/* -*- mode: c; c-basic-offset: 8; -*-
 * vim: noexpandtab sw=8 ts=8 sts=0:
 *
 * dlmfs.c
 *
 * Code which implements the kernel side of a minimal userspace
 * interface to our DLM. This file handles the virtual file system
 * used for communication with userspace. Credit should go to ramfs,
 * which was a template for the fs side of this module.
 *
 * Copyright (C) 2003, 2004 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.
 */

/* Simple VFS hooks based on: */
/*
 * Resizable simple ram filesystem for Linux.
 *
 * Copyright (C) 2000 Linus Torvalds.
 *               2000 Transmeta Corp.
 */

#include <linux/module.h>
#include <linux/fs.h>
#include <linux/pagemap.h>
#include <linux/types.h>
#include <linux/slab.h>
#include <linux/highmem.h>
#include <linux/init.h>
#include <linux/string.h>
#include <linux/backing-dev.h>

#include <asm/uaccess.h>


#include "cluster/nodemanager.h"
#include "cluster/heartbeat.h"
#include "cluster/tcp.h"

#include "dlmapi.h"

#include "userdlm.h"

#include "dlmfsver.h"

#define MLOG_MASK_PREFIX ML_DLMFS
#include "cluster/masklog.h"

static const struct super_operations dlmfs_ops;
static const struct file_operations dlmfs_file_operations;
static const struct inode_operations dlmfs_dir_inode_operations;
static const struct inode_operations dlmfs_root_inode_operations;
static const struct inode_operations dlmfs_file_inode_operations;
static struct kmem_cache *dlmfs_inode_cache;

struct workqueue_struct *user_dlm_worker;

/*
 * decodes a set of open flags into a valid lock level and a set of flags.
 * returns < 0 if we have invalid flags
 * flags which mean something to us:
 * O_RDONLY -> PRMODE level
 * O_WRONLY -> EXMODE level
 *
 * O_NONBLOCK -> LKM_NOQUEUE
 */
static int dlmfs_decode_open_flags(int open_flags,
                                   int *level,
                                   int *flags)
{
        if (open_flags & (O_WRONLY|O_RDWR))
                *level = LKM_EXMODE;
        else
                *level = LKM_PRMODE;

        *flags = 0;
        if (open_flags & O_NONBLOCK)
                *flags |= LKM_NOQUEUE;

        return 0;
}

static int dlmfs_file_open(struct inode *inode,
                           struct file *file)
{
        int status, level, flags;
        struct dlmfs_filp_private *fp = NULL;
        struct dlmfs_inode_private *ip;

        if (S_ISDIR(inode->i_mode))
                BUG();

        mlog(0, "open called on inode %lu, flags 0x%x\n", inode->i_ino,
                file->f_flags);

        status = dlmfs_decode_open_flags(file->f_flags, &level, &flags);
        if (status < 0)
                goto bail;

        /* We don't want to honor O_APPEND at read/write time as it
         * doesn't make sense for LVB writes. */
        file->f_flags &= ~O_APPEND;

        fp = kmalloc(sizeof(*fp), GFP_NOFS);
        if (!fp) {
                status = -ENOMEM;
                goto bail;
        }
        fp->fp_lock_level = level;

        ip = DLMFS_I(inode);

        status = user_dlm_cluster_lock(&ip->ip_lockres, level, flags);
        if (status < 0) {
                /* this is a strange error to return here but I want
                 * to be able userspace to be able to distinguish a
                 * valid lock request from one that simply couldn't be
                 * granted. */
                if (flags & LKM_NOQUEUE && status == -EAGAIN)
                        status = -ETXTBSY;
                kfree(fp);
                goto bail;
        }

        file->private_data = fp;
bail:
        return status;
}

static int dlmfs_file_release(struct inode *inode,
                              struct file *file)
{
        int level, status;
        struct dlmfs_inode_private *ip = DLMFS_I(inode);
        struct dlmfs_filp_private *fp =
                (struct dlmfs_filp_private *) file->private_data;

        if (S_ISDIR(inode->i_mode))
                BUG();

        mlog(0, "close called on inode %lu\n", inode->i_ino);

        status = 0;
        if (fp) {
                level = fp->fp_lock_level;
                if (level != LKM_IVMODE)
                        user_dlm_cluster_unlock(&ip->ip_lockres, level);

                kfree(fp);
                file->private_data = NULL;
        }

        return 0;
}

static ssize_t dlmfs_file_read(struct file *filp,
                               char __user *buf,
                               size_t count,
                               loff_t *ppos)
{
        int bytes_left;
        ssize_t readlen;
        char *lvb_buf;
        struct inode *inode = filp->f_path.dentry->d_inode;

        mlog(0, "inode %lu, count = %zu, *ppos = %llu\n",
                inode->i_ino, count, *ppos);

        if (*ppos >= i_size_read(inode))
                return 0;

        if (!count)
                return 0;

        if (!access_ok(VERIFY_WRITE, buf, count))
                return -EFAULT;

