/*
 * linux/fs/nfs/delegation.c
 *
 * Copyright (C) 2004 Trond Myklebust
 *
 * NFS file delegation management
 *
 */
#include <linux/completion.h>
#include <linux/kthread.h>
#include <linux/module.h>
#include <linux/sched.h>
#include <linux/slab.h>
#include <linux/spinlock.h>

#include <linux/nfs4.h>
#include <linux/nfs_fs.h>
#include <linux/nfs_xdr.h>

#include "nfs4_fs.h"
#include "delegation.h"
#include "internal.h"

static void nfs_free_delegation(struct nfs_delegation *delegation)
{
        if (delegation->cred) {
                put_rpccred(delegation->cred);
                delegation->cred = NULL;
        }
        kfree_rcu(delegation, rcu);
}

/**
 * nfs_mark_delegation_referenced - set delegation's REFERENCED flag
 * @delegation: delegation to process
 *
 */
void nfs_mark_delegation_referenced(struct nfs_delegation *delegation)
{
        set_bit(NFS_DELEGATION_REFERENCED, &delegation->flags);
}

/**
 * nfs_have_delegation - check if inode has a delegation
 * @inode: inode to check
 * @flags: delegation types to check for
 *
 * Returns one if inode has the indicated delegation, otherwise zero.
 */
int nfs4_have_delegation(struct inode *inode, fmode_t flags)
{
        struct nfs_delegation *delegation;
        int ret = 0;

        flags &= FMODE_READ|FMODE_WRITE;
        rcu_read_lock();
        delegation = rcu_dereference(NFS_I(inode)->delegation);
        if (delegation != NULL && (delegation->type & flags) == flags &&
            !test_bit(NFS_DELEGATION_RETURNING, &delegation->flags)) {
                nfs_mark_delegation_referenced(delegation);
                ret = 1;
        }
        rcu_read_unlock();
        return ret;
}

static int nfs_delegation_claim_locks(struct nfs_open_context *ctx, struct nfs4_state *state, const nfs4_stateid *stateid)
{
        struct inode *inode = state->inode;
        struct file_lock *fl;
        int status = 0;

        if (inode->i_flock == NULL)
                goto out;

        /* Protect inode->i_flock using the i_lock */
        spin_lock(&inode->i_lock);
        for (fl = inode->i_flock; fl != NULL; fl = fl->fl_next) {
                if (!(fl->fl_flags & (FL_POSIX|FL_FLOCK)))
                        continue;
                if (nfs_file_open_context(fl->fl_file) != ctx)
                        continue;
                spin_unlock(&inode->i_lock);
                status = nfs4_lock_delegation_recall(fl, state, stateid);
                if (status < 0)
                        goto out;
                spin_lock(&inode->i_lock);
        }
        spin_unlock(&inode->i_lock);
out:
        return status;
}

static int nfs_delegation_claim_opens(struct inode *inode, const nfs4_stateid *stateid)
{
        struct nfs_inode *nfsi = NFS_I(inode);
        struct nfs_open_context *ctx;
        struct nfs4_state_owner *sp;
        struct nfs4_state *state;
        unsigned int seq;
        int err;

again:
        spin_lock(&inode->i_lock);
        list_for_each_entry(ctx, &nfsi->open_files, list) {
                state = ctx->state;
                if (state == NULL)
                        continue;
                if (!test_bit(NFS_DELEGATED_STATE, &state->flags))
                        continue;
                if (!nfs4_stateid_match(&state->stateid, stateid))
                        continue;
                get_nfs_open_context(ctx);
                spin_unlock(&inode->i_lock);
                sp = state->owner;
                /* Block nfs4_proc_unlck */
                mutex_lock(&sp->so_delegreturn_mutex);
                seq = raw_seqcount_begin(&sp->so_reclaim_seqcount);
                err = nfs4_open_delegation_recall(ctx, state, stateid);
                if (!err)
                        err = nfs_delegation_claim_locks(ctx, state, stateid);
                if (!err && read_seqcount_retry(&sp->so_reclaim_seqcount, seq))
                        err = -EAGAIN;
                mutex_unlock(&sp->so_delegreturn_mutex);
                put_nfs_open_context(ctx);
                if (err != 0)
                        return err;
                goto again;
        }
        spin_unlock(&inode->i_lock);
        return 0;
}

