// SPDX-License-Identifier: GPL-2.0
/*
 * linux/fs/nfs/callback_proc.c
 *
 * Copyright (C) 2004 Trond Myklebust
 *
 * NFSv4 callback procedures
 */
#include <linux/nfs4.h>
#include <linux/nfs_fs.h>
#include <linux/slab.h>
#include <linux/rcupdate.h>
#include "nfs4_fs.h"
#include "callback.h"
#include "delegation.h"
#include "internal.h"
#include "pnfs.h"
#include "nfs4session.h"
#include "nfs4trace.h"

#define NFSDBG_FACILITY NFSDBG_CALLBACK

__be32 nfs4_callback_getattr(void *argp, void *resp,
                             struct cb_process_state *cps)
{
        struct cb_getattrargs *args = argp;
        struct cb_getattrres *res = resp;
        struct nfs_delegation *delegation;
        struct inode *inode;

        res->status = htonl(NFS4ERR_OP_NOT_IN_SESSION);
        if (!cps->clp) /* Always set for v4.0. Set in cb_sequence for v4.1 */
                goto out;

        res->bitmap[0] = res->bitmap[1] = 0;
        res->status = htonl(NFS4ERR_BADHANDLE);

        dprintk_rcu("NFS: GETATTR callback request from %s\n",
                rpc_peeraddr2str(cps->clp->cl_rpcclient, RPC_DISPLAY_ADDR));

        inode = nfs_delegation_find_inode(cps->clp, &args->fh);
        if (IS_ERR(inode)) {
                if (inode == ERR_PTR(-EAGAIN))
                        res->status = htonl(NFS4ERR_DELAY);
                trace_nfs4_cb_getattr(cps->clp, &args->fh, NULL,
                                -ntohl(res->status));
                goto out;
        }
        rcu_read_lock();
        delegation = nfs4_get_valid_delegation(inode);
        if (delegation == NULL || (delegation->type & FMODE_WRITE) == 0)
                goto out_iput;
        res->size = i_size_read(inode);
        res->change_attr = delegation->change_attr;
        if (nfs_have_writebacks(inode))
                res->change_attr++;
        res->ctime = inode->i_ctime;
        res->mtime = inode->i_mtime;
        res->bitmap[0] = (FATTR4_WORD0_CHANGE|FATTR4_WORD0_SIZE) &
                args->bitmap[0];
        res->bitmap[1] = (FATTR4_WORD1_TIME_METADATA|FATTR4_WORD1_TIME_MODIFY) &
                args->bitmap[1];
        res->status = 0;
out_iput:
        rcu_read_unlock();
        trace_nfs4_cb_getattr(cps->clp, &args->fh, inode, -ntohl(res->status));
        nfs_iput_and_deactive(inode);
out:
        dprintk("%s: exit with status = %d\n", __func__, ntohl(res->status));
        return res->status;
}

__be32 nfs4_callback_recall(void *argp, void *resp,
                            struct cb_process_state *cps)
{
        struct cb_recallargs *args = argp;
        struct inode *inode;
        __be32 res;
        
        res = htonl(NFS4ERR_OP_NOT_IN_SESSION);
        if (!cps->clp) /* Always set for v4.0. Set in cb_sequence for v4.1 */
                goto out;

        dprintk_rcu("NFS: RECALL callback request from %s\n",
                rpc_peeraddr2str(cps->clp->cl_rpcclient, RPC_DISPLAY_ADDR));

        res = htonl(NFS4ERR_BADHANDLE);
        inode = nfs_delegation_find_inode(cps->clp, &args->fh);
        if (IS_ERR(inode)) {
                if (inode == ERR_PTR(-EAGAIN))
                        res = htonl(NFS4ERR_DELAY);
                trace_nfs4_cb_recall(cps->clp, &args->fh, NULL,
                                &args->stateid, -ntohl(res));
                goto out;
        }
        /* Set up a helper thread to actually return the delegation */
        switch (nfs_async_inode_return_delegation(inode, &args->stateid)) {
        case 0:
                res = 0;
                break;
        case -ENOENT:
                res = htonl(NFS4ERR_BAD_STATEID);
                break;
        default:
                res = htonl(NFS4ERR_RESOURCE);
        }
        trace_nfs4_cb_recall(cps->clp, &args->fh, inode,
                        &args->stateid, -ntohl(res));
        nfs_iput_and_deactive(inode);
out:
        dprintk("%s: exit with status = %d\n", __func__, ntohl(res));
        return res;
}

