/*
*  Copyright (c) 2001 The Regents of the University of Michigan.
*  All rights reserved.
*
*  Kendrick Smith <kmsmith@umich.edu>
*  Andy Adamson <kandros@umich.edu>
*
*  Redistribution and use in source and binary forms, with or without
*  modification, are permitted provided that the following conditions
*  are met:
*
*  1. Redistributions of source code must retain the above copyright
*     notice, this list of conditions and the following disclaimer.
*  2. Redistributions in binary form must reproduce the above copyright
*     notice, this list of conditions and the following disclaimer in the
*     documentation and/or other materials provided with the distribution.
*  3. Neither the name of the University nor the names of its
*     contributors may be used to endorse or promote products derived
*     from this software without specific prior written permission.
*
*  THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
*  WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
*  MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
*  DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
*  FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
*  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
*  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
*  BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
*  LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
*  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
*  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*
*/

#include <linux/file.h>
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/namei.h>
#include <linux/swap.h>
#include <linux/pagemap.h>
#include <linux/ratelimit.h>
#include <linux/sunrpc/svcauth_gss.h>
#include <linux/sunrpc/addr.h>
#include <linux/jhash.h>
#include "xdr4.h"
#include "xdr4cb.h"
#include "vfs.h"
#include "current_stateid.h"

#include "netns.h"
#include "pnfs.h"

#define NFSDDBG_FACILITY                NFSDDBG_PROC

#define all_ones {{~0,~0},~0}
static const stateid_t one_stateid = {
        .si_generation = ~0,
        .si_opaque = all_ones,
};
static const stateid_t zero_stateid = {
        /* all fields zero */
};
static const stateid_t currentstateid = {
        .si_generation = 1,
};

static u64 current_sessionid = 1;

#define ZERO_STATEID(stateid) (!memcmp((stateid), &zero_stateid, sizeof(stateid_t)))
#define ONE_STATEID(stateid)  (!memcmp((stateid), &one_stateid, sizeof(stateid_t)))
#define CURRENT_STATEID(stateid) (!memcmp((stateid), &currentstateid, sizeof(stateid_t)))

/* forward declarations */
static bool check_for_locks(struct nfs4_file *fp, struct nfs4_lockowner *lowner);
static void nfs4_free_ol_stateid(struct nfs4_stid *stid);

/* Locking: */

/*
 * Currently used for the del_recall_lru and file hash table.  In an
 * effort to decrease the scope of the client_mutex, this spinlock may
 * eventually cover more:
 */
static DEFINE_SPINLOCK(state_lock);

/*
 * A waitqueue for all in-progress 4.0 CLOSE operations that are waiting for
 * the refcount on the open stateid to drop.
 */
static DECLARE_WAIT_QUEUE_HEAD(close_wq);

static struct kmem_cache *openowner_slab;
static struct kmem_cache *lockowner_slab;
static struct kmem_cache *file_slab;
static struct kmem_cache *stateid_slab;
static struct kmem_cache *deleg_slab;
static struct kmem_cache *odstate_slab;

static void free_session(struct nfsd4_session *);

static const struct nfsd4_callback_ops nfsd4_cb_recall_ops;

static bool is_session_dead(struct nfsd4_session *ses)
{
        return ses->se_flags & NFS4_SESSION_DEAD;
}

static __be32 mark_session_dead_locked(struct nfsd4_session *ses, int ref_held_by_me)
{
        if (atomic_read(&ses->se_ref) > ref_held_by_me)
                return nfserr_jukebox;
        ses->se_flags |= NFS4_SESSION_DEAD;
        return nfs_ok;
}

static bool is_client_expired(struct nfs4_client *clp)
{
        return clp->cl_time == 0;
}

static __be32 get_client_locked(struct nfs4_client *clp)
{
        struct nfsd_net *nn = net_generic(clp->net, nfsd_net_id);

        lockdep_assert_held(&nn->client_lock);

        if (is_client_expired(clp))
                return nfserr_expired;
        atomic_inc(&clp->cl_refcount);
        return nfs_ok;
}

/* must be called under the client_lock */
static inline void
renew_client_locked(struct nfs4_client *clp)
{
        struct nfsd_net *nn = net_generic(clp->net, nfsd_net_id);

        if (is_client_expired(clp)) {
                WARN_ON(1);
                printk("%s: client (clientid %08x/%08x) already expired\n",
                        __func__,
                        clp->cl_clientid.cl_boot,
                        clp->cl_clientid.cl_id);
                return;
        }

        dprintk("renewing client (clientid %08x/%08x)\n",
                        clp->cl_clientid.cl_boot,
                        clp->cl_clientid.cl_id);
        list_move_tail(&clp->cl_lru, &nn->client_lru);
        clp->cl_time = get_seconds();
}

static void put_client_renew_locked(struct nfs4_client *clp)
{
        struct nfsd_net *nn = net_generic(clp->net, nfsd_net_id);

        lockdep_assert_held(&nn->client_lock);

        if (!atomic_dec_and_test(&clp->cl_refcount))
                return;
        if (!is_client_expired(clp))
                renew_client_locked(clp);
}

static void put_client_renew(struct nfs4_client *clp)
{
        struct nfsd_net *nn = net_generic(clp->net, nfsd_net_id);

        if (!atomic_dec_and_lock(&clp->cl_refcount, &nn->client_lock))
                return;
        if (!is_client_expired(clp))
                renew_client_locked(clp);
        spin_unlock(&nn->client_lock);
}

static __be32 nfsd4_get_session_locked(struct nfsd4_session *ses)
{
        __be32 status;

        if (is_session_dead(ses))
                return nfserr_badsession;
        status = get_client_locked(ses->se_client);
        if (status)
                return status;
        atomic_inc(&ses->se_ref);
        return nfs_ok;
}

static void nfsd4_put_session_locked(struct nfsd4_session *ses)
{
        struct nfs4_client *clp = ses->se_client;
        struct nfsd_net *nn = net_generic(clp->net, nfsd_net_id);

        lockdep_assert_held(&nn->client_lock);

        if (atomic_dec_and_test(&ses->se_ref) && is_session_dead(ses))
                free_session(ses);
        put_client_renew_locked(clp);
}

static void nfsd4_put_session(struct nfsd4_session *ses)
{
        struct nfs4_client *clp = ses->se_client;
        struct nfsd_net *nn = net_generic(clp->net, nfsd_net_id);

        spin_lock(&nn->client_lock);
        nfsd4_put_session_locked(ses);
        spin_unlock(&nn->client_lock);
}

static inline struct nfs4_stateowner *
nfs4_get_stateowner(struct nfs4_stateowner *sop)
{
        atomic_inc(&sop->so_count);
        return sop;
}

static int
same_owner_str(struct nfs4_stateowner *sop, struct xdr_netobj *owner)
{
        return (sop->so_owner.len == owner->len) &&
                0 == memcmp(sop->so_owner.data, owner->data, owner->len);
}

static struct nfs4_openowner *
find_openstateowner_str_locked(unsigned int hashval, struct nfsd4_open *open,
                        struct nfs4_client *clp)
{
        struct nfs4_stateowner *so;

        lockdep_assert_held(&clp->cl_lock);

        list_for_each_entry(so, &clp->cl_ownerstr_hashtbl[hashval],
                            so_strhash) {
                if (!so->so_is_open_owner)
                        continue;
                if (same_owner_str(so, &open->op_owner))
                        return openowner(nfs4_get_stateowner(so));
        }
        return NULL;
}

static struct nfs4_openowner *
find_openstateowner_str(unsigned int hashval, struct nfsd4_open *open,
                        struct nfs4_client *clp)
{
        struct nfs4_openowner *oo;

        spin_lock(&clp->cl_lock);
        oo = find_openstateowner_str_locked(hashval, open, clp);
        spin_unlock(&clp->cl_lock);
        return oo;
}

static inline u32
opaque_hashval(const void *ptr, int nbytes)
{
        unsigned char *cptr = (unsigned char *) ptr;

        u32 x = 0;
        while (nbytes--) {
                x *= 37;
                x += *cptr++;
        }
        return x;
}

static void nfsd4_free_file_rcu(struct rcu_head *rcu)
{
        struct nfs4_file *fp = container_of(rcu, struct nfs4_file, fi_rcu);

        kmem_cache_free(file_slab, fp);
}

void
put_nfs4_file(struct nfs4_file *fi)
{
        might_lock(&state_lock);

        if (atomic_dec_and_lock(&fi->fi_ref, &state_lock)) {
                hlist_del_rcu(&fi->fi_hash);
                spin_unlock(&state_lock);
                WARN_ON_ONCE(!list_empty(&fi->fi_clnt_odstate));
                WARN_ON_ONCE(!list_empty(&fi->fi_delegations));
                call_rcu(&fi->fi_rcu, nfsd4_free_file_rcu);
        }
}

static struct file *
__nfs4_get_fd(struct nfs4_file *f, int oflag)
{
        if (f->fi_fds[oflag])
                return get_file(f->fi_fds[oflag]);
        return NULL;
}

static struct file *
find_writeable_file_locked(struct nfs4_file *f)
{
        struct file *ret;

        lockdep_assert_held(&f->fi_lock);

        ret = __nfs4_get_fd(f, O_WRONLY);
        if (!ret)
                ret = __nfs4_get_fd(f, O_RDWR);
        return ret;
}

static struct file *
find_writeable_file(struct nfs4_file *f)
{
        struct file *ret;

        spin_lock(&f->fi_lock);
        ret = find_writeable_file_locked(f);
        spin_unlock(&f->fi_lock);

        return ret;
}

static struct file *find_readable_file_locked(struct nfs4_file *f)
{
        struct file *ret;

        lockdep_assert_held(&f->fi_lock);

        ret = __nfs4_get_fd(f, O_RDONLY);
        if (!ret)
                ret = __nfs4_get_fd(f, O_RDWR);
        return ret;
}

static struct file *
find_readable_file(struct nfs4_file *f)
{
        struct file *ret;

        spin_lock(&f->fi_lock);
        ret = find_readable_file_locked(f);
        spin_unlock(&f->fi_lock);

        return ret;
}

struct file *
find_any_file(struct nfs4_file *f)
{
        struct file *ret;

        spin_lock(&f->fi_lock);
        ret = __nfs4_get_fd(f, O_RDWR);
        if (!ret) {
                ret = __nfs4_get_fd(f, O_WRONLY);
                if (!ret)
                        ret = __nfs4_get_fd(f, O_RDONLY);
        }
        spin_unlock(&f->fi_lock);
        return ret;
}

static atomic_long_t num_delegations;
unsigned long max_delegations;

/*
 * Open owner state (share locks)
 */

/* hash tables for lock and open owners */
#define OWNER_HASH_BITS              8
#define OWNER_HASH_SIZE             (1 << OWNER_HASH_BITS)
#define OWNER_HASH_MASK             (OWNER_HASH_SIZE - 1)

static unsigned int ownerstr_hashval(struct xdr_netobj *ownername)
{
        unsigned int ret;

        ret = opaque_hashval(ownername->data, ownername->len);
        return ret & OWNER_HASH_MASK;
}

/* hash table for nfs4_file */
#define FILE_HASH_BITS                   8
#define FILE_HASH_SIZE                  (1 << FILE_HASH_BITS)

static unsigned int nfsd_fh_hashval(struct knfsd_fh *fh)
{
        return jhash2(fh->fh_base.fh_pad, XDR_QUADLEN(fh->fh_size), 0);
}

static unsigned int file_hashval(struct knfsd_fh *fh)
{
        return nfsd_fh_hashval(fh) & (FILE_HASH_SIZE - 1);
}

static struct hlist_head file_hashtbl[FILE_HASH_SIZE];

static void
__nfs4_file_get_access(struct nfs4_file *fp, u32 access)
{
        lockdep_assert_held(&fp->fi_lock);

        if (access & NFS4_SHARE_ACCESS_WRITE)
                atomic_inc(&fp->fi_access[O_WRONLY]);
        if (access & NFS4_SHARE_ACCESS_READ)
                atomic_inc(&fp->fi_access[O_RDONLY]);
}

static __be32
nfs4_file_get_access(struct nfs4_file *fp, u32 access)
{
        lockdep_assert_held(&fp->fi_lock);

        /* Does this access mode make sense? */
        if (access & ~NFS4_SHARE_ACCESS_BOTH)
                return nfserr_inval;

        /* Does it conflict with a deny mode already set? */
        if ((access & fp->fi_share_deny) != 0)
                return nfserr_share_denied;

