->slot_tbl_lock);
-        rpc_init_wait_queue(&tbl->slot_tbl_waitq, "BackChannel Slot table");
-        init_completion(&tbl->complete);
-
-        session->session_state = 1<<NFS4_SESSION_INITING;
-
-        session->clp = clp;
-        return session;
-}
-
-void nfs4_destroy_session(struct nfs4_session *session)
-{
-        struct rpc_xprt *xprt;
-        struct rpc_cred *cred;
-
-        cred = nfs4_get_exchange_id_cred(session->clp);
-        nfs4_proc_destroy_session(session, cred);
-        if (cred)
-                put_rpccred(cred);
-
-        rcu_read_lock();
-        xprt = rcu_dereference(session->clp->cl_rpcclient->cl_xprt);
-        rcu_read_unlock();
-        dprintk("%s Destroy backchannel for xprt %p\n",
-                __func__, xprt);
-        xprt_destroy_backchannel(xprt, NFS41_BC_MIN_CALLBACKS);
-        nfs4_destroy_slot_tables(session);
-        kfree(session);
-}
-
 /*
  * Initialize the values to be used by the client in CREATE_SESSION
  * If nfs4_init_session set the fore channel request and response sizes,
@@ -6047,100 +5730,6 @@ int nfs4_proc_destroy_session(struct nfs4_session *session,
 }
 
 /*
- * With sessions, the client is not marked ready until after a
- * successful EXCHANGE_ID and CREATE_SESSION.
- *
- * Map errors cl_cons_state errors to EPROTONOSUPPORT to indicate
- * other versions of NFS can be tried.
- */
-static int nfs41_check_session_ready(struct nfs_client *clp)
-{
-        int ret;
-        
-        if (clp->cl_cons_state == NFS_CS_SESSION_INITING) {
-                ret = nfs4_client_recover_expired_lease(clp);
-                if (ret)
-                        return ret;
-        }
-        if (clp->cl_cons_state < NFS_CS_READY)
-                return -EPROTONOSUPPORT;
-        smp_rmb();
-        return 0;
-}
-
-int nfs4_init_session(struct nfs_server *server)
-{
-        struct nfs_client *clp = server->nfs_client;
-        struct nfs4_session *session;
-        unsigned int target_max_rqst_sz = NFS_MAX_FILE_IO_SIZE;
-        unsigned int target_max_resp_sz = NFS_MAX_FILE_IO_SIZE;
-
-        if (!nfs4_has_session(clp))
-                return 0;
-
-        if (server->rsize != 0)
-                target_max_resp_sz = server->rsize;
-        target_max_resp_sz += nfs41_maxread_overhead;
-
-        if (server->wsize != 0)
-                target_max_rqst_sz = server->wsize;
-        target_max_rqst_sz += nfs41_maxwrite_overhead;
-
-        session = clp->cl_session;
-        spin_lock(&clp->cl_lock);
-        if (test_and_clear_bit(NFS4_SESSION_INITING, &session->session_state)) {
-                /* Initialise targets and channel attributes */
-                session->fc_target_max_rqst_sz = target_max_rqst_sz;
-                session->fc_attrs.max_rqst_sz = target_max_rqst_sz;
-                session->fc_target_max_resp_sz = target_max_resp_sz;
-                session->fc_attrs.max_resp_sz = target_max_resp_sz;
-        } else {
-                /* Just adjust the targets */
-                if (target_max_rqst_sz > session->fc_target_max_rqst_sz) {
-                        session->fc_target_max_rqst_sz = target_max_rqst_sz;
-                        set_bit(NFS4CLNT_SESSION_RESET, &clp->cl_state);
-                }
-                if (target_max_resp_sz > session->fc_target_max_resp_sz) {
-                        session->fc_target_max_resp_sz = target_max_resp_sz;
-                        set_bit(NFS4CLNT_SESSION_RESET, &clp->cl_state);
-                }
-        }
-        spin_unlock(&clp->cl_lock);
-
-        if (test_bit(NFS4CLNT_SESSION_RESET, &clp->cl_state))
-                nfs4_schedule_lease_recovery(clp);
-
-        return nfs41_check_session_ready(clp);
-}
-
-int nfs4_init_ds_session(struct nfs_client *clp, unsigned long lease_time)
-{
-        struct nfs4_session *session = clp->cl_session;
-        int ret;
-
-        spin_lock(&clp->cl_lock);
-        if (test_and_clear_bit(NFS4_SESSION_INITING, &session->session_state)) {
-                /*
-                 * Do not set NFS_CS_CHECK_LEASE_TIME instead set the
-                 * DS lease to be equal to the MDS lease.