#if defined(CONFIG_NFS_V4_1)

/*
 * Lookup a layout inode by stateid
 *
 * Note: returns a refcount on the inode and superblock
 */
static struct inode *nfs_layout_find_inode_by_stateid(struct nfs_client *clp,
                const nfs4_stateid *stateid)
        __must_hold(RCU)
{
        struct nfs_server *server;
        struct inode *inode;
        struct pnfs_layout_hdr *lo;

        rcu_read_lock();
        list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link) {
                list_for_each_entry_rcu(lo, &server->layouts, plh_layouts) {
                        if (!pnfs_layout_is_valid(lo))
                                continue;
                        if (stateid != NULL &&
                            !nfs4_stateid_match_other(stateid, &lo->plh_stateid))
                                continue;
                        if (!nfs_sb_active(server->super))
                                continue;
                        inode = igrab(lo->plh_inode);
                        rcu_read_unlock();
                        if (inode)
                                return inode;
                        nfs_sb_deactive(server->super);
                        return ERR_PTR(-EAGAIN);
                }
        }
        rcu_read_unlock();
        return ERR_PTR(-ENOENT);
}

/*
 * Lookup a layout inode by filehandle.
 *
 * Note: returns a refcount on the inode and superblock
 *
 */
static struct inode *nfs_layout_find_inode_by_fh(struct nfs_client *clp,
                const struct nfs_fh *fh)
{
        struct nfs_server *server;
        struct nfs_inode *nfsi;
        struct inode *inode;
        struct pnfs_layout_hdr *lo;

        rcu_read_lock();
        list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link) {
                list_for_each_entry_rcu(lo, &server->layouts, plh_layouts) {
                        nfsi = NFS_I(lo->plh_inode);
                        if (nfs_compare_fh(fh, &nfsi->fh))
                                continue;
                        if (nfsi->layout != lo)
                                continue;
                        if (!nfs_sb_active(server->super))
                                continue;
                        inode = igrab(lo->plh_inode);
                        rcu_read_unlock();
                        if (inode)
                                return inode;
                        nfs_sb_deactive(server->super);
                        return ERR_PTR(-EAGAIN);
                }
        }
        rcu_read_unlock();
        return ERR_PTR(-ENOENT);
}

static struct inode *nfs_layout_find_inode(struct nfs_client *clp,
                const struct nfs_fh *fh,
                const nfs4_stateid *stateid)
{
        struct inode *inode;

        inode = nfs_layout_find_inode_by_stateid(clp, stateid);
        if (inode == ERR_PTR(-ENOENT))
                inode = nfs_layout_find_inode_by_fh(clp, fh);
        return inode;
}

/*
 * Enforce RFC5661 section 12.5.5.2.1. (Layout Recall and Return Sequencing)
 */
static u32 pnfs_check_callback_stateid(struct pnfs_layout_hdr *lo,
                                        const nfs4_stateid *new)
{
        u32 oldseq, newseq;

        /* Is the stateid not initialised? */
        if (!pnfs_layout_is_valid(lo))
                return NFS4ERR_NOMATCHING_LAYOUT;

        /* Mismatched stateid? */
        if (!nfs4_stateid_match_other(&lo->plh_stateid, new))
                return NFS4ERR_BAD_STATEID;

        newseq = be32_to_cpu(new->seqid);
        /* Are we already in a layout recall situation? */
        if (test_bit(NFS_LAYOUT_RETURN_REQUESTED, &lo->plh_flags) &&
            lo->plh_return_seq != 0) {
                if (newseq < lo->plh_return_seq)
                        return NFS4ERR_OLD_STATEID;
                if (newseq > lo->plh_return_seq)
                        return NFS4ERR_DELAY;
                goto out;
        }

        /* Check that the stateid matches what we think it should be. */
        oldseq = be32_to_cpu(lo->plh_stateid.seqid);
        if (newseq > oldseq + 1)
                return NFS4ERR_DELAY;
        /* Crazy server! */
        if (newseq <= oldseq)
                return NFS4ERR_OLD_STATEID;
out:
        return NFS_OK;
}

static u32 initiate_file_draining(struct nfs_client *clp,
                                  struct cb_layoutrecallargs *args)
{
        struct inode *ino;
        struct pnfs_layout_hdr *lo;
        u32 rv = NFS4ERR_NOMATCHING_LAYOUT;
        LIST_HEAD(free_me_list);

        ino = nfs_layout_find_inode(clp, &args->cbl_fh, &args->cbl_stateid);
        if (IS_ERR(ino)) {
                if (ino == ERR_PTR(-EAGAIN))
                        rv = NFS4ERR_DELAY;
                goto out_noput;
        }

        pnfs_layoutcommit_inode(ino, false);


        spin_lock(&ino->i_lock);
        lo = NFS_I(ino)->layout;
        if (!lo) {
                spin_unlock(&ino->i_lock);
                goto out;
        }
        pnfs_get_layout_hdr(lo);
        rv = pnfs_check_callback_stateid(lo, &args->cbl_stateid);
        if (rv != NFS_OK)
                goto unlock;