        __nfs4_file_get_access(fp, access);
        return nfs_ok;
}

static __be32 nfs4_file_check_deny(struct nfs4_file *fp, u32 deny)
{
        /* Common case is that there is no deny mode. */
        if (deny) {
                /* Does this deny mode make sense? */
                if (deny & ~NFS4_SHARE_DENY_BOTH)
                        return nfserr_inval;

                if ((deny & NFS4_SHARE_DENY_READ) &&
                    atomic_read(&fp->fi_access[O_RDONLY]))
                        return nfserr_share_denied;

                if ((deny & NFS4_SHARE_DENY_WRITE) &&
                    atomic_read(&fp->fi_access[O_WRONLY]))
                        return nfserr_share_denied;
        }
        return nfs_ok;
}

static void __nfs4_file_put_access(struct nfs4_file *fp, int oflag)
{
        might_lock(&fp->fi_lock);

        if (atomic_dec_and_lock(&fp->fi_access[oflag], &fp->fi_lock)) {
                struct file *f1 = NULL;
                struct file *f2 = NULL;

                swap(f1, fp->fi_fds[oflag]);
                if (atomic_read(&fp->fi_access[1 - oflag]) == 0)
                        swap(f2, fp->fi_fds[O_RDWR]);
                spin_unlock(&fp->fi_lock);
                if (f1)
                        fput(f1);
                if (f2)
                        fput(f2);
        }
}

static void nfs4_file_put_access(struct nfs4_file *fp, u32 access)
{
        WARN_ON_ONCE(access & ~NFS4_SHARE_ACCESS_BOTH);

        if (access & NFS4_SHARE_ACCESS_WRITE)
                __nfs4_file_put_access(fp, O_WRONLY);
        if (access & NFS4_SHARE_ACCESS_READ)
                __nfs4_file_put_access(fp, O_RDONLY);
}

/*
 * Allocate a new open/delegation state counter. This is needed for
 * pNFS for proper return on close semantics.
 *
 * Note that we only allocate it for pNFS-enabled exports, otherwise
 * all pointers to struct nfs4_clnt_odstate are always NULL.
 */
static struct nfs4_clnt_odstate *
alloc_clnt_odstate(struct nfs4_client *clp)
{
        struct nfs4_clnt_odstate *co;

        co = kmem_cache_zalloc(odstate_slab, GFP_KERNEL);
        if (co) {
                co->co_client = clp;
                atomic_set(&co->co_odcount, 1);
        }
        return co;
}

static void
hash_clnt_odstate_locked(struct nfs4_clnt_odstate *co)
{
        struct nfs4_file *fp = co->co_file;

        lockdep_assert_held(&fp->fi_lock);
        list_add(&co->co_perfile, &fp->fi_clnt_odstate);
}

static inline void
get_clnt_odstate(struct nfs4_clnt_odstate *co)
{
        if (co)
                atomic_inc(&co->co_odcount);
}

static void
put_clnt_odstate(struct nfs4_clnt_odstate *co)
{
        struct nfs4_file *fp;

        if (!co)
                return;

        fp = co->co_file;
        if (atomic_dec_and_lock(&co->co_odcount, &fp->fi_lock)) {
                list_del(&co->co_perfile);
                spin_unlock(&fp->fi_lock);

                nfsd4_return_all_file_layouts(co->co_client, fp);
                kmem_cache_free(odstate_slab, co);
        }
}

static struct nfs4_clnt_odstate *
find_or_hash_clnt_odstate(struct nfs4_file *fp, struct nfs4_clnt_odstate *new)
{
        struct nfs4_clnt_odstate *co;
        struct nfs4_client *cl;

        if (!new)
                return NULL;

        cl = new->co_client;

        spin_lock(&fp->fi_lock);
        list_for_each_entry(co, &fp->fi_clnt_odstate, co_perfile) {
                if (co->co_client == cl) {
                        get_clnt_odstate(co);
                        goto out;
                }
        }
        co = new;
        co->co_file = fp;
        hash_clnt_odstate_locked(new);
out:
        spin_unlock(&fp->fi_lock);
        return co;
}

struct nfs4_stid *nfs4_alloc_stid(struct nfs4_client *cl,
                                         struct kmem_cache *slab)
{
        struct nfs4_stid *stid;
        int new_id;

        stid = kmem_cache_zalloc(slab, GFP_KERNEL);
        if (!stid)
                return NULL;

        idr_preload(GFP_KERNEL);
        spin_lock(&cl->cl_lock);
        new_id = idr_alloc_cyclic(&cl->cl_stateids, stid, 0, 0, GFP_NOWAIT);
        spin_unlock(&cl->cl_lock);
        idr_preload_end();
        if (new_id < 0)
                goto out_free;
        stid->sc_client = cl;
        stid->sc_stateid.si_opaque.so_id = new_id;
        stid->sc_stateid.si_opaque.so_clid = cl->cl_clientid;
        /* Will be incremented before return to client: */
        atomic_set(&stid->sc_count, 1);
        spin_lock_init(&stid->sc_lock);

        /*
         * It shouldn't be a problem to reuse an opaque stateid value.
         * I don't think it is for 4.1.  But with 4.0 I worry that, for
         * example, a stray write retransmission could be accepted by
         * the server when it should have been rejected.  Therefore,
         * adopt a trick from the sctp code to attempt to maximize the
         * amount of time until an id is reused, by ensuring they always
         * "increase" (mod INT_MAX):
         */
        return stid;
out_free:
        kmem_cache_free(slab, stid);
        return NULL;
}

static struct nfs4_ol_stateid * nfs4_alloc_open_stateid(struct nfs4_client *clp)
{
        struct nfs4_stid *stid;
        struct nfs4_ol_stateid *stp;

        stid = nfs4_alloc_stid(clp, stateid_slab);
        if (!stid)
                return NULL;

        stp = openlockstateid(stid);
        stp->st_stid.sc_free = nfs4_free_ol_stateid;
        return stp;
}

static void nfs4_free_deleg(struct nfs4_stid *stid)
{
        kmem_cache_free(deleg_slab, stid);
        atomic_long_dec(&num_delegations);
}

/*
 * When we recall a delegation, we should be careful not to hand it
 * out again straight away.
 * To ensure this we keep a pair of bloom filters ('new' and 'old')
 * in which the filehandles of recalled delegations are "stored".
 * If a filehandle appear in either filter, a delegation is blocked.
 * When a delegation is recalled, the filehandle is stored in the "new"
 * filter.
 * Every 30 seconds we swap the filters and clear the "new" one,
 * unless both are empty of course.
 *
 * Each filter is 256 bits.  We hash the filehandle to 32bit and use the
 * low 3 bytes as hash-table indices.
 *
 * 'blocked_delegations_lock', which is always taken in block_delegations(),
 * is used to manage concurrent access.  Testing does not need the lock
 * except when swapping the two filters.
 */
static DEFINE_SPINLOCK(blocked_delegations_lock);
static struct bloom_pair {
        int     entries, old_entries;
        time_t  swap_time;
        int     new; /* index into 'set' */
        DECLARE_BITMAP(set[2], 256);
} blocked_delegations;

static int delegation_blocked(struct knfsd_fh *fh)
{
        u32 hash;
        struct bloom_pair *bd = &blocked_delegations;

        if (bd->entries == 0)
                return 0;
        if (seconds_since_boot() - bd->swap_time > 30) {
                spin_lock(&blocked_delegations_lock);
                if (seconds_since_boot() - bd->swap_time > 30) {
                        bd->entries -= bd->old_entries;
                        bd->old_entries = bd->entries;
                        memset(bd->set[bd->new], 0,
                               sizeof(bd->set[0]));
                        bd->new = 1-bd->new;
                        bd->swap_time = seconds_since_boot();
                }
                spin_unlock(&blocked_delegations_lock);
        }
        hash = jhash(&fh->fh_base, fh->fh_size, 0);
        if (test_bit(hash&255, bd->set[0]) &&
            test_bit((hash>>8)&255, bd->set[0]) &&
            test_bit((hash>>16)&255, bd->set[0]))
                return 1;

        if (test_bit(hash&255, bd->set[1]) &&
            test_bit((hash>>8)&255, bd->set[1]) &&
            test_bit((hash>>16)&255, bd->set[1]))
                return 1;

        return 0;
}

static void block_delegations(struct knfsd_fh *fh)
{
        u32 hash;
        struct bloom_pair *bd = &blocked_delegations;

        hash = jhash(&fh->fh_base, fh->fh_size, 0);

        spin_lock(&blocked_delegations_lock);
        __set_bit(hash&255, bd->set[bd->new]);
        __set_bit((hash>>8)&255, bd->set[bd->new]);
        __set_bit((hash>>16)&255, bd->set[bd->new]);
        if (bd->entries == 0)
                bd->swap_time = seconds_since_boot();
        bd->entries += 1;
        spin_unlock(&blocked_delegations_lock);
}

static struct nfs4_delegation *
alloc_init_deleg(struct nfs4_client *clp, struct svc_fh *current_fh,
                 struct nfs4_clnt_odstate *odstate)
{
        struct nfs4_delegation *dp;
        long n;

        dprintk("NFSD alloc_init_deleg\n");
        n = atomic_long_inc_return(&num_delegations);
        if (n < 0 || n > max_delegations)
                goto out_dec;
        if (delegation_blocked(&current_fh->fh_handle))
                goto out_dec;
        dp = delegstateid(nfs4_alloc_stid(clp, deleg_slab));
        if (dp == NULL)
                goto out_dec;

        dp->dl_stid.sc_free = nfs4_free_deleg;
        /*
         * delegation seqid's are never incremented.  The 4.1 special
         * meaning of seqid 0 isn't meaningful, really, but let's avoid
         * 0 anyway just for consistency and use 1:
         */
        dp->dl_stid.sc_stateid.si_generation = 1;
        INIT_LIST_HEAD(&dp->dl_perfile);
        INIT_LIST_HEAD(&dp->dl_perclnt);
        INIT_LIST_HEAD(&dp->dl_recall_lru);
        dp->dl_clnt_odstate = odstate;
        get_clnt_odstate(odstate);
        dp->dl_type = NFS4_OPEN_DELEGATE_READ;
        dp->dl_retries = 1;
        nfsd4_init_cb(&dp->dl_recall, dp->dl_stid.sc_client,
                      &nfsd4_cb_recall_ops, NFSPROC4_CLNT_CB_RECALL);
        return dp;
out_dec:
        atomic_long_dec(&num_delegations);
        return NULL;
}

void
nfs4_put_stid(struct nfs4_stid *s)
{
        struct nfs4_file *fp = s->sc_file;
        struct nfs4_client *clp = s->sc_client;

        might_lock(&clp->cl_lock);

        if (!atomic_dec_and_lock(&s->sc_count, &clp->cl_lock)) {
                wake_up_all(&close_wq);
                return;
        }
        idr_remove(&clp->cl_stateids, s->sc_stateid.si_opaque.so_id);
        spin_unlock(&clp->cl_lock);
        s->sc_free(s);
        if (fp)
                put_nfs4_file(fp);
}

void
nfs4_inc_and_copy_stateid(stateid_t *dst, struct nfs4_stid *stid)
{
        stateid_t *src = &stid->sc_stateid;

        spin_lock(&stid->sc_lock);
        if (unlikely(++src->si_generation == 0))
                src->si_generation = 1;
        memcpy(dst, src, sizeof(*dst));
        spin_unlock(&stid->sc_lock);
}

static void nfs4_put_deleg_lease(struct nfs4_file *fp)
{
        struct file *filp = NULL;

        spin_lock(&fp->fi_lock);
        if (fp->fi_deleg_file && --fp->fi_delegees == 0)
                swap(filp, fp->fi_deleg_file);
        spin_unlock(&fp->fi_lock);

        if (filp) {
                vfs_setlease(filp, F_UNLCK, NULL, (void **)&fp);
                fput(filp);
        }
}

void nfs4_unhash_stid(struct nfs4_stid *s)
{
        s->sc_type = 0;
}

/**
 * nfs4_get_existing_delegation - Discover if this delegation already exists
 * @clp:     a pointer to the nfs4_client we're granting a delegation to
 * @fp:      a pointer to the nfs4_file we're granting a delegation on
 *
 * Return:
 *      On success: NULL if an existing delegation was not found.
 *
 *      On error: -EAGAIN if one was previously granted to this nfs4_client
 *                 for this nfs4_file.
 *
 */

static int
nfs4_get_existing_delegation(struct nfs4_client *clp, struct nfs4_file *fp)
{
        struct nfs4_delegation *searchdp = NULL;
        struct nfs4_client *searchclp = NULL;

        lockdep_assert_held(&state_lock);
        lockdep_assert_held(&fp->fi_lock);

        list_for_each_entry(searchdp, &fp->fi_delegations, dl_perfile) {
                searchclp = searchdp->dl_stid.sc_client;
                if (clp == searchclp) {
                        return -EAGAIN;
                }
        }
        return 0;
}

