/* -*- mode: c; c-basic-offset: 8; -*-
 * vim: noexpandtab sw=8 ts=8 sts=0:
 *
 * userdlm.c
 *
 * Code which implements the kernel side of a minimal userspace
 * interface to our DLM.
 *
 * Many of the functions here are pared down versions of dlmglue.c
 * functions.
 *
 * Copyright (C) 2003, 2004 Oracle.  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.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 */

#include <linux/signal.h>
#include <linux/sched/signal.h>

#include <linux/module.h>
#include <linux/fs.h>
#include <linux/types.h>
#include <linux/crc32.h>

#include "ocfs2_lockingver.h"
#include "stackglue.h"
#include "userdlm.h"

#define MLOG_MASK_PREFIX ML_DLMFS
#include "cluster/masklog.h"


static inline struct user_lock_res *user_lksb_to_lock_res(struct ocfs2_dlm_lksb *lksb)
{
        return container_of(lksb, struct user_lock_res, l_lksb);
}

static inline int user_check_wait_flag(struct user_lock_res *lockres,
                                       int flag)
{
        int ret;

        spin_lock(&lockres->l_lock);
        ret = lockres->l_flags & flag;
        spin_unlock(&lockres->l_lock);

        return ret;
}

static inline void user_wait_on_busy_lock(struct user_lock_res *lockres)

{
        wait_event(lockres->l_event,
                   !user_check_wait_flag(lockres, USER_LOCK_BUSY));
}

static inline void user_wait_on_blocked_lock(struct user_lock_res *lockres)

{
        wait_event(lockres->l_event,
                   !user_check_wait_flag(lockres, USER_LOCK_BLOCKED));
}

/* I heart container_of... */
static inline struct ocfs2_cluster_connection *
cluster_connection_from_user_lockres(struct user_lock_res *lockres)
{
        struct dlmfs_inode_private *ip;

        ip = container_of(lockres,
                          struct dlmfs_inode_private,
                          ip_lockres);
        return ip->ip_conn;
}

static struct inode *
user_dlm_inode_from_user_lockres(struct user_lock_res *lockres)
{
        struct dlmfs_inode_private *ip;

        ip = container_of(lockres,
                          struct dlmfs_inode_private,
                          ip_lockres);
        return &ip->ip_vfs_inode;
}

static inline void user_recover_from_dlm_error(struct user_lock_res *lockres)
{
        spin_lock(&lockres->l_lock);
        lockres->l_flags &= ~USER_LOCK_BUSY;
        spin_unlock(&lockres->l_lock);
}

#define user_log_dlm_error(_func, _stat, _lockres) do {                 \
        mlog(ML_ERROR, "Dlm error %d while calling %s on "              \
                "resource %.*s\n", _stat, _func,                        \
                _lockres->l_namelen, _lockres->l_name);                 \
} while (0)

/* WARNING: This function lives in a world where the only three lock
 * levels are EX, PR, and NL. It *will* have to be adjusted when more
 * lock types are added. */
static inline int user_highest_compat_lock_level(int level)
{
        int new_level = DLM_LOCK_EX;

        if (level == DLM_LOCK_EX)
                new_level = DLM_LOCK_NL;
        else if (level == DLM_LOCK_PR)
                new_level = DLM_LOCK_PR;
        return new_level;
}

static void user_ast(struct ocfs2_dlm_lksb *lksb)
{
        struct user_lock_res *lockres = user_lksb_to_lock_res(lksb);
        int status;

        mlog(ML_BASTS, "AST fired for lockres %.*s, level %d => %d\n",
             lockres->l_namelen, lockres->l_name, lockres->l_level,
             lockres->l_requested);

        spin_lock(&lockres->l_lock);

        status = ocfs2_dlm_lock_status(&lockres->l_lksb);
        if (status) {
                mlog(ML_ERROR, "lksb status value of %u on lockres %.*s\n",
                     status, lockres->l_namelen, lockres->l_name);
                spin_unlock(&lockres->l_lock);
                return;
        }

        mlog_bug_on_msg(lockres->l_requested == DLM_LOCK_IV,
                        "Lockres %.*s, requested ivmode. flags 0x%x\n",
                        lockres->l_namelen, lockres->l_name, lockres->l_flags);