        /* don't read past the lvb */
        if ((count + *ppos) > i_size_read(inode))
                readlen = i_size_read(inode) - *ppos;
        else
                readlen = count - *ppos;

        lvb_buf = kmalloc(readlen, GFP_NOFS);
        if (!lvb_buf)
                return -ENOMEM;

        user_dlm_read_lvb(inode, lvb_buf, readlen);
        bytes_left = __copy_to_user(buf, lvb_buf, readlen);
        readlen -= bytes_left;

        kfree(lvb_buf);

        *ppos = *ppos + readlen;

        mlog(0, "read %zd bytes\n", readlen);
        return readlen;
}

static ssize_t dlmfs_file_write(struct file *filp,
                                const char __user *buf,
                                size_t count,
                                loff_t *ppos)
{
        int bytes_left;
        ssize_t writelen;
        char *lvb_buf;
        struct inode *inode = filp->f_path.dentry->d_inode;

        mlog(0, "inode %lu, count = %zu, *ppos = %llu\n",
                inode->i_ino, count, *ppos);

        if (*ppos >= i_size_read(inode))
                return -ENOSPC;

        if (!count)
                return 0;

        if (!access_ok(VERIFY_READ, buf, count))
                return -EFAULT;

        /* don't write past the lvb */
        if ((count + *ppos) > i_size_read(inode))
                writelen = i_size_read(inode) - *ppos;
        else
                writelen = count - *ppos;

        lvb_buf = kmalloc(writelen, GFP_NOFS);
        if (!lvb_buf)
                return -ENOMEM;

        bytes_left = copy_from_user(lvb_buf, buf, writelen);
        writelen -= bytes_left;
        if (writelen)
                user_dlm_write_lvb(inode, lvb_buf, writelen);

        kfree(lvb_buf);

        *ppos = *ppos + writelen;
        mlog(0, "wrote %zd bytes\n", writelen);
        return writelen;
}

static void dlmfs_init_once(struct kmem_cache *cachep,
                            void *foo)
{
        struct dlmfs_inode_private *ip =
                (struct dlmfs_inode_private *) foo;

        ip->ip_dlm = NULL;
        ip->ip_parent = NULL;

        inode_init_once(&ip->ip_vfs_inode);
}

static struct inode *dlmfs_alloc_inode(struct super_block *sb)
{
        struct dlmfs_inode_private *ip;

        ip = kmem_cache_alloc(dlmfs_inode_cache, GFP_NOFS);
        if (!ip)
                return NULL;

        return &ip->ip_vfs_inode;
}

static void dlmfs_destroy_inode(struct inode *inode)
{
        kmem_cache_free(dlmfs_inode_cache, DLMFS_I(inode));
}

static void dlmfs_clear_inode(struct inode *inode)
{
        int status;
        struct dlmfs_inode_private *ip;

        if (!inode)
                return;

        mlog(0, "inode %lu\n", inode->i_ino);

        ip = DLMFS_I(inode);

        if (S_ISREG(inode->i_mode)) {
                status = user_dlm_destroy_lock(&ip->ip_lockres);
                if (status < 0)
                        mlog_errno(status);
                iput(ip->ip_parent);
                goto clear_fields;
        }

        mlog(0, "we're a directory, ip->ip_dlm = 0x%p\n", ip->ip_dlm);
        /* we must be a directory. If required, lets unregister the
         * dlm context now. */
        if (ip->ip_dlm)
                user_dlm_unregister_context(ip->ip_dlm);
clear_fields:
        ip->ip_parent = NULL;
        ip->ip_dlm = NULL;
}

static struct backing_dev_info dlmfs_backing_dev_info = {
        .ra_pages       = 0,    /* No readahead */
        .capabilities   = BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_WRITEBACK,
};

static struct inode *dlmfs_get_root_inode(struct super_block *sb)
{
        struct inode *inode = new_inode(sb);
        int mode = S_IFDIR | 0755;
        struct dlmfs_inode_private *ip;

        if (inode) {
                ip = DLMFS_I(inode);

                inode->i_mode = mode;
                inode->i_uid = current->fsuid;
                inode->i_gid = current->fsgid;
                inode->i_blocks = 0;
                inode->i_mapping->backing_dev_info = &dlmfs_backing_dev_info;
                inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;
                inc_nlink(inode);

                inode->i_fop = &simple_dir_operations;
                inode->i_op = &dlmfs_root_inode_operations;
        }

        return inode;
}

static struct inode *dlmfs_get_inode(struct inode *parent,
                                     struct dentry *dentry,
                                     int mode)
{
        struct super_block *sb = parent->i_sb;
        struct inode * inode = new_inode(sb);
        struct dlmfs_inode_private *ip;

        if (!inode)
                return NULL;

        inode->i_mode = mode;
        inode->i_uid = current->fsuid;
        inode->i_gid = current->fsgid;
        inode->i_blocks = 0;
        inode->i_mapping->backing_dev_info = &dlmfs_backing_dev_info;
        inode->i_atime = inode->i_mtime = inode->i_ctime = CURRENT_TIME;

        ip = DLMFS_I(inode);
        ip->ip_dlm = DLMFS_I(parent)->ip_dlm;

        switch (mode & S_IFMT) {
        default:
                /* for now we don't support anything other than
                 * directories and regular files. */
                BUG();
                break;
        case S_IFREG:
                inode->i_op = &dlmfs_file_inode_operations;
                inode->i_fop = &dlmfs_file_operations;

                i_size_write(inode,  DLM_LVB_LEN);

                user_dlm_lock_res_init(&ip->ip_lockres, dentry);