/**
 * hash_delegation_locked - Add a delegation to the appropriate lists
 * @dp:     a pointer to the nfs4_delegation we are adding.
 * @fp:     a pointer to the nfs4_file we're granting a delegation on
 *
 * Return:
 *      On success: NULL if the delegation was successfully hashed.
 *
 *      On error: -EAGAIN if one was previously granted to this
 *                 nfs4_client for this nfs4_file. Delegation is not hashed.
 *
 */

static int
hash_delegation_locked(struct nfs4_delegation *dp, struct nfs4_file *fp)
{
        int status;
        struct nfs4_client *clp = dp->dl_stid.sc_client;

        lockdep_assert_held(&state_lock);
        lockdep_assert_held(&fp->fi_lock);

        status = nfs4_get_existing_delegation(clp, fp);
        if (status)
                return status;
        ++fp->fi_delegees;
        atomic_inc(&dp->dl_stid.sc_count);
        dp->dl_stid.sc_type = NFS4_DELEG_STID;
        list_add(&dp->dl_perfile, &fp->fi_delegations);
        list_add(&dp->dl_perclnt, &clp->cl_delegations);
        return 0;
}

static bool
unhash_delegation_locked(struct nfs4_delegation *dp)
{
        struct nfs4_file *fp = dp->dl_stid.sc_file;

        lockdep_assert_held(&state_lock);

        if (list_empty(&dp->dl_perfile))
                return false;

        dp->dl_stid.sc_type = NFS4_CLOSED_DELEG_STID;
        /* Ensure that deleg break won't try to requeue it */
        ++dp->dl_time;
        spin_lock(&fp->fi_lock);
        list_del_init(&dp->dl_perclnt);
        list_del_init(&dp->dl_recall_lru);
        list_del_init(&dp->dl_perfile);
        spin_unlock(&fp->fi_lock);
        return true;
}

static void destroy_delegation(struct nfs4_delegation *dp)
{
        bool unhashed;

        spin_lock(&state_lock);
        unhashed = unhash_delegation_locked(dp);
        spin_unlock(&state_lock);
        if (unhashed) {
                put_clnt_odstate(dp->dl_clnt_odstate);
                nfs4_put_deleg_lease(dp->dl_stid.sc_file);
                nfs4_put_stid(&dp->dl_stid);
        }
}

static void revoke_delegation(struct nfs4_delegation *dp)
{
        struct nfs4_client *clp = dp->dl_stid.sc_client;

        WARN_ON(!list_empty(&dp->dl_recall_lru));

        put_clnt_odstate(dp->dl_clnt_odstate);
        nfs4_put_deleg_lease(dp->dl_stid.sc_file);

        if (clp->cl_minorversion == 0)
                nfs4_put_stid(&dp->dl_stid);
        else {
                dp->dl_stid.sc_type = NFS4_REVOKED_DELEG_STID;
                spin_lock(&clp->cl_lock);
                list_add(&dp->dl_recall_lru, &clp->cl_revoked);
                spin_unlock(&clp->cl_lock);
        }
}

/* 
 * SETCLIENTID state 
 */

static unsigned int clientid_hashval(u32 id)
{
        return id & CLIENT_HASH_MASK;
}

static unsigned int clientstr_hashval(const char *name)
{
        return opaque_hashval(name, 8) & CLIENT_HASH_MASK;
}

/*
 * We store the NONE, READ, WRITE, and BOTH bits separately in the
 * st_{access,deny}_bmap field of the stateid, in order to track not
 * only what share bits are currently in force, but also what
 * combinations of share bits previous opens have used.  This allows us
 * to enforce the recommendation of rfc 3530 14.2.19 that the server
 * return an error if the client attempt to downgrade to a combination
 * of share bits not explicable by closing some of its previous opens.
 *
 * XXX: This enforcement is actually incomplete, since we don't keep
 * track of access/deny bit combinations; so, e.g., we allow:
 *
 *      OPEN allow read, deny write
 *      OPEN allow both, deny none
 *      DOWNGRADE allow read, deny none
 *
 * which we should reject.
 */
static unsigned int
bmap_to_share_mode(unsigned long bmap) {
        int i;
        unsigned int access = 0;

        for (i = 1; i < 4; i++) {
                if (test_bit(i, &bmap))
                        access |= i;
        }
        return access;
}

/* set share access for a given stateid */
static inline void
set_access(u32 access, struct nfs4_ol_stateid *stp)
{
        unsigned char mask = 1 << access;

        WARN_ON_ONCE(access > NFS4_SHARE_ACCESS_BOTH);
        stp->st_access_bmap |= mask;
}

/* clear share access for a given stateid */
static inline void
clear_access(u32 access, struct nfs4_ol_stateid *stp)
{
        unsigned char mask = 1 << access;

        WARN_ON_ONCE(access > NFS4_SHARE_ACCESS_BOTH);
        stp->st_access_bmap &= ~mask;
}

/* test whether a given stateid has access */
static inline bool
test_access(u32 access, struct nfs4_ol_stateid *stp)
{
        unsigned char mask = 1 << access;

        return (bool)(stp->st_access_bmap & mask);
}

/* set share deny for a given stateid */
static inline void
set_deny(u32 deny, struct nfs4_ol_stateid *stp)
{
        unsigned char mask = 1 << deny;

        WARN_ON_ONCE(deny > NFS4_SHARE_DENY_BOTH);
        stp->st_deny_bmap |= mask;
}

/* clear share deny for a given stateid */
static inline void
clear_deny(u32 deny, struct nfs4_ol_stateid *stp)
{
        unsigned char mask = 1 << deny;

        WARN_ON_ONCE(deny > NFS4_SHARE_DENY_BOTH);
        stp->st_deny_bmap &= ~mask;
}

/* test whether a given stateid is denying specific access */
static inline bool
test_deny(u32 deny, struct nfs4_ol_stateid *stp)
{
        unsigned char mask = 1 << deny;

        return (bool)(stp->st_deny_bmap & mask);
}

static int nfs4_access_to_omode(u32 access)
{
        switch (access & NFS4_SHARE_ACCESS_BOTH) {
        case NFS4_SHARE_ACCESS_READ:
                return O_RDONLY;
        case NFS4_SHARE_ACCESS_WRITE:
                return O_WRONLY;
        case NFS4_SHARE_ACCESS_BOTH:
                return O_RDWR;
        }
        WARN_ON_ONCE(1);
        return O_RDONLY;
}

/*
 * A stateid that had a deny mode associated with it is being released
 * or downgraded. Recalculate the deny mode on the file.
 */
static void
recalculate_deny_mode(struct nfs4_file *fp)
{
        struct nfs4_ol_stateid *stp;

        spin_lock(&fp->fi_lock);
        fp->fi_share_deny = 0;
        list_for_each_entry(stp, &fp->fi_stateids, st_perfile)
                fp->fi_share_deny |= bmap_to_share_mode(stp->st_deny_bmap);
        spin_unlock(&fp->fi_lock);
}

static void
reset_union_bmap_deny(u32 deny, struct nfs4_ol_stateid *stp)
{
        int i;
        bool change = false;

        for (i = 1; i < 4; i++) {
                if ((i & deny) != i) {
                        change = true;
                        clear_deny(i, stp);
                }
        }

        /* Recalculate per-file deny mode if there was a change */
        if (change)
                recalculate_deny_mode(stp->st_stid.sc_file);
}

/* release all access and file references for a given stateid */
static void
release_all_access(struct nfs4_ol_stateid *stp)
{
        int i;
        struct nfs4_file *fp = stp->st_stid.sc_file;

        if (fp && stp->st_deny_bmap != 0)
                recalculate_deny_mode(fp);

        for (i = 1; i < 4; i++) {
                if (test_access(i, stp))
                        nfs4_file_put_access(stp->st_stid.sc_file, i);
                clear_access(i, stp);
        }
}

static inline void nfs4_free_stateowner(struct nfs4_stateowner *sop)
{
        kfree(sop->so_owner.data);
        sop->so_ops->so_free(sop);
}

static void nfs4_put_stateowner(struct nfs4_stateowner *sop)
{
        struct nfs4_client *clp = sop->so_client;

        might_lock(&clp->cl_lock);

        if (!atomic_dec_and_lock(&sop->so_count, &clp->cl_lock))
                return;
        sop->so_ops->so_unhash(sop);
        spin_unlock(&clp->cl_lock);
        nfs4_free_stateowner(sop);
}

static bool unhash_ol_stateid(struct nfs4_ol_stateid *stp)
{
        struct nfs4_file *fp = stp->st_stid.sc_file;

        lockdep_assert_held(&stp->st_stateowner->so_client->cl_lock);

        if (list_empty(&stp->st_perfile))
                return false;

        spin_lock(&fp->fi_lock);
        list_del_init(&stp->st_perfile);
        spin_unlock(&fp->fi_lock);
        list_del(&stp->st_perstateowner);
        return true;
}

static void nfs4_free_ol_stateid(struct nfs4_stid *stid)
{
        struct nfs4_ol_stateid *stp = openlockstateid(stid);

        put_clnt_odstate(stp->st_clnt_odstate);
        release_all_access(stp);
        if (stp->st_stateowner)
                nfs4_put_stateowner(stp->st_stateowner);
        kmem_cache_free(stateid_slab, stid);
}

static void nfs4_free_lock_stateid(struct nfs4_stid *stid)
{
        struct nfs4_ol_stateid *stp = openlockstateid(stid);
        struct nfs4_lockowner *lo = lockowner(stp->st_stateowner);
        struct file *file;

        file = find_any_file(stp->st_stid.sc_file);
        if (file)
                filp_close(file, (fl_owner_t)lo);
        nfs4_free_ol_stateid(stid);
}

/*
 * Put the persistent reference to an already unhashed generic stateid, while
 * holding the cl_lock. If it's the last reference, then put it onto the
 * reaplist for later destruction.
 */
static void put_ol_stateid_locked(struct nfs4_ol_stateid *stp,
                                       struct list_head *reaplist)
{
        struct nfs4_stid *s = &stp->st_stid;
        struct nfs4_client *clp = s->sc_client;

        lockdep_assert_held(&clp->cl_lock);

        WARN_ON_ONCE(!list_empty(&stp->st_locks));

        if (!atomic_dec_and_test(&s->sc_count)) {
                wake_up_all(&close_wq);
                return;
        }

        idr_remove(&clp->cl_stateids, s->sc_stateid.si_opaque.so_id);
        list_add(&stp->st_locks, reaplist);
}

static bool unhash_lock_stateid(struct nfs4_ol_stateid *stp)
{
        struct nfs4_openowner *oo = openowner(stp->st_openstp->st_stateowner);

        lockdep_assert_held(&oo->oo_owner.so_client->cl_lock);

        list_del_init(&stp->st_locks);
        nfs4_unhash_stid(&stp->st_stid);
        return unhash_ol_stateid(stp);
}

static void release_lock_stateid(struct nfs4_ol_stateid *stp)
{
        struct nfs4_openowner *oo = openowner(stp->st_openstp->st_stateowner);
        bool unhashed;

        spin_lock(&oo->oo_owner.so_client->cl_lock);
        unhashed = unhash_lock_stateid(stp);
        spin_unlock(&oo->oo_owner.so_client->cl_lock);
        if (unhashed)
                nfs4_put_stid(&stp->st_stid);
}

static void unhash_lockowner_locked(struct nfs4_lockowner *lo)
{
        struct nfs4_client *clp = lo->lo_owner.so_client;

        lockdep_assert_held(&clp->cl_lock);

        list_del_init(&lo->lo_owner.so_strhash);
}

/*
 * Free a list of generic stateids that were collected earlier after being
 * fully unhashed.
 */
static void
free_ol_stateid_reaplist(struct list_head *reaplist)
{
        struct nfs4_ol_stateid *stp;
        struct nfs4_file *fp;

        might_sleep();

        while (!list_empty(reaplist)) {
                stp = list_first_entry(reaplist, struct nfs4_ol_stateid,
                                       st_locks);
                list_del(&stp->st_locks);
                fp = stp->st_stid.sc_file;
                stp->st_stid.sc_free(&stp->st_stid);
                if (fp)
                        put_nfs4_file(fp);
        }
}

static void release_lockowner(struct nfs4_lockowner *lo)
{
        struct nfs4_client *clp = lo->lo_owner.so_client;
        struct nfs4_ol_stateid *stp;
        struct list_head reaplist;