-                 */
-                clp->cl_lease_time = lease_time;
-                clp->cl_last_renewal = jiffies;
-        }
-        spin_unlock(&clp->cl_lock);
-
-        ret = nfs41_check_session_ready(clp);
-        if (ret)
-                return ret;
-        /* Test for the DS role */
-        if (!is_ds_client(clp))
-                return -ENODEV;
-        return 0;
-}
-EXPORT_SYMBOL_GPL(nfs4_init_ds_session);
-
-
-/*
  * Renew the cl_session lease.
  */
 struct nfs4_sequence_data {
diff --git a/fs/nfs/nfs4session.c b/fs/nfs/nfs4session.c
new file mode 100644
index 000000000000..701170293ceb
--- /dev/null
+++ b/fs/nfs/nfs4session.c
@@ -0,0 +1,436 @@
+/*
+ * fs/nfs/nfs4session.c
+ *
+ * Copyright (c) 2012 Trond Myklebust <Trond.Myklebust@netapp.com>
+ *
+ */
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/string.h>
+#include <linux/printk.h>
+#include <linux/slab.h>
+#include <linux/sunrpc/sched.h>
+#include <linux/sunrpc/bc_xprt.h>
+#include <linux/nfs.h>
+#include <linux/nfs4.h>
+#include <linux/nfs_fs.h>
+#include <linux/module.h>
+
+#include "nfs4_fs.h"
+#include "internal.h"
+#include "nfs4session.h"
+#include "callback.h"
+
+#define NFSDBG_FACILITY         NFSDBG_STATE
+
+/*
+ * nfs4_shrink_slot_table - free retired slots from the slot table
+ */
+static void nfs4_shrink_slot_table(struct nfs4_slot_table  *tbl, u32 newsize)
+{
+        struct nfs4_slot **p;
+        if (newsize >= tbl->max_slots)
+                return;
+
+        p = &tbl->slots;
+        while (newsize--)
+                p = &(*p)->next;
+        while (*p) {
+                struct nfs4_slot *slot = *p;
+
+                *p = slot->next;
+                kfree(slot);
+                tbl->max_slots--;
+        }
+}
+
+/*
+ * nfs4_free_slot - free a slot and efficiently update slot table.
+ *
+ * freeing a slot is trivially done by clearing its respective bit
+ * in the bitmap.
+ * If the freed slotid equals highest_used_slotid we want to update it
+ * so that the server would be able to size down the slot table if needed,
+ * otherwise we know that the highest_used_slotid is still in use.
+ * When updating highest_used_slotid there may be "holes" in the bitmap
+ * so we need to scan down from highest_used_slotid to 0 looking for the now
+ * highest slotid in use.
+ * If none found, highest_used_slotid is set to NFS4_NO_SLOT.