/**
 * nfs_inode_reclaim_delegation - process a delegation reclaim request
 * @inode: inode to process
 * @cred: credential to use for request
 * @res: new delegation state from server
 *
 */
void nfs_inode_reclaim_delegation(struct inode *inode, struct rpc_cred *cred,
                                  struct nfs_openres *res)
{
        struct nfs_delegation *delegation;
        struct rpc_cred *oldcred = NULL;

        rcu_read_lock();
        delegation = rcu_dereference(NFS_I(inode)->delegation);
        if (delegation != NULL) {
                spin_lock(&delegation->lock);
                if (delegation->inode != NULL) {
                        nfs4_stateid_copy(&delegation->stateid, &res->delegation);
                        delegation->type = res->delegation_type;
                        delegation->maxsize = res->maxsize;
                        oldcred = delegation->cred;
                        delegation->cred = get_rpccred(cred);
                        clear_bit(NFS_DELEGATION_NEED_RECLAIM,
                                  &delegation->flags);
                        NFS_I(inode)->delegation_state = delegation->type;
                        spin_unlock(&delegation->lock);
                        put_rpccred(oldcred);
                        rcu_read_unlock();
                } else {
                        /* We appear to have raced with a delegation return. */
                        spin_unlock(&delegation->lock);
                        rcu_read_unlock();
                        nfs_inode_set_delegation(inode, cred, res);
                }
        } else {
                rcu_read_unlock();
        }
}

static int nfs_do_return_delegation(struct inode *inode, struct nfs_delegation *delegation, int issync)
{
        int res = 0;

        res = nfs4_proc_delegreturn(inode, delegation->cred, &delegation->stateid, issync);
        nfs_free_delegation(delegation);
        return res;
}

static struct inode *nfs_delegation_grab_inode(struct nfs_delegation *delegation)
{
        struct inode *inode = NULL;

        spin_lock(&delegation->lock);
        if (delegation->inode != NULL)
                inode = igrab(delegation->inode);
        spin_unlock(&delegation->lock);
        return inode;
}

static struct nfs_delegation *
nfs_start_delegation_return_locked(struct nfs_inode *nfsi)
{
        struct nfs_delegation *ret = NULL;
        struct nfs_delegation *delegation = rcu_dereference(nfsi->delegation);

        if (delegation == NULL)
                goto out;
        spin_lock(&delegation->lock);
        if (!test_and_set_bit(NFS_DELEGATION_RETURNING, &delegation->flags))
                ret = delegation;
        spin_unlock(&delegation->lock);
out:
        return ret;
}

static struct nfs_delegation *
nfs_start_delegation_return(struct nfs_inode *nfsi)
{
        struct nfs_delegation *delegation;

        rcu_read_lock();
        delegation = nfs_start_delegation_return_locked(nfsi);
        rcu_read_unlock();
        return delegation;
}

static void
nfs_abort_delegation_return(struct nfs_delegation *delegation,
                struct nfs_client *clp)
{

        spin_lock(&delegation->lock);
        clear_bit(NFS_DELEGATION_RETURNING, &delegation->flags);
        set_bit(NFS_DELEGATION_RETURN, &delegation->flags);
        spin_unlock(&delegation->lock);
        set_bit(NFS4CLNT_DELEGRETURN, &clp->cl_state);
}

static struct nfs_delegation *
nfs_detach_delegation_locked(struct nfs_inode *nfsi,
                struct nfs_delegation *delegation,
                struct nfs_client *clp)
{
        struct nfs_delegation *deleg_cur =
                rcu_dereference_protected(nfsi->delegation,
                                lockdep_is_held(&clp->cl_lock));

        if (deleg_cur == NULL || delegation != deleg_cur)
                return NULL;

        spin_lock(&delegation->lock);
        set_bit(NFS_DELEGATION_RETURNING, &delegation->flags);
        list_del_rcu(&delegation->super_list);
        delegation->inode = NULL;
        nfsi->delegation_state = 0;
        rcu_assign_pointer(nfsi->delegation, NULL);
        spin_unlock(&delegation->lock);
        return delegation;
}

static struct nfs_delegation *nfs_detach_delegation(struct nfs_inode *nfsi,
                struct nfs_delegation *delegation,
                struct nfs_server *server)
{
        struct nfs_client *clp = server->nfs_client;

        spin_lock(&clp->cl_lock);
        delegation = nfs_detach_delegation_locked(nfsi, delegation, clp);
        spin_unlock(&clp->cl_lock);
        return delegation;
}

static struct nfs_delegation *
nfs_inode_detach_delegation(struct inode *inode)
{
        struct nfs_inode *nfsi = NFS_I(inode);
        struct nfs_server *server = NFS_SERVER(inode);
        struct nfs_delegation *delegation;

        delegation = nfs_start_delegation_return(nfsi);
        if (delegation == NULL)
                return NULL;
        return nfs_detach_delegation(nfsi, delegation, server);
}