        /* we're downconverting. */
        if (lockres->l_requested < lockres->l_level) {
                if (lockres->l_requested <=
                    user_highest_compat_lock_level(lockres->l_blocking)) {
                        lockres->l_blocking = DLM_LOCK_NL;
                        lockres->l_flags &= ~USER_LOCK_BLOCKED;
                }
        }

        lockres->l_level = lockres->l_requested;
        lockres->l_requested = DLM_LOCK_IV;
        lockres->l_flags |= USER_LOCK_ATTACHED;
        lockres->l_flags &= ~USER_LOCK_BUSY;

        spin_unlock(&lockres->l_lock);

        wake_up(&lockres->l_event);
}

static inline void user_dlm_grab_inode_ref(struct user_lock_res *lockres)
{
        struct inode *inode;
        inode = user_dlm_inode_from_user_lockres(lockres);
        if (!igrab(inode))
                BUG();
}

static void user_dlm_unblock_lock(struct work_struct *work);

static void __user_dlm_queue_lockres(struct user_lock_res *lockres)
{
        if (!(lockres->l_flags & USER_LOCK_QUEUED)) {
                user_dlm_grab_inode_ref(lockres);

                INIT_WORK(&lockres->l_work, user_dlm_unblock_lock);

                queue_work(user_dlm_worker, &lockres->l_work);
                lockres->l_flags |= USER_LOCK_QUEUED;
        }
}

static void __user_dlm_cond_queue_lockres(struct user_lock_res *lockres)
{
        int queue = 0;

        if (!(lockres->l_flags & USER_LOCK_BLOCKED))
                return;

        switch (lockres->l_blocking) {
        case DLM_LOCK_EX:
                if (!lockres->l_ex_holders && !lockres->l_ro_holders)
                        queue = 1;
                break;
        case DLM_LOCK_PR:
                if (!lockres->l_ex_holders)
                        queue = 1;
                break;
        default:
                BUG();
        }

        if (queue)
                __user_dlm_queue_lockres(lockres);
}

static void user_bast(struct ocfs2_dlm_lksb *lksb, int level)
{
        struct user_lock_res *lockres = user_lksb_to_lock_res(lksb);

        mlog(ML_BASTS, "BAST fired for lockres %.*s, blocking %d, level %d\n",
             lockres->l_namelen, lockres->l_name, level, lockres->l_level);

        spin_lock(&lockres->l_lock);
        lockres->l_flags |= USER_LOCK_BLOCKED;
        if (level > lockres->l_blocking)
                lockres->l_blocking = level;

        __user_dlm_queue_lockres(lockres);
        spin_unlock(&lockres->l_lock);

        wake_up(&lockres->l_event);
}

static void user_unlock_ast(struct ocfs2_dlm_lksb *lksb, int status)
{
        struct user_lock_res *lockres = user_lksb_to_lock_res(lksb);

        mlog(ML_BASTS, "UNLOCK AST fired for lockres %.*s, flags 0x%x\n",
             lockres->l_namelen, lockres->l_name, lockres->l_flags);

        if (status)
                mlog(ML_ERROR, "dlm returns status %d\n", status);

        spin_lock(&lockres->l_lock);
        /* The teardown flag gets set early during the unlock process,
         * so test the cancel flag to make sure that this ast isn't
         * for a concurrent cancel. */
        if (lockres->l_flags & USER_LOCK_IN_TEARDOWN
            && !(lockres->l_flags & USER_LOCK_IN_CANCEL)) {
                lockres->l_level = DLM_LOCK_IV;
        } else if (status == DLM_CANCELGRANT) {
                /* We tried to cancel a convert request, but it was
                 * already granted. Don't clear the busy flag - the
                 * ast should've done this already. */
                BUG_ON(!(lockres->l_flags & USER_LOCK_IN_CANCEL));
                lockres->l_flags &= ~USER_LOCK_IN_CANCEL;
                goto out_noclear;
        } else {
                BUG_ON(!(lockres->l_flags & USER_LOCK_IN_CANCEL));
                /* Cancel succeeded, we want to re-queue */
                lockres->l_requested = DLM_LOCK_IV; /* cancel an
                                                    * upconvert
                                                    * request. */
                lockres->l_flags &= ~USER_LOCK_IN_CANCEL;
                /* we want the unblock thread to look at it again
                 * now. */
                if (lockres->l_flags & USER_LOCK_BLOCKED)
                        __user_dlm_queue_lockres(lockres);
        }

        lockres->l_flags &= ~USER_LOCK_BUSY;
out_noclear:
        spin_unlock(&lockres->l_lock);

        wake_up(&lockres->l_event);
}

/*
 * This is the userdlmfs locking protocol version.
 *
 * See fs/ocfs2/dlmglue.c for more details on locking versions.
 */
static struct ocfs2_locking_protocol user_dlm_lproto = {
        .lp_max_version = {
                .pv_major = OCFS2_LOCKING_PROTOCOL_MAJOR,
                .pv_minor = OCFS2_LOCKING_PROTOCOL_MINOR,
        },
        .lp_lock_ast            = user_ast,
        .lp_blocking_ast        = user_bast,
        .lp_unlock_ast          = user_unlock_ast,
};

