/*
 *   Copyright (c) 2017 Red Hat, Inc. <http://www.redhat.com>
 *   This file is part of GlusterFS.
 *
 *   This file is licensed to you under your choice of the GNU Lesser
 *   General Public License, version 3 or any later version (LGPLv3 or
 *   later), or the GNU General Public License, version 2 (GPLv2), in all
 *   cases as published by the Free Software Foundation.
 */

#include "nl-cache.h"
#include "timer-wheel.h"
#include "statedump.h"

/* Caching guidelines:
 * This xlator serves negative lookup(ENOENT lookups) from the cache,
 * there by making create faster.
 *   What is cached?
 *      Negative lookup cache is stored for each directory, and has 2 entries:
 *      - Negative entries: Populated only when lookup/stat returns ENOENT.
 *        Fuse mostly sends only one lookup before create, hence negative entry
 *        cache is almost useless. But for SMB access, multiple lookups/stats
 *        are sent before creating the file. Hence the negative entry cache.
 *        It can exist even when the positive entry cache is invalid. It also
 *        has the entries that were deleted from this directory.
 *        Freed on receiving upcall(with dentry change flag) or on expiring
 *        timeout of the cache.
 *
 *      - Positive entries: Populated as a part of readdirp, and as a part of
 *        mkdir followed by creates inside that directory. Lookups and other
 *        fops do not populate the positive entry (as it can grow long and is
 *        of no value add)
 *        Freed on receiving upcall(with dentry change flag) or on expiring
 *        timeout of the cache.
 *
 *   Data structures to store cache?
 *      The cache of any directory is stored in the inode_ctx of the directory.
 *      Negative entries are stored as list of strings.
 *             Search - O(n)
 *             Add    - O(1)
 *             Delete - O(n) - as it has to be searched before deleting
 *      Positive entries are stored as a list, each list node has a pointer
 *          to the inode of the positive entry or the name of the entry.
 *          Since the client side inode table already will have inodes for
 *          positive entries, we just take a ref of that inode and store as
 *          positive entry cache. In cases like hardlinks and readdirp where
 *          inode is NULL, we store the names.
 *          Name Search - O(n)
 *          Inode Search - O(1) - Actually complexity of inode_find()
 *          Name/inode Add - O(1)
 *          Name Delete - O(n)
 *          Inode Delete - O(1)
 *
 * Locking order:
 *
 * TODO:
 * - Fill Positive entries on readdir/p, after which in lookup_cbk check if the
 *   name is in PE and replace it with inode.
 * - fini, PARENET_DOWN, disable caching
 * - Virtual setxattr to dump the inode_ctx, to ease debugging
 * - Handle dht_nuke xattr: clear all cache
 * - Special handling for .meta and .trashcan?
 */

int __nlc_inode_ctx_timer_start (xlator_t *this, inode_t *inode, nlc_ctx_t *nlc_ctx);
int __nlc_add_to_lru (xlator_t *this, inode_t *inode, nlc_ctx_t *nlc_ctx);
void nlc_remove_from_lru (xlator_t *this, inode_t *inode);
void __nlc_inode_ctx_timer_delete (xlator_t *this, nlc_ctx_t *nlc_ctx);
gf_boolean_t __nlc_search_ne (nlc_ctx_t *nlc_ctx, const char *name);
void __nlc_free_pe (xlator_t *this, nlc_ctx_t *nlc_ctx, nlc_pe_t *pe);
void __nlc_free_ne (xlator_t *this, nlc_ctx_t *nlc_ctx, nlc_ne_t *ne);

static int32_t
nlc_get_cache_timeout (xlator_t *this)
{
        nlc_conf_t *conf = NULL;

        conf = this->private;

        /* Cache timeout is generally not meant to be changed often,
         * once set, hence not within locks */
        return conf->cache_timeout;
}


static gf_boolean_t
__nlc_is_cache_valid (xlator_t *this, nlc_ctx_t *nlc_ctx)
{
        nlc_conf_t   *conf         = NULL;
        time_t       last_val_time;
        gf_boolean_t ret           = _gf_false;

        GF_VALIDATE_OR_GOTO (this->name, nlc_ctx, out);

        conf = this->private;

        LOCK (&conf->lock);
        {
                last_val_time = conf->last_child_down;
        }
        UNLOCK (&conf->lock);

        if ((last_val_time <= nlc_ctx->cache_time) &&
            (nlc_ctx->cache_time != 0))
                ret = _gf_true;
out:
        return ret;
}


void
nlc_update_child_down_time (xlator_t *this, time_t *now)
{
        nlc_conf_t *conf = NULL;

        conf = this->private;

        LOCK (&conf->lock);
        {
                conf->last_child_down = *now;
        }
        UNLOCK (&conf->lock);

        return;
}


void
nlc_disable_cache (xlator_t *this)
{
        nlc_conf_t *conf = NULL;

        conf = this->private;

