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

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

#include <trace/events/dlm.h>

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

static DEFINE_SPINLOCK(ops_lock);
static LIST_HEAD(send_list);
static LIST_HEAD(recv_list);
static DECLARE_WAIT_QUEUE_HEAD(send_wq);
static DECLARE_WAIT_QUEUE_HEAD(recv_wq);

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

struct plock_op {
        struct list_head list;
        int done;
        struct dlm_plock_info info;
        /* if set indicates async handling */
        struct plock_async_data *data;
};

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 struct plock_op *plock_lookup_waiter(const struct dlm_plock_info *info)
{
        struct plock_op *op = NULL, *iter;

        list_for_each_entry(iter, &recv_list, list) {
                if (iter->info.fsid == info->fsid &&
                    iter->info.number == info->number &&
                    iter->info.owner == info->owner &&
                    iter->info.pid == info->pid &&
                    iter->info.start == info->start &&
                    iter->info.end == info->end &&
                    iter->info.ex == info->ex &&
                    iter->info.wait) {
                        op = iter;
                        break;
                }
        }

        return op;
}

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 dlm_release_plock_op(struct plock_op *op)
{
        kfree(op->data);
        kfree(op);
}

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

static int do_lock_cancel(const struct dlm_plock_info *orig_info)
{
        struct plock_op *op;
        int rv;

        op = kzalloc_obj(*op, GFP_NOFS);
        if (!op)
                return -ENOMEM;

        op->info = *orig_info;
        op->info.optype = DLM_PLOCK_OP_CANCEL;
        op->info.wait = 0;

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

        rv = op->info.rv;

        dlm_release_plock_op(op);
        return rv;
}

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

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

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

        op->info.optype         = DLM_PLOCK_OP_LOCK;
        op->info.pid            = fl->c.flc_pid;
        op->info.ex             = lock_is_write(fl);
        op->info.wait           = !!(fl->c.flc_flags & FL_SLEEP);
        op->info.fsid           = ls->ls_global_id;
        op->info.number         = number;
        op->info.start          = fl->fl_start;
        op->info.end            = fl->fl_end;
        op->info.owner = (__u64)(long) fl->c.flc_owner;
        /* async handling */
        if (fl->fl_lmops && fl->fl_lmops->lm_grant) {
                op_data = kzalloc_obj(*op_data, GFP_NOFS);
                if (!op_data) {
                        dlm_release_plock_op(op);
                        rv = -ENOMEM;
                        goto out;
                }

                op_data->callback = fl->fl_lmops->lm_grant;
                locks_init_lock(&op_data->flc);
                locks_copy_lock(&op_data->flc, fl);
                op_data->fl             = fl;
                op_data->file   = file;

                op->data = op_data;

                send_op(op);
                rv = FILE_LOCK_DEFERRED;
                goto out;
        }

        send_op(op);

        if (op->info.wait) {
                rv = wait_event_interruptible(recv_wq, (op->done != 0));
                if (rv == -ERESTARTSYS) {
                        spin_lock(&ops_lock);
                        /* recheck under ops_lock if we got a done != 0,
                         * if so this interrupt case should be ignored
                         */
                        if (op->done != 0) {
                                spin_unlock(&ops_lock);
                                goto do_lock_wait;
                        }
                        spin_unlock(&ops_lock);

                        rv = do_lock_cancel(&op->info);
                        switch (rv) {
                        case 0:
                                /* waiter was deleted in user space, answer will never come
                                 * remove original request. The original request must be
                                 * on recv_list because the answer of do_lock_cancel()
                                 * synchronized it.
                                 */
                                spin_lock(&ops_lock);
                                list_del(&op->list);
                                spin_unlock(&ops_lock);
                                rv = -EINTR;
                                break;
                        case -ENOENT:
                                /* cancellation wasn't successful but op should be done */
                                fallthrough;
                        default:
                                /* internal error doing cancel we need to wait */
                                goto wait;
                        }

                        log_debug(ls, "%s: wait interrupted %x %llx pid %d",
                                  __func__, ls->ls_global_id,
                                  (unsigned long long)number, op->info.pid);
                        dlm_release_plock_op(op);
                        goto out;
                }
        } else {
wait:
                wait_event(recv_wq, (op->done != 0));
        }

do_lock_wait:

        WARN_ON(!list_empty(&op->list));

        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);
        }

        dlm_release_plock_op(op);
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 plock_async_data *op_data = op->data;
        struct file *file;
        struct file_lock *fl;
        struct file_lock *flc;
        int (*notify)(struct file_lock *fl, int result) = NULL;
        int rv = 0;

        WARN_ON(!list_empty(&op->list));

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

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

        /* got fs lock; bookkeep locally as well: */
        flc->c.flc_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("%s: lock granted after lock request failed; dangling lock!",
                          __func__);
                goto out;
        }

out:
        dlm_release_plock_op(op);
        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 saved_flags = fl->c.flc_flags;

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

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

        /* cause the vfs unlock to return ENOENT if lock is not found */
        fl->c.flc_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->c.flc_pid;
        op->info.fsid           = ls->ls_global_id;
        op->info.number         = number;
        op->info.start          = fl->fl_start;
        op->info.end            = fl->fl_end;
        op->info.owner = (__u64)(long) fl->c.flc_owner;

        if (fl->c.flc_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));

        WARN_ON(!list_empty(&op->list));

        rv = op->info.rv;