static inline void user_dlm_drop_inode_ref(struct user_lock_res *lockres)
{
        struct inode *inode;
        inode = user_dlm_inode_from_user_lockres(lockres);
        iput(inode);
}

static void user_dlm_unblock_lock(struct work_struct *work)
{
        int new_level, status;
        struct user_lock_res *lockres =
                container_of(work, struct user_lock_res, l_work);
        struct ocfs2_cluster_connection *conn =
                cluster_connection_from_user_lockres(lockres);

        mlog(0, "lockres %.*s\n", lockres->l_namelen, lockres->l_name);

        spin_lock(&lockres->l_lock);

        mlog_bug_on_msg(!(lockres->l_flags & USER_LOCK_QUEUED),
                        "Lockres %.*s, flags 0x%x\n",
                        lockres->l_namelen, lockres->l_name, lockres->l_flags);

        /* notice that we don't clear USER_LOCK_BLOCKED here. If it's
         * set, we want user_ast clear it. */
        lockres->l_flags &= ~USER_LOCK_QUEUED;

        /* It's valid to get here and no longer be blocked - if we get
         * several basts in a row, we might be queued by the first
         * one, the unblock thread might run and clear the queued
         * flag, and finally we might get another bast which re-queues
         * us before our ast for the downconvert is called. */
        if (!(lockres->l_flags & USER_LOCK_BLOCKED)) {
                mlog(ML_BASTS, "lockres %.*s USER_LOCK_BLOCKED\n",
                     lockres->l_namelen, lockres->l_name);
                spin_unlock(&lockres->l_lock);
                goto drop_ref;
        }

        if (lockres->l_flags & USER_LOCK_IN_TEARDOWN) {
                mlog(ML_BASTS, "lockres %.*s USER_LOCK_IN_TEARDOWN\n",
                     lockres->l_namelen, lockres->l_name);
                spin_unlock(&lockres->l_lock);
                goto drop_ref;
        }

        if (lockres->l_flags & USER_LOCK_BUSY) {
                if (lockres->l_flags & USER_LOCK_IN_CANCEL) {
                        mlog(ML_BASTS, "lockres %.*s USER_LOCK_IN_CANCEL\n",
                             lockres->l_namelen, lockres->l_name);
                        spin_unlock(&lockres->l_lock);
                        goto drop_ref;
                }

                lockres->l_flags |= USER_LOCK_IN_CANCEL;
                spin_unlock(&lockres->l_lock);

                status = ocfs2_dlm_unlock(conn, &lockres->l_lksb,
                                          DLM_LKF_CANCEL);
                if (status)
                        user_log_dlm_error("ocfs2_dlm_unlock", status, lockres);
                goto drop_ref;
        }

        /* If there are still incompat holders, we can exit safely
         * without worrying about re-queueing this lock as that will
         * happen on the last call to user_cluster_unlock. */
        if ((lockres->l_blocking == DLM_LOCK_EX)
            && (lockres->l_ex_holders || lockres->l_ro_holders)) {
                spin_unlock(&lockres->l_lock);
                mlog(ML_BASTS, "lockres %.*s, EX/PR Holders %u,%u\n",
                     lockres->l_namelen, lockres->l_name,
                     lockres->l_ex_holders, lockres->l_ro_holders);
                goto drop_ref;
        }

        if ((lockres->l_blocking == DLM_LOCK_PR)
            && lockres->l_ex_holders) {
                spin_unlock(&lockres->l_lock);
                mlog(ML_BASTS, "lockres %.*s, EX Holders %u\n",
                     lockres->l_namelen, lockres->l_name,
                     lockres->l_ex_holders);
                goto drop_ref;
        }

        /* yay, we can downconvert now. */
        new_level = user_highest_compat_lock_level(lockres->l_blocking);
        lockres->l_requested = new_level;
        lockres->l_flags |= USER_LOCK_BUSY;
        mlog(ML_BASTS, "lockres %.*s, downconvert %d => %d\n",
             lockres->l_namelen, lockres->l_name, lockres->l_level, new_level);
        spin_unlock(&lockres->l_lock);

