clntlock.c

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/*
 * linux/fs/lockd/clntlock.c
 *
 * Lock handling for the client side NLM implementation
 *
 * Copyright (C) 1996, Olaf Kirch <[email protected]>
 */

#include <linux/module.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/time.h>
#include <linux/nfs_fs.h>
#include <linux/sunrpc/clnt.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);

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);
    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);
    if (host == NULL) {
        lockd_down(nlm_init->net);
        return ERR_PTR(-ENOLCK);
    }

    return host;
}
EXPORT_SYMBOL_GPL(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;
    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(fl_blocked->fl_file->f_path.dentry->d_inode) ,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 file_lock *fl, *next;
    u32 nsmstate;
    struct net *net = host->net;

    allow_signal(SIGKILL);

    down_write(&host->h_rwsem);
    lockd_up(net);  /* 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) != 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);
    return 0;
}