        /*
         * Enforce RFC5661 Section 12.5.5.2.1.5 (Bulk Recall and Return)
         */
        if (test_bit(NFS_LAYOUT_BULK_RECALL, &lo->plh_flags)) {
                rv = NFS4ERR_DELAY;
                goto unlock;
        }

        pnfs_set_layout_stateid(lo, &args->cbl_stateid, NULL, true);
        switch (pnfs_mark_matching_lsegs_return(lo, &free_me_list,
                                &args->cbl_range,
                                be32_to_cpu(args->cbl_stateid.seqid))) {
        case 0:
        case -EBUSY:
                /* There are layout segments that need to be returned */
                rv = NFS4_OK;
                break;
        case -ENOENT:
                /* Embrace your forgetfulness! */
                rv = NFS4ERR_NOMATCHING_LAYOUT;

                if (NFS_SERVER(ino)->pnfs_curr_ld->return_range) {
                        NFS_SERVER(ino)->pnfs_curr_ld->return_range(lo,
                                &args->cbl_range);
                }
        }
unlock:
        spin_unlock(&ino->i_lock);
        pnfs_free_lseg_list(&free_me_list);
        /* Free all lsegs that are attached to commit buckets */
        nfs_commit_inode(ino, 0);
        pnfs_put_layout_hdr(lo);
out:
        nfs_iput_and_deactive(ino);
out_noput:
        trace_nfs4_cb_layoutrecall_file(clp, &args->cbl_fh, ino,
                        &args->cbl_stateid, -rv);
        return rv;
}

static u32 initiate_bulk_draining(struct nfs_client *clp,
                                  struct cb_layoutrecallargs *args)
{
        int stat;

        if (args->cbl_recall_type == RETURN_FSID)
                stat = pnfs_destroy_layouts_byfsid(clp, &args->cbl_fsid, true);
        else
                stat = pnfs_destroy_layouts_byclid(clp, true);
        if (stat != 0)
                return NFS4ERR_DELAY;
        return NFS4ERR_NOMATCHING_LAYOUT;
}

static u32 do_callback_layoutrecall(struct nfs_client *clp,
                                    struct cb_layoutrecallargs *args)
{
        if (args->cbl_recall_type == RETURN_FILE)
                return initiate_file_draining(clp, args);
        return initiate_bulk_draining(clp, args);
}

__be32 nfs4_callback_layoutrecall(void *argp, void *resp,
                                  struct cb_process_state *cps)
{
        struct cb_layoutrecallargs *args = argp;
        u32 res = NFS4ERR_OP_NOT_IN_SESSION;

        if (cps->clp)
                res = do_callback_layoutrecall(cps->clp, args);
        return cpu_to_be32(res);
}

static void pnfs_recall_all_layouts(struct nfs_client *clp)
{
        struct cb_layoutrecallargs args;

        /* Pretend we got a CB_LAYOUTRECALL(ALL) */
        memset(&args, 0, sizeof(args));
        args.cbl_recall_type = RETURN_ALL;
        /* FIXME we ignore errors, what should we do? */
        do_callback_layoutrecall(clp, &args);
}

__be32 nfs4_callback_devicenotify(void *argp, void *resp,
                                  struct cb_process_state *cps)
{
        struct cb_devicenotifyargs *args = argp;
        int i;
        __be32 res = 0;
        struct nfs_client *clp = cps->clp;
        struct nfs_server *server = NULL;

        if (!clp) {
                res = cpu_to_be32(NFS4ERR_OP_NOT_IN_SESSION);
                goto out;
        }

        for (i = 0; i < args->ndevs; i++) {
                struct cb_devicenotifyitem *dev = &args->devs[i];