        /* need lock downconvert request now... */
        status = ocfs2_dlm_lock(conn, new_level, &lockres->l_lksb,
                                DLM_LKF_CONVERT|DLM_LKF_VALBLK,
                                lockres->l_name,
                                lockres->l_namelen);
        if (status) {
                user_log_dlm_error("ocfs2_dlm_lock", status, lockres);
                user_recover_from_dlm_error(lockres);
        }

drop_ref:
        user_dlm_drop_inode_ref(lockres);
}

static inline void user_dlm_inc_holders(struct user_lock_res *lockres,
                                        int level)
{
        switch(level) {
        case DLM_LOCK_EX:
                lockres->l_ex_holders++;
                break;
        case DLM_LOCK_PR:
                lockres->l_ro_holders++;
                break;
        default:
                BUG();
        }
}

/* predict what lock level we'll be dropping down to on behalf
 * of another node, and return true if the currently wanted
 * level will be compatible with it. */
static inline int
user_may_continue_on_blocked_lock(struct user_lock_res *lockres,
                                  int wanted)
{
        BUG_ON(!(lockres->l_flags & USER_LOCK_BLOCKED));

        return wanted <= user_highest_compat_lock_level(lockres->l_blocking);
}

int user_dlm_cluster_lock(struct user_lock_res *lockres,
                          int level,
                          int lkm_flags)
{
        int status, local_flags;
        struct ocfs2_cluster_connection *conn =
                cluster_connection_from_user_lockres(lockres);

        if (level != DLM_LOCK_EX &&
            level != DLM_LOCK_PR) {
                mlog(ML_ERROR, "lockres %.*s: invalid request!\n",
                     lockres->l_namelen, lockres->l_name);
                status = -EINVAL;
                goto bail;
        }

        mlog(ML_BASTS, "lockres %.*s, level %d, flags = 0x%x\n",
             lockres->l_namelen, lockres->l_name, level, lkm_flags);

again:
        if (signal_pending(current)) {
                status = -ERESTARTSYS;
                goto bail;
        }

        spin_lock(&lockres->l_lock);

        /* We only compare against the currently granted level
         * here. If the lock is blocked waiting on a downconvert,
         * we'll get caught below. */
        if ((lockres->l_flags & USER_LOCK_BUSY) &&
            (level > lockres->l_level)) {
                /* is someone sitting in dlm_lock? If so, wait on
                 * them. */
                spin_unlock(&lockres->l_lock);

                user_wait_on_busy_lock(lockres);
                goto again;
        }

        if ((lockres->l_flags & USER_LOCK_BLOCKED) &&
            (!user_may_continue_on_blocked_lock(lockres, level))) {
                /* is the lock is currently blocked on behalf of
                 * another node */
                spin_unlock(&lockres->l_lock);

                user_wait_on_blocked_lock(lockres);
                goto again;
        }

        if (level > lockres->l_level) {
                local_flags = lkm_flags | DLM_LKF_VALBLK;
                if (lockres->l_level != DLM_LOCK_IV)
                        local_flags |= DLM_LKF_CONVERT;

                lockres->l_requested = level;
                lockres->l_flags |= USER_LOCK_BUSY;
                spin_unlock(&lockres->l_lock);

                BUG_ON(level == DLM_LOCK_IV);
                BUG_ON(level == DLM_LOCK_NL);

                /* call dlm_lock to upgrade lock now */
                status = ocfs2_dlm_lock(conn, level, &lockres->l_lksb,
                                        local_flags, lockres->l_name,
                                        lockres->l_namelen);
                if (status) {
                        if ((lkm_flags & DLM_LKF_NOQUEUE) &&
                            (status != -EAGAIN))
                                user_log_dlm_error("ocfs2_dlm_lock",
                                                   status, lockres);
                        user_recover_from_dlm_error(lockres);
                        goto bail;
                }

                user_wait_on_busy_lock(lockres);
                goto again;
        }

        user_dlm_inc_holders(lockres, level);
        spin_unlock(&lockres->l_lock);

        status = 0;
bail:
        return status;
}

static inline void user_dlm_dec_holders(struct user_lock_res *lockres,
                                        int level)
{
        switch(level) {
        case DLM_LOCK_EX:
                BUG_ON(!lockres->l_ex_holders);
                lockres->l_ex_holders--;
                break;
        case DLM_LOCK_PR:
                BUG_ON(!lockres->l_ro_holders);
                lockres->l_ro_holders--;
                break;
        default:
                BUG();
        }
}

void user_dlm_cluster_unlock(struct user_lock_res *lockres,
                             int level)
{
        if (level != DLM_LOCK_EX &&
            level != DLM_LOCK_PR) {
                mlog(ML_ERROR, "lockres %.*s: invalid request!\n",
                     lockres->l_namelen, lockres->l_name);
                return;
        }

        spin_lock(&lockres->l_lock);
        user_dlm_dec_holders(lockres, level);
        __user_dlm_cond_queue_lockres(lockres);
        spin_unlock(&lockres->l_lock);
}

void user_dlm_write_lvb(struct inode *inode,
                        const char *val,
                        unsigned int len)
{
        struct user_lock_res *lockres = &DLMFS_I(inode)->ip_lockres;
        char *lvb;