+ *
+ * Must be called while holding tbl->slot_tbl_lock
+ */
+void nfs4_free_slot(struct nfs4_slot_table *tbl, struct nfs4_slot *slot)
+{
+        u32 slotid = slot->slot_nr;
+
+        /* clear used bit in bitmap */
+        __clear_bit(slotid, tbl->used_slots);
+
+        /* update highest_used_slotid when it is freed */
+        if (slotid == tbl->highest_used_slotid) {
+                u32 new_max = find_last_bit(tbl->used_slots, slotid);
+                if (new_max < slotid)
+                        tbl->highest_used_slotid = new_max;
+                else {
+                        tbl->highest_used_slotid = NFS4_NO_SLOT;
+                        nfs4_session_drain_complete(tbl->session, tbl);
+                }
+        }
+        dprintk("%s: slotid %u highest_used_slotid %d\n", __func__,
+                slotid, tbl->highest_used_slotid);
+}
+
+static struct nfs4_slot *nfs4_new_slot(struct nfs4_slot_table  *tbl,
+                u32 slotid, u32 seq_init, gfp_t gfp_mask)
+{
+        struct nfs4_slot *slot;
+
+        slot = kzalloc(sizeof(*slot), gfp_mask);
+        if (slot) {
+                slot->table = tbl;
+                slot->slot_nr = slotid;
+                slot->seq_nr = seq_init;
+        }
+        return slot;
+}
+
+static struct nfs4_slot *nfs4_find_or_create_slot(struct nfs4_slot_table  *tbl,
+                u32 slotid, u32 seq_init, gfp_t gfp_mask)
+{
+        struct nfs4_slot **p, *slot;
+
+        p = &tbl->slots;
+        for (;;) {
+                if (*p == NULL) {
+                        *p = nfs4_new_slot(tbl, tbl->max_slots,
+                                        seq_init, gfp_mask);
+                        if (*p == NULL)
+                                break;
+                        tbl->max_slots++;
+                }
+                slot = *p;
+                if (slot->slot_nr == slotid)
+                        return slot;
+                p = &slot->next;
+        }
+        return ERR_PTR(-ENOMEM);
+}
+
+/*
+ * nfs4_alloc_slot - efficiently look for a free slot
+ *
+ * nfs4_alloc_slot looks for an unset bit in the used_slots bitmap.
+ * If found, we mark the slot as used, update the highest_used_slotid,
+ * and respectively set up the sequence operation args.
+ *
+ * Note: must be called with under the slot_tbl_lock.
+ */
+struct nfs4_slot *nfs4_alloc_slot(struct nfs4_slot_table *tbl)
+{
+        struct nfs4_slot *ret = ERR_PTR(-EBUSY);
+        u32 slotid;
+
+        dprintk("--> %s used_slots=%04lx highest_used=%u max_slots=%u\n",
+                __func__, tbl->used_slots[0], tbl->highest_used_slotid,
+                tbl->max_slotid + 1);
+        slotid = find_first_zero_bit(tbl->used_slots, tbl->max_slotid + 1);
+        if (slotid > tbl->max_slotid)
+                goto out;
+        ret = nfs4_find_or_create_slot(tbl, slotid, 1, GFP_NOWAIT);
+        if (IS_ERR(ret))
+                goto out;
+        __set_bit(slotid, tbl->used_slots);
+        if (slotid > tbl->highest_used_slotid ||
+                        tbl->highest_used_slotid == NFS4_NO_SLOT)
+                tbl->highest_used_slotid = slotid;
+        ret->renewal_time = jiffies;
+        ret->generation = tbl->generation;
+
+out:
+        dprintk("<-- %s used_slots=%04lx highest_used=%d slotid=%d \n",
+                __func__, tbl->used_slots[0], tbl->highest_used_slotid,
+                !IS_ERR(ret) ? ret->slot_nr : -1);
+        return ret;
+}
+
+static int nfs4_grow_slot_table(struct nfs4_slot_table *tbl,
+                 u32 max_reqs, u32 ivalue)
+{
+        if (max_reqs <= tbl->max_slots)
+                return 0;