        INIT_LIST_HEAD(&reaplist);

        spin_lock(&clp->cl_lock);
        unhash_lockowner_locked(lo);
        while (!list_empty(&lo->lo_owner.so_stateids)) {
                stp = list_first_entry(&lo->lo_owner.so_stateids,
                                struct nfs4_ol_stateid, st_perstateowner);
                WARN_ON(!unhash_lock_stateid(stp));
                put_ol_stateid_locked(stp, &reaplist);
        }
        spin_unlock(&clp->cl_lock);
        free_ol_stateid_reaplist(&reaplist);
        nfs4_put_stateowner(&lo->lo_owner);
}

static void release_open_stateid_locks(struct nfs4_ol_stateid *open_stp,
                                       struct list_head *reaplist)
{
        struct nfs4_ol_stateid *stp;

        lockdep_assert_held(&open_stp->st_stid.sc_client->cl_lock);

        while (!list_empty(&open_stp->st_locks)) {
                stp = list_entry(open_stp->st_locks.next,
                                struct nfs4_ol_stateid, st_locks);
                WARN_ON(!unhash_lock_stateid(stp));
                put_ol_stateid_locked(stp, reaplist);
        }
}

static bool unhash_open_stateid(struct nfs4_ol_stateid *stp,
                                struct list_head *reaplist)
{
        bool unhashed;

        lockdep_assert_held(&stp->st_stid.sc_client->cl_lock);

        unhashed = unhash_ol_stateid(stp);
        release_open_stateid_locks(stp, reaplist);
        return unhashed;
}

static void release_open_stateid(struct nfs4_ol_stateid *stp)
{
        LIST_HEAD(reaplist);

        spin_lock(&stp->st_stid.sc_client->cl_lock);
        if (unhash_open_stateid(stp, &reaplist))
                put_ol_stateid_locked(stp, &reaplist);
        spin_unlock(&stp->st_stid.sc_client->cl_lock);
        free_ol_stateid_reaplist(&reaplist);
}

static void unhash_openowner_locked(struct nfs4_openowner *oo)
{
        struct nfs4_client *clp = oo->oo_owner.so_client;

        lockdep_assert_held(&clp->cl_lock);

        list_del_init(&oo->oo_owner.so_strhash);
        list_del_init(&oo->oo_perclient);
}

static void release_last_closed_stateid(struct nfs4_openowner *oo)
{
        struct nfsd_net *nn = net_generic(oo->oo_owner.so_client->net,
                                          nfsd_net_id);
        struct nfs4_ol_stateid *s;

        spin_lock(&nn->client_lock);
        s = oo->oo_last_closed_stid;
        if (s) {
                list_del_init(&oo->oo_close_lru);
                oo->oo_last_closed_stid = NULL;
        }
        spin_unlock(&nn->client_lock);
        if (s)
                nfs4_put_stid(&s->st_stid);
}

static void release_openowner(struct nfs4_openowner *oo)
{
        struct nfs4_ol_stateid *stp;
        struct nfs4_client *clp = oo->oo_owner.so_client;
        struct list_head reaplist;

        INIT_LIST_HEAD(&reaplist);

        spin_lock(&clp->cl_lock);
        unhash_openowner_locked(oo);
        while (!list_empty(&oo->oo_owner.so_stateids)) {
                stp = list_first_entry(&oo->oo_owner.so_stateids,
                                struct nfs4_ol_stateid, st_perstateowner);
                if (unhash_open_stateid(stp, &reaplist))
                        put_ol_stateid_locked(stp, &reaplist);
        }
        spin_unlock(&clp->cl_lock);
        free_ol_stateid_reaplist(&reaplist);
        release_last_closed_stateid(oo);
        nfs4_put_stateowner(&oo->oo_owner);
}

static inline int
hash_sessionid(struct nfs4_sessionid *sessionid)
{
        struct nfsd4_sessionid *sid = (struct nfsd4_sessionid *)sessionid;

        return sid->sequence % SESSION_HASH_SIZE;
}

#ifdef CONFIG_SUNRPC_DEBUG
static inline void
dump_sessionid(const char *fn, struct nfs4_sessionid *sessionid)
{
        u32 *ptr = (u32 *)(&sessionid->data[0]);
        dprintk("%s: %u:%u:%u:%u\n", fn, ptr[0], ptr[1], ptr[2], ptr[3]);
}
#else
static inline void
dump_sessionid(const char *fn, struct nfs4_sessionid *sessionid)
{
}
#endif

/*
 * Bump the seqid on cstate->replay_owner, and clear replay_owner if it
 * won't be used for replay.
 */
void nfsd4_bump_seqid(struct nfsd4_compound_state *cstate, __be32 nfserr)
{
        struct nfs4_stateowner *so = cstate->replay_owner;

        if (nfserr == nfserr_replay_me)
                return;

        if (!seqid_mutating_err(ntohl(nfserr))) {
                nfsd4_cstate_clear_replay(cstate);
                return;
        }
        if (!so)
                return;
        if (so->so_is_open_owner)
                release_last_closed_stateid(openowner(so));
        so->so_seqid++;
        return;
}

static void
gen_sessionid(struct nfsd4_session *ses)
{
        struct nfs4_client *clp = ses->se_client;
        struct nfsd4_sessionid *sid;

        sid = (struct nfsd4_sessionid *)ses->se_sessionid.data;
        sid->clientid = clp->cl_clientid;
        sid->sequence = current_sessionid++;
        sid->reserved = 0;
}

/*
 * The protocol defines ca_maxresponssize_cached to include the size of
 * the rpc header, but all we need to cache is the data starting after
 * the end of the initial SEQUENCE operation--the rest we regenerate
 * each time.  Therefore we can advertise a ca_maxresponssize_cached
 * value that is the number of bytes in our cache plus a few additional
 * bytes.  In order to stay on the safe side, and not promise more than
 * we can cache, those additional bytes must be the minimum possible: 24
 * bytes of rpc header (xid through accept state, with AUTH_NULL
 * verifier), 12 for the compound header (with zero-length tag), and 44
 * for the SEQUENCE op response:
 */
#define NFSD_MIN_HDR_SEQ_SZ  (24 + 12 + 44)

static void
free_session_slots(struct nfsd4_session *ses)
{
        int i;

        for (i = 0; i < ses->se_fchannel.maxreqs; i++)
                kfree(ses->se_slots[i]);
}

/*
 * We don't actually need to cache the rpc and session headers, so we
 * can allocate a little less for each slot:
 */
static inline u32 slot_bytes(struct nfsd4_channel_attrs *ca)
{
        u32 size;

        if (ca->maxresp_cached < NFSD_MIN_HDR_SEQ_SZ)
                size = 0;
        else
                size = ca->maxresp_cached - NFSD_MIN_HDR_SEQ_SZ;
        return size + sizeof(struct nfsd4_slot);
}

/*
 * XXX: If we run out of reserved DRC memory we could (up to a point)
 * re-negotiate active sessions and reduce their slot usage to make
 * room for new connections. For now we just fail the create session.
 */
static u32 nfsd4_get_drc_mem(struct nfsd4_channel_attrs *ca)
{
        u32 slotsize = slot_bytes(ca);
        u32 num = ca->maxreqs;
        int avail;

        spin_lock(&nfsd_drc_lock);
        avail = min((unsigned long)NFSD_MAX_MEM_PER_SESSION,
                    nfsd_drc_max_mem - nfsd_drc_mem_used);
        num = min_t(int, num, avail / slotsize);
        nfsd_drc_mem_used += num * slotsize;
        spin_unlock(&nfsd_drc_lock);

        return num;
}

static void nfsd4_put_drc_mem(struct nfsd4_channel_attrs *ca)
{
        int slotsize = slot_bytes(ca);

        spin_lock(&nfsd_drc_lock);
        nfsd_drc_mem_used -= slotsize * ca->maxreqs;
        spin_unlock(&nfsd_drc_lock);
}

static struct nfsd4_session *alloc_session(struct nfsd4_channel_attrs *fattrs,
                                           struct nfsd4_channel_attrs *battrs)
{
        int numslots = fattrs->maxreqs;
        int slotsize = slot_bytes(fattrs);
        struct nfsd4_session *new;
        int mem, i;

        BUILD_BUG_ON(NFSD_MAX_SLOTS_PER_SESSION * sizeof(struct nfsd4_slot *)
                        + sizeof(struct nfsd4_session) > PAGE_SIZE);
        mem = numslots * sizeof(struct nfsd4_slot *);

        new = kzalloc(sizeof(*new) + mem, GFP_KERNEL);
        if (!new)
                return NULL;
        /* allocate each struct nfsd4_slot and data cache in one piece */
        for (i = 0; i < numslots; i++) {
                new->se_slots[i] = kzalloc(slotsize, GFP_KERNEL);
                if (!new->se_slots[i])
                        goto out_free;
        }

        memcpy(&new->se_fchannel, fattrs, sizeof(struct nfsd4_channel_attrs));
        memcpy(&new->se_bchannel, battrs, sizeof(struct nfsd4_channel_attrs));

        return new;
out_free:
        while (i--)
                kfree(new->se_slots[i]);
        kfree(new);
        return NULL;
}

static void free_conn(struct nfsd4_conn *c)
{
        svc_xprt_put(c->cn_xprt);
        kfree(c);
}

static void nfsd4_conn_lost(struct svc_xpt_user *u)
{
        struct nfsd4_conn *c = container_of(u, struct nfsd4_conn, cn_xpt_user);
        struct nfs4_client *clp = c->cn_session->se_client;

        spin_lock(&clp->cl_lock);
        if (!list_empty(&c->cn_persession)) {
                list_del(&c->cn_persession);
                free_conn(c);
        }
        nfsd4_probe_callback(clp);
        spin_unlock(&clp->cl_lock);
}

static struct nfsd4_conn *alloc_conn(struct svc_rqst *rqstp, u32 flags)
{
        struct nfsd4_conn *conn;

        conn = kmalloc(sizeof(struct nfsd4_conn), GFP_KERNEL);
        if (!conn)
                return NULL;
        svc_xprt_get(rqstp->rq_xprt);
        conn->cn_xprt = rqstp->rq_xprt;
        conn->cn_flags = flags;
        INIT_LIST_HEAD(&conn->cn_xpt_user.list);
        return conn;
}

static void __nfsd4_hash_conn(struct nfsd4_conn *conn, struct nfsd4_session *ses)
{
        conn->cn_session = ses;
        list_add(&conn->cn_persession, &ses->se_conns);
}

static void nfsd4_hash_conn(struct nfsd4_conn *conn, struct nfsd4_session *ses)
{
        struct nfs4_client *clp = ses->se_client;

        spin_lock(&clp->cl_lock);
        __nfsd4_hash_conn(conn, ses);
        spin_unlock(&clp->cl_lock);
}

static int nfsd4_register_conn(struct nfsd4_conn *conn)
{
        conn->cn_xpt_user.callback = nfsd4_conn_lost;
        return register_xpt_user(conn->cn_xprt, &conn->cn_xpt_user);
}

static void nfsd4_init_conn(struct svc_rqst *rqstp, struct nfsd4_conn *conn, struct nfsd4_session *ses)
{
        int ret;

        nfsd4_hash_conn(conn, ses);
        ret = nfsd4_register_conn(conn);
        if (ret)
                /* oops; xprt is already down: */
                nfsd4_conn_lost(&conn->cn_xpt_user);
        /* We may have gained or lost a callback channel: */
        nfsd4_probe_callback_sync(ses->se_client);
}

static struct nfsd4_conn *alloc_conn_from_crses(struct svc_rqst *rqstp, struct nfsd4_create_session *cses)
{
        u32 dir = NFS4_CDFC4_FORE;

        if (cses->flags & SESSION4_BACK_CHAN)
                dir |= NFS4_CDFC4_BACK;
        return alloc_conn(rqstp, dir);
}

/* must be called under client_lock */
static void nfsd4_del_conns(struct nfsd4_session *s)
{
        struct nfs4_client *clp = s->se_client;
        struct nfsd4_conn *c;

        spin_lock(&clp->cl_lock);
        while (!list_empty(&s->se_conns)) {
                c = list_first_entry(&s->se_conns, struct nfsd4_conn, cn_persession);
                list_del_init(&c->cn_persession);
                spin_unlock(&clp->cl_lock);

                unregister_xpt_user(c->cn_xprt, &c->cn_xpt_user);
                free_conn(c);

                spin_lock(&clp->cl_lock);
        }
        spin_unlock(&clp->cl_lock);
}

static void __free_session(struct nfsd4_session *ses)
{
        free_session_slots(ses);
        kfree(ses);
}

static void free_session(struct nfsd4_session *ses)
{
        nfsd4_del_conns(ses);
        nfsd4_put_drc_mem(&ses->se_fchannel);
        __free_session(ses);
}

static void init_session(struct svc_rqst *rqstp, struct nfsd4_session *new, struct nfs4_client *clp, struct nfsd4_create_session *cses)
{
        int idx;
        struct nfsd_net *nn = net_generic(SVC_NET(rqstp), nfsd_net_id);

        new->se_client = clp;
        gen_sessionid(new);

