/*
 * 2007+ Copyright (c) Evgeniy Polyakov <zbr@ioremap.net>
 * All rights reserved.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 */

#include <linux/module.h>
#include <linux/crypto.h>
#include <linux/fs.h>
#include <linux/jhash.h>
#include <linux/hash.h>
#include <linux/ktime.h>
#include <linux/mempool.h>
#include <linux/mm.h>
#include <linux/mount.h>
#include <linux/pagemap.h>
#include <linux/parser.h>
#include <linux/poll.h>
#include <linux/swap.h>
#include <linux/slab.h>
#include <linux/statfs.h>
#include <linux/writeback.h>

#include "netfs.h"

static struct kmem_cache *netfs_trans_dst;
static mempool_t *netfs_trans_dst_pool;

static void netfs_trans_init_static(struct netfs_trans *t, int num, int size)
{
        t->page_num = num;
        t->total_size = size;
        atomic_set(&t->refcnt, 1);

        spin_lock_init(&t->dst_lock);
        INIT_LIST_HEAD(&t->dst_list);
}

static int netfs_trans_send_pages(struct netfs_trans *t, struct netfs_state *st)
{
        int err = 0;
        unsigned int i, attached_pages = t->attached_pages, ci;
        struct msghdr msg;
        struct page **pages = (t->eng)?t->eng->pages:t->pages;
        struct page *p;
        unsigned int size;

        msg.msg_name = NULL;
        msg.msg_namelen = 0;
        msg.msg_control = NULL;
        msg.msg_controllen = 0;
        msg.msg_flags = MSG_WAITALL | MSG_MORE;

        ci = 0;
        for (i=0; i<t->page_num; ++i) {
                struct page *page = pages[ci];
                struct netfs_cmd cmd;
                struct iovec io;

                p = t->pages[i];

                if (!p)
                        continue;

                size = page_private(p);

                io.iov_base = &cmd;
                io.iov_len = sizeof(struct netfs_cmd);

                cmd.cmd = NETFS_WRITE_PAGE;
                cmd.ext = 0;
                cmd.id = 0;
                cmd.size = size;
                cmd.start = p->index;
                cmd.start <<= PAGE_CACHE_SHIFT;
                cmd.csize = 0;
                cmd.cpad = 0;
                cmd.iv = pohmelfs_gen_iv(t);

                netfs_convert_cmd(&cmd);

                msg.msg_iov = &io;
                msg.msg_iovlen = 1;
                msg.msg_flags = MSG_WAITALL | MSG_MORE;

                err = kernel_sendmsg(st->socket, &msg, (struct kvec *)msg.msg_iov, 1, sizeof(struct netfs_cmd));
                if (err <= 0) {
                        printk("%s: %d/%d failed to send transaction header: t: %p, gen: %u, err: %d.\n",
                                        __func__, i, t->page_num, t, t->gen, err);
                        if (err == 0)
                                err = -ECONNRESET;
                        goto err_out;
                }

                msg.msg_flags = MSG_WAITALL | (attached_pages == 1 ? 0 :
                                MSG_MORE);

                err = kernel_sendpage(st->socket, page, 0, size, msg.msg_flags);
                if (err <= 0) {
                        printk("%s: %d/%d failed to send transaction page: t: %p, gen: %u, size: %u, err: %d.\n",
                                        __func__, i, t->page_num, t, t->gen, size, err);
                        if (err == 0)
                                err = -ECONNRESET;
                        goto err_out;
                }

                dprintk("%s: %d/%d sent t: %p, gen: %u, page: %p/%p, size: %u.\n",
                        __func__, i, t->page_num, t, t->gen, page, p, size);

                err = 0;
                attached_pages--;
                if (!attached_pages)
                        break;
                ci++;

                continue;

err_out:
                printk("%s: t: %p, gen: %u, err: %d.\n", __func__, t, t->gen, err);
                netfs_state_exit(st);
                break;
        }

        return err;
}

int netfs_trans_send(struct netfs_trans *t, struct netfs_state *st)
{
        int err;
        struct msghdr msg;