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

out_free:
        dlm_release_plock_op(op);
out:
        dlm_put_lockspace(ls);
        fl->c.flc_flags = saved_flags;
        return rv;
}
EXPORT_SYMBOL_GPL(dlm_posix_unlock);

/*
 * NOTE: This implementation can only handle async lock requests as nfs
 * do it. It cannot handle cancellation of a pending lock request sitting
 * in wait_event(), but for now only nfs is the only user local kernel
 * user.
 */
int dlm_posix_cancel(dlm_lockspace_t *lockspace, u64 number, struct file *file,
                     struct file_lock *fl)
{
        struct dlm_plock_info info;
        struct plock_op *op;
        struct dlm_ls *ls;
        int rv;

        /* this only works for async request for now and nfs is the only
         * kernel user right now.
         */
        if (WARN_ON_ONCE(!fl->fl_lmops || !fl->fl_lmops->lm_grant))
                return -EOPNOTSUPP;

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

        memset(&info, 0, sizeof(info));
        info.pid = fl->c.flc_pid;
        info.ex = lock_is_write(fl);
        info.fsid = ls->ls_global_id;
        dlm_put_lockspace(ls);
        info.number = number;
        info.start = fl->fl_start;
        info.end = fl->fl_end;
        info.owner = (__u64)(long) fl->c.flc_owner;

        rv = do_lock_cancel(&info);
        switch (rv) {
        case 0:
                spin_lock(&ops_lock);
                /* lock request to cancel must be on recv_list because
                 * do_lock_cancel() synchronizes it.
                 */
                op = plock_lookup_waiter(&info);
                if (WARN_ON_ONCE(!op)) {
                        spin_unlock(&ops_lock);
                        rv = -ENOLCK;
                        break;
                }

                list_del(&op->list);
                spin_unlock(&ops_lock);
                WARN_ON(op->info.optype != DLM_PLOCK_OP_LOCK);
                op->data->callback(op->data->fl, -EINTR);
                dlm_release_plock_op(op);
                rv = -EINTR;
                break;
        case -ENOENT:
                /* if cancel wasn't successful we probably were to late
                 * or it was a non-blocking lock request, so just unlock it.
                 */
                rv = dlm_posix_unlock(lockspace, number, file, fl);
                break;
        default:
                break;
        }

        return rv;
}
EXPORT_SYMBOL_GPL(dlm_posix_cancel);

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

        op->info.optype         = DLM_PLOCK_OP_GET;
        op->info.pid            = fl->c.flc_pid;
        op->info.ex             = lock_is_write(fl);
        op->info.fsid           = ls->ls_global_id;
        op->info.number         = number;
        op->info.start          = fl->fl_start;
        op->info.end            = fl->fl_end;
        op->info.owner = (__u64)(long) fl->c.flc_owner;

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

        WARN_ON(!list_empty(&op->list));

        /* 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->c.flc_type = F_UNLCK;
        if (rv == -ENOENT)
                rv = 0;
        else if (rv > 0) {
                locks_init_lock(fl);
                fl->c.flc_type = (op->info.ex) ? F_WRLCK : F_RDLCK;
                fl->c.flc_flags = FL_POSIX;
                fl->c.flc_pid = op->info.pid;
                if (op->info.nodeid != dlm_our_nodeid())
                        fl->c.flc_pid = -fl->c.flc_pid;
                fl->fl_start = op->info.start;
                fl->fl_end = op->info.end;
                rv = 0;
        }

        dlm_release_plock_op(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_first_entry(&send_list, struct plock_op, list);
                if (op->info.flags & DLM_PLOCK_FL_CLOSE)
                        list_del(&op->list);
                else
                        list_move_tail(&op->list, &recv_list);
                memcpy(&info, &op->info, sizeof(info));
        }
        spin_unlock(&ops_lock);

        if (!op)
                return -EAGAIN;

        trace_dlm_plock_read(&info);

        /* 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)
                dlm_release_plock_op(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 plock_op *op = NULL, *iter;
        struct dlm_plock_info info;
        int do_callback = 0;

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

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

        trace_dlm_plock_write(&info);

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

        /*
         * The results for waiting ops (SETLKW) can be returned in any
         * order, so match all fields to find the op.  The results for
         * non-waiting ops are returned in the order that they were sent
         * to userspace, so match the result with the first non-waiting op.
         */
        spin_lock(&ops_lock);
        if (info.wait) {
                op = plock_lookup_waiter(&info);
        } else {
                list_for_each_entry(iter, &recv_list, list) {
                        if (!iter->info.wait &&
                            iter->info.fsid == info.fsid) {
                                op = iter;
                                break;
                        }
                }
        }

        if (op) {
                /* Sanity check that op and info match. */
                if (info.wait)
                        WARN_ON(op->info.optype != DLM_PLOCK_OP_LOCK);
                else
                        WARN_ON(op->info.number != info.number ||
                                op->info.owner != info.owner ||
                                op->info.optype != info.optype);

                list_del_init(&op->list);
                memcpy(&op->info, &info, sizeof(info));
                if (op->data)
                        do_callback = 1;
                else
                        op->done = 1;
        }
        spin_unlock(&ops_lock);

        if (op) {
                if (do_callback)
                        dlm_plock_callback(op);
                else
                        wake_up(&recv_wq);
        } else
                pr_debug("%s: no op %x %llx", __func__,
                         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;

        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);
        WARN_ON(!list_empty(&send_list));
        WARN_ON(!list_empty(&recv_list));
}