+        if (!IS_ERR(nfs4_find_or_create_slot(tbl, max_reqs - 1, ivalue, GFP_NOFS)))
+                return 0;
+        return -ENOMEM;
+}
+
+static void nfs4_reset_slot_table(struct nfs4_slot_table *tbl,
+                u32 server_highest_slotid,
+                u32 ivalue)
+{
+        struct nfs4_slot **p;
+
+        nfs4_shrink_slot_table(tbl, server_highest_slotid + 1);
+        p = &tbl->slots;
+        while (*p) {
+                (*p)->seq_nr = ivalue;
+                p = &(*p)->next;
+        }
+        tbl->highest_used_slotid = NFS4_NO_SLOT;
+        tbl->target_highest_slotid = server_highest_slotid;
+        tbl->server_highest_slotid = server_highest_slotid;
+        tbl->max_slotid = server_highest_slotid;
+}
+
+/*
+ * (re)Initialise a slot table
+ */
+static int nfs4_realloc_slot_table(struct nfs4_slot_table *tbl,
+                u32 max_reqs, u32 ivalue)
+{
+        int ret;
+
+        dprintk("--> %s: max_reqs=%u, tbl->max_slots %d\n", __func__,
+                max_reqs, tbl->max_slots);
+
+        if (max_reqs > NFS4_MAX_SLOT_TABLE)
+                max_reqs = NFS4_MAX_SLOT_TABLE;
+
+        ret = nfs4_grow_slot_table(tbl, max_reqs, ivalue);
+        if (ret)
+                goto out;
+
+        spin_lock(&tbl->slot_tbl_lock);
+        nfs4_reset_slot_table(tbl, max_reqs - 1, ivalue);
+        spin_unlock(&tbl->slot_tbl_lock);
+
+        dprintk("%s: tbl=%p slots=%p max_slots=%d\n", __func__,
+                tbl, tbl->slots, tbl->max_slots);
+out:
+        dprintk("<-- %s: return %d\n", __func__, ret);
+        return ret;
+}
+
+/* Destroy the slot table */
+static void nfs4_destroy_slot_tables(struct nfs4_session *session)
+{
+        nfs4_shrink_slot_table(&session->fc_slot_table, 0);
+        nfs4_shrink_slot_table(&session->bc_slot_table, 0);
+}
+
+/* Update the client's idea of target_highest_slotid */
+static void nfs41_set_target_slotid_locked(struct nfs4_slot_table *tbl,
+                u32 target_highest_slotid)
+{
+        unsigned int max_slotid, i;
+
+        if (tbl->target_highest_slotid == target_highest_slotid)
+                return;
+        tbl->target_highest_slotid = target_highest_slotid;
+        tbl->generation++;
+
+        max_slotid = min(NFS4_MAX_SLOT_TABLE - 1, tbl->target_highest_slotid);
+        for (i = tbl->max_slotid + 1; i <= max_slotid; i++)
+                rpc_wake_up_next(&tbl->slot_tbl_waitq);
+        tbl->max_slotid = max_slotid;
+}
+
+void nfs41_set_target_slotid(struct nfs4_slot_table *tbl,
+                u32 target_highest_slotid)
+{
+        spin_lock(&tbl->slot_tbl_lock);
+        nfs41_set_target_slotid_locked(tbl, target_highest_slotid);
+        spin_unlock(&tbl->slot_tbl_lock);
+}
+
+static void nfs41_set_server_slotid_locked(struct nfs4_slot_table *tbl,
+                u32 highest_slotid)
+{
+        if (tbl->server_highest_slotid == highest_slotid)
+                return;
+        if (tbl->highest_used_slotid > highest_slotid)
+                return;
+        /* Deallocate slots */
+        nfs4_shrink_slot_table(tbl, highest_slotid + 1);
+        tbl->server_highest_slotid = highest_slotid;
+}
+
+void nfs41_update_target_slotid(struct nfs4_slot_table *tbl,
+                struct nfs4_slot *slot,
+                struct nfs4_sequence_res *res)
+{
+        spin_lock(&tbl->slot_tbl_lock);
+        if (tbl->generation != slot->generation)
+                goto out;
+        nfs41_set_server_slotid_locked(tbl, res->sr_highest_slotid);
+        nfs41_set_target_slotid_locked(tbl, res->sr_target_highest_slotid);
+out:
+        spin_unlock(&tbl->slot_tbl_lock);
+}
+
