locks.c

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/* -*- mode: c; c-basic-offset: 8; -*-
 * vim: noexpandtab sw=8 ts=8 sts=0:
 *
 * locks.c
 *
 * Userspace file locking support
 *
 * Copyright (C) 2007 Oracle.  All rights reserved.
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * General Public License for more details.
 *
 * You should have received a copy of the GNU General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
 * Boston, MA 021110-1307, USA.
 */

#include <linux/fs.h>
#include <linux/fcntl.h>

#include <cluster/masklog.h>

#include "ocfs2.h"

#include "dlmglue.h"
#include "file.h"
#include "inode.h"
#include "locks.h"

static int ocfs2_do_flock(struct file *file, struct inode *inode,
              int cmd, struct file_lock *fl)
{
    int ret = 0, level = 0, trylock = 0;
    struct ocfs2_file_private *fp = file->private_data;
    struct ocfs2_lock_res *lockres = &fp->fp_flock;

    if (fl->fl_type == F_WRLCK)
        level = 1;
    if (!IS_SETLKW(cmd))
        trylock = 1;

    mutex_lock(&fp->fp_mutex);

    if (lockres->l_flags & OCFS2_LOCK_ATTACHED &&
        lockres->l_level > LKM_NLMODE) {
        int old_level = 0;

        if (lockres->l_level == LKM_EXMODE)
            old_level = 1;

        if (level == old_level)
            goto out;

        /*
         * Converting an existing lock is not guaranteed to be
         * atomic, so we can get away with simply unlocking
         * here and allowing the lock code to try at the new
         * level.
         */

        flock_lock_file_wait(file,
                     &(struct file_lock){.fl_type = F_UNLCK});

        ocfs2_file_unlock(file);
    }

    ret = ocfs2_file_lock(file, level, trylock);
    if (ret) {
        if (ret == -EAGAIN && trylock)
            ret = -EWOULDBLOCK;
        else
            mlog_errno(ret);
        goto out;
    }

    ret = flock_lock_file_wait(file, fl);

out:
    mutex_unlock(&fp->fp_mutex);

    return ret;
}

static int ocfs2_do_funlock(struct file *file, int cmd, struct file_lock *fl)
{
    int ret;
    struct ocfs2_file_private *fp = file->private_data;

    mutex_lock(&fp->fp_mutex);
    ocfs2_file_unlock(file);
    ret = flock_lock_file_wait(file, fl);
    mutex_unlock(&fp->fp_mutex);

    return ret;
}

/*
 * Overall flow of ocfs2_flock() was influenced by gfs2_flock().
 */
int ocfs2_flock(struct file *file, int cmd, struct file_lock *fl)
{
    struct inode *inode = file->f_mapping->host;
    struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);

    if (!(fl->fl_flags & FL_FLOCK))
        return -ENOLCK;
    if (__mandatory_lock(inode))
        return -ENOLCK;

    if ((osb->s_mount_opt & OCFS2_MOUNT_LOCALFLOCKS) ||
        ocfs2_mount_local(osb))
        return flock_lock_file_wait(file, fl);

    if (fl->fl_type == F_UNLCK)
        return ocfs2_do_funlock(file, cmd, fl);
    else
        return ocfs2_do_flock(file, inode, cmd, fl);
}

int ocfs2_lock(struct file *file, int cmd, struct file_lock *fl)
{
    struct inode *inode = file->f_mapping->host;
    struct ocfs2_super *osb = OCFS2_SB(inode->i_sb);

    if (!(fl->fl_flags & FL_POSIX))
        return -ENOLCK;
    if (__mandatory_lock(inode) && fl->fl_type != F_UNLCK)
        return -ENOLCK;

    return ocfs2_plock(osb->cconn, OCFS2_I(inode)->ip_blkno, file, cmd, fl);
}