        LOCK (&conf->lock);
        {
                conf->disable_cache = _gf_true;
        }
        UNLOCK (&conf->lock);

        return;
}


static int
__nlc_inode_ctx_get (xlator_t *this, inode_t *inode, nlc_ctx_t **nlc_ctx_p,
                     nlc_pe_t **nlc_pe_p)
{
        int              ret = 0;
        nlc_ctx_t        *nlc_ctx = NULL;
        nlc_pe_t         *nlc_pe = NULL;
        uint64_t         nlc_ctx_int = 0;
        uint64_t         nlc_pe_int = 0;

        ret = __inode_ctx_get2 (inode, this, &nlc_ctx_int, &nlc_pe_int);
        if (ret == 0 && nlc_ctx_p) {
                nlc_ctx = (void *) (long) (nlc_ctx_int);
                *nlc_ctx_p = nlc_ctx;
        }
        if (ret == 0 && nlc_pe_p) {
                nlc_pe = (void *) (long) (nlc_pe_int);
                *nlc_pe_p = nlc_pe;
        }
        return ret;
}


static int
nlc_inode_ctx_set (xlator_t *this, inode_t *inode, nlc_ctx_t *nlc_ctx,
                   nlc_pe_t *nlc_pe_p)
{
        int   ret = -1;

        /* The caller may choose to set one of the ctxs, hence check
         * if the ctx1/2 is non zero and then send the address. If we
         * blindly send the address of both the ctxs, it may reset the
         * ctx the caller had sent NULL(intended as leave untouched) for.*/
        LOCK(&inode->lock);
        {
                ret = __inode_ctx_set2 (inode, this,
                                        nlc_ctx ? (uint64_t *) &nlc_ctx : 0,
                                        nlc_pe_p ? (uint64_t *) &nlc_pe_p : 0);
        }
        UNLOCK(&inode->lock);
        return ret;
}


static void
nlc_inode_ctx_get (xlator_t *this, inode_t *inode, nlc_ctx_t **nlc_ctx_p,
                   nlc_pe_t **nlc_pe_p)
{
        int ret = 0;

        LOCK (&inode->lock);
        {
                ret = __nlc_inode_ctx_get (this, inode, nlc_ctx_p, nlc_pe_p);
                if (ret < 0)
                        gf_msg_debug (this->name, 0, "inode ctx get failed for "
                                      "inode:%p", inode);
        }
        UNLOCK (&inode->lock);

        return;
}


static void
__nlc_inode_clear_entries (xlator_t *this, nlc_ctx_t *nlc_ctx)
{
        nlc_pe_t         *pe         = NULL;
        nlc_pe_t         *tmp        = NULL;
        nlc_ne_t         *ne         = NULL;
        nlc_ne_t         *tmp1       = NULL;

        if (!nlc_ctx)
                goto out;

        if (IS_PE_VALID (nlc_ctx->state))
                list_for_each_entry_safe (pe, tmp, &nlc_ctx->pe, list) {
                        __nlc_free_pe (this, nlc_ctx, pe);
                }

        if (IS_NE_VALID (nlc_ctx->state))
                list_for_each_entry_safe (ne, tmp1, &nlc_ctx->ne, list) {
                        __nlc_free_ne (this, nlc_ctx, ne);
                }

        nlc_ctx->cache_time = 0;
        nlc_ctx->state = 0;
        GF_ASSERT (nlc_ctx->cache_size == sizeof (*nlc_ctx));
        GF_ASSERT (nlc_ctx->refd_inodes == 0);
out:
        return;
}


static void
nlc_init_invalid_ctx (xlator_t *this, inode_t *inode, nlc_ctx_t *nlc_ctx)
{
        nlc_conf_t                 *conf   = NULL;
        int                         ret    = -1;

        conf = this->private;

        LOCK (&nlc_ctx->lock);
        {
                if (__nlc_is_cache_valid (this, nlc_ctx))
                        goto unlock;

                /* The cache/nlc_ctx can be invalid for 2 reasons:
                 * - Because of a child-down/timer expiry, cache is
                 *   invalid but the nlc_ctx is not yet cleaned up.
                 * - nlc_ctx is cleaned up, because of invalidations
                 *   or lru prune etc.*/

                /* If the cache is present but invalid, clear the cache and
                 * reset the timer. */
                __nlc_inode_clear_entries (this, nlc_ctx);

                /* If timer is present, then it is already part of lru as well
                 * Hence reset the timer and return.*/
                if (nlc_ctx->timer) {
                        gf_tw_mod_timer_pending (conf->timer_wheel,
                                                 nlc_ctx->timer,
                                                 conf->cache_timeout);
                        time (&nlc_ctx->cache_time);
                        goto unlock;
                }