        BUG_ON(len > DLM_LVB_LEN);

        spin_lock(&lockres->l_lock);

        BUG_ON(lockres->l_level < DLM_LOCK_EX);
        lvb = ocfs2_dlm_lvb(&lockres->l_lksb);
        memcpy(lvb, val, len);

        spin_unlock(&lockres->l_lock);
}

ssize_t user_dlm_read_lvb(struct inode *inode,
                          char *val,
                          unsigned int len)
{
        struct user_lock_res *lockres = &DLMFS_I(inode)->ip_lockres;
        char *lvb;
        ssize_t ret = len;

        BUG_ON(len > DLM_LVB_LEN);

        spin_lock(&lockres->l_lock);

        BUG_ON(lockres->l_level < DLM_LOCK_PR);
        if (ocfs2_dlm_lvb_valid(&lockres->l_lksb)) {
                lvb = ocfs2_dlm_lvb(&lockres->l_lksb);
                memcpy(val, lvb, len);
        } else
                ret = 0;

        spin_unlock(&lockres->l_lock);
        return ret;
}

void user_dlm_lock_res_init(struct user_lock_res *lockres,
                            struct dentry *dentry)
{
        memset(lockres, 0, sizeof(*lockres));

        spin_lock_init(&lockres->l_lock);
        init_waitqueue_head(&lockres->l_event);
        lockres->l_level = DLM_LOCK_IV;
        lockres->l_requested = DLM_LOCK_IV;
        lockres->l_blocking = DLM_LOCK_IV;

        /* should have been checked before getting here. */
        BUG_ON(dentry->d_name.len >= USER_DLM_LOCK_ID_MAX_LEN);

        memcpy(lockres->l_name,
               dentry->d_name.name,
               dentry->d_name.len);
        lockres->l_namelen = dentry->d_name.len;
}

int user_dlm_destroy_lock(struct user_lock_res *lockres)
{
        int status = -EBUSY;
        struct ocfs2_cluster_connection *conn =
                cluster_connection_from_user_lockres(lockres);

        mlog(ML_BASTS, "lockres %.*s\n", lockres->l_namelen, lockres->l_name);

        spin_lock(&lockres->l_lock);
        if (lockres->l_flags & USER_LOCK_IN_TEARDOWN) {
                spin_unlock(&lockres->l_lock);
                return 0;
        }

        lockres->l_flags |= USER_LOCK_IN_TEARDOWN;

        while (lockres->l_flags & USER_LOCK_BUSY) {
                spin_unlock(&lockres->l_lock);

                user_wait_on_busy_lock(lockres);

                spin_lock(&lockres->l_lock);
        }

        if (lockres->l_ro_holders || lockres->l_ex_holders) {
                spin_unlock(&lockres->l_lock);
                goto bail;
        }

        status = 0;
        if (!(lockres->l_flags & USER_LOCK_ATTACHED)) {
                spin_unlock(&lockres->l_lock);
                goto bail;
        }

        lockres->l_flags &= ~USER_LOCK_ATTACHED;
        lockres->l_flags |= USER_LOCK_BUSY;
        spin_unlock(&lockres->l_lock);

        status = ocfs2_dlm_unlock(conn, &lockres->l_lksb, DLM_LKF_VALBLK);
        if (status) {
                user_log_dlm_error("ocfs2_dlm_unlock", status, lockres);
                goto bail;
        }

        user_wait_on_busy_lock(lockres);

        status = 0;
bail:
        return status;
}

static void user_dlm_recovery_handler_noop(int node_num,
                                           void *recovery_data)
{
        /* We ignore recovery events */
        return;
}

void user_dlm_set_locking_protocol(void)
{
        ocfs2_stack_glue_set_max_proto_version(&user_dlm_lproto.lp_max_version);
}

struct ocfs2_cluster_connection *user_dlm_register(const struct qstr *name)
{
        int rc;
        struct ocfs2_cluster_connection *conn;

        rc = ocfs2_cluster_connect_agnostic(name->name, name->len,
                                            &user_dlm_lproto,
                                            user_dlm_recovery_handler_noop,
                                            NULL, &conn);
        if (rc)
                mlog_errno(rc);

        return rc ? ERR_PTR(rc) : conn;
}

void user_dlm_unregister(struct ocfs2_cluster_connection *conn)
{
        ocfs2_cluster_disconnect(conn, 0);
}