/**
 * nfs_inode_set_delegation - set up a delegation on an inode
 * @inode: inode to which delegation applies
 * @cred: cred to use for subsequent delegation processing
 * @res: new delegation state from server
 *
 * Returns zero on success, or a negative errno value.
 */
int nfs_inode_set_delegation(struct inode *inode, struct rpc_cred *cred, struct nfs_openres *res)
{
        struct nfs_server *server = NFS_SERVER(inode);
        struct nfs_client *clp = server->nfs_client;
        struct nfs_inode *nfsi = NFS_I(inode);
        struct nfs_delegation *delegation, *old_delegation;
        struct nfs_delegation *freeme = NULL;
        int status = 0;

        delegation = kmalloc(sizeof(*delegation), GFP_NOFS);
        if (delegation == NULL)
                return -ENOMEM;
        nfs4_stateid_copy(&delegation->stateid, &res->delegation);
        delegation->type = res->delegation_type;
        delegation->maxsize = res->maxsize;
        delegation->change_attr = inode->i_version;
        delegation->cred = get_rpccred(cred);
        delegation->inode = inode;
        delegation->flags = 1<<NFS_DELEGATION_REFERENCED;
        spin_lock_init(&delegation->lock);

        spin_lock(&clp->cl_lock);
        old_delegation = rcu_dereference_protected(nfsi->delegation,
                                        lockdep_is_held(&clp->cl_lock));
        if (old_delegation != NULL) {
                if (nfs4_stateid_match(&delegation->stateid,
                                        &old_delegation->stateid) &&
                                delegation->type == old_delegation->type) {
                        goto out;
                }
                /*
                 * Deal with broken servers that hand out two
                 * delegations for the same file.
                 * Allow for upgrades to a WRITE delegation, but
                 * nothing else.
                 */
                dfprintk(FILE, "%s: server %s handed out "
                                "a duplicate delegation!\n",
                                __func__, clp->cl_hostname);
                if (delegation->type == old_delegation->type ||
                    !(delegation->type & FMODE_WRITE)) {
                        freeme = delegation;
                        delegation = NULL;
                        goto out;
                }
                freeme = nfs_detach_delegation_locked(nfsi, 
                                old_delegation, clp);
                if (freeme == NULL)
                        goto out;
        }
        list_add_rcu(&delegation->super_list, &server->delegations);
        nfsi->delegation_state = delegation->type;
        rcu_assign_pointer(nfsi->delegation, delegation);
        delegation = NULL;

        /* Ensure we revalidate the attributes and page cache! */
        spin_lock(&inode->i_lock);
        nfsi->cache_validity |= NFS_INO_REVAL_FORCED;
        spin_unlock(&inode->i_lock);

out:
        spin_unlock(&clp->cl_lock);
        if (delegation != NULL)
                nfs_free_delegation(delegation);
        if (freeme != NULL)
                nfs_do_return_delegation(inode, freeme, 0);
        return status;
}

/*
 * Basic procedure for returning a delegation to the server
 */
static int nfs_end_delegation_return(struct inode *inode, struct nfs_delegation *delegation, int issync)
{
        struct nfs_client *clp = NFS_SERVER(inode)->nfs_client;
        struct nfs_inode *nfsi = NFS_I(inode);
        int err;

        if (delegation == NULL)
                return 0;
        do {
                err = nfs_delegation_claim_opens(inode, &delegation->stateid);
                if (!issync || err != -EAGAIN)
                        break;
                /*
                 * Guard against state recovery
                 */
                err = nfs4_wait_clnt_recover(clp);
        } while (err == 0);

        if (err) {
                nfs_abort_delegation_return(delegation, clp);
                goto out;
        }
        if (!nfs_detach_delegation(nfsi, delegation, NFS_SERVER(inode)))
                goto out;