                /* If timer was NULL, the nlc_ctx is already cleanedup,
                 * and we need to start timer and add to lru, so that it is
                 * ready to cache entries a fresh */
                ret = __nlc_inode_ctx_timer_start (this, inode, nlc_ctx);
                if (ret < 0)
                        goto unlock;

                ret = __nlc_add_to_lru (this, inode, nlc_ctx);
                if (ret < 0) {
                        __nlc_inode_ctx_timer_delete (this, nlc_ctx);
                        goto unlock;
                }
        }
unlock:
        UNLOCK (&nlc_ctx->lock);

        return;
}

static nlc_ctx_t *
nlc_inode_ctx_get_set (xlator_t *this, inode_t *inode, nlc_ctx_t **nlc_ctx_p,
                       nlc_pe_t **nlc_pe_p)
{
        int                         ret    = 0;
        nlc_ctx_t                  *nlc_ctx = NULL;
        nlc_conf_t                 *conf   = NULL;

        conf = this->private;

        LOCK (&inode->lock);
        {
                ret = __nlc_inode_ctx_get (this, inode, &nlc_ctx, nlc_pe_p);
                if (nlc_ctx)
                        goto unlock;

                nlc_ctx = GF_CALLOC (sizeof (*nlc_ctx), 1, gf_nlc_mt_nlc_ctx_t);
                if (!nlc_ctx)
                        goto unlock;

                LOCK_INIT (&nlc_ctx->lock);
                INIT_LIST_HEAD (&nlc_ctx->pe);
                INIT_LIST_HEAD (&nlc_ctx->ne);

                ret = __nlc_inode_ctx_timer_start (this, inode, nlc_ctx);
                if (ret < 0)
                        goto unlock;

                ret = __nlc_add_to_lru (this, inode, nlc_ctx);
                if (ret < 0) {
                        __nlc_inode_ctx_timer_delete (this, nlc_ctx);
                        goto unlock;
                }

                ret = __inode_ctx_set2 (inode, this, (uint64_t *) &nlc_ctx, NULL);
                if (ret) {
                        gf_msg (this->name, GF_LOG_ERROR, ENOMEM,
                                NLC_MSG_NO_MEMORY, "inode ctx set failed");
                        __nlc_inode_ctx_timer_delete (this, nlc_ctx);
                        nlc_remove_from_lru (this, inode);
                        goto unlock;
                }

                /*TODO: also sizeof (gf_tw_timer_list) + nlc_timer_data_t ?*/
                nlc_ctx->cache_size = sizeof (*nlc_ctx);
                GF_ATOMIC_ADD (conf->current_cache_size, nlc_ctx->cache_size);
        }
unlock:
        UNLOCK (&inode->lock);

        if (ret == 0 && nlc_ctx_p) {
                *nlc_ctx_p = nlc_ctx;
                nlc_init_invalid_ctx (this, inode, nlc_ctx);
        }

        if (ret < 0 && nlc_ctx) {
                LOCK_DESTROY (&nlc_ctx->lock);
                GF_FREE (nlc_ctx);
                nlc_ctx = NULL;
                goto out;
        }

out:
        return nlc_ctx;
}


nlc_local_t *
nlc_local_init (call_frame_t *frame, xlator_t *this, glusterfs_fop_t fop,
                loc_t *loc, loc_t *loc2)
{
        nlc_local_t *local = NULL;

        local = GF_CALLOC (sizeof (*local), 1, gf_nlc_mt_nlc_local_t);
        if (!local)
                goto out;

        if (loc)
                loc_copy (&local->loc, loc);
        if (loc2)
                loc_copy (&local->loc2, loc2);

        local->fop = fop;
        frame->local = local;
out:
        return local;
}


void
nlc_local_wipe (xlator_t *this, nlc_local_t *local)
{
        if (!local)
                goto out;

        loc_wipe (&local->loc);

        loc_wipe (&local->loc2);

        GF_FREE (local);
out:
        return;
}


static void
__nlc_set_dir_state (nlc_ctx_t *nlc_ctx, uint64_t new_state)
{
        nlc_ctx->state |= new_state;

        return;
}


void
nlc_set_dir_state (xlator_t *this, inode_t *inode, uint64_t state)
{
        nlc_ctx_t        *nlc_ctx = NULL;

        if (inode->ia_type != IA_IFDIR) {
                gf_msg_callingfn (this->name, GF_LOG_ERROR, EINVAL,
                                  NLC_MSG_EINVAL, "inode is not of type dir");
                goto out;
        }

        nlc_inode_ctx_get_set (this, inode, &nlc_ctx, NULL);
        if (!nlc_ctx)
                goto out;

        LOCK (&nlc_ctx->lock);
        {
                __nlc_set_dir_state (nlc_ctx, state);
        }
        UNLOCK (&nlc_ctx->lock);
out:
        return;
}


static void
nlc_cache_timeout_handler (struct gf_tw_timer_list *timer,
                           void *data, unsigned long calltime)
{
        nlc_timer_data_t *tmp     = data;
        nlc_ctx_t        *nlc_ctx = NULL;

        nlc_inode_ctx_get (tmp->this, tmp->inode, &nlc_ctx, NULL);
        if (!nlc_ctx)
                goto out;

