// SPDX-License-Identifier: GPL-2.0-only
/*
 * linux/fs/lockd/clntlock.c
 *
 * Lock handling for the client side NLM implementation
 *
 * Copyright (C) 1996, Olaf Kirch <okir@monad.swb.de>
 */

#include <linux/module.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/time.h>
#include <linux/nfs_fs.h>
#include <linux/sunrpc/addr.h>
#include <linux/sunrpc/svc.h>
#include <linux/lockd/lockd.h>
#include <linux/kthread.h>

#define NLMDBG_FACILITY         NLMDBG_CLIENT

/*
 * Local function prototypes
 */
static int                      reclaimer(void *ptr);

/*
 * The following functions handle blocking and granting from the
 * client perspective.
 */

/*
 * This is the representation of a blocked client lock.
 */
struct nlm_wait {
        struct list_head        b_list;         /* linked list */
        wait_queue_head_t       b_wait;         /* where to wait on */
        struct nlm_host *       b_host;
        struct file_lock *      b_lock;         /* local file lock */
        unsigned short          b_reclaim;      /* got to reclaim lock */
        __be32                  b_status;       /* grant callback status */
};

static LIST_HEAD(nlm_blocked);
static DEFINE_SPINLOCK(nlm_blocked_lock);

/**
 * nlmclnt_init - Set up per-NFS mount point lockd data structures
 * @nlm_init: pointer to arguments structure
 *
 * Returns pointer to an appropriate nlm_host struct,
 * or an ERR_PTR value.
 */
struct nlm_host *nlmclnt_init(const struct nlmclnt_initdata *nlm_init)
{
        struct nlm_host *host;
        u32 nlm_version = (nlm_init->nfs_version == 2) ? 1 : 4;
        int status;

        status = lockd_up(nlm_init->net, nlm_init->cred);
        if (status < 0)
                return ERR_PTR(status);

        host = nlmclnt_lookup_host(nlm_init->address, nlm_init->addrlen,
                                   nlm_init->protocol, nlm_version,
                                   nlm_init->hostname, nlm_init->noresvport,
                                   nlm_init->net, nlm_init->cred);
        if (host == NULL)
                goto out_nohost;
        if (host->h_rpcclnt == NULL && nlm_bind_host(host) == NULL)
                goto out_nobind;

        host->h_nlmclnt_ops = nlm_init->nlmclnt_ops;
        return host;
out_nobind:
        nlmclnt_release_host(host);
out_nohost:
        lockd_down(nlm_init->net);
        return ERR_PTR(-ENOLCK);
}
EXPORT_SYMBOL_GPL(nlmclnt_init);

/**
 * nlmclnt_done - Release resources allocated by nlmclnt_init()
 * @host: nlm_host structure reserved by nlmclnt_init()
 *
 */
void nlmclnt_done(struct nlm_host *host)
{
        struct net *net = host->net;

        nlmclnt_release_host(host);
        lockd_down(net);
}
EXPORT_SYMBOL_GPL(nlmclnt_done);

/*
 * Queue up a lock for blocking so that the GRANTED request can see it
 */
struct nlm_wait *nlmclnt_prepare_block(struct nlm_host *host, struct file_lock *fl)
{
        struct nlm_wait *block;

        block = kmalloc(sizeof(*block), GFP_KERNEL);
        if (block != NULL) {
                block->b_host = host;
                block->b_lock = fl;
                init_waitqueue_head(&block->b_wait);
                block->b_status = nlm_lck_blocked;

                spin_lock(&nlm_blocked_lock);
                list_add(&block->b_list, &nlm_blocked);
                spin_unlock(&nlm_blocked_lock);
        }
        return block;
}

void nlmclnt_finish_block(struct nlm_wait *block)
{
        if (block == NULL)
                return;
        spin_lock(&nlm_blocked_lock);
        list_del(&block->b_list);
        spin_unlock(&nlm_blocked_lock);
        kfree(block);
}

/*
 * Block on a lock
 */
int nlmclnt_block(struct nlm_wait *block, struct nlm_rqst *req, long timeout)
{
        long ret;

        /* A borken server might ask us to block even if we didn't
         * request it. Just say no!
         */
        if (block == NULL)
                return -EAGAIN;

        /* Go to sleep waiting for GRANT callback. Some servers seem
         * to lose callbacks, however, so we're going to poll from
         * time to time just to make sure.
         *
         * For now, the retry frequency is pretty high; normally 
         * a 1 minute timeout would do. See the comment before
         * nlmclnt_lock for an explanation.
         */
        ret = wait_event_interruptible_timeout(block->b_wait,
                        block->b_status != nlm_lck_blocked,
                        timeout);
        if (ret < 0)
                return -ERESTARTSYS;
        /* Reset the lock status after a server reboot so we resend */
        if (block->b_status == nlm_lck_denied_grace_period)
                block->b_status = nlm_lck_blocked;
        req->a_res.status = block->b_status;
        return 0;
}

