// SPDX-License-Identifier: GPL-2.0-only
/*
 * Copyright (C) 2005-2008 Red Hat, Inc.  All rights reserved.
 */

#include <linux/fs.h>
#include <linux/miscdevice.h>
#include <linux/poll.h>
#include <linux/dlm.h>
#include <linux/dlm_plock.h>
#include <linux/slab.h>

#include "dlm_internal.h"
#include "lockspace.h"

static spinlock_t ops_lock;
static struct list_head send_list;
static struct list_head recv_list;
static wait_queue_head_t send_wq;
static wait_queue_head_t recv_wq;

struct plock_op {
        struct list_head list;
        int done;
        struct dlm_plock_info info;
};

struct plock_xop {
        struct plock_op xop;
        int (*callback)(struct file_lock *fl, int result);
        void *fl;
        void *file;
        struct file_lock flc;
};


static inline void set_version(struct dlm_plock_info *info)
{
        info->version[0] = DLM_PLOCK_VERSION_MAJOR;
        info->version[1] = DLM_PLOCK_VERSION_MINOR;
        info->version[2] = DLM_PLOCK_VERSION_PATCH;
}

static int check_version(struct dlm_plock_info *info)
{
        if ((DLM_PLOCK_VERSION_MAJOR != info->version[0]) ||
            (DLM_PLOCK_VERSION_MINOR < info->version[1])) {
                log_print("plock device version mismatch: "
                          "kernel (%u.%u.%u), user (%u.%u.%u)",
                          DLM_PLOCK_VERSION_MAJOR,
                          DLM_PLOCK_VERSION_MINOR,
                          DLM_PLOCK_VERSION_PATCH,
                          info->version[0],
                          info->version[1],
                          info->version[2]);
                return -EINVAL;
        }
        return 0;
}

static void send_op(struct plock_op *op)
{
        set_version(&op->info);
        INIT_LIST_HEAD(&op->list);
        spin_lock(&ops_lock);
        list_add_tail(&op->list, &send_list);
        spin_unlock(&ops_lock);
        wake_up(&send_wq);
}

/* If a process was killed while waiting for the only plock on a file,
   locks_remove_posix will not see any lock on the file so it won't
   send an unlock-close to us to pass on to userspace to clean up the
   abandoned waiter.  So, we have to insert the unlock-close when the
   lock call is interrupted. */

static void do_unlock_close(struct dlm_ls *ls, u64 number,
                            struct file *file, struct file_lock *fl)
{
        struct plock_op *op;

        op = kzalloc(sizeof(*op), GFP_NOFS);
        if (!op)
                return;

        op->info.optype         = DLM_PLOCK_OP_UNLOCK;
        op->info.pid            = fl->fl_pid;
        op->info.fsid           = ls->ls_global_id;
        op->info.number         = number;
        op->info.start          = 0;
        op->info.end            = OFFSET_MAX;
        if (fl->fl_lmops && fl->fl_lmops->lm_grant)
                op->info.owner  = (__u64) fl->fl_pid;
        else
                op->info.owner  = (__u64)(long) fl->fl_owner;

        op->info.flags |= DLM_PLOCK_FL_CLOSE;
        send_op(op);
}

int dlm_posix_lock(dlm_lockspace_t *lockspace, u64 number, struct file *file,
                   int cmd, struct file_lock *fl)
{
        struct dlm_ls *ls;
        struct plock_op *op;
        struct plock_xop *xop;
        int rv;

        ls = dlm_find_lockspace_local(lockspace);
        if (!ls)
                return -EINVAL;

        xop = kzalloc(sizeof(*xop), GFP_NOFS);
        if (!xop) {
                rv = -ENOMEM;
                goto out;
        }