        /* Taking nlc_ctx->lock will lead to deadlock, hence updating
         * the cache is invalid outside of lock, instead of clear_cache.
         * Since cache_time is assigned outside of lock, the value can
         * be invalid for short time, this may result in false negative
         * which is better than deadlock */
        nlc_ctx->cache_time = 0;
out:
        return;
}


void
__nlc_inode_ctx_timer_delete (xlator_t *this, nlc_ctx_t *nlc_ctx)
{
        nlc_conf_t                  *conf   = NULL;

        conf = this->private;

        if (nlc_ctx->timer)
                gf_tw_del_timer (conf->timer_wheel, nlc_ctx->timer);

        if (nlc_ctx->timer_data) {
                inode_unref (nlc_ctx->timer_data->inode);
                GF_FREE (nlc_ctx->timer_data);
                nlc_ctx->timer_data = NULL;
        }

        GF_FREE (nlc_ctx->timer);
        nlc_ctx->timer = NULL;

        return;
}


int
__nlc_inode_ctx_timer_start (xlator_t *this, inode_t *inode, nlc_ctx_t *nlc_ctx)
{
        struct gf_tw_timer_list    *timer  = NULL;
        nlc_timer_data_t           *tmp    = NULL;
        nlc_conf_t                 *conf   = NULL;
        int                         ret    = -1;

        conf = this->private;

        /* We are taking inode_table->lock within inode->lock
         * as the only other caller which takes inode->lock within
         * inode_table->lock and cause deadlock is inode_table_destroy.
         * Hopefully, there can be no fop when inode_table_destroy is
         * being called. */
        tmp = GF_CALLOC (1, sizeof (*tmp), gf_nlc_mt_nlc_timer_data_t);
        if (!tmp)
                goto out;
        tmp->inode = inode_ref (inode);
        tmp->this = this;

        timer = GF_CALLOC (1, sizeof (*timer),
                           gf_common_mt_tw_timer_list);
        if (!timer)
                goto out;

        INIT_LIST_HEAD (&timer->entry);
        timer->expires = nlc_get_cache_timeout (this);
        timer->function = nlc_cache_timeout_handler;
        timer->data = tmp;
        nlc_ctx->timer = timer;
        nlc_ctx->timer_data = tmp;
        gf_tw_add_timer (conf->timer_wheel, timer);

        time (&nlc_ctx->cache_time);
        gf_msg_trace (this->name, 0, "Registering timer:%p, inode:%p, "
                      "gfid:%s", timer, inode, uuid_utoa (inode->gfid));

        ret = 0;

out:
        if (ret < 0) {
                if (tmp && tmp->inode)
                        inode_unref (tmp->inode);
                GF_FREE (tmp);
                GF_FREE (timer);
        }

        return ret;
}


int
__nlc_add_to_lru (xlator_t *this, inode_t *inode, nlc_ctx_t *nlc_ctx)
{
        nlc_lru_node_t              *lru_ino   = NULL;
        uint64_t                    nlc_pe_int = 0;
        nlc_conf_t                  *conf      = NULL;
        int                          ret       = -1;

        conf = this->private;

        lru_ino = GF_CALLOC (1, sizeof (*lru_ino), gf_nlc_mt_nlc_lru_node);
        if (!lru_ino)
                goto out;

        INIT_LIST_HEAD (&lru_ino->list);
        lru_ino->inode = inode_ref (inode);
        LOCK (&conf->lock);
        {
                list_add_tail (&lru_ino->list, &conf->lru);
        }
        UNLOCK (&conf->lock);

        nlc_ctx->refd_inodes = 0;
        ret = __inode_ctx_get2 (inode, this, NULL, &nlc_pe_int);
        if (nlc_pe_int == 0)
                GF_ATOMIC_ADD (conf->refd_inodes, 1);

        ret = 0;

out:
        return ret;
}


void
nlc_remove_from_lru (xlator_t *this, inode_t *inode)
{
        nlc_lru_node_t              *lru_node   = NULL;
        nlc_lru_node_t              *tmp        = NULL;
        nlc_lru_node_t              *tmp1       = NULL;
        nlc_conf_t                  *conf       = NULL;

        conf = this->private;

        LOCK (&conf->lock);
        {
                list_for_each_entry_safe (lru_node, tmp, &conf->lru, list) {
                        if (inode == lru_node->inode) {
                                list_del (&lru_node->list);
                                tmp1 = lru_node;
                                break;
                        }
                }
        }
        UNLOCK (&conf->lock);

        if (tmp1) {
                inode_unref (tmp1->inode);
                GF_FREE (tmp1);
        }

        return;
}


void
nlc_lru_prune (xlator_t *this, inode_t *inode)
{
        nlc_lru_node_t              *lru_node   = NULL;
        nlc_lru_node_t              *prune_node = NULL;
        nlc_lru_node_t              *tmp        = NULL;
        nlc_conf_t                  *conf       = NULL;

        conf = this->private;