        err = nfs_do_return_delegation(inode, delegation, issync);
out:
        return err;
}

static bool nfs_delegation_need_return(struct nfs_delegation *delegation)
{
        bool ret = false;

        if (test_and_clear_bit(NFS_DELEGATION_RETURN, &delegation->flags))
                ret = true;
        if (test_and_clear_bit(NFS_DELEGATION_RETURN_IF_CLOSED, &delegation->flags) && !ret) {
                struct inode *inode;

                spin_lock(&delegation->lock);
                inode = delegation->inode;
                if (inode && list_empty(&NFS_I(inode)->open_files))
                        ret = true;
                spin_unlock(&delegation->lock);
        }
        return ret;
}

/**
 * nfs_client_return_marked_delegations - return previously marked delegations
 * @clp: nfs_client to process
 *
 * Note that this function is designed to be called by the state
 * manager thread. For this reason, it cannot flush the dirty data,
 * since that could deadlock in case of a state recovery error.
 *
 * Returns zero on success, or a negative errno value.
 */
int nfs_client_return_marked_delegations(struct nfs_client *clp)
{
        struct nfs_delegation *delegation;
        struct nfs_server *server;
        struct inode *inode;
        int err = 0;

restart:
        rcu_read_lock();
        list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link) {
                list_for_each_entry_rcu(delegation, &server->delegations,
                                                                super_list) {
                        if (!nfs_delegation_need_return(delegation))
                                continue;
                        inode = nfs_delegation_grab_inode(delegation);
                        if (inode == NULL)
                                continue;
                        delegation = nfs_start_delegation_return_locked(NFS_I(inode));
                        rcu_read_unlock();

                        err = nfs_end_delegation_return(inode, delegation, 0);
                        iput(inode);
                        if (!err)
                                goto restart;
                        set_bit(NFS4CLNT_DELEGRETURN, &clp->cl_state);
                        return err;
                }
        }
        rcu_read_unlock();
        return 0;
}

/**
 * nfs_inode_return_delegation_noreclaim - return delegation, don't reclaim opens
 * @inode: inode to process
 *
 * Does not protect against delegation reclaims, therefore really only safe
 * to be called from nfs4_clear_inode().
 */
void nfs_inode_return_delegation_noreclaim(struct inode *inode)
{
        struct nfs_delegation *delegation;

        delegation = nfs_inode_detach_delegation(inode);
        if (delegation != NULL)
                nfs_do_return_delegation(inode, delegation, 0);
}

/**
 * nfs_inode_return_delegation - synchronously return a delegation
 * @inode: inode to process
 *
 * This routine will always flush any dirty data to disk on the
 * assumption that if we need to return the delegation, then
 * we should stop caching.
 *
 * Returns zero on success, or a negative errno value.
 */
int nfs4_inode_return_delegation(struct inode *inode)
{
        struct nfs_inode *nfsi = NFS_I(inode);
        struct nfs_delegation *delegation;
        int err = 0;

        nfs_wb_all(inode);
        delegation = nfs_start_delegation_return(nfsi);
        if (delegation != NULL)
                err = nfs_end_delegation_return(inode, delegation, 1);
        return err;
}

static void nfs_mark_return_if_closed_delegation(struct nfs_server *server,
                struct nfs_delegation *delegation)
{
        set_bit(NFS_DELEGATION_RETURN_IF_CLOSED, &delegation->flags);
        set_bit(NFS4CLNT_DELEGRETURN, &server->nfs_client->cl_state);
}

static void nfs_mark_return_delegation(struct nfs_server *server,
                struct nfs_delegation *delegation)
{
        set_bit(NFS_DELEGATION_RETURN, &delegation->flags);
        set_bit(NFS4CLNT_DELEGRETURN, &server->nfs_client->cl_state);
}

static bool nfs_server_mark_return_all_delegations(struct nfs_server *server)
{
        struct nfs_delegation *delegation;
        bool ret = false;

        list_for_each_entry_rcu(delegation, &server->delegations, super_list) {
                nfs_mark_return_delegation(server, delegation);
                ret = true;
        }
        return ret;
}

static void nfs_client_mark_return_all_delegations(struct nfs_client *clp)
{
        struct nfs_server *server;

        rcu_read_lock();
        list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link)
                nfs_server_mark_return_all_delegations(server);
        rcu_read_unlock();
}

static void nfs_delegation_run_state_manager(struct nfs_client *clp)
{
        if (test_bit(NFS4CLNT_DELEGRETURN, &clp->cl_state))
                nfs4_schedule_state_manager(clp);
}