                if (!server ||
                    server->pnfs_curr_ld->id != dev->cbd_layout_type) {
                        rcu_read_lock();
                        list_for_each_entry_rcu(server, &clp->cl_superblocks, client_link)
                                if (server->pnfs_curr_ld &&
                                    server->pnfs_curr_ld->id == dev->cbd_layout_type) {
                                        rcu_read_unlock();
                                        goto found;
                                }
                        rcu_read_unlock();
                        continue;
                }

        found:
                nfs4_delete_deviceid(server->pnfs_curr_ld, clp, &dev->cbd_dev_id);
        }

out:
        kfree(args->devs);
        return res;
}

/*
 * Validate the sequenceID sent by the server.
 * Return success if the sequenceID is one more than what we last saw on
 * this slot, accounting for wraparound.  Increments the slot's sequence.
 *
 * We don't yet implement a duplicate request cache, instead we set the
 * back channel ca_maxresponsesize_cached to zero. This is OK for now
 * since we only currently implement idempotent callbacks anyway.
 *
 * We have a single slot backchannel at this time, so we don't bother
 * checking the used_slots bit array on the table.  The lower layer guarantees
 * a single outstanding callback request at a time.
 */
static __be32
validate_seqid(const struct nfs4_slot_table *tbl, const struct nfs4_slot *slot,
                const struct cb_sequenceargs * args)
{
        __be32 ret;

        ret = cpu_to_be32(NFS4ERR_BADSLOT);
        if (args->csa_slotid > tbl->server_highest_slotid)
                goto out_err;

        /* Replay */
        if (args->csa_sequenceid == slot->seq_nr) {
                ret = cpu_to_be32(NFS4ERR_DELAY);
                if (nfs4_test_locked_slot(tbl, slot->slot_nr))
                        goto out_err;

                /* Signal process_op to set this error on next op */
                ret = cpu_to_be32(NFS4ERR_RETRY_UNCACHED_REP);
                if (args->csa_cachethis == 0)
                        goto out_err;

                /* Liar! We never allowed you to set csa_cachethis != 0 */
                ret = cpu_to_be32(NFS4ERR_SEQ_FALSE_RETRY);
                goto out_err;
        }

        /* Note: wraparound relies on seq_nr being of type u32 */
        /* Misordered request */
        ret = cpu_to_be32(NFS4ERR_SEQ_MISORDERED);
        if (args->csa_sequenceid != slot->seq_nr + 1)
                goto out_err;

        return cpu_to_be32(NFS4_OK);

out_err:
        trace_nfs4_cb_seqid_err(args, ret);
        return ret;
}

/*
 * For each referring call triple, check the session's slot table for
 * a match.  If the slot is in use and the sequence numbers match, the
 * client is still waiting for a response to the original request.
 */
static int referring_call_exists(struct nfs_client *clp,
                                  uint32_t nrclists,
                                  struct referring_call_list *rclists,
                                  spinlock_t *lock)
        __releases(lock)
        __acquires(lock)
{
        int status = 0;
        int i, j;
        struct nfs4_session *session;
        struct nfs4_slot_table *tbl;
        struct referring_call_list *rclist;
        struct referring_call *ref;

        /*
         * XXX When client trunking is implemented, this becomes
         * a session lookup from within the loop
         */
        session = clp->cl_session;
        tbl = &session->fc_slot_table;

        for (i = 0; i < nrclists; i++) {
                rclist = &rclists[i];
                if (memcmp(session->sess_id.data,
                           rclist->rcl_sessionid.data,
                           NFS4_MAX_SESSIONID_LEN) != 0)
                        continue;

                for (j = 0; j < rclist->rcl_nrefcalls; j++) {
                        ref = &rclist->rcl_refcalls[j];
                        spin_unlock(lock);
                        status = nfs4_slot_wait_on_seqid(tbl, ref->rc_slotid,
                                        ref->rc_sequenceid, HZ >> 1) < 0;
                        spin_lock(lock);
                        if (status)
                                goto out;
                }
        }

out:
        return status;
}

__be32 nfs4_callback_sequence(void *argp, void *resp,
                              struct cb_process_state *cps)
{
        struct cb_sequenceargs *args = argp;
        struct cb_sequenceres *res = resp;
        struct nfs4_slot_table *tbl;
        struct nfs4_slot *slot;
        struct nfs_client *clp;
        int i;
        __be32 status = htonl(NFS4ERR_BADSESSION);

        clp = nfs4_find_client_sessionid(cps->net, args->csa_addr,
                                         &args->csa_sessionid, cps->minorversion);
        if (clp == NULL)
                goto out;

        if (!(clp->cl_session->flags & SESSION4_BACK_CHAN))
                goto out;

        tbl = &clp->cl_session->bc_slot_table;