        BUG_ON(!t->iovec.iov_len);
        BUG_ON(t->iovec.iov_len > 1024*1024*1024);

        netfs_state_lock_send(st);
        if (!st->socket) {
                err = netfs_state_init(st);
                if (err)
                        goto err_out_unlock_return;
        }

        msg.msg_iov = &t->iovec;
        msg.msg_iovlen = 1;
        msg.msg_name = NULL;
        msg.msg_namelen = 0;
        msg.msg_control = NULL;
        msg.msg_controllen = 0;
        msg.msg_flags = MSG_WAITALL;

        if (t->attached_pages)
                msg.msg_flags |= MSG_MORE;

        err = kernel_sendmsg(st->socket, &msg, (struct kvec *)msg.msg_iov, 1, t->iovec.iov_len);
        if (err <= 0) {
                printk("%s: failed to send contig transaction: t: %p, gen: %u, size: %zu, err: %d.\n",
                                __func__, t, t->gen, t->iovec.iov_len, err);
                if (err == 0)
                        err = -ECONNRESET;
                goto err_out_unlock_return;
        }

        dprintk("%s: sent %s transaction: t: %p, gen: %u, size: %zu, page_num: %u.\n",
                        __func__, (t->page_num)?"partial":"full",
                        t, t->gen, t->iovec.iov_len, t->page_num);

        err = 0;
        if (t->attached_pages)
                err = netfs_trans_send_pages(t, st);

err_out_unlock_return:

        if (st->need_reset)
                netfs_state_exit(st);

        netfs_state_unlock_send(st);

        dprintk("%s: t: %p, gen: %u, err: %d.\n",
                __func__, t, t->gen, err);

        t->result = err;
        return err;
}

static inline int netfs_trans_cmp(unsigned int gen, unsigned int new)
{
        if (gen < new)
                return 1;
        if (gen > new)
                return -1;
        return 0;
}

struct netfs_trans_dst *netfs_trans_search(struct netfs_state *st, unsigned int gen)
{
        struct rb_root *root = &st->trans_root;
        struct rb_node *n = root->rb_node;
        struct netfs_trans_dst *tmp, *ret = NULL;
        struct netfs_trans *t;
        int cmp;

        while (n) {
                tmp = rb_entry(n, struct netfs_trans_dst, state_entry);
                t = tmp->trans;

                cmp = netfs_trans_cmp(t->gen, gen);
                if (cmp < 0)
                        n = n->rb_left;
                else if (cmp > 0)
                        n = n->rb_right;
                else {
                        ret = tmp;
                        break;
                }
        }

        return ret;
}

static int netfs_trans_insert(struct netfs_trans_dst *ndst, struct netfs_state *st)
{
        struct rb_root *root = &st->trans_root;
        struct rb_node **n = &root->rb_node, *parent = NULL;
        struct netfs_trans_dst *ret = NULL, *tmp;
        struct netfs_trans *t = NULL, *new = ndst->trans;
        int cmp;

        while (*n) {
                parent = *n;

                tmp = rb_entry(parent, struct netfs_trans_dst, state_entry);
                t = tmp->trans;

                cmp = netfs_trans_cmp(t->gen, new->gen);
                if (cmp < 0)
                        n = &parent->rb_left;
                else if (cmp > 0)
                        n = &parent->rb_right;
                else {
                        ret = tmp;
                        break;
                }
        }

        if (ret) {
                printk("%s: exist: old: gen: %u, flags: %x, send_time: %lu, "
                                "new: gen: %u, flags: %x, send_time: %lu.\n",
                        __func__, t->gen, t->flags, ret->send_time,
                        new->gen, new->flags, ndst->send_time);
                return -EEXIST;
        }

        rb_link_node(&ndst->state_entry, parent, n);
        rb_insert_color(&ndst->state_entry, root);
        ndst->send_time = jiffies;

        return 0;
}

int netfs_trans_remove_nolock(struct netfs_trans_dst *dst, struct netfs_state *st)
{
        if (dst && dst->state_entry.rb_parent_color) {
                rb_erase(&dst->state_entry, &st->trans_root);
                dst->state_entry.rb_parent_color = 0;
                return 1;
        }
        return 0;
}

static int netfs_trans_remove_state(struct netfs_trans_dst *dst)
{
        int ret;
        struct netfs_state *st = dst->state;

        mutex_lock(&st->trans_lock);
        ret = netfs_trans_remove_nolock(dst, st);
        mutex_unlock(&st->trans_lock);