+/*
+ * Initialize or reset the forechannel and backchannel tables
+ */
+int nfs4_setup_session_slot_tables(struct nfs4_session *ses)
+{
+        struct nfs4_slot_table *tbl;
+        int status;
+
+        dprintk("--> %s\n", __func__);
+        /* Fore channel */
+        tbl = &ses->fc_slot_table;
+        tbl->session = ses;
+        status = nfs4_realloc_slot_table(tbl, ses->fc_attrs.max_reqs, 1);
+        if (status) /* -ENOMEM */
+                return status;
+        /* Back channel */
+        tbl = &ses->bc_slot_table;
+        tbl->session = ses;
+        status = nfs4_realloc_slot_table(tbl, ses->bc_attrs.max_reqs, 0);
+        if (status && tbl->slots == NULL)
+                /* Fore and back channel share a connection so get
+                 * both slot tables or neither */
+                nfs4_destroy_slot_tables(ses);
+        return status;
+}
+
+struct nfs4_session *nfs4_alloc_session(struct nfs_client *clp)
+{
+        struct nfs4_session *session;
+        struct nfs4_slot_table *tbl;
+
+        session = kzalloc(sizeof(struct nfs4_session), GFP_NOFS);
+        if (!session)
+                return NULL;
+
+        tbl = &session->fc_slot_table;
+        tbl->highest_used_slotid = NFS4_NO_SLOT;
+        spin_lock_init(&tbl->slot_tbl_lock);
+        rpc_init_priority_wait_queue(&tbl->slot_tbl_waitq, "ForeChannel Slot table");
+        init_completion(&tbl->complete);
+
+        tbl = &session->bc_slot_table;
+        tbl->highest_used_slotid = NFS4_NO_SLOT;
+        spin_lock_init(&tbl->slot_tbl_lock);
+        rpc_init_wait_queue(&tbl->slot_tbl_waitq, "BackChannel Slot table");
+        init_completion(&tbl->complete);
+
+        session->session_state = 1<<NFS4_SESSION_INITING;
+
+        session->clp = clp;
+        return session;
+}
+
+void nfs4_destroy_session(struct nfs4_session *session)
+{
+        struct rpc_xprt *xprt;
+        struct rpc_cred *cred;
+
+        cred = nfs4_get_exchange_id_cred(session->clp);
+        nfs4_proc_destroy_session(session, cred);
+        if (cred)
+                put_rpccred(cred);
+
+        rcu_read_lock();
+        xprt = rcu_dereference(session->clp->cl_rpcclient->cl_xprt);
+        rcu_read_unlock();
+        dprintk("%s Destroy backchannel for xprt %p\n",
+                __func__, xprt);
+        xprt_destroy_backchannel(xprt, NFS41_BC_MIN_CALLBACKS);
+        nfs4_destroy_slot_tables(session);
+        kfree(session);
+}
+
+/*
+ * With sessions, the client is not marked ready until after a
+ * successful EXCHANGE_ID and CREATE_SESSION.
+ *
+ * Map errors cl_cons_state errors to EPROTONOSUPPORT to indicate
+ * other versions of NFS can be tried.
+ */
+static int nfs41_check_session_ready(struct nfs_client *clp)
+{
+        int ret;
+        
+        if (clp->cl_cons_state == NFS_CS_SESSION_INITING) {
+                ret = nfs4_client_recover_expired_lease(clp);
+                if (ret)
+                        return ret;
+        }
+        if (clp->cl_cons_state < NFS_CS_READY)
+                return -EPROTONOSUPPORT;
+        smp_rmb();
+        return 0;
+}
+
+int nfs4_init_session(struct nfs_server *server)
+{
+        struct nfs_client *clp = server->nfs_client;
+        struct nfs4_session *session;
+        unsigned int target_max_rqst_sz = NFS_MAX_FILE_IO_SIZE;
+        unsigned int target_max_resp_sz = NFS_MAX_FILE_IO_SIZE;
+
+        if (!nfs4_has_session(clp))
+                return 0;
+
+        if (server->rsize != 0)
+                target_max_resp_sz = server->rsize;
+        target_max_resp_sz += nfs41_maxread_overhead;
+
+        if (server->wsize != 0)