        op = &xop->xop;
        op->info.optype         = DLM_PLOCK_OP_LOCK;
        op->info.pid            = fl->fl_pid;
        op->info.ex             = (fl->fl_type == F_WRLCK);
        op->info.wait           = IS_SETLKW(cmd);
        op->info.fsid           = ls->ls_global_id;
        op->info.number         = number;
        op->info.start          = fl->fl_start;
        op->info.end            = fl->fl_end;
        if (fl->fl_lmops && fl->fl_lmops->lm_grant) {
                /* fl_owner is lockd which doesn't distinguish
                   processes on the nfs client */
                op->info.owner  = (__u64) fl->fl_pid;
                xop->callback   = fl->fl_lmops->lm_grant;
                locks_init_lock(&xop->flc);
                locks_copy_lock(&xop->flc, fl);
                xop->fl         = fl;
                xop->file       = file;
        } else {
                op->info.owner  = (__u64)(long) fl->fl_owner;
                xop->callback   = NULL;
        }

        send_op(op);

        if (xop->callback == NULL) {
                rv = wait_event_interruptible(recv_wq, (op->done != 0));
                if (rv == -ERESTARTSYS) {
                        log_debug(ls, "dlm_posix_lock: wait killed %llx",
                                  (unsigned long long)number);
                        spin_lock(&ops_lock);
                        list_del(&op->list);
                        spin_unlock(&ops_lock);
                        kfree(xop);
                        do_unlock_close(ls, number, file, fl);
                        goto out;
                }
        } else {
                rv = FILE_LOCK_DEFERRED;
                goto out;
        }

        spin_lock(&ops_lock);
        if (!list_empty(&op->list)) {
                log_error(ls, "dlm_posix_lock: op on list %llx",
                          (unsigned long long)number);
                list_del(&op->list);
        }
        spin_unlock(&ops_lock);

        rv = op->info.rv;

        if (!rv) {
                if (locks_lock_file_wait(file, fl) < 0)
                        log_error(ls, "dlm_posix_lock: vfs lock error %llx",
                                  (unsigned long long)number);
        }

        kfree(xop);
out:
        dlm_put_lockspace(ls);
        return rv;
}
EXPORT_SYMBOL_GPL(dlm_posix_lock);

/* Returns failure iff a successful lock operation should be canceled */
static int dlm_plock_callback(struct plock_op *op)
{
        struct file *file;
        struct file_lock *fl;
        struct file_lock *flc;
        int (*notify)(struct file_lock *fl, int result) = NULL;
        struct plock_xop *xop = (struct plock_xop *)op;
        int rv = 0;

        spin_lock(&ops_lock);
        if (!list_empty(&op->list)) {
                log_print("dlm_plock_callback: op on list %llx",
                          (unsigned long long)op->info.number);
                list_del(&op->list);
        }
        spin_unlock(&ops_lock);

        /* check if the following 2 are still valid or make a copy */
        file = xop->file;
        flc = &xop->flc;
        fl = xop->fl;
        notify = xop->callback;

        if (op->info.rv) {
                notify(fl, op->info.rv);
                goto out;
        }

        /* got fs lock; bookkeep locally as well: */
        flc->fl_flags &= ~FL_SLEEP;
        if (posix_lock_file(file, flc, NULL)) {
                /*
                 * This can only happen in the case of kmalloc() failure.
                 * The filesystem's own lock is the authoritative lock,
                 * so a failure to get the lock locally is not a disaster.
                 * As long as the fs cannot reliably cancel locks (especially
                 * in a low-memory situation), we're better off ignoring
                 * this failure than trying to recover.
                 */
                log_print("dlm_plock_callback: vfs lock error %llx file %p fl %p",
                          (unsigned long long)op->info.number, file, fl);
        }

        rv = notify(fl, 0);
        if (rv) {
                /* XXX: We need to cancel the fs lock here: */
                log_print("dlm_plock_callback: lock granted after lock request "
                          "failed; dangling lock!\n");
                goto out;
        }

out:
        kfree(xop);
        return rv;
}

int dlm_posix_unlock(dlm_lockspace_t *lockspace, u64 number, struct file *file,
                     struct file_lock *fl)
{
        struct dlm_ls *ls;
        struct plock_op *op;
        int rv;
        unsigned char fl_flags = fl->fl_flags;

        ls = dlm_find_lockspace_local(lockspace);
        if (!ls)
                return -EINVAL;

        op = kzalloc(sizeof(*op), GFP_NOFS);
        if (!op) {
                rv = -ENOMEM;
                goto out;
        }

