/*
 * GPL HEADER START
 *
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License version 2 only,
 * as published by the Free Software Foundation.
 *
 * 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 version 2 for more details (a copy is included
 * in the LICENSE file that accompanied this code).
 *
 * You should have received a copy of the GNU General Public License
 * version 2 along with this program; If not, see
 * http://www.gnu.org/licenses/gpl-2.0.html
 *
 * GPL HEADER END
 */
/*
 * Copyright (c) 2010, Oracle and/or its affiliates. All rights reserved.
 * Use is subject to license terms.
 *
 * Copyright (c) 2012, Intel Corporation.
 */
/*
 * This file is part of Lustre, http://www.lustre.org/
 * Lustre is a trademark of Sun Microsystems, Inc.
 *
 * Author: Nathan Rutman <nathan.rutman@sun.com>
 *
 * Kernel <-> userspace communication routines.
 * Using pipes for all arches.
 */

#define DEBUG_SUBSYSTEM S_CLASS
#define D_KUC D_OTHER

#include "../include/obd_support.h"
#include "../include/lustre_kernelcomm.h"

/**
 * libcfs_kkuc_msg_put - send an message from kernel to userspace
 * @param fp to send the message to
 * @param payload Payload data.  First field of payload is always
 *   struct kuc_hdr
 */
int libcfs_kkuc_msg_put(struct file *filp, void *payload)
{
        struct kuc_hdr *kuch = (struct kuc_hdr *)payload;
        ssize_t count = kuch->kuc_msglen;
        loff_t offset = 0;
        mm_segment_t fs;
        int rc = -ENXIO;

        if (IS_ERR_OR_NULL(filp))
                return -EBADF;

        if (kuch->kuc_magic != KUC_MAGIC) {
                CERROR("KernelComm: bad magic %x\n", kuch->kuc_magic);
                return rc;
        }

        fs = get_fs();
        set_fs(KERNEL_DS);
        while (count > 0) {
                rc = vfs_write(filp, (void __force __user *)payload,
                               count, &offset);
                if (rc < 0)
                        break;
                count -= rc;
                payload += rc;
                rc = 0;
        }
        set_fs(fs);

        if (rc < 0)
                CWARN("message send failed (%d)\n", rc);
        else
                CDEBUG(D_KUC, "Sent message rc=%d, fp=%p\n", rc, filp);

        return rc;
}
EXPORT_SYMBOL(libcfs_kkuc_msg_put);

/*
 * Broadcast groups are global across all mounted filesystems;
 * i.e. registering for a group on 1 fs will get messages for that
 * group from any fs
 */
/** A single group registration has a uid and a file pointer */
struct kkuc_reg {
        struct list_head kr_chain;
        int              kr_uid;
        struct file     *kr_fp;
        char             kr_data[0];
};

static struct list_head kkuc_groups[KUC_GRP_MAX + 1] = {};
/* Protect message sending against remove and adds */
static DECLARE_RWSEM(kg_sem);

/** Add a receiver to a broadcast group
 * @param filp pipe to write into
 * @param uid identifier for this receiver
 * @param group group number
 * @param data user data
 */
int libcfs_kkuc_group_add(struct file *filp, int uid, unsigned int group,
                          void *data, size_t data_len)
{
        struct kkuc_reg *reg;

        if (group > KUC_GRP_MAX) {
                CDEBUG(D_WARNING, "Kernelcomm: bad group %d\n", group);
                return -EINVAL;
        }

        /* fput in group_rem */
        if (!filp)
                return -EBADF;

        /* freed in group_rem */
        reg = kmalloc(sizeof(*reg) + data_len, 0);
        if (!reg)
                return -ENOMEM;

        reg->kr_fp = filp;
        reg->kr_uid = uid;
        memcpy(reg->kr_data, data, data_len);

        down_write(&kg_sem);
        if (!kkuc_groups[group].next)
                INIT_LIST_HEAD(&kkuc_groups[group]);
        list_add(&reg->kr_chain, &kkuc_groups[group]);
        up_write(&kg_sem);

        CDEBUG(D_KUC, "Added uid=%d fp=%p to group %d\n", uid, filp, group);

        return 0;
}
EXPORT_SYMBOL(libcfs_kkuc_group_add);

int libcfs_kkuc_group_rem(int uid, unsigned int group)
{
        struct kkuc_reg *reg, *next;

        if (!kkuc_groups[group].next)
                return 0;

        if (!uid) {
                /* Broadcast a shutdown message */
                struct kuc_hdr lh;

                lh.kuc_magic = KUC_MAGIC;
                lh.kuc_transport = KUC_TRANSPORT_GENERIC;
                lh.kuc_msgtype = KUC_MSG_SHUTDOWN;
                lh.kuc_msglen = sizeof(lh);
                libcfs_kkuc_group_put(group, &lh);
        }

        down_write(&kg_sem);
        list_for_each_entry_safe(reg, next, &kkuc_groups[group], kr_chain) {
                if (!uid || (uid == reg->kr_uid)) {
                        list_del(&reg->kr_chain);
                        CDEBUG(D_KUC, "Removed uid=%d fp=%p from group %d\n",
                               reg->kr_uid, reg->kr_fp, group);
                        if (reg->kr_fp)
                                fput(reg->kr_fp);
                        kfree(reg);
                }
        }
        up_write(&kg_sem);

        return 0;
}
EXPORT_SYMBOL(libcfs_kkuc_group_rem);

int libcfs_kkuc_group_put(unsigned int group, void *payload)
{
        struct kkuc_reg *reg;
        int rc = 0;
        int one_success = 0;

        down_write(&kg_sem);
        list_for_each_entry(reg, &kkuc_groups[group], kr_chain) {
                if (reg->kr_fp) {
                        rc = libcfs_kkuc_msg_put(reg->kr_fp, payload);
                        if (!rc) {
                                one_success = 1;
                        } else if (rc == -EPIPE) {
                                fput(reg->kr_fp);
                                reg->kr_fp = NULL;
                        }
                }
        }
        up_write(&kg_sem);

        /*
         * don't return an error if the message has been delivered
         * at least to one agent
         */
        if (one_success)
                rc = 0;

        return rc;
}
EXPORT_SYMBOL(libcfs_kkuc_group_put);

/**
 * Calls a callback function for each link of the given kuc group.
 * @param group the group to call the function on.
 * @param cb_func the function to be called.
 * @param cb_arg extra argument to be passed to the callback function.
 */
int libcfs_kkuc_group_foreach(unsigned int group, libcfs_kkuc_cb_t cb_func,
                              void *cb_arg)
{
        struct kkuc_reg *reg;
        int rc = 0;

        if (group > KUC_GRP_MAX) {
                CDEBUG(D_WARNING, "Kernelcomm: bad group %d\n", group);
                return -EINVAL;
        }

        /* no link for this group */
        if (!kkuc_groups[group].next)
                return 0;

        down_read(&kg_sem);
        list_for_each_entry(reg, &kkuc_groups[group], kr_chain) {
                if (reg->kr_fp)
                        rc = cb_func(reg->kr_data, cb_arg);
        }
        up_read(&kg_sem);

        return rc;
}
EXPORT_SYMBOL(libcfs_kkuc_group_foreach);