        return ret;
}

/*
 * Create new destination for given transaction associated with given network state.
 * Transaction's reference counter is bumped and will be dropped when either
 * reply is received or when async timeout detection task will fail resending
 * and drop transaction.
 */
static int netfs_trans_push_dst(struct netfs_trans *t, struct netfs_state *st)
{
        struct netfs_trans_dst *dst;
        int err;

        dst = mempool_alloc(netfs_trans_dst_pool, GFP_KERNEL);
        if (!dst)
                return -ENOMEM;

        dst->retries = 0;
        dst->send_time = 0;
        dst->state = st;
        dst->trans = t;
        netfs_trans_get(t);

        mutex_lock(&st->trans_lock);
        err = netfs_trans_insert(dst, st);
        mutex_unlock(&st->trans_lock);

        if (err)
                goto err_out_free;

        spin_lock(&t->dst_lock);
        list_add_tail(&dst->trans_entry, &t->dst_list);
        spin_unlock(&t->dst_lock);

        return 0;

err_out_free:
        t->result = err;
        netfs_trans_put(t);
        mempool_free(dst, netfs_trans_dst_pool);
        return err;
}

static void netfs_trans_free_dst(struct netfs_trans_dst *dst)
{
        netfs_trans_put(dst->trans);
        mempool_free(dst, netfs_trans_dst_pool);
}

static void netfs_trans_remove_dst(struct netfs_trans_dst *dst)
{
        if (netfs_trans_remove_state(dst))
                netfs_trans_free_dst(dst);
}

/*
 * Drop destination transaction entry when we know it.
 */
void netfs_trans_drop_dst(struct netfs_trans_dst *dst)
{
        struct netfs_trans *t = dst->trans;

        spin_lock(&t->dst_lock);
        list_del_init(&dst->trans_entry);
        spin_unlock(&t->dst_lock);

        netfs_trans_remove_dst(dst);
}

/*
 * Drop destination transaction entry when we know it and when we
 * already removed dst from state tree.
 */
void netfs_trans_drop_dst_nostate(struct netfs_trans_dst *dst)
{
        struct netfs_trans *t = dst->trans;

        spin_lock(&t->dst_lock);
        list_del_init(&dst->trans_entry);
        spin_unlock(&t->dst_lock);

        netfs_trans_free_dst(dst);
}

/*
 * This drops destination transaction entry from appropriate network state
 * tree and drops related reference counter. It is possible that transaction
 * will be freed here if its reference counter hits zero.
 * Destination transaction entry will be freed.
 */
void netfs_trans_drop_trans(struct netfs_trans *t, struct netfs_state *st)
{
        struct netfs_trans_dst *dst, *tmp, *ret = NULL;

        spin_lock(&t->dst_lock);
        list_for_each_entry_safe(dst, tmp, &t->dst_list, trans_entry) {
                if (dst->state == st) {
                        ret = dst;
                        list_del(&dst->trans_entry);
                        break;
                }
        }
        spin_unlock(&t->dst_lock);

        if (ret)
                netfs_trans_remove_dst(ret);
}

/*
 * This drops destination transaction entry from appropriate network state
 * tree and drops related reference counter. It is possible that transaction
 * will be freed here if its reference counter hits zero.
 * Destination transaction entry will be freed.
 */
void netfs_trans_drop_last(struct netfs_trans *t, struct netfs_state *st)
{
        struct netfs_trans_dst *dst, *tmp, *ret;

        spin_lock(&t->dst_lock);
        ret = list_entry(t->dst_list.prev, struct netfs_trans_dst, trans_entry);
        if (ret->state != st) {
                ret = NULL;
                list_for_each_entry_safe(dst, tmp, &t->dst_list, trans_entry) {
                        if (dst->state == st) {
                                ret = dst;
                                list_del_init(&dst->trans_entry);
                                break;
                        }
                }
        } else {
                list_del(&ret->trans_entry);
        }
        spin_unlock(&t->dst_lock);

        if (ret)
                netfs_trans_remove_dst(ret);
}

static int netfs_trans_push(struct netfs_trans *t, struct netfs_state *st)
{
        int err;

        err = netfs_trans_push_dst(t, st);
        if (err)
                return err;

        err = netfs_trans_send(t, st);
        if (err)
                goto err_out_free;

        if (t->flags & NETFS_TRANS_SINGLE_DST)
                pohmelfs_switch_active(st->psb);

        return 0;

err_out_free:
        t->result = err;
        netfs_trans_drop_last(t, st);