/**
 * nfs_expire_all_delegations
 * @clp: client to process
 *
 */
void nfs_expire_all_delegations(struct nfs_client *clp)
{
        nfs_client_mark_return_all_delegations(clp);
        nfs_delegation_run_state_manager(clp);
}

/**
 * nfs_super_return_all_delegations - return delegations for one superblock
 * @sb: sb to process
 *
 */
void nfs_server_return_all_delegations(struct nfs_server *server)
{
        struct nfs_client *clp = server->nfs_client;
        bool need_wait;

        if (clp == NULL)
                return;

        rcu_read_lock();
        need_wait = nfs_server_mark_return_all_delegations(server);
        rcu_read_unlock();

        if (need_wait) {
                nfs4_schedule_state_manager(clp);
                nfs4_wait_clnt_recover(clp);
        }
}

static void nfs_mark_return_unused_delegation_types(struct nfs_server *server,
                                                 fmode_t flags)
{
        struct nfs_delegation *delegation;

        list_for_each_entry_rcu(delegation, &server->delegations, super_list) {
                if ((delegation->type == (FMODE_READ|FMODE_WRITE)) && !(flags & FMODE_WRITE))
                        continue;
                if (delegation->type & flags)
                        nfs_mark_return_if_closed_delegation(server, delegation);
        }
}

static void nfs_client_mark_return_unused_delegation_types(struct nfs_client *clp,
                                                        fmode_t flags)
{
        struct nfs_server *server;

        rcu_read_lock();
        list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link)
                nfs_mark_return_unused_delegation_types(server, flags);
        rcu_read_unlock();
}

void nfs_remove_bad_delegation(struct inode *inode)
{
        struct nfs_delegation *delegation;

        delegation = nfs_inode_detach_delegation(inode);
        if (delegation) {
                nfs_inode_find_state_and_recover(inode, &delegation->stateid);
                nfs_free_delegation(delegation);
        }
}
EXPORT_SYMBOL_GPL(nfs_remove_bad_delegation);

/**
 * nfs_expire_unused_delegation_types
 * @clp: client to process
 * @flags: delegation types to expire
 *
 */
void nfs_expire_unused_delegation_types(struct nfs_client *clp, fmode_t flags)
{
        nfs_client_mark_return_unused_delegation_types(clp, flags);
        nfs_delegation_run_state_manager(clp);
}

static void nfs_mark_return_unreferenced_delegations(struct nfs_server *server)
{
        struct nfs_delegation *delegation;

        list_for_each_entry_rcu(delegation, &server->delegations, super_list) {
                if (test_and_clear_bit(NFS_DELEGATION_REFERENCED, &delegation->flags))
                        continue;
                nfs_mark_return_if_closed_delegation(server, delegation);
        }
}

/**
 * nfs_expire_unreferenced_delegations - Eliminate unused delegations
 * @clp: nfs_client to process
 *
 */
void nfs_expire_unreferenced_delegations(struct nfs_client *clp)
{
        struct nfs_server *server;

        rcu_read_lock();
        list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link)
                nfs_mark_return_unreferenced_delegations(server);
        rcu_read_unlock();

        nfs_delegation_run_state_manager(clp);
}

/**
 * nfs_async_inode_return_delegation - asynchronously return a delegation
 * @inode: inode to process
 * @stateid: state ID information
 *
 * Returns zero on success, or a negative errno value.
 */
int nfs_async_inode_return_delegation(struct inode *inode,
                                      const nfs4_stateid *stateid)
{
        struct nfs_server *server = NFS_SERVER(inode);
        struct nfs_client *clp = server->nfs_client;
        struct nfs_delegation *delegation;

        filemap_flush(inode->i_mapping);

        rcu_read_lock();
        delegation = rcu_dereference(NFS_I(inode)->delegation);

        if (!clp->cl_mvops->match_stateid(&delegation->stateid, stateid)) {
                rcu_read_unlock();
                return -ENOENT;
        }
        nfs_mark_return_delegation(server, delegation);
        rcu_read_unlock();

        nfs_delegation_run_state_manager(clp);
        return 0;
}

static struct inode *
nfs_delegation_find_inode_server(struct nfs_server *server,
                                 const struct nfs_fh *fhandle)
{
        struct nfs_delegation *delegation;
        struct inode *res = NULL;

        list_for_each_entry_rcu(delegation, &server->delegations, super_list) {
                spin_lock(&delegation->lock);
                if (delegation->inode != NULL &&
                    nfs_compare_fh(fhandle, &NFS_I(delegation->inode)->fh) == 0) {
                        res = igrab(delegation->inode);
                }
                spin_unlock(&delegation->lock);
                if (res != NULL)
                        break;
        }
        return res;
}