        LOCK (&conf->lock);
        {
                if ((GF_ATOMIC_GET(conf->refd_inodes) < conf->inode_limit) &&
                   (GF_ATOMIC_GET(conf->current_cache_size) < conf->cache_size))
                        goto unlock;

                list_for_each_entry_safe (lru_node, tmp, &conf->lru, list) {
                        list_del (&lru_node->list);
                        prune_node = lru_node;
                        goto unlock;
                }
        }
unlock:
        UNLOCK (&conf->lock);

        if (prune_node) {
                nlc_inode_clear_cache (this, prune_node->inode, NLC_LRU_PRUNE);
                inode_unref (prune_node->inode);
                GF_FREE (prune_node);
        }
        return;
}


void
nlc_clear_all_cache (xlator_t *this)
{
        nlc_conf_t                  *conf       = NULL;
        struct list_head            clear_list;
        nlc_lru_node_t              *prune_node = NULL;
        nlc_lru_node_t              *tmp        = NULL;

        conf = this->private;

        INIT_LIST_HEAD (&clear_list);

        LOCK (&conf->lock);
        {
                list_replace_init (&conf->lru, &clear_list);
        }
        UNLOCK (&conf->lock);

        list_for_each_entry_safe (prune_node, tmp, &clear_list, list) {
                list_del (&prune_node->list);
                nlc_inode_clear_cache (this, prune_node->inode, NLC_LRU_PRUNE);
                inode_unref (prune_node->inode);
                GF_FREE (prune_node);
        }

        return;
}


void
__nlc_free_pe (xlator_t *this, nlc_ctx_t *nlc_ctx, nlc_pe_t *pe)
{
        uint64_t          pe_int      = 0;
        nlc_conf_t       *conf        = NULL;
        uint64_t          nlc_ctx_int = 0;

        conf = this->private;

        if (pe->inode) {
                inode_ctx_reset1 (pe->inode, this, &pe_int);
                inode_ctx_get2 (pe->inode, this, &nlc_ctx_int, NULL);
                inode_unref (pe->inode);
        }
        list_del (&pe->list);

        nlc_ctx->cache_size -= sizeof (*pe) + sizeof (pe->name);
        GF_ATOMIC_SUB (conf->current_cache_size,
                       (sizeof (*pe) + sizeof (pe->name)));

        nlc_ctx->refd_inodes -= 1;
        if (nlc_ctx_int == 0)
                GF_ATOMIC_SUB (conf->refd_inodes, 1);

        GF_FREE (pe->name);
        GF_FREE (pe);

        return;
}


void
__nlc_free_ne (xlator_t *this, nlc_ctx_t *nlc_ctx, nlc_ne_t *ne)
{
        nlc_conf_t                  *conf   = NULL;

        conf = this->private;

        list_del (&ne->list);
        GF_FREE (ne->name);
        GF_FREE (ne);

        nlc_ctx->cache_size -= sizeof (*ne) + sizeof (ne->name);
        GF_ATOMIC_SUB (conf->current_cache_size,
                       (sizeof (*ne) + sizeof (ne->name)));

        return;
}


void
nlc_inode_clear_cache (xlator_t *this, inode_t *inode, int reason)
{
        nlc_ctx_t        *nlc_ctx    = NULL;

        nlc_inode_ctx_get (this, inode, &nlc_ctx, NULL);
        if (!nlc_ctx)
                goto out;

        LOCK (&nlc_ctx->lock);
        {
                __nlc_inode_ctx_timer_delete (this, nlc_ctx);

                __nlc_inode_clear_entries (this, nlc_ctx);
        }
        UNLOCK (&nlc_ctx->lock);

        if (reason != NLC_LRU_PRUNE)
                nlc_remove_from_lru (this, inode);

out:
        return;
}


static void
__nlc_del_pe (xlator_t *this, nlc_ctx_t *nlc_ctx, inode_t *entry_ino,
              const char *name, gf_boolean_t multilink)
{
        nlc_pe_t         *pe     = NULL;
        nlc_pe_t         *tmp    = NULL;
        gf_boolean_t     found  = _gf_false;
        uint64_t         pe_int = 0;

        if (!IS_PE_VALID (nlc_ctx->state))
                goto out;

        if (!entry_ino)
                goto name_search;