        INIT_LIST_HEAD(&new->se_conns);

        new->se_cb_seq_nr = 1;
        new->se_flags = cses->flags;
        new->se_cb_prog = cses->callback_prog;
        new->se_cb_sec = cses->cb_sec;
        atomic_set(&new->se_ref, 0);
        idx = hash_sessionid(&new->se_sessionid);
        list_add(&new->se_hash, &nn->sessionid_hashtbl[idx]);
        spin_lock(&clp->cl_lock);
        list_add(&new->se_perclnt, &clp->cl_sessions);
        spin_unlock(&clp->cl_lock);

        {
                struct sockaddr *sa = svc_addr(rqstp);
                /*
                 * This is a little silly; with sessions there's no real
                 * use for the callback address.  Use the peer address
                 * as a reasonable default for now, but consider fixing
                 * the rpc client not to require an address in the
                 * future:
                 */
                rpc_copy_addr((struct sockaddr *)&clp->cl_cb_conn.cb_addr, sa);
                clp->cl_cb_conn.cb_addrlen = svc_addr_len(sa);
        }
}

/* caller must hold client_lock */
static struct nfsd4_session *
__find_in_sessionid_hashtbl(struct nfs4_sessionid *sessionid, struct net *net)
{
        struct nfsd4_session *elem;
        int idx;
        struct nfsd_net *nn = net_generic(net, nfsd_net_id);

        lockdep_assert_held(&nn->client_lock);

        dump_sessionid(__func__, sessionid);
        idx = hash_sessionid(sessionid);
        /* Search in the appropriate list */
        list_for_each_entry(elem, &nn->sessionid_hashtbl[idx], se_hash) {
                if (!memcmp(elem->se_sessionid.data, sessionid->data,
                            NFS4_MAX_SESSIONID_LEN)) {
                        return elem;
                }
        }

        dprintk("%s: session not found\n", __func__);
        return NULL;
}

static struct nfsd4_session *
find_in_sessionid_hashtbl(struct nfs4_sessionid *sessionid, struct net *net,
                __be32 *ret)
{
        struct nfsd4_session *session;
        __be32 status = nfserr_badsession;

        session = __find_in_sessionid_hashtbl(sessionid, net);
        if (!session)
                goto out;
        status = nfsd4_get_session_locked(session);
        if (status)
                session = NULL;
out:
        *ret = status;
        return session;
}

/* caller must hold client_lock */
static void
unhash_session(struct nfsd4_session *ses)
{
        struct nfs4_client *clp = ses->se_client;
        struct nfsd_net *nn = net_generic(clp->net, nfsd_net_id);

        lockdep_assert_held(&nn->client_lock);

        list_del(&ses->se_hash);
        spin_lock(&ses->se_client->cl_lock);
        list_del(&ses->se_perclnt);
        spin_unlock(&ses->se_client->cl_lock);
}

/* SETCLIENTID and SETCLIENTID_CONFIRM Helper functions */
static int
STALE_CLIENTID(clientid_t *clid, struct nfsd_net *nn)
{
        /*
         * We're assuming the clid was not given out from a boot
         * precisely 2^32 (about 136 years) before this one.  That seems
         * a safe assumption:
         */
        if (clid->cl_boot == (u32)nn->boot_time)
                return 0;
        dprintk("NFSD stale clientid (%08x/%08x) boot_time %08lx\n",
                clid->cl_boot, clid->cl_id, nn->boot_time);
        return 1;
}

/* 
 * XXX Should we use a slab cache ?
 * This type of memory management is somewhat inefficient, but we use it
 * anyway since SETCLIENTID is not a common operation.
 */
static struct nfs4_client *alloc_client(struct xdr_netobj name)
{
        struct nfs4_client *clp;
        int i;

        clp = kzalloc(sizeof(struct nfs4_client), GFP_KERNEL);
        if (clp == NULL)
                return NULL;
        clp->cl_name.data = kmemdup(name.data, name.len, GFP_KERNEL);
        if (clp->cl_name.data == NULL)
                goto err_no_name;
        clp->cl_ownerstr_hashtbl = kmalloc(sizeof(struct list_head) *
                        OWNER_HASH_SIZE, GFP_KERNEL);
        if (!clp->cl_ownerstr_hashtbl)
                goto err_no_hashtbl;
        for (i = 0; i < OWNER_HASH_SIZE; i++)
                INIT_LIST_HEAD(&clp->cl_ownerstr_hashtbl[i]);
        clp->cl_name.len = name.len;
        INIT_LIST_HEAD(&clp->cl_sessions);
        idr_init(&clp->cl_stateids);
        atomic_set(&clp->cl_refcount, 0);
        clp->cl_cb_state = NFSD4_CB_UNKNOWN;
        INIT_LIST_HEAD(&clp->cl_idhash);
        INIT_LIST_HEAD(&clp->cl_openowners);
        INIT_LIST_HEAD(&clp->cl_delegations);
        INIT_LIST_HEAD(&clp->cl_lru);
        INIT_LIST_HEAD(&clp->cl_revoked);
#ifdef CONFIG_NFSD_PNFS
        INIT_LIST_HEAD(&clp->cl_lo_states);
#endif
        spin_lock_init(&clp->cl_lock);
        rpc_init_wait_queue(&clp->cl_cb_waitq, "Backchannel slot table");
        return clp;
err_no_hashtbl:
        kfree(clp->cl_name.data);
err_no_name:
        kfree(clp);
        return NULL;
}

static void
free_client(struct nfs4_client *clp)
{
        while (!list_empty(&clp->cl_sessions)) {
                struct nfsd4_session *ses;
                ses = list_entry(clp->cl_sessions.next, struct nfsd4_session,
                                se_perclnt);
                list_del(&ses->se_perclnt);
                WARN_ON_ONCE(atomic_read(&ses->se_ref));
                free_session(ses);
        }
        rpc_destroy_wait_queue(&clp->cl_cb_waitq);
        free_svc_cred(&clp->cl_cred);
        kfree(clp->cl_ownerstr_hashtbl);
        kfree(clp->cl_name.data);
        idr_destroy(&clp->cl_stateids);
        kfree(clp);
}

/* must be called under the client_lock */
static void
unhash_client_locked(struct nfs4_client *clp)
{
        struct nfsd_net *nn = net_generic(clp->net, nfsd_net_id);
        struct nfsd4_session *ses;

        lockdep_assert_held(&nn->client_lock);

        /* Mark the client as expired! */
        clp->cl_time = 0;
        /* Make it invisible */
        if (!list_empty(&clp->cl_idhash)) {
                list_del_init(&clp->cl_idhash);
                if (test_bit(NFSD4_CLIENT_CONFIRMED, &clp->cl_flags))
                        rb_erase(&clp->cl_namenode, &nn->conf_name_tree);
                else
                        rb_erase(&clp->cl_namenode, &nn->unconf_name_tree);
        }
        list_del_init(&clp->cl_lru);
        spin_lock(&clp->cl_lock);
        list_for_each_entry(ses, &clp->cl_sessions, se_perclnt)
                list_del_init(&ses->se_hash);
        spin_unlock(&clp->cl_lock);
}

static void
unhash_client(struct nfs4_client *clp)
{
        struct nfsd_net *nn = net_generic(clp->net, nfsd_net_id);

        spin_lock(&nn->client_lock);
        unhash_client_locked(clp);
        spin_unlock(&nn->client_lock);
}

static __be32 mark_client_expired_locked(struct nfs4_client *clp)
{
        if (atomic_read(&clp->cl_refcount))
                return nfserr_jukebox;
        unhash_client_locked(clp);
        return nfs_ok;
}

static void
__destroy_client(struct nfs4_client *clp)
{
        struct nfs4_openowner *oo;
        struct nfs4_delegation *dp;
        struct list_head reaplist;

        INIT_LIST_HEAD(&reaplist);
        spin_lock(&state_lock);
        while (!list_empty(&clp->cl_delegations)) {
                dp = list_entry(clp->cl_delegations.next, struct nfs4_delegation, dl_perclnt);
                WARN_ON(!unhash_delegation_locked(dp));
                list_add(&dp->dl_recall_lru, &reaplist);
        }
        spin_unlock(&state_lock);
        while (!list_empty(&reaplist)) {
                dp = list_entry(reaplist.next, struct nfs4_delegation, dl_recall_lru);
                list_del_init(&dp->dl_recall_lru);
                put_clnt_odstate(dp->dl_clnt_odstate);
                nfs4_put_deleg_lease(dp->dl_stid.sc_file);
                nfs4_put_stid(&dp->dl_stid);
        }
        while (!list_empty(&clp->cl_revoked)) {
                dp = list_entry(clp->cl_revoked.next, struct nfs4_delegation, dl_recall_lru);
                list_del_init(&dp->dl_recall_lru);
                nfs4_put_stid(&dp->dl_stid);
        }
        while (!list_empty(&clp->cl_openowners)) {
                oo = list_entry(clp->cl_openowners.next, struct nfs4_openowner, oo_perclient);
                nfs4_get_stateowner(&oo->oo_owner);
                release_openowner(oo);
        }
        nfsd4_return_all_client_layouts(clp);
        nfsd4_shutdown_callback(clp);
        if (clp->cl_cb_conn.cb_xprt)
                svc_xprt_put(clp->cl_cb_conn.cb_xprt);
        free_client(clp);
}

static void
destroy_client(struct nfs4_client *clp)
{
        unhash_client(clp);
        __destroy_client(clp);
}

static void expire_client(struct nfs4_client *clp)
{
        unhash_client(clp);
        nfsd4_client_record_remove(clp);
        __destroy_client(clp);
}

static void copy_verf(struct nfs4_client *target, nfs4_verifier *source)
{
        memcpy(target->cl_verifier.data, source->data,
                        sizeof(target->cl_verifier.data));
}

static void copy_clid(struct nfs4_client *target, struct nfs4_client *source)
{
        target->cl_clientid.cl_boot = source->cl_clientid.cl_boot; 
        target->cl_clientid.cl_id = source->cl_clientid.cl_id; 
}

int strdup_if_nonnull(char **target, char *source)
{
        if (source) {
                *target = kstrdup(source, GFP_KERNEL);
                if (!*target)
                        return -ENOMEM;
        } else
                *target = NULL;
        return 0;
}

static int copy_cred(struct svc_cred *target, struct svc_cred *source)
{
        int ret;

        ret = strdup_if_nonnull(&target->cr_principal, source->cr_principal);
        if (ret)
                return ret;
        ret = strdup_if_nonnull(&target->cr_raw_principal,
                                        source->cr_raw_principal);
        if (ret)
                return ret;
        target->cr_flavor = source->cr_flavor;
        target->cr_uid = source->cr_uid;
        target->cr_gid = source->cr_gid;
        target->cr_group_info = source->cr_group_info;
        get_group_info(target->cr_group_info);
        target->cr_gss_mech = source->cr_gss_mech;
        if (source->cr_gss_mech)
                gss_mech_get(source->cr_gss_mech);
        return 0;
}

static int
compare_blob(const struct xdr_netobj *o1, const struct xdr_netobj *o2)
{
        if (o1->len < o2->len)
                return -1;
        if (o1->len > o2->len)
                return 1;
        return memcmp(o1->data, o2->data, o1->len);
}

static int same_name(const char *n1, const char *n2)
{
        return 0 == memcmp(n1, n2, HEXDIR_LEN);
}

static int
same_verf(nfs4_verifier *v1, nfs4_verifier *v2)
{
        return 0 == memcmp(v1->data, v2->data, sizeof(v1->data));
}

static int
same_clid(clientid_t *cl1, clientid_t *cl2)
{
        return (cl1->cl_boot == cl2->cl_boot) && (cl1->cl_id == cl2->cl_id);
}

static bool groups_equal(struct group_info *g1, struct group_info *g2)
{
        int i;

        if (g1->ngroups != g2->ngroups)
                return false;
        for (i=0; i<g1->ngroups; i++)
                if (!gid_eq(GROUP_AT(g1, i), GROUP_AT(g2, i)))
                        return false;
        return true;
}