        /* Set up res before grabbing the spinlock */
        memcpy(&res->csr_sessionid, &args->csa_sessionid,
               sizeof(res->csr_sessionid));
        res->csr_sequenceid = args->csa_sequenceid;
        res->csr_slotid = args->csa_slotid;

        spin_lock(&tbl->slot_tbl_lock);
        /* state manager is resetting the session */
        if (test_bit(NFS4_SLOT_TBL_DRAINING, &tbl->slot_tbl_state)) {
                status = htonl(NFS4ERR_DELAY);
                /* Return NFS4ERR_BADSESSION if we're draining the session
                 * in order to reset it.
                 */
                if (test_bit(NFS4CLNT_SESSION_RESET, &clp->cl_state))
                        status = htonl(NFS4ERR_BADSESSION);
                goto out_unlock;
        }

        status = htonl(NFS4ERR_BADSLOT);
        slot = nfs4_lookup_slot(tbl, args->csa_slotid);
        if (IS_ERR(slot))
                goto out_unlock;

        res->csr_highestslotid = tbl->server_highest_slotid;
        res->csr_target_highestslotid = tbl->target_highest_slotid;

        status = validate_seqid(tbl, slot, args);
        if (status)
                goto out_unlock;
        if (!nfs4_try_to_lock_slot(tbl, slot)) {
                status = htonl(NFS4ERR_DELAY);
                goto out_unlock;
        }
        cps->slot = slot;

        /* The ca_maxresponsesize_cached is 0 with no DRC */
        if (args->csa_cachethis != 0) {
                status = htonl(NFS4ERR_REP_TOO_BIG_TO_CACHE);
                goto out_unlock;
        }

        /*
         * Check for pending referring calls.  If a match is found, a
         * related callback was received before the response to the original
         * call.
         */
        if (referring_call_exists(clp, args->csa_nrclists, args->csa_rclists,
                                &tbl->slot_tbl_lock) < 0) {
                status = htonl(NFS4ERR_DELAY);
                goto out_unlock;
        }

        /*
         * RFC5661 20.9.3
         * If CB_SEQUENCE returns an error, then the state of the slot
         * (sequence ID, cached reply) MUST NOT change.
         */
        slot->seq_nr = args->csa_sequenceid;
out_unlock:
        spin_unlock(&tbl->slot_tbl_lock);

out:
        cps->clp = clp; /* put in nfs4_callback_compound */
        for (i = 0; i < args->csa_nrclists; i++)
                kfree(args->csa_rclists[i].rcl_refcalls);
        kfree(args->csa_rclists);

        if (status == htonl(NFS4ERR_RETRY_UNCACHED_REP)) {
                cps->drc_status = status;
                status = 0;
        } else
                res->csr_status = status;

        trace_nfs4_cb_sequence(args, res, status);
        return status;
}

static bool
validate_bitmap_values(unsigned int mask)
{
        return (mask & ~RCA4_TYPE_MASK_ALL) == 0;
}

__be32 nfs4_callback_recallany(void *argp, void *resp,
                               struct cb_process_state *cps)
{
        struct cb_recallanyargs *args = argp;
        __be32 status;
        fmode_t flags = 0;
        bool schedule_manager = false;

        status = cpu_to_be32(NFS4ERR_OP_NOT_IN_SESSION);
        if (!cps->clp) /* set in cb_sequence */
                goto out;

        dprintk_rcu("NFS: RECALL_ANY callback request from %s\n",
                rpc_peeraddr2str(cps->clp->cl_rpcclient, RPC_DISPLAY_ADDR));

        status = cpu_to_be32(NFS4ERR_INVAL);
        if (!validate_bitmap_values(args->craa_type_mask))
                goto out;

        status = cpu_to_be32(NFS4_OK);
        if (args->craa_type_mask & BIT(RCA4_TYPE_MASK_RDATA_DLG))
                flags = FMODE_READ;
        if (args->craa_type_mask & BIT(RCA4_TYPE_MASK_WDATA_DLG))
                flags |= FMODE_WRITE;
        if (flags)
                nfs_expire_unused_delegation_types(cps->clp, flags);

        if (args->craa_type_mask & BIT(RCA4_TYPE_MASK_FILE_LAYOUT))
                pnfs_recall_all_layouts(cps->clp);

        if (args->craa_type_mask & BIT(PNFS_FF_RCA4_TYPE_MASK_READ)) {
                set_bit(NFS4CLNT_RECALL_ANY_LAYOUT_READ, &cps->clp->cl_state);
                schedule_manager = true;
        }
        if (args->craa_type_mask & BIT(PNFS_FF_RCA4_TYPE_MASK_RW)) {
                set_bit(NFS4CLNT_RECALL_ANY_LAYOUT_RW, &cps->clp->cl_state);
                schedule_manager = true;
        }
        if (schedule_manager)
                nfs4_schedule_state_manager(cps->clp);

out:
        dprintk("%s: exit with status = %d\n", __func__, ntohl(status));
        return status;
}