        /* If there are hardlinks first search names, followed by inodes */
        if (multilink) {
                list_for_each_entry_safe (pe, tmp, &nlc_ctx->pe, list) {
                        if (pe->name && (strcmp (pe->name, name) == 0)) {
                                found = _gf_true;
                                goto out;
                        }
                }
                inode_ctx_reset1 (entry_ino, this, &pe_int);
                if (pe_int) {
                        pe = (void *) (long) (pe_int);
                        found = _gf_true;
                        goto out;
                }
                goto out;
        }

        inode_ctx_reset1 (entry_ino, this, &pe_int);
        if (pe_int) {
                pe = (void *) (long) (pe_int);
                found = _gf_true;
                goto out;
        }

name_search:
        list_for_each_entry_safe (pe, tmp, &nlc_ctx->pe, list) {
                if (pe->name && (strcmp (pe->name, name) == 0)) {
                        found = _gf_true;
                        break;
                        /* TODO: can there be duplicates? */
                }
        }

out:
        if (found)
                __nlc_free_pe (this, nlc_ctx, pe);

        return;
}


static void
__nlc_del_ne (xlator_t *this, nlc_ctx_t *nlc_ctx, const char *name)
{
        nlc_ne_t  *ne     = NULL;
        nlc_ne_t  *tmp    = NULL;

        if (!IS_NE_VALID (nlc_ctx->state))
                goto out;

        list_for_each_entry_safe (ne, tmp, &nlc_ctx->ne, list) {
                if (strcmp (ne->name, name) == 0) {
                        __nlc_free_ne (this, nlc_ctx, ne);
                        break;
                }
        }
out:
        return;
}


static void
__nlc_add_pe (xlator_t *this, nlc_ctx_t *nlc_ctx, inode_t *entry_ino,
              const char *name)
{
        nlc_pe_t             *pe         = NULL;
        int                  ret         = -1;
        nlc_conf_t           *conf       = NULL;
        uint64_t             nlc_ctx_int = 0;

        conf = this->private;

        /* TODO: There can be no duplicate entries, as it is added only
        during create. In case there arises duplicate entries, search PE
        found = __nlc_search (entries, name, _gf_false);
        can use bit vector to have simple search than sequential search */

        pe = GF_CALLOC (sizeof (*pe), 1, gf_nlc_mt_nlc_pe_t);
        if (!pe)
                goto out;

        if (entry_ino) {
                pe->inode = inode_ref (entry_ino);
                nlc_inode_ctx_set (this, entry_ino, NULL, pe);
        } else if (name) {
                pe->name = gf_strdup (name);
                if (!pe->name)
                        goto out;
        }

        list_add (&pe->list, &nlc_ctx->pe);

        nlc_ctx->cache_size += sizeof (*pe) + sizeof (pe->name);
        GF_ATOMIC_ADD (conf->current_cache_size,
                       (sizeof (*pe) + sizeof (pe->name)));

        nlc_ctx->refd_inodes += 1;
        inode_ctx_get2 (entry_ino, this, &nlc_ctx_int, NULL);
        if (nlc_ctx_int == 0)
                GF_ATOMIC_ADD (conf->refd_inodes, 1);

        ret = 0;
out:
        if (ret)
                GF_FREE (pe);

        return;
}


static void
__nlc_add_ne (xlator_t *this, nlc_ctx_t *nlc_ctx, const char *name)
{
        nlc_ne_t                    *ne     = NULL;
        int                         ret     = -1;
        nlc_conf_t                  *conf   = NULL;

        conf = this->private;

        /* TODO: search ne before adding to get rid of duplicate entries
        found = __nlc_search (entries, name, _gf_false);
        can use bit vector to have faster search than sequential search */

        ne = GF_CALLOC (sizeof (*ne), 1, gf_nlc_mt_nlc_ne_t);
        if (!ne)
                goto out;

        ne->name = gf_strdup (name);
        if (!ne->name)
                goto out;

        list_add (&ne->list, &nlc_ctx->ne);

        nlc_ctx->cache_size += sizeof (*ne) + sizeof (ne->name);
        GF_ATOMIC_ADD (conf->current_cache_size,
                       (sizeof (*ne) + sizeof (ne->name)));
        ret = 0;
out:
        if (ret)
                GF_FREE (ne);

        return;
}


void
nlc_dir_add_ne (xlator_t *this, inode_t *inode, const char *name)
{
        nlc_ctx_t        *nlc_ctx = NULL;

        if (inode->ia_type != IA_IFDIR) {
                gf_msg_callingfn (this->name, GF_LOG_ERROR, EINVAL,
                                  NLC_MSG_EINVAL, "inode is not of type dir");
                goto out;
        }

        nlc_inode_ctx_get_set (this, inode, &nlc_ctx, NULL);
        if (!nlc_ctx)
                goto out;

        LOCK (&nlc_ctx->lock);
        {
                /* There is one possibility where we need to search before
                 * adding NE: when there are two parallel lookups on a non
                 * existent file */
                if (!__nlc_search_ne (nlc_ctx, name)) {
                        __nlc_add_ne (this, nlc_ctx, name);
                        __nlc_set_dir_state (nlc_ctx, NLC_NE_VALID);
                }
        }
        UNLOCK (&nlc_ctx->lock);
out:
        return;
}


void
nlc_dir_remove_pe (xlator_t *this, inode_t *parent, inode_t *entry_ino,
                   const char *name, gf_boolean_t multilink)
{
        nlc_ctx_t        *nlc_ctx = NULL;

        if (parent->ia_type != IA_IFDIR) {
                gf_msg_callingfn (this->name, GF_LOG_ERROR, EINVAL,
                                  NLC_MSG_EINVAL, "inode is not of type dir");
                goto out;
        }

        nlc_inode_ctx_get (this, parent, &nlc_ctx, NULL);
        if (!nlc_ctx)
                goto out;