        return err;
}

int netfs_trans_finish_send(struct netfs_trans *t, struct pohmelfs_sb *psb)
{
        struct pohmelfs_config *c;
        int err = -ENODEV;
        struct netfs_state *st;
#if 0
        dprintk("%s: t: %p, gen: %u, size: %u, page_num: %u, active: %p.\n",
                __func__, t, t->gen, t->iovec.iov_len, t->page_num, psb->active_state);
#endif
        mutex_lock(&psb->state_lock);
        list_for_each_entry(c, &psb->state_list, config_entry) {
                st = &c->state;

                if (t->flags & NETFS_TRANS_SINGLE_DST) {
                        if (!(st->ctl.perm & POHMELFS_IO_PERM_READ))
                                continue;
                } else {
                        if (!(st->ctl.perm & POHMELFS_IO_PERM_WRITE))
                                continue;
                }

                if (psb->active_state && (psb->active_state->state.ctl.prio >= st->ctl.prio) &&
                                (t->flags & NETFS_TRANS_SINGLE_DST))
                        st = &psb->active_state->state;

                err = netfs_trans_push(t, st);
                if (!err && (t->flags & NETFS_TRANS_SINGLE_DST))
                        break;
        }

        mutex_unlock(&psb->state_lock);
#if 0
        dprintk("%s: fully sent t: %p, gen: %u, size: %u, page_num: %u, err: %d.\n",
                __func__, t, t->gen, t->iovec.iov_len, t->page_num, err);
#endif
        if (err)
                t->result = err;
        return err;
}

int netfs_trans_finish(struct netfs_trans *t, struct pohmelfs_sb *psb)
{
        int err;
        struct netfs_cmd *cmd = t->iovec.iov_base;

        t->gen = atomic_inc_return(&psb->trans_gen);

        cmd->size = t->iovec.iov_len - sizeof(struct netfs_cmd) +
                t->attached_size + t->attached_pages * sizeof(struct netfs_cmd);
        cmd->cmd = NETFS_TRANS;
        cmd->start = t->gen;
        cmd->id = 0;

        if (psb->perform_crypto) {
                cmd->ext = psb->crypto_attached_size;
                cmd->csize = psb->crypto_attached_size;
        }

        dprintk("%s: t: %u, size: %u, iov_len: %zu, attached_size: %u, attached_pages: %u.\n",
                        __func__, t->gen, cmd->size, t->iovec.iov_len, t->attached_size, t->attached_pages);
        err = pohmelfs_trans_crypt(t, psb);
        if (err) {
                t->result = err;
                netfs_convert_cmd(cmd);
                dprintk("%s: trans: %llu, crypto_attached_size: %u, attached_size: %u, attached_pages: %d, trans_size: %u, err: %d.\n",
                        __func__, cmd->start, psb->crypto_attached_size, t->attached_size, t->attached_pages, cmd->size, err);
        }
        netfs_trans_put(t);
        return err;
}

/*
 * Resend transaction to remote server(s).
 * If new servers were added into superblock, we can try to send data
 * to them too.
 *
 * It is called under superblock's state_lock, so we can safely
 * dereference psb->state_list. Also, transaction's reference counter is
 * bumped, so it can not go away under us, thus we can safely access all
 * its members. State is locked.
 *
 * This function returns 0 if transaction was successfully sent to at
 * least one destination target.
 */
int netfs_trans_resend(struct netfs_trans *t, struct pohmelfs_sb *psb)
{
        struct netfs_trans_dst *dst;
        struct netfs_state *st;
        struct pohmelfs_config *c;
        int err, exist, error = -ENODEV;

        list_for_each_entry(c, &psb->state_list, config_entry) {
                st = &c->state;

                exist = 0;
                spin_lock(&t->dst_lock);
                list_for_each_entry(dst, &t->dst_list, trans_entry) {
                        if (st == dst->state) {
                                exist = 1;
                                break;
                        }
                }
                spin_unlock(&t->dst_lock);

                if (exist) {
                        if (!(t->flags & NETFS_TRANS_SINGLE_DST) ||
                                        (c->config_entry.next == &psb->state_list)) {
                                dprintk("%s: resending st: %p, t: %p, gen: %u.\n",
                                                __func__, st, t, t->gen);
                                err = netfs_trans_send(t, st);
                                if (!err)
                                        error = 0;
                        }
                        continue;
                }