/* Reduce the fore channel's max_slots to the target value */
__be32 nfs4_callback_recallslot(void *argp, void *resp,
                                struct cb_process_state *cps)
{
        struct cb_recallslotargs *args = argp;
        struct nfs4_slot_table *fc_tbl;
        __be32 status;

        status = htonl(NFS4ERR_OP_NOT_IN_SESSION);
        if (!cps->clp) /* set in cb_sequence */
                goto out;

        dprintk_rcu("NFS: CB_RECALL_SLOT request from %s target highest slotid %u\n",
                rpc_peeraddr2str(cps->clp->cl_rpcclient, RPC_DISPLAY_ADDR),
                args->crsa_target_highest_slotid);

        fc_tbl = &cps->clp->cl_session->fc_slot_table;

        status = htonl(NFS4_OK);

        nfs41_set_target_slotid(fc_tbl, args->crsa_target_highest_slotid);
        nfs41_notify_server(cps->clp);
out:
        dprintk("%s: exit with status = %d\n", __func__, ntohl(status));
        return status;
}

__be32 nfs4_callback_notify_lock(void *argp, void *resp,
                                 struct cb_process_state *cps)
{
        struct cb_notify_lock_args *args = argp;

        if (!cps->clp) /* set in cb_sequence */
                return htonl(NFS4ERR_OP_NOT_IN_SESSION);

        dprintk_rcu("NFS: CB_NOTIFY_LOCK request from %s\n",
                rpc_peeraddr2str(cps->clp->cl_rpcclient, RPC_DISPLAY_ADDR));

        /* Don't wake anybody if the string looked bogus */
        if (args->cbnl_valid)
                __wake_up(&cps->clp->cl_lock_waitq, TASK_NORMAL, 0, args);

        return htonl(NFS4_OK);
}
#endif /* CONFIG_NFS_V4_1 */
#ifdef CONFIG_NFS_V4_2
static void nfs4_copy_cb_args(struct nfs4_copy_state *cp_state,
                                struct cb_offloadargs *args)
{
        cp_state->count = args->wr_count;
        cp_state->error = args->error;
        if (!args->error) {
                cp_state->verf.committed = args->wr_writeverf.committed;
                memcpy(&cp_state->verf.verifier.data[0],
                        &args->wr_writeverf.verifier.data[0],
                        NFS4_VERIFIER_SIZE);
        }
}

__be32 nfs4_callback_offload(void *data, void *dummy,
                             struct cb_process_state *cps)
{
        struct cb_offloadargs *args = data;
        struct nfs_server *server;
        struct nfs4_copy_state *copy, *tmp_copy;
        bool found = false;

        copy = kzalloc(sizeof(struct nfs4_copy_state), GFP_NOFS);
        if (!copy)
                return htonl(NFS4ERR_SERVERFAULT);

        spin_lock(&cps->clp->cl_lock);
        rcu_read_lock();
        list_for_each_entry_rcu(server, &cps->clp->cl_superblocks,
                                client_link) {
                list_for_each_entry(tmp_copy, &server->ss_copies, copies) {
                        if (memcmp(args->coa_stateid.other,
                                        tmp_copy->stateid.other,
                                        sizeof(args->coa_stateid.other)))
                                continue;
                        nfs4_copy_cb_args(tmp_copy, args);
                        complete(&tmp_copy->completion);
                        found = true;
                        goto out;
                }
        }
out:
        rcu_read_unlock();
        if (!found) {
                memcpy(&copy->stateid, &args->coa_stateid, NFS4_STATEID_SIZE);
                nfs4_copy_cb_args(copy, args);
                list_add_tail(&copy->copies, &cps->clp->pending_cb_stateids);
        } else
                kfree(copy);
        spin_unlock(&cps->clp->cl_lock);

        return 0;
}
#endif /* CONFIG_NFS_V4_2 */