/*
 * RFC 3530 language requires clid_inuse be returned when the
 * "principal" associated with a requests differs from that previously
 * used.  We use uid, gid's, and gss principal string as our best
 * approximation.  We also don't want to allow non-gss use of a client
 * established using gss: in theory cr_principal should catch that
 * change, but in practice cr_principal can be null even in the gss case
 * since gssd doesn't always pass down a principal string.
 */
static bool is_gss_cred(struct svc_cred *cr)
{
        /* Is cr_flavor one of the gss "pseudoflavors"?: */
        return (cr->cr_flavor > RPC_AUTH_MAXFLAVOR);
}


static bool
same_creds(struct svc_cred *cr1, struct svc_cred *cr2)
{
        if ((is_gss_cred(cr1) != is_gss_cred(cr2))
                || (!uid_eq(cr1->cr_uid, cr2->cr_uid))
                || (!gid_eq(cr1->cr_gid, cr2->cr_gid))
                || !groups_equal(cr1->cr_group_info, cr2->cr_group_info))
                return false;
        if (cr1->cr_principal == cr2->cr_principal)
                return true;
        if (!cr1->cr_principal || !cr2->cr_principal)
                return false;
        return 0 == strcmp(cr1->cr_principal, cr2->cr_principal);
}

static bool svc_rqst_integrity_protected(struct svc_rqst *rqstp)
{
        struct svc_cred *cr = &rqstp->rq_cred;
        u32 service;

        if (!cr->cr_gss_mech)
                return false;
        service = gss_pseudoflavor_to_service(cr->cr_gss_mech, cr->cr_flavor);
        return service == RPC_GSS_SVC_INTEGRITY ||
               service == RPC_GSS_SVC_PRIVACY;
}

static bool mach_creds_match(struct nfs4_client *cl, struct svc_rqst *rqstp)
{
        struct svc_cred *cr = &rqstp->rq_cred;

        if (!cl->cl_mach_cred)
                return true;
        if (cl->cl_cred.cr_gss_mech != cr->cr_gss_mech)
                return false;
        if (!svc_rqst_integrity_protected(rqstp))
                return false;
        if (cl->cl_cred.cr_raw_principal)
                return 0 == strcmp(cl->cl_cred.cr_raw_principal,
                                                cr->cr_raw_principal);
        if (!cr->cr_principal)
                return false;
        return 0 == strcmp(cl->cl_cred.cr_principal, cr->cr_principal);
}

static void gen_confirm(struct nfs4_client *clp, struct nfsd_net *nn)
{
        __be32 verf[2];

        /*
         * This is opaque to client, so no need to byte-swap. Use
         * __force to keep sparse happy
         */

        verf[0] = (__force __be32)get_seconds();
        verf[1] = (__force __be32)nn->clverifier_counter++;
        memcpy(clp->cl_confirm.data, verf, sizeof(clp->cl_confirm.data));
}

static void gen_clid(struct nfs4_client *clp, struct nfsd_net *nn)
{
        clp->cl_clientid.cl_boot = nn->boot_time;
        clp->cl_clientid.cl_id = nn->clientid_counter++;
        gen_confirm(clp, nn);
}

static struct nfs4_stid *
find_stateid_locked(struct nfs4_client *cl, stateid_t *t)
{
        struct nfs4_stid *ret;

        ret = idr_find(&cl->cl_stateids, t->si_opaque.so_id);
        if (!ret || !ret->sc_type)
                return NULL;
        return ret;
}

static struct nfs4_stid *
find_stateid_by_type(struct nfs4_client *cl, stateid_t *t, char typemask)
{
        struct nfs4_stid *s;

        spin_lock(&cl->cl_lock);
        s = find_stateid_locked(cl, t);
        if (s != NULL) {
                if (typemask & s->sc_type)
                        atomic_inc(&s->sc_count);
                else
                        s = NULL;
        }
        spin_unlock(&cl->cl_lock);
        return s;
}

static struct nfs4_client *create_client(struct xdr_netobj name,
                struct svc_rqst *rqstp, nfs4_verifier *verf)
{
        struct nfs4_client *clp;
        struct sockaddr *sa = svc_addr(rqstp);
        int ret;
        struct net *net = SVC_NET(rqstp);

        clp = alloc_client(name);
        if (clp == NULL)
                return NULL;

        ret = copy_cred(&clp->cl_cred, &rqstp->rq_cred);
        if (ret) {
                free_client(clp);
                return NULL;
        }
        nfsd4_init_cb(&clp->cl_cb_null, clp, NULL, NFSPROC4_CLNT_CB_NULL);
        clp->cl_time = get_seconds();
        clear_bit(0, &clp->cl_cb_slot_busy);
        copy_verf(clp, verf);
        rpc_copy_addr((struct sockaddr *) &clp->cl_addr, sa);
        clp->cl_cb_session = NULL;
        clp->net = net;
        return clp;
}

static void
add_clp_to_name_tree(struct nfs4_client *new_clp, struct rb_root *root)
{
        struct rb_node **new = &(root->rb_node), *parent = NULL;
        struct nfs4_client *clp;

        while (*new) {
                clp = rb_entry(*new, struct nfs4_client, cl_namenode);
                parent = *new;

                if (compare_blob(&clp->cl_name, &new_clp->cl_name) > 0)
                        new = &((*new)->rb_left);
                else
                        new = &((*new)->rb_right);
        }

        rb_link_node(&new_clp->cl_namenode, parent, new);
        rb_insert_color(&new_clp->cl_namenode, root);
}

static struct nfs4_client *
find_clp_in_name_tree(struct xdr_netobj *name, struct rb_root *root)
{
        int cmp;
        struct rb_node *node = root->rb_node;
        struct nfs4_client *clp;

        while (node) {
                clp = rb_entry(node, struct nfs4_client, cl_namenode);
                cmp = compare_blob(&clp->cl_name, name);
                if (cmp > 0)
                        node = node->rb_left;
                else if (cmp < 0)
                        node = node->rb_right;
                else
                        return clp;
        }
        return NULL;
}

static void
add_to_unconfirmed(struct nfs4_client *clp)
{
        unsigned int idhashval;
        struct nfsd_net *nn = net_generic(clp->net, nfsd_net_id);

        lockdep_assert_held(&nn->client_lock);

        clear_bit(NFSD4_CLIENT_CONFIRMED, &clp->cl_flags);
        add_clp_to_name_tree(clp, &nn->unconf_name_tree);
        idhashval = clientid_hashval(clp->cl_clientid.cl_id);
        list_add(&clp->cl_idhash, &nn->unconf_id_hashtbl[idhashval]);
        renew_client_locked(clp);
}

static void
move_to_confirmed(struct nfs4_client *clp)
{
        unsigned int idhashval = clientid_hashval(clp->cl_clientid.cl_id);
        struct nfsd_net *nn = net_generic(clp->net, nfsd_net_id);

        lockdep_assert_held(&nn->client_lock);

        dprintk("NFSD: move_to_confirm nfs4_client %p\n", clp);
        list_move(&clp->cl_idhash, &nn->conf_id_hashtbl[idhashval]);
        rb_erase(&clp->cl_namenode, &nn->unconf_name_tree);
        add_clp_to_name_tree(clp, &nn->conf_name_tree);
        set_bit(NFSD4_CLIENT_CONFIRMED, &clp->cl_flags);
        renew_client_locked(clp);
}

static struct nfs4_client *
find_client_in_id_table(struct list_head *tbl, clientid_t *clid, bool sessions)
{
        struct nfs4_client *clp;
        unsigned int idhashval = clientid_hashval(clid->cl_id);

        list_for_each_entry(clp, &tbl[idhashval], cl_idhash) {
                if (same_clid(&clp->cl_clientid, clid)) {
                        if ((bool)clp->cl_minorversion != sessions)
                                return NULL;
                        renew_client_locked(clp);
                        return clp;
                }
        }
        return NULL;
}

static struct nfs4_client *
find_confirmed_client(clientid_t *clid, bool sessions, struct nfsd_net *nn)
{
        struct list_head *tbl = nn->conf_id_hashtbl;

        lockdep_assert_held(&nn->client_lock);
        return find_client_in_id_table(tbl, clid, sessions);
}

static struct nfs4_client *
find_unconfirmed_client(clientid_t *clid, bool sessions, struct nfsd_net *nn)
{
        struct list_head *tbl = nn->unconf_id_hashtbl;

        lockdep_assert_held(&nn->client_lock);
        return find_client_in_id_table(tbl, clid, sessions);
}

static bool clp_used_exchangeid(struct nfs4_client *clp)
{
        return clp->cl_exchange_flags != 0;
} 

static struct nfs4_client *
find_confirmed_client_by_name(struct xdr_netobj *name, struct nfsd_net *nn)
{
        lockdep_assert_held(&nn->client_lock);
        return find_clp_in_name_tree(name, &nn->conf_name_tree);
}

static struct nfs4_client *
find_unconfirmed_client_by_name(struct xdr_netobj *name, struct nfsd_net *nn)
{
        lockdep_assert_held(&nn->client_lock);
        return find_clp_in_name_tree(name, &nn->unconf_name_tree);
}

static void
gen_callback(struct nfs4_client *clp, struct nfsd4_setclientid *se, struct svc_rqst *rqstp)
{
        struct nfs4_cb_conn *conn = &clp->cl_cb_conn;
        struct sockaddr *sa = svc_addr(rqstp);
        u32 scopeid = rpc_get_scope_id(sa);
        unsigned short expected_family;

        /* Currently, we only support tcp and tcp6 for the callback channel */
        if (se->se_callback_netid_len == 3 &&
            !memcmp(se->se_callback_netid_val, "tcp", 3))
                expected_family = AF_INET;
        else if (se->se_callback_netid_len == 4 &&
                 !memcmp(se->se_callback_netid_val, "tcp6", 4))
                expected_family = AF_INET6;
        else
                goto out_err;

        conn->cb_addrlen = rpc_uaddr2sockaddr(clp->net, se->se_callback_addr_val,
                                            se->se_callback_addr_len,
                                            (struct sockaddr *)&conn->cb_addr,
                                            sizeof(conn->cb_addr));

        if (!conn->cb_addrlen || conn->cb_addr.ss_family != expected_family)
                goto out_err;

        if (conn->cb_addr.ss_family == AF_INET6)
                ((struct sockaddr_in6 *)&conn->cb_addr)->sin6_scope_id = scopeid;

        conn->cb_prog = se->se_callback_prog;
        conn->cb_ident = se->se_callback_ident;
        memcpy(&conn->cb_saddr, &rqstp->rq_daddr, rqstp->rq_daddrlen);
        return;
out_err:
        conn->cb_addr.ss_family = AF_UNSPEC;
        conn->cb_addrlen = 0;
        dprintk(KERN_INFO "NFSD: this client (clientid %08x/%08x) "
                "will not receive delegations\n",
                clp->cl_clientid.cl_boot, clp->cl_clientid.cl_id);

        return;
}

/*
 * Cache a reply. nfsd4_check_resp_size() has bounded the cache size.
 */
static void
nfsd4_store_cache_entry(struct nfsd4_compoundres *resp)
{
        struct xdr_buf *buf = resp->xdr.buf;
        struct nfsd4_slot *slot = resp->cstate.slot;
        unsigned int base;

        dprintk("--> %s slot %p\n", __func__, slot);

        slot->sl_opcnt = resp->opcnt;
        slot->sl_status = resp->cstate.status;

        slot->sl_flags |= NFSD4_SLOT_INITIALIZED;
        if (nfsd4_not_cached(resp)) {
                slot->sl_datalen = 0;
                return;
        }
        base = resp->cstate.data_offset;
        slot->sl_datalen = buf->len - base;
        if (read_bytes_from_xdr_buf(buf, base, slot->sl_data, slot->sl_datalen))
                WARN(1, "%s: sessions DRC could not cache compound\n",
                     __func__);
        return;
}

/*
 * Encode the replay sequence operation from the slot values.
 * If cachethis is FALSE encode the uncached rep error on the next
 * operation which sets resp->p and increments resp->opcnt for
 * nfs4svc_encode_compoundres.
 *
 */
static __be32
nfsd4_enc_sequence_replay(struct nfsd4_compoundargs *args,
                          struct nfsd4_compoundres *resp)
{
        struct nfsd4_op *op;
        struct nfsd4_slot *slot = resp->cstate.slot;

        /* Encode the replayed sequence operation */
        op = &args->ops[resp->opcnt - 1];
        nfsd4_encode_operation(resp, op);

        /* Return nfserr_retry_uncached_rep in next operation. */
        if (args->opcnt > 1 && !(slot->sl_flags & NFSD4_SLOT_CACHETHIS)) {
                op = &args->ops[resp->opcnt++];
                op->status = nfserr_retry_uncached_rep;
                nfsd4_encode_operation(resp, op);
        }
        return op->status;
}