+                target_max_rqst_sz = server->wsize;
+        target_max_rqst_sz += nfs41_maxwrite_overhead;
+
+        session = clp->cl_session;
+        spin_lock(&clp->cl_lock);
+        if (test_and_clear_bit(NFS4_SESSION_INITING, &session->session_state)) {
+                /* Initialise targets and channel attributes */
+                session->fc_target_max_rqst_sz = target_max_rqst_sz;
+                session->fc_attrs.max_rqst_sz = target_max_rqst_sz;
+                session->fc_target_max_resp_sz = target_max_resp_sz;
+                session->fc_attrs.max_resp_sz = target_max_resp_sz;
+        } else {
+                /* Just adjust the targets */
+                if (target_max_rqst_sz > session->fc_target_max_rqst_sz) {
+                        session->fc_target_max_rqst_sz = target_max_rqst_sz;
+                        set_bit(NFS4CLNT_SESSION_RESET, &clp->cl_state);
+                }
+                if (target_max_resp_sz > session->fc_target_max_resp_sz) {
+                        session->fc_target_max_resp_sz = target_max_resp_sz;
+                        set_bit(NFS4CLNT_SESSION_RESET, &clp->cl_state);
+                }
+        }
+        spin_unlock(&clp->cl_lock);
+
+        if (test_bit(NFS4CLNT_SESSION_RESET, &clp->cl_state))
+                nfs4_schedule_lease_recovery(clp);
+
+        return nfs41_check_session_ready(clp);
+}
+
+int nfs4_init_ds_session(struct nfs_client *clp, unsigned long lease_time)
+{
+        struct nfs4_session *session = clp->cl_session;
+        int ret;
+
+        spin_lock(&clp->cl_lock);
+        if (test_and_clear_bit(NFS4_SESSION_INITING, &session->session_state)) {
+                /*
+                 * Do not set NFS_CS_CHECK_LEASE_TIME instead set the
+                 * DS lease to be equal to the MDS lease.
+                 */
+                clp->cl_lease_time = lease_time;
+                clp->cl_last_renewal = jiffies;
+        }
+        spin_unlock(&clp->cl_lock);
+
+        ret = nfs41_check_session_ready(clp);
+        if (ret)
+                return ret;
+        /* Test for the DS role */
+        if (!is_ds_client(clp))
+                return -ENODEV;
+        return 0;
+}
+EXPORT_SYMBOL_GPL(nfs4_init_ds_session);
+
+
diff --git a/fs/nfs/nfs4session.h b/fs/nfs/nfs4session.h
new file mode 100644
index 000000000000..cb47b1eb0886
--- /dev/null
+++ b/fs/nfs/nfs4session.h
@@ -0,0 +1,35 @@
+/*
+ * fs/nfs/nfs4session.h
+ *
+ * Copyright (c) 2012 Trond Myklebust <Trond.Myklebust@netapp.com>
+ *
+ */
+#ifndef __LINUX_FS_NFS_NFS4SESSION_H
+#define __LINUX_FS_NFS_NFS4SESSION_H
+
+#if defined(CONFIG_NFS_V4_1)
+extern struct nfs4_slot *nfs4_alloc_slot(struct nfs4_slot_table *tbl);
+extern void nfs4_free_slot(struct nfs4_slot_table *tbl, struct nfs4_slot *slot);
+
+extern void nfs41_set_target_slotid(struct nfs4_slot_table *tbl,
+                u32 target_highest_slotid);
+extern void nfs41_update_target_slotid(struct nfs4_slot_table *tbl,
+                struct nfs4_slot *slot,
+                struct nfs4_sequence_res *res);
+
+extern int nfs4_setup_session_slot_tables(struct nfs4_session *ses);
+
+extern struct nfs4_session *nfs4_alloc_session(struct nfs_client *clp);
+extern void nfs4_destroy_session(struct nfs4_session *session);
+extern int nfs4_init_session(struct nfs_server *server);
+extern int nfs4_init_ds_session(struct nfs_client *, unsigned long);
+
+#else /* defined(CONFIG_NFS_V4_1) */
+
+static inline int nfs4_init_session(struct nfs_server *server)
+{
+        return 0;
+}
+
+#endif /* defined(CONFIG_NFS_V4_1) */
+#endif /* __LINUX_FS_NFS_NFS4SESSION_H */