/**
 * nfs_delegation_find_inode - retrieve the inode associated with a delegation
 * @clp: client state handle
 * @fhandle: filehandle from a delegation recall
 *
 * Returns pointer to inode matching "fhandle," or NULL if a matching inode
 * cannot be found.
 */
struct inode *nfs_delegation_find_inode(struct nfs_client *clp,
                                        const struct nfs_fh *fhandle)
{
        struct nfs_server *server;
        struct inode *res = NULL;

        rcu_read_lock();
        list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link) {
                res = nfs_delegation_find_inode_server(server, fhandle);
                if (res != NULL)
                        break;
        }
        rcu_read_unlock();
        return res;
}

static void nfs_delegation_mark_reclaim_server(struct nfs_server *server)
{
        struct nfs_delegation *delegation;

        list_for_each_entry_rcu(delegation, &server->delegations, super_list)
                set_bit(NFS_DELEGATION_NEED_RECLAIM, &delegation->flags);
}

/**
 * nfs_delegation_mark_reclaim - mark all delegations as needing to be reclaimed
 * @clp: nfs_client to process
 *
 */
void nfs_delegation_mark_reclaim(struct nfs_client *clp)
{
        struct nfs_server *server;

        rcu_read_lock();
        list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link)
                nfs_delegation_mark_reclaim_server(server);
        rcu_read_unlock();
}

/**
 * nfs_delegation_reap_unclaimed - reap unclaimed delegations after reboot recovery is done
 * @clp: nfs_client to process
 *
 */
void nfs_delegation_reap_unclaimed(struct nfs_client *clp)
{
        struct nfs_delegation *delegation;
        struct nfs_server *server;
        struct inode *inode;

restart:
        rcu_read_lock();
        list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link) {
                list_for_each_entry_rcu(delegation, &server->delegations,
                                                                super_list) {
                        if (test_bit(NFS_DELEGATION_NEED_RECLAIM,
                                                &delegation->flags) == 0)
                                continue;
                        inode = nfs_delegation_grab_inode(delegation);
                        if (inode == NULL)
                                continue;
                        delegation = nfs_detach_delegation(NFS_I(inode),
                                        delegation, server);
                        rcu_read_unlock();

                        if (delegation != NULL)
                                nfs_free_delegation(delegation);
                        iput(inode);
                        goto restart;
                }
        }
        rcu_read_unlock();
}

/**
 * nfs_delegations_present - check for existence of delegations
 * @clp: client state handle
 *
 * Returns one if there are any nfs_delegation structures attached
 * to this nfs_client.
 */
int nfs_delegations_present(struct nfs_client *clp)
{
        struct nfs_server *server;
        int ret = 0;

        rcu_read_lock();
        list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link)
                if (!list_empty(&server->delegations)) {
                        ret = 1;
                        break;
                }
        rcu_read_unlock();
        return ret;
}

/**
 * nfs4_copy_delegation_stateid - Copy inode's state ID information
 * @dst: stateid data structure to fill in
 * @inode: inode to check
 * @flags: delegation type requirement
 *
 * Returns "true" and fills in "dst->data" * if inode had a delegation,
 * otherwise "false" is returned.
 */
bool nfs4_copy_delegation_stateid(nfs4_stateid *dst, struct inode *inode,
                fmode_t flags)
{
        struct nfs_inode *nfsi = NFS_I(inode);
        struct nfs_delegation *delegation;
        bool ret;

        flags &= FMODE_READ|FMODE_WRITE;
        rcu_read_lock();
        delegation = rcu_dereference(nfsi->delegation);
        ret = (delegation != NULL && (delegation->type & flags) == flags);
        if (ret) {
                nfs4_stateid_copy(dst, &delegation->stateid);
                nfs_mark_delegation_referenced(delegation);
        }
        rcu_read_unlock();
        return ret;
}