        LOCK (&nlc_ctx->lock);
        {
                if (!__nlc_is_cache_valid (this, nlc_ctx))
                        goto unlock;

                __nlc_del_pe (this, nlc_ctx, entry_ino, name, multilink);
                __nlc_add_ne (this, nlc_ctx, name);
                __nlc_set_dir_state (nlc_ctx, NLC_NE_VALID);
        }
unlock:
        UNLOCK (&nlc_ctx->lock);
out:
        return;
}


void
nlc_dir_add_pe (xlator_t *this, inode_t *inode, inode_t *entry_ino,
                const char *name)
{
        nlc_ctx_t        *nlc_ctx = NULL;

        if (inode->ia_type != IA_IFDIR) {
                gf_msg_callingfn (this->name, GF_LOG_ERROR, EINVAL,
                                  NLC_MSG_EINVAL, "inode is not of type dir");
                goto out;
        }

        nlc_inode_ctx_get_set (this, inode, &nlc_ctx, NULL);
        if (!nlc_ctx)
                goto out;

        LOCK (&nlc_ctx->lock);
        {
                __nlc_del_ne (this, nlc_ctx, name);
                __nlc_add_pe (this, nlc_ctx, entry_ino, name);
                if (!IS_PE_VALID (nlc_ctx->state))
                        __nlc_set_dir_state (nlc_ctx, NLC_PE_PARTIAL);
        }
        UNLOCK (&nlc_ctx->lock);
out:
        return;
}


gf_boolean_t
__nlc_search_ne (nlc_ctx_t *nlc_ctx, const char *name)
{
        gf_boolean_t  found = _gf_false;
        nlc_ne_t     *ne    = NULL;
        nlc_ne_t     *tmp   = NULL;

        if (!IS_NE_VALID (nlc_ctx->state))
                goto out;

        list_for_each_entry_safe (ne, tmp, &nlc_ctx->ne, list) {
                if (strcmp (ne->name, name) == 0) {
                        found = _gf_true;
                        break;
                }
        }
out:
        return found;
}


static gf_boolean_t
__nlc_search_pe (nlc_ctx_t *nlc_ctx, const char *name)
{
        gf_boolean_t   found = _gf_false;
        nlc_pe_t      *pe    = NULL;
        nlc_pe_t      *tmp   = NULL;

        if (!IS_PE_VALID (nlc_ctx->state))
                goto out;

        list_for_each_entry_safe (pe, tmp, &nlc_ctx->pe, list) {
               if (pe->name && (strcmp (pe->name, name) == 0)) {
                        found = _gf_true;
                        break;
               }
        }
out:
        return found;
}


static char *
__nlc_get_pe (nlc_ctx_t *nlc_ctx, const char *name, gf_boolean_t case_insensitive)
{
        char          *found = NULL;
        nlc_pe_t      *pe    = NULL;
        nlc_pe_t      *tmp   = NULL;

        if (!IS_PE_VALID (nlc_ctx->state))
                goto out;

        if (case_insensitive) {
                list_for_each_entry_safe (pe, tmp, &nlc_ctx->pe, list) {
                        if (pe->name &&
                            (strcasecmp (pe->name, name) == 0)) {
                                found = pe->name;
                                break;
                        }
                }
        } else {
                list_for_each_entry_safe (pe, tmp, &nlc_ctx->pe, list) {
                        if (pe->name &&
                            (strcmp (pe->name, name) == 0)) {
                                found = pe->name;
                                break;
                        }
               }
        }
out:
        return found;
}


gf_boolean_t
nlc_is_negative_lookup (xlator_t *this, loc_t *loc)
{
        nlc_ctx_t       *nlc_ctx   = NULL;
        inode_t         *inode     = NULL;
        gf_boolean_t     neg_entry = _gf_false;

        inode = loc->parent;
        GF_VALIDATE_OR_GOTO (this->name, inode, out);

        if (inode->ia_type != IA_IFDIR) {
                gf_msg_callingfn (this->name, GF_LOG_ERROR, EINVAL,
                                  NLC_MSG_EINVAL, "inode is not of type dir");
                goto out;
        }

        nlc_inode_ctx_get (this, inode, &nlc_ctx, NULL);
        if (!nlc_ctx)
                goto out;