        /* cause the vfs unlock to return ENOENT if lock is not found */
        fl->fl_flags |= FL_EXISTS;

        rv = locks_lock_file_wait(file, fl);
        if (rv == -ENOENT) {
                rv = 0;
                goto out_free;
        }
        if (rv < 0) {
                log_error(ls, "dlm_posix_unlock: vfs unlock error %d %llx",
                          rv, (unsigned long long)number);
        }

        op->info.optype         = DLM_PLOCK_OP_UNLOCK;
        op->info.pid            = fl->fl_pid;
        op->info.fsid           = ls->ls_global_id;
        op->info.number         = number;
        op->info.start          = fl->fl_start;
        op->info.end            = fl->fl_end;
        if (fl->fl_lmops && fl->fl_lmops->lm_grant)
                op->info.owner  = (__u64) fl->fl_pid;
        else
                op->info.owner  = (__u64)(long) fl->fl_owner;

        if (fl->fl_flags & FL_CLOSE) {
                op->info.flags |= DLM_PLOCK_FL_CLOSE;
                send_op(op);
                rv = 0;
                goto out;
        }

        send_op(op);
        wait_event(recv_wq, (op->done != 0));

        spin_lock(&ops_lock);
        if (!list_empty(&op->list)) {
                log_error(ls, "dlm_posix_unlock: op on list %llx",
                          (unsigned long long)number);
                list_del(&op->list);
        }
        spin_unlock(&ops_lock);

        rv = op->info.rv;

        if (rv == -ENOENT)
                rv = 0;

out_free:
        kfree(op);
out:
        dlm_put_lockspace(ls);
        fl->fl_flags = fl_flags;
        return rv;
}
EXPORT_SYMBOL_GPL(dlm_posix_unlock);

int dlm_posix_get(dlm_lockspace_t *lockspace, u64 number, struct file *file,
                  struct file_lock *fl)
{
        struct dlm_ls *ls;
        struct plock_op *op;
        int rv;

        ls = dlm_find_lockspace_local(lockspace);
        if (!ls)
                return -EINVAL;

        op = kzalloc(sizeof(*op), GFP_NOFS);
        if (!op) {
                rv = -ENOMEM;
                goto out;
        }

        op->info.optype         = DLM_PLOCK_OP_GET;
        op->info.pid            = fl->fl_pid;
        op->info.ex             = (fl->fl_type == F_WRLCK);
        op->info.fsid           = ls->ls_global_id;
        op->info.number         = number;
        op->info.start          = fl->fl_start;
        op->info.end            = fl->fl_end;
        if (fl->fl_lmops && fl->fl_lmops->lm_grant)
                op->info.owner  = (__u64) fl->fl_pid;
        else
                op->info.owner  = (__u64)(long) fl->fl_owner;

        send_op(op);
        wait_event(recv_wq, (op->done != 0));

        spin_lock(&ops_lock);
        if (!list_empty(&op->list)) {
                log_error(ls, "dlm_posix_get: op on list %llx",
                          (unsigned long long)number);
                list_del(&op->list);
        }
        spin_unlock(&ops_lock);

        /* info.rv from userspace is 1 for conflict, 0 for no-conflict,
           -ENOENT if there are no locks on the file */

        rv = op->info.rv;

        fl->fl_type = F_UNLCK;
        if (rv == -ENOENT)
                rv = 0;
        else if (rv > 0) {
                locks_init_lock(fl);
                fl->fl_type = (op->info.ex) ? F_WRLCK : F_RDLCK;
                fl->fl_flags = FL_POSIX;
                fl->fl_pid = -op->info.pid;
                fl->fl_start = op->info.start;
                fl->fl_end = op->info.end;
                rv = 0;
        }

        kfree(op);
out:
        dlm_put_lockspace(ls);
        return rv;
}
EXPORT_SYMBOL_GPL(dlm_posix_get);