/*
 * The sequence operation is not cached because we can use the slot and
 * session values.
 */
static __be32
nfsd4_replay_cache_entry(struct nfsd4_compoundres *resp,
                         struct nfsd4_sequence *seq)
{
        struct nfsd4_slot *slot = resp->cstate.slot;
        struct xdr_stream *xdr = &resp->xdr;
        __be32 *p;
        __be32 status;

        dprintk("--> %s slot %p\n", __func__, slot);

        status = nfsd4_enc_sequence_replay(resp->rqstp->rq_argp, resp);
        if (status)
                return status;

        p = xdr_reserve_space(xdr, slot->sl_datalen);
        if (!p) {
                WARN_ON_ONCE(1);
                return nfserr_serverfault;
        }
        xdr_encode_opaque_fixed(p, slot->sl_data, slot->sl_datalen);
        xdr_commit_encode(xdr);

        resp->opcnt = slot->sl_opcnt;
        return slot->sl_status;
}

/*
 * Set the exchange_id flags returned by the server.
 */
static void
nfsd4_set_ex_flags(struct nfs4_client *new, struct nfsd4_exchange_id *clid)
{
#ifdef CONFIG_NFSD_PNFS
        new->cl_exchange_flags |= EXCHGID4_FLAG_USE_PNFS_MDS;
#else
        new->cl_exchange_flags |= EXCHGID4_FLAG_USE_NON_PNFS;
#endif

        /* Referrals are supported, Migration is not. */
        new->cl_exchange_flags |= EXCHGID4_FLAG_SUPP_MOVED_REFER;

        /* set the wire flags to return to client. */
        clid->flags = new->cl_exchange_flags;
}

static bool client_has_openowners(struct nfs4_client *clp)
{
        struct nfs4_openowner *oo;

        list_for_each_entry(oo, &clp->cl_openowners, oo_perclient) {
                if (!list_empty(&oo->oo_owner.so_stateids))
                        return true;
        }
        return false;
}

static bool client_has_state(struct nfs4_client *clp)
{
        return client_has_openowners(clp)
#ifdef CONFIG_NFSD_PNFS
                || !list_empty(&clp->cl_lo_states)
#endif
                || !list_empty(&clp->cl_delegations)
                || !list_empty(&clp->cl_sessions);
}

__be32
nfsd4_exchange_id(struct svc_rqst *rqstp,
                  struct nfsd4_compound_state *cstate,
                  struct nfsd4_exchange_id *exid)
{
        struct nfs4_client *conf, *new;
        struct nfs4_client *unconf = NULL;
        __be32 status;
        char                    addr_str[INET6_ADDRSTRLEN];
        nfs4_verifier           verf = exid->verifier;
        struct sockaddr         *sa = svc_addr(rqstp);
        bool    update = exid->flags & EXCHGID4_FLAG_UPD_CONFIRMED_REC_A;
        struct nfsd_net         *nn = net_generic(SVC_NET(rqstp), nfsd_net_id);

        rpc_ntop(sa, addr_str, sizeof(addr_str));
        dprintk("%s rqstp=%p exid=%p clname.len=%u clname.data=%p "
                "ip_addr=%s flags %x, spa_how %d\n",
                __func__, rqstp, exid, exid->clname.len, exid->clname.data,
                addr_str, exid->flags, exid->spa_how);

        if (exid->flags & ~EXCHGID4_FLAG_MASK_A)
                return nfserr_inval;

        new = create_client(exid->clname, rqstp, &verf);
        if (new == NULL)
                return nfserr_jukebox;

        switch (exid->spa_how) {
        case SP4_MACH_CRED:
                if (!svc_rqst_integrity_protected(rqstp)) {
                        status = nfserr_inval;
                        goto out_nolock;
                }
                /*
                 * Sometimes userspace doesn't give us a principal.
                 * Which is a bug, really.  Anyway, we can't enforce
                 * MACH_CRED in that case, better to give up now:
                 */
                if (!new->cl_cred.cr_principal &&
                                        !new->cl_cred.cr_raw_principal) {
                        status = nfserr_serverfault;
                        goto out_nolock;
                }
                new->cl_mach_cred = true;
        case SP4_NONE:
                break;
        default:                                /* checked by xdr code */
                WARN_ON_ONCE(1);
        case SP4_SSV:
                status = nfserr_encr_alg_unsupp;
                goto out_nolock;
        }

        /* Cases below refer to rfc 5661 section 18.35.4: */
        spin_lock(&nn->client_lock);
        conf = find_confirmed_client_by_name(&exid->clname, nn);
        if (conf) {
                bool creds_match = same_creds(&conf->cl_cred, &rqstp->rq_cred);
                bool verfs_match = same_verf(&verf, &conf->cl_verifier);

                if (update) {
                        if (!clp_used_exchangeid(conf)) { /* buggy client */
                                status = nfserr_inval;
                                goto out;
                        }
                        if (!mach_creds_match(conf, rqstp)) {
                                status = nfserr_wrong_cred;
                                goto out;
                        }
                        if (!creds_match) { /* case 9 */
                                status = nfserr_perm;
                                goto out;
                        }
                        if (!verfs_match) { /* case 8 */
                                status = nfserr_not_same;
                                goto out;
                        }
                        /* case 6 */
                        exid->flags |= EXCHGID4_FLAG_CONFIRMED_R;
                        goto out_copy;
                }
                if (!creds_match) { /* case 3 */
                        if (client_has_state(conf)) {
                                status = nfserr_clid_inuse;
                                goto out;
                        }
                        goto out_new;
                }
                if (verfs_match) { /* case 2 */
                        conf->cl_exchange_flags |= EXCHGID4_FLAG_CONFIRMED_R;
                        goto out_copy;
                }
                /* case 5, client reboot */
                conf = NULL;
                goto out_new;
        }

        if (update) { /* case 7 */
                status = nfserr_noent;
                goto out;
        }

        unconf  = find_unconfirmed_client_by_name(&exid->clname, nn);
        if (unconf) /* case 4, possible retry or client restart */
                unhash_client_locked(unconf);

        /* case 1 (normal case) */
out_new:
        if (conf) {
                status = mark_client_expired_locked(conf);
                if (status)
                        goto out;
        }
        new->cl_minorversion = cstate->minorversion;

        gen_clid(new, nn);
        add_to_unconfirmed(new);
        swap(new, conf);
out_copy:
        exid->clientid.cl_boot = conf->cl_clientid.cl_boot;
        exid->clientid.cl_id = conf->cl_clientid.cl_id;

        exid->seqid = conf->cl_cs_slot.sl_seqid + 1;
        nfsd4_set_ex_flags(conf, exid);

        dprintk("nfsd4_exchange_id seqid %d flags %x\n",
                conf->cl_cs_slot.sl_seqid, conf->cl_exchange_flags);
        status = nfs_ok;

out:
        spin_unlock(&nn->client_lock);
out_nolock:
        if (new)
                expire_client(new);
        if (unconf)
                expire_client(unconf);
        return status;
}

static __be32
check_slot_seqid(u32 seqid, u32 slot_seqid, int slot_inuse)
{
        dprintk("%s enter. seqid %d slot_seqid %d\n", __func__, seqid,
                slot_seqid);

        /* The slot is in use, and no response has been sent. */
        if (slot_inuse) {
                if (seqid == slot_seqid)
                        return nfserr_jukebox;
                else
                        return nfserr_seq_misordered;
        }
        /* Note unsigned 32-bit arithmetic handles wraparound: */
        if (likely(seqid == slot_seqid + 1))
                return nfs_ok;
        if (seqid == slot_seqid)
                return nfserr_replay_cache;
        return nfserr_seq_misordered;
}

/*
 * Cache the create session result into the create session single DRC
 * slot cache by saving the xdr structure. sl_seqid has been set.
 * Do this for solo or embedded create session operations.
 */
static void
nfsd4_cache_create_session(struct nfsd4_create_session *cr_ses,
                           struct nfsd4_clid_slot *slot, __be32 nfserr)
{
        slot->sl_status = nfserr;
        memcpy(&slot->sl_cr_ses, cr_ses, sizeof(*cr_ses));
}

static __be32
nfsd4_replay_create_session(struct nfsd4_create_session *cr_ses,
                            struct nfsd4_clid_slot *slot)
{
        memcpy(cr_ses, &slot->sl_cr_ses, sizeof(*cr_ses));
        return slot->sl_status;
}

#define NFSD_MIN_REQ_HDR_SEQ_SZ ((\
                        2 * 2 + /* credential,verifier: AUTH_NULL, length 0 */ \
                        1 +     /* MIN tag is length with zero, only length */ \
                        3 +     /* version, opcount, opcode */ \
                        XDR_QUADLEN(NFS4_MAX_SESSIONID_LEN) + \
                                /* seqid, slotID, slotID, cache */ \
                        4 ) * sizeof(__be32))

#define NFSD_MIN_RESP_HDR_SEQ_SZ ((\
                        2 +     /* verifier: AUTH_NULL, length 0 */\
                        1 +     /* status */ \
                        1 +     /* MIN tag is length with zero, only length */ \
                        3 +     /* opcount, opcode, opstatus*/ \
                        XDR_QUADLEN(NFS4_MAX_SESSIONID_LEN) + \
                                /* seqid, slotID, slotID, slotID, status */ \
                        5 ) * sizeof(__be32))

static __be32 check_forechannel_attrs(struct nfsd4_channel_attrs *ca, struct nfsd_net *nn)
{
        u32 maxrpc = nn->nfsd_serv->sv_max_mesg;

        if (ca->maxreq_sz < NFSD_MIN_REQ_HDR_SEQ_SZ)
                return nfserr_toosmall;
        if (ca->maxresp_sz < NFSD_MIN_RESP_HDR_SEQ_SZ)
                return nfserr_toosmall;
        ca->headerpadsz = 0;
        ca->maxreq_sz = min_t(u32, ca->maxreq_sz, maxrpc);
        ca->maxresp_sz = min_t(u32, ca->maxresp_sz, maxrpc);
        ca->maxops = min_t(u32, ca->maxops, NFSD_MAX_OPS_PER_COMPOUND);
        ca->maxresp_cached = min_t(u32, ca->maxresp_cached,
                        NFSD_SLOT_CACHE_SIZE + NFSD_MIN_HDR_SEQ_SZ);
        ca->maxreqs = min_t(u32, ca->maxreqs, NFSD_MAX_SLOTS_PER_SESSION);
        /*
         * Note decreasing slot size below client's request may make it
         * difficult for client to function correctly, whereas
         * decreasing the number of slots will (just?) affect
         * performance.  When short on memory we therefore prefer to
         * decrease number of slots instead of their size.  Clients that
         * request larger slots than they need will get poor results:
         */
        ca->maxreqs = nfsd4_get_drc_mem(ca);
        if (!ca->maxreqs)
                return nfserr_jukebox;

        return nfs_ok;
}

/*
 * Server's NFSv4.1 backchannel support is AUTH_SYS-only for now.
 * These are based on similar macros in linux/sunrpc/msg_prot.h .
 */
#define RPC_MAX_HEADER_WITH_AUTH_SYS \
        (RPC_CALLHDRSIZE + 2 * (2 + UNX_CALLSLACK))

#define RPC_MAX_REPHEADER_WITH_AUTH_SYS \
        (RPC_REPHDRSIZE + (2 + NUL_REPLYSLACK))

#define NFSD_CB_MAX_REQ_SZ      ((NFS4_enc_cb_recall_sz + \
                                 RPC_MAX_HEADER_WITH_AUTH_SYS) * sizeof(__be32))
#define NFSD_CB_MAX_RESP_SZ     ((NFS4_dec_cb_recall_sz + \
                                 RPC_MAX_REPHEADER_WITH_AUTH_SYS) * \
                                 sizeof(__be32))

static __be32 check_backchannel_attrs(struct nfsd4_channel_attrs *ca)
{
        ca->headerpadsz = 0;

        if (ca->maxreq_sz < NFSD_CB_MAX_REQ_SZ)
                return nfserr_toosmall;
        if (ca->maxresp_sz < NFSD_CB_MAX_RESP_SZ)
                return nfserr_toosmall;
        ca->maxresp_cached = 0;
        if (ca->maxops < 2)
                return nfserr_toosmall;

        return nfs_ok;
}

static __be32 nfsd4_check_cb_sec(struct nfsd4_cb_sec *cbs)
{
        switch (cbs->flavor) {
        case RPC_AUTH_NULL:
        case RPC_AUTH_UNIX:
                return nfs_ok;
        default:
                /*
                 * GSS case: the spec doesn't allow us to return this
                 * error.  But it also doesn't allow us not to support
                 * GSS.
                 * I'd rather this fail hard than return some error the
                 * client might think it can already handle:
                 */
                return nfserr_encr_alg_unsupp;
        }
}