/*
 * The server lockd has called us back to tell us the lock was granted
 */
__be32 nlmclnt_grant(const struct sockaddr *addr, const struct nlm_lock *lock)
{
        const struct file_lock *fl = &lock->fl;
        const struct nfs_fh *fh = &lock->fh;
        struct nlm_wait *block;
        __be32 res = nlm_lck_denied;

        /*
         * Look up blocked request based on arguments. 
         * Warning: must not use cookie to match it!
         */
        spin_lock(&nlm_blocked_lock);
        list_for_each_entry(block, &nlm_blocked, b_list) {
                struct file_lock *fl_blocked = block->b_lock;

                if (fl_blocked->fl_start != fl->fl_start)
                        continue;
                if (fl_blocked->fl_end != fl->fl_end)
                        continue;
                /*
                 * Careful! The NLM server will return the 32-bit "pid" that
                 * we put on the wire: in this case the lockowner "pid".
                 */
                if (fl_blocked->fl_u.nfs_fl.owner->pid != lock->svid)
                        continue;
                if (!rpc_cmp_addr(nlm_addr(block->b_host), addr))
                        continue;
                if (nfs_compare_fh(NFS_FH(locks_inode(fl_blocked->fl_file)), fh) != 0)
                        continue;
                /* Alright, we found a lock. Set the return status
                 * and wake up the caller
                 */
                block->b_status = nlm_granted;
                wake_up(&block->b_wait);
                res = nlm_granted;
        }
        spin_unlock(&nlm_blocked_lock);
        return res;
}

/*
 * The following procedures deal with the recovery of locks after a
 * server crash.
 */

/*
 * Reclaim all locks on server host. We do this by spawning a separate
 * reclaimer thread.
 */
void
nlmclnt_recovery(struct nlm_host *host)
{
        struct task_struct *task;

        if (!host->h_reclaiming++) {
                nlm_get_host(host);
                task = kthread_run(reclaimer, host, "%s-reclaim", host->h_name);
                if (IS_ERR(task))
                        printk(KERN_ERR "lockd: unable to spawn reclaimer "
                                "thread. Locks for %s won't be reclaimed! "
                                "(%ld)\n", host->h_name, PTR_ERR(task));
        }
}

static int
reclaimer(void *ptr)
{
        struct nlm_host   *host = (struct nlm_host *) ptr;
        struct nlm_wait   *block;
        struct nlm_rqst   *req;
        struct file_lock *fl, *next;
        u32 nsmstate;
        struct net *net = host->net;

        req = kmalloc(sizeof(*req), GFP_KERNEL);
        if (!req)
                return 0;

        allow_signal(SIGKILL);

        down_write(&host->h_rwsem);
        lockd_up(net, NULL);    /* note: this cannot fail as lockd is already running */

        dprintk("lockd: reclaiming locks for host %s\n", host->h_name);

restart:
        nsmstate = host->h_nsmstate;

        /* Force a portmap getport - the peer's lockd will
         * most likely end up on a different port.
         */
        host->h_nextrebind = jiffies;
        nlm_rebind_host(host);

        /* First, reclaim all locks that have been granted. */
        list_splice_init(&host->h_granted, &host->h_reclaim);
        list_for_each_entry_safe(fl, next, &host->h_reclaim, fl_u.nfs_fl.list) {
                list_del_init(&fl->fl_u.nfs_fl.list);

                /*
                 * sending this thread a SIGKILL will result in any unreclaimed
                 * locks being removed from the h_granted list. This means that
                 * the kernel will not attempt to reclaim them again if a new
                 * reclaimer thread is spawned for this host.
                 */
                if (signalled())
                        continue;
                if (nlmclnt_reclaim(host, fl, req) != 0)
                        continue;
                list_add_tail(&fl->fl_u.nfs_fl.list, &host->h_granted);
                if (host->h_nsmstate != nsmstate) {
                        /* Argh! The server rebooted again! */
                        goto restart;
                }
        }

        host->h_reclaiming = 0;
        up_write(&host->h_rwsem);
        dprintk("NLM: done reclaiming locks for host %s\n", host->h_name);

        /* Now, wake up all processes that sleep on a blocked lock */
        spin_lock(&nlm_blocked_lock);
        list_for_each_entry(block, &nlm_blocked, b_list) {
                if (block->b_host == host) {
                        block->b_status = nlm_lck_denied_grace_period;
                        wake_up(&block->b_wait);
                }
        }
        spin_unlock(&nlm_blocked_lock);

        /* Release host handle after use */
        nlmclnt_release_host(host);
        lockd_down(net);
        kfree(req);
        return 0;
}