        LOCK (&nlc_ctx->lock);
        {
                if (!__nlc_is_cache_valid (this, nlc_ctx))
                        goto unlock;

                if (__nlc_search_ne (nlc_ctx, loc->name)) {
                        neg_entry = _gf_true;
                        goto unlock;
                }
                if ((nlc_ctx->state & NLC_PE_FULL) &&
                    !__nlc_search_pe (nlc_ctx, loc->name)) {
                        neg_entry = _gf_true;
                        goto unlock;
                }
        }
unlock:
        UNLOCK (&nlc_ctx->lock);

out:
        return neg_entry;
}


gf_boolean_t
nlc_get_real_file_name (xlator_t *this, loc_t *loc, const char *fname,
                        int32_t *op_ret, int32_t *op_errno, dict_t *dict)
{
        nlc_ctx_t        *nlc_ctx     = NULL;
        inode_t         *inode      = NULL;
        gf_boolean_t     hit        = _gf_false;
        char            *found_file = NULL;
        int              ret        = 0;

        GF_VALIDATE_OR_GOTO (this->name, loc, out);
        GF_VALIDATE_OR_GOTO (this->name, fname, out);
        GF_VALIDATE_OR_GOTO (this->name, op_ret, out);
        GF_VALIDATE_OR_GOTO (this->name, op_errno, out);
        GF_VALIDATE_OR_GOTO (this->name, dict, out);

        inode = loc->inode;
        GF_VALIDATE_OR_GOTO (this->name, inode, out);

        if (inode->ia_type != IA_IFDIR) {
                gf_msg_callingfn (this->name, GF_LOG_ERROR, EINVAL,
                                  NLC_MSG_EINVAL, "inode is not of type dir");
                goto out;
        }

        nlc_inode_ctx_get (this, inode, &nlc_ctx, NULL);
        if (!nlc_ctx)
                goto out;

        LOCK (&nlc_ctx->lock);
        {
                if (!__nlc_is_cache_valid (this, nlc_ctx))
                        goto unlock;

                found_file = __nlc_get_pe (nlc_ctx, fname, _gf_true);
                if (found_file) {
                        ret = dict_set_dynstr (dict, GF_XATTR_GET_REAL_FILENAME_KEY,
                                               gf_strdup (found_file));
                        if (ret < 0)
                                goto unlock;
                        *op_ret = strlen (found_file) + 1;
                        hit = _gf_true;
                        goto unlock;
                }
                if (!found_file && (nlc_ctx->state & NLC_PE_FULL)) {
                        *op_ret = -1;
                        *op_errno = ENOENT;
                        hit = _gf_true;
                        goto unlock;
                }
        }
unlock:
        UNLOCK (&nlc_ctx->lock);

out:
        return hit;
}


void
nlc_dump_inodectx (xlator_t *this, inode_t *inode)
{
        int32_t     ret                            = -1;
        char       *path                           = NULL;
        char       key_prefix[GF_DUMP_MAX_BUF_LEN] = {0, };
        char       uuid_str[64]                    = {0,};
        nlc_ctx_t   *nlc_ctx                         = NULL;
        nlc_pe_t    *pe                             = NULL;
        nlc_pe_t    *tmp                            = NULL;
        nlc_ne_t    *ne                             = NULL;
        nlc_ne_t    *tmp1                           = NULL;

        nlc_inode_ctx_get (this, inode, &nlc_ctx, NULL);

        if (!nlc_ctx)
                goto out;

        ret = TRY_LOCK (&nlc_ctx->lock);
        if (!ret) {
                gf_proc_dump_build_key (key_prefix,
                                        "xlator.performance.nl-cache",
                                        "nlc_inode");
                gf_proc_dump_add_section (key_prefix);

                __inode_path (inode, NULL, &path);
                if (path != NULL) {
                        gf_proc_dump_write ("path", "%s", path);
                        GF_FREE (path);
                }

                uuid_utoa_r (inode->gfid, uuid_str);

                gf_proc_dump_write ("inode", "%p", inode);
                gf_proc_dump_write ("gfid", "%s", uuid_str);

                gf_proc_dump_write ("state", "%"PRIu64, nlc_ctx->state);
                gf_proc_dump_write ("timer", "%p", nlc_ctx->timer);
                gf_proc_dump_write ("cache-time", "%lld", nlc_ctx->cache_time);
                gf_proc_dump_write ("cache-size", "%zu", nlc_ctx->cache_size);
                gf_proc_dump_write ("refd-inodes", "%"PRIu64, nlc_ctx->refd_inodes);

                if (IS_PE_VALID (nlc_ctx->state))
                        list_for_each_entry_safe (pe, tmp, &nlc_ctx->pe, list) {
                                gf_proc_dump_write ("pe", "%p, %s", pe,
                                                    pe->inode, pe->name);
                        }

                if (IS_NE_VALID (nlc_ctx->state))
                        list_for_each_entry_safe (ne, tmp1, &nlc_ctx->ne, list) {
                                gf_proc_dump_write ("ne", "%s", ne->name);
                        }

                UNLOCK (&nlc_ctx->lock);
        }

        if (ret && nlc_ctx)
                gf_proc_dump_write ("Unable to dump the inode information",
                                    "(Lock acquisition failed) %p (gfid: %s)",
                                    nlc_ctx, uuid_str);
out:
        return;
}