/* a read copies out one plock request from the send list */
static ssize_t dev_read(struct file *file, char __user *u, size_t count,
                        loff_t *ppos)
{
        struct dlm_plock_info info;
        struct plock_op *op = NULL;

        if (count < sizeof(info))
                return -EINVAL;

        spin_lock(&ops_lock);
        if (!list_empty(&send_list)) {
                op = list_entry(send_list.next, struct plock_op, list);
                if (op->info.flags & DLM_PLOCK_FL_CLOSE)
                        list_del(&op->list);
                else
                        list_move(&op->list, &recv_list);
                memcpy(&info, &op->info, sizeof(info));
        }
        spin_unlock(&ops_lock);

        if (!op)
                return -EAGAIN;

        /* there is no need to get a reply from userspace for unlocks
           that were generated by the vfs cleaning up for a close
           (the process did not make an unlock call). */

        if (op->info.flags & DLM_PLOCK_FL_CLOSE)
                kfree(op);

        if (copy_to_user(u, &info, sizeof(info)))
                return -EFAULT;
        return sizeof(info);
}

/* a write copies in one plock result that should match a plock_op
   on the recv list */
static ssize_t dev_write(struct file *file, const char __user *u, size_t count,
                         loff_t *ppos)
{
        struct dlm_plock_info info;
        struct plock_op *op;
        int found = 0, do_callback = 0;

        if (count != sizeof(info))
                return -EINVAL;

        if (copy_from_user(&info, u, sizeof(info)))
                return -EFAULT;

        if (check_version(&info))
                return -EINVAL;

        spin_lock(&ops_lock);
        list_for_each_entry(op, &recv_list, list) {
                if (op->info.fsid == info.fsid &&
                    op->info.number == info.number &&
                    op->info.owner == info.owner) {
                        struct plock_xop *xop = (struct plock_xop *)op;
                        list_del_init(&op->list);
                        memcpy(&op->info, &info, sizeof(info));
                        if (xop->callback)
                                do_callback = 1;
                        else
                                op->done = 1;
                        found = 1;
                        break;
                }
        }
        spin_unlock(&ops_lock);

        if (found) {
                if (do_callback)
                        dlm_plock_callback(op);
                else
                        wake_up(&recv_wq);
        } else
                log_print("dev_write no op %x %llx", info.fsid,
                          (unsigned long long)info.number);
        return count;
}

static __poll_t dev_poll(struct file *file, poll_table *wait)
{
        __poll_t mask = 0;

        poll_wait(file, &send_wq, wait);

        spin_lock(&ops_lock);
        if (!list_empty(&send_list))
                mask = EPOLLIN | EPOLLRDNORM;
        spin_unlock(&ops_lock);

        return mask;
}

static const struct file_operations dev_fops = {
        .read    = dev_read,
        .write   = dev_write,
        .poll    = dev_poll,
        .owner   = THIS_MODULE,
        .llseek  = noop_llseek,
};

static struct miscdevice plock_dev_misc = {
        .minor = MISC_DYNAMIC_MINOR,
        .name = DLM_PLOCK_MISC_NAME,
        .fops = &dev_fops
};

int dlm_plock_init(void)
{
        int rv;

        spin_lock_init(&ops_lock);
        INIT_LIST_HEAD(&send_list);
        INIT_LIST_HEAD(&recv_list);
        init_waitqueue_head(&send_wq);
        init_waitqueue_head(&recv_wq);

        rv = misc_register(&plock_dev_misc);
        if (rv)
                log_print("dlm_plock_init: misc_register failed %d", rv);
        return rv;
}

void dlm_plock_exit(void)
{
        misc_deregister(&plock_dev_misc);
}