plock.c

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/*
 * Copyright (C) 2005-2008 Red Hat, Inc.  All rights reserved.
 *
 * This copyrighted material is made available to anyone wishing to use,
 * modify, copy, or redistribute it subject to the terms and conditions
 * of the GNU General Public License version 2.
 */

#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;
    void *callback;
    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_killable(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 (posix_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)(void *, void *, int) = 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, NULL, 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, NULL, 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;

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

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

    if (posix_lock_file_wait(file, fl) < 0)
        log_error(ls, "dlm_posix_unlock: vfs unlock error %llx",
              (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;

    kfree(op);
out:
    dlm_put_lockspace(ls);
    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 unsigned int dev_poll(struct file *file, poll_table *wait)
{
    unsigned int mask = 0;

    poll_wait(file, &send_wq, wait);

    spin_lock(&ops_lock);
    if (!list_empty(&send_list))
        mask = POLLIN | POLLRDNORM;
    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)
{
    if (misc_deregister(&plock_dev_misc) < 0)
        log_print("dlm_plock_exit: misc_deregister failed");
}