                dprintk("%s: pushing/resending st: %p, t: %p, gen: %u.\n",
                                __func__, st, t, t->gen);
                err = netfs_trans_push(t, st);
                if (err)
                        continue;
                error = 0;
                if (t->flags & NETFS_TRANS_SINGLE_DST)
                        break;
        }

        t->result = error;
        return error;
}

void *netfs_trans_add(struct netfs_trans *t, unsigned int size)
{
        struct iovec *io = &t->iovec;
        void *ptr;

        if (size > t->total_size) {
                ptr = ERR_PTR(-EINVAL);
                goto out;
        }

        if (io->iov_len + size > t->total_size) {
                dprintk("%s: too big size t: %p, gen: %u, iov_len: %zu, size: %u, total: %u.\n",
                                __func__, t, t->gen, io->iov_len, size, t->total_size);
                ptr = ERR_PTR(-E2BIG);
                goto out;
        }

        ptr = io->iov_base + io->iov_len;
        io->iov_len += size;

out:
        dprintk("%s: t: %p, gen: %u, size: %u, total: %zu.\n",
                __func__, t, t->gen, size, io->iov_len);
        return ptr;
}

void netfs_trans_free(struct netfs_trans *t)
{
        if (t->eng)
                pohmelfs_crypto_thread_make_ready(t->eng->thread);
        kfree(t);
}

struct netfs_trans *netfs_trans_alloc(struct pohmelfs_sb *psb, unsigned int size,
                unsigned int flags, unsigned int nr)
{
        struct netfs_trans *t;
        unsigned int num, cont, pad, size_no_trans;
        unsigned int crypto_added = 0;
        struct netfs_cmd *cmd;

        if (psb->perform_crypto)
                crypto_added = psb->crypto_attached_size;

        /*
         * |sizeof(struct netfs_trans)|
         * |sizeof(struct netfs_cmd)| - transaction header
         * |size| - buffer with requested size
         * |padding| - crypto padding, zero bytes
         * |nr * sizeof(struct page *)| - array of page pointers
         *
         * Overall size should be less than PAGE_SIZE for guaranteed allocation.
         */

        cont = size;
        size = ALIGN(size, psb->crypto_align_size);
        pad = size - cont;

        size_no_trans = size + sizeof(struct netfs_cmd) * 2 + crypto_added;

        cont = sizeof(struct netfs_trans) + size_no_trans;

        num = (PAGE_SIZE - cont)/sizeof(struct page *);

        if (nr > num)
                nr = num;

        t = kzalloc(cont + nr*sizeof(struct page *), GFP_NOIO);
        if (!t)
                goto err_out_exit;

        t->iovec.iov_base = (void *)(t + 1);
        t->pages = (struct page **)(t->iovec.iov_base + size_no_trans);

        /*
         * Reserving space for transaction header.
         */
        t->iovec.iov_len = sizeof(struct netfs_cmd) + crypto_added;

        netfs_trans_init_static(t, nr, size_no_trans);

        t->flags = flags;
        t->psb = psb;

        cmd = (struct netfs_cmd *)t->iovec.iov_base;

        cmd->size = size;
        cmd->cpad = pad;
        cmd->csize = crypto_added;

        dprintk("%s: t: %p, gen: %u, size: %u, padding: %u, align_size: %u, flags: %x, "
                        "page_num: %u, base: %p, pages: %p.\n",
                        __func__, t, t->gen, size, pad, psb->crypto_align_size, flags, nr,
                        t->iovec.iov_base, t->pages);

        return t;

err_out_exit:
        return NULL;
}

int netfs_trans_init(void)
{
        int err = -ENOMEM;

        netfs_trans_dst = kmem_cache_create("netfs_trans_dst", sizeof(struct netfs_trans_dst),
                        0, 0, NULL);
        if (!netfs_trans_dst)
                goto err_out_exit;

        netfs_trans_dst_pool = mempool_create_slab_pool(256, netfs_trans_dst);
        if (!netfs_trans_dst_pool)
                goto err_out_free;

        return 0;

err_out_free:
        kmem_cache_destroy(netfs_trans_dst);
err_out_exit:
        return err;
}

void netfs_trans_exit(void)
{
        mempool_destroy(netfs_trans_dst_pool);
        kmem_cache_destroy(netfs_trans_dst);
}