__be32
nfsd4_create_session(struct svc_rqst *rqstp,
                     struct nfsd4_compound_state *cstate,
                     struct nfsd4_create_session *cr_ses)
{
        struct sockaddr *sa = svc_addr(rqstp);
        struct nfs4_client *conf, *unconf;
        struct nfs4_client *old = NULL;
        struct nfsd4_session *new;
        struct nfsd4_conn *conn;
        struct nfsd4_clid_slot *cs_slot = NULL;
        __be32 status = 0;
        struct nfsd_net *nn = net_generic(SVC_NET(rqstp), nfsd_net_id);

        if (cr_ses->flags & ~SESSION4_FLAG_MASK_A)
                return nfserr_inval;
        status = nfsd4_check_cb_sec(&cr_ses->cb_sec);
        if (status)
                return status;
        status = check_forechannel_attrs(&cr_ses->fore_channel, nn);
        if (status)
                return status;
        status = check_backchannel_attrs(&cr_ses->back_channel);
        if (status)
                goto out_release_drc_mem;
        status = nfserr_jukebox;
        new = alloc_session(&cr_ses->fore_channel, &cr_ses->back_channel);
        if (!new)
                goto out_release_drc_mem;
        conn = alloc_conn_from_crses(rqstp, cr_ses);
        if (!conn)
                goto out_free_session;

        spin_lock(&nn->client_lock);
        unconf = find_unconfirmed_client(&cr_ses->clientid, true, nn);
        conf = find_confirmed_client(&cr_ses->clientid, true, nn);
        WARN_ON_ONCE(conf && unconf);

        if (conf) {
                status = nfserr_wrong_cred;
                if (!mach_creds_match(conf, rqstp))
                        goto out_free_conn;
                cs_slot = &conf->cl_cs_slot;
                status = check_slot_seqid(cr_ses->seqid, cs_slot->sl_seqid, 0);
                if (status) {
                        if (status == nfserr_replay_cache)
                                status = nfsd4_replay_create_session(cr_ses, cs_slot);
                        goto out_free_conn;
                }
        } else if (unconf) {
                if (!same_creds(&unconf->cl_cred, &rqstp->rq_cred) ||
                    !rpc_cmp_addr(sa, (struct sockaddr *) &unconf->cl_addr)) {
                        status = nfserr_clid_inuse;
                        goto out_free_conn;
                }
                status = nfserr_wrong_cred;
                if (!mach_creds_match(unconf, rqstp))
                        goto out_free_conn;
                cs_slot = &unconf->cl_cs_slot;
                status = check_slot_seqid(cr_ses->seqid, cs_slot->sl_seqid, 0);
                if (status) {
                        /* an unconfirmed replay returns misordered */
                        status = nfserr_seq_misordered;
                        goto out_free_conn;
                }
                old = find_confirmed_client_by_name(&unconf->cl_name, nn);
                if (old) {
                        status = mark_client_expired_locked(old);
                        if (status) {
                                old = NULL;
                                goto out_free_conn;
                        }
                }
                move_to_confirmed(unconf);
                conf = unconf;
        } else {
                status = nfserr_stale_clientid;
                goto out_free_conn;
        }
        status = nfs_ok;
        /* Persistent sessions are not supported */
        cr_ses->flags &= ~SESSION4_PERSIST;
        /* Upshifting from TCP to RDMA is not supported */
        cr_ses->flags &= ~SESSION4_RDMA;

        init_session(rqstp, new, conf, cr_ses);
        nfsd4_get_session_locked(new);

        memcpy(cr_ses->sessionid.data, new->se_sessionid.data,
               NFS4_MAX_SESSIONID_LEN);
        cs_slot->sl_seqid++;
        cr_ses->seqid = cs_slot->sl_seqid;

        /* cache solo and embedded create sessions under the client_lock */
        nfsd4_cache_create_session(cr_ses, cs_slot, status);
        spin_unlock(&nn->client_lock);
        /* init connection and backchannel */
        nfsd4_init_conn(rqstp, conn, new);
        nfsd4_put_session(new);
        if (old)
                expire_client(old);
        return status;
out_free_conn:
        spin_unlock(&nn->client_lock);
        free_conn(conn);
        if (old)
                expire_client(old);
out_free_session:
        __free_session(new);
out_release_drc_mem:
        nfsd4_put_drc_mem(&cr_ses->fore_channel);
        return status;
}

static __be32 nfsd4_map_bcts_dir(u32 *dir)
{
        switch (*dir) {
        case NFS4_CDFC4_FORE:
        case NFS4_CDFC4_BACK:
                return nfs_ok;
        case NFS4_CDFC4_FORE_OR_BOTH:
        case NFS4_CDFC4_BACK_OR_BOTH:
                *dir = NFS4_CDFC4_BOTH;
                return nfs_ok;
        };
        return nfserr_inval;
}

__be32 nfsd4_backchannel_ctl(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate, struct nfsd4_backchannel_ctl *bc)
{
        struct nfsd4_session *session = cstate->session;
        struct nfsd_net *nn = net_generic(SVC_NET(rqstp), nfsd_net_id);
        __be32 status;

        status = nfsd4_check_cb_sec(&bc->bc_cb_sec);
        if (status)
                return status;
        spin_lock(&nn->client_lock);
        session->se_cb_prog = bc->bc_cb_program;
        session->se_cb_sec = bc->bc_cb_sec;
        spin_unlock(&nn->client_lock);

        nfsd4_probe_callback(session->se_client);

        return nfs_ok;
}

__be32 nfsd4_bind_conn_to_session(struct svc_rqst *rqstp,
                     struct nfsd4_compound_state *cstate,
                     struct nfsd4_bind_conn_to_session *bcts)
{
        __be32 status;
        struct nfsd4_conn *conn;
        struct nfsd4_session *session;
        struct net *net = SVC_NET(rqstp);
        struct nfsd_net *nn = net_generic(net, nfsd_net_id);

        if (!nfsd4_last_compound_op(rqstp))
                return nfserr_not_only_op;
        spin_lock(&nn->client_lock);
        session = find_in_sessionid_hashtbl(&bcts->sessionid, net, &status);
        spin_unlock(&nn->client_lock);
        if (!session)
                goto out_no_session;
        status = nfserr_wrong_cred;
        if (!mach_creds_match(session->se_client, rqstp))
                goto out;
        status = nfsd4_map_bcts_dir(&bcts->dir);
        if (status)
                goto out;
        conn = alloc_conn(rqstp, bcts->dir);
        status = nfserr_jukebox;
        if (!conn)
                goto out;
        nfsd4_init_conn(rqstp, conn, session);
        status = nfs_ok;
out:
        nfsd4_put_session(session);
out_no_session:
        return status;
}

static bool nfsd4_compound_in_session(struct nfsd4_session *session, struct nfs4_sessionid *sid)
{
        if (!session)
                return 0;
        return !memcmp(sid, &session->se_sessionid, sizeof(*sid));
}

__be32
nfsd4_destroy_session(struct svc_rqst *r,
                      struct nfsd4_compound_state *cstate,
                      struct nfsd4_destroy_session *sessionid)
{
        struct nfsd4_session *ses;
        __be32 status;
        int ref_held_by_me = 0;
        struct net *net = SVC_NET(r);
        struct nfsd_net *nn = net_generic(net, nfsd_net_id);

        status = nfserr_not_only_op;
        if (nfsd4_compound_in_session(cstate->session, &sessionid->sessionid)) {
                if (!nfsd4_last_compound_op(r))
                        goto out;
                ref_held_by_me++;
        }
        dump_sessionid(__func__, &sessionid->sessionid);
        spin_lock(&nn->client_lock);
        ses = find_in_sessionid_hashtbl(&sessionid->sessionid, net, &status);
        if (!ses)
                goto out_client_lock;
        status = nfserr_wrong_cred;
        if (!mach_creds_match(ses->se_client, r))
                goto out_put_session;
        status = mark_session_dead_locked(ses, 1 + ref_held_by_me);
        if (status)
                goto out_put_session;
        unhash_session(ses);
        spin_unlock(&nn->client_lock);

        nfsd4_probe_callback_sync(ses->se_client);

        spin_lock(&nn->client_lock);
        status = nfs_ok;
out_put_session:
        nfsd4_put_session_locked(ses);
out_client_lock:
        spin_unlock(&nn->client_lock);
out:
        return status;
}

static struct nfsd4_conn *__nfsd4_find_conn(struct svc_xprt *xpt, struct nfsd4_session *s)
{
        struct nfsd4_conn *c;

        list_for_each_entry(c, &s->se_conns, cn_persession) {
                if (c->cn_xprt == xpt) {
                        return c;
                }
        }
        return NULL;
}

static __be32 nfsd4_sequence_check_conn(struct nfsd4_conn *new, struct nfsd4_session *ses)
{
        struct nfs4_client *clp = ses->se_client;
        struct nfsd4_conn *c;
        __be32 status = nfs_ok;
        int ret;

        spin_lock(&clp->cl_lock);
        c = __nfsd4_find_conn(new->cn_xprt, ses);
        if (c)
                goto out_free;
        status = nfserr_conn_not_bound_to_session;
        if (clp->cl_mach_cred)
                goto out_free;
        __nfsd4_hash_conn(new, ses);
        spin_unlock(&clp->cl_lock);
        ret = nfsd4_register_conn(new);
        if (ret)
                /* oops; xprt is already down: */
                nfsd4_conn_lost(&new->cn_xpt_user);
        return nfs_ok;
out_free:
        spin_unlock(&clp->cl_lock);
        free_conn(new);
        return status;
}

static bool nfsd4_session_too_many_ops(struct svc_rqst *rqstp, struct nfsd4_session *session)
{
        struct nfsd4_compoundargs *args = rqstp->rq_argp;

        return args->opcnt > session->se_fchannel.maxops;
}

static bool nfsd4_request_too_big(struct svc_rqst *rqstp,
                                  struct nfsd4_session *session)
{
        struct xdr_buf *xb = &rqstp->rq_arg;

        return xb->len > session->se_fchannel.maxreq_sz;
}

__be32
nfsd4_sequence(struct svc_rqst *rqstp,
               struct nfsd4_compound_state *cstate,
               struct nfsd4_sequence *seq)
{
        struct nfsd4_compoundres *resp = rqstp->rq_resp;
        struct xdr_stream *xdr = &resp->xdr;
        struct nfsd4_session *session;
        struct nfs4_client *clp;
        struct nfsd4_slot *slot;
        struct nfsd4_conn *conn;
        __be32 status;
        int buflen;
        struct net *net = SVC_NET(rqstp);
        struct nfsd_net *nn = net_generic(net, nfsd_net_id);

        if (resp->opcnt != 1)
                return nfserr_sequence_pos;

        /*
         * Will be either used or freed by nfsd4_sequence_check_conn
         * below.
         */
        conn = alloc_conn(rqstp, NFS4_CDFC4_FORE);
        if (!conn)
                return nfserr_jukebox;

        spin_lock(&nn->client_lock);
        session = find_in_sessionid_hashtbl(&seq->sessionid, net, &status);
        if (!session)
                goto out_no_session;
        clp = session->se_client;

        status = nfserr_too_many_ops;
        if (nfsd4_session_too_many_ops(rqstp, session))
                goto out_put_session;

        status = nfserr_req_too_big;
        if (nfsd4_request_too_big(rqstp, session))
                goto out_put_session;

        status = nfserr_badslot;
        if (seq->slotid >= session->se_fchannel.maxreqs)
                goto out_put_session;

        slot = session->se_slots[seq->slotid];
        dprintk("%s: slotid %d\n", __func__, seq->slotid);

        /* We do not negotiate the number of slots yet, so set the
         * maxslots to the session maxreqs which is used to encode
         * sr_highest_slotid and the sr_target_slot id to maxslots */
        seq->maxslots = session->se_fchannel.maxreqs;

        status = check_slot_seqid(seq->seqid, slot->sl_seqid,
                                        slot->sl_flags & NFSD4_SLOT_INUSE);
        if (status == nfserr_replay_cache) {
                status = nfserr_seq_misordered;
                if (!(slot->sl_flags & NFSD4_SLOT_INITIALIZED))
                        goto out_put_session;
                cstate->slot = slot;
                cstate->session = session;
                cstate->clp = clp;
                /* Return the cached reply status and set cstate->status
                 * for nfsd4_proc_compound processing */
                status = nfsd4_replay_cache_entry(resp, seq);
                cstate->status = nfserr_replay_cache;
                goto out;
        }
        if (status)
                goto out_put_session;

        status = nfsd4_sequence_check_conn(conn, session);
        conn = NULL;
        if (status)
                goto out_put_session;