                /* released at clear_inode time, this insures that we
                 * get to drop the dlm reference on each lock *before*
                 * we call the unregister code for releasing parent
                 * directories. */
                ip->ip_parent = igrab(parent);
                BUG_ON(!ip->ip_parent);
                break;
        case S_IFDIR:
                inode->i_op = &dlmfs_dir_inode_operations;
                inode->i_fop = &simple_dir_operations;

                /* directory inodes start off with i_nlink ==
                 * 2 (for "." entry) */
                inc_nlink(inode);
                break;
        }

        if (parent->i_mode & S_ISGID) {
                inode->i_gid = parent->i_gid;
                if (S_ISDIR(mode))
                        inode->i_mode |= S_ISGID;
        }

        return inode;
}

/*
 * File creation. Allocate an inode, and we're done..
 */
/* SMP-safe */
static int dlmfs_mkdir(struct inode * dir,
                       struct dentry * dentry,
                       int mode)
{
        int status;
        struct inode *inode = NULL;
        struct qstr *domain = &dentry->d_name;
        struct dlmfs_inode_private *ip;
        struct dlm_ctxt *dlm;

        mlog(0, "mkdir %.*s\n", domain->len, domain->name);

        /* verify that we have a proper domain */
        if (domain->len >= O2NM_MAX_NAME_LEN) {
                status = -EINVAL;
                mlog(ML_ERROR, "invalid domain name for directory.\n");
                goto bail;
        }

        inode = dlmfs_get_inode(dir, dentry, mode | S_IFDIR);
        if (!inode) {
                status = -ENOMEM;
                mlog_errno(status);
                goto bail;
        }

        ip = DLMFS_I(inode);

        dlm = user_dlm_register_context(domain);
        if (IS_ERR(dlm)) {
                status = PTR_ERR(dlm);
                mlog(ML_ERROR, "Error %d could not register domain \"%.*s\"\n",
                     status, domain->len, domain->name);
                goto bail;
        }
        ip->ip_dlm = dlm;

        inc_nlink(dir);
        d_instantiate(dentry, inode);
        dget(dentry);   /* Extra count - pin the dentry in core */

        status = 0;
bail:
        if (status < 0)
                iput(inode);
        return status;
}

static int dlmfs_create(struct inode *dir,
                        struct dentry *dentry,
                        int mode,
                        struct nameidata *nd)
{
        int status = 0;
        struct inode *inode;
        struct qstr *name = &dentry->d_name;

        mlog(0, "create %.*s\n", name->len, name->name);

        /* verify name is valid and doesn't contain any dlm reserved
         * characters */
        if (name->len >= USER_DLM_LOCK_ID_MAX_LEN ||
            name->name[0] == '$') {
                status = -EINVAL;
                mlog(ML_ERROR, "invalid lock name, %.*s\n", name->len,
                     name->name);
                goto bail;
        }

        inode = dlmfs_get_inode(dir, dentry, mode | S_IFREG);
        if (!inode) {
                status = -ENOMEM;
                mlog_errno(status);
                goto bail;
        }

        d_instantiate(dentry, inode);
        dget(dentry);   /* Extra count - pin the dentry in core */
bail:
        return status;
}

static int dlmfs_unlink(struct inode *dir,
                        struct dentry *dentry)
{
        int status;
        struct inode *inode = dentry->d_inode;

        mlog(0, "unlink inode %lu\n", inode->i_ino);

        /* if there are no current holders, or none that are waiting
         * to acquire a lock, this basically destroys our lockres. */
        status = user_dlm_destroy_lock(&DLMFS_I(inode)->ip_lockres);
        if (status < 0) {
                mlog(ML_ERROR, "unlink %.*s, error %d from destroy\n",
                     dentry->d_name.len, dentry->d_name.name, status);
                goto bail;
        }
        status = simple_unlink(dir, dentry);
bail:
        return status;
}

static int dlmfs_fill_super(struct super_block * sb,
                            void * data,
                            int silent)
{
        struct inode * inode;
        struct dentry * root;

        sb->s_maxbytes = MAX_LFS_FILESIZE;
        sb->s_blocksize = PAGE_CACHE_SIZE;
        sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
        sb->s_magic = DLMFS_MAGIC;
        sb->s_op = &dlmfs_ops;
        inode = dlmfs_get_root_inode(sb);
        if (!inode)
                return -ENOMEM;

        root = d_alloc_root(inode);
        if (!root) {
                iput(inode);
                return -ENOMEM;
        }
        sb->s_root = root;
        return 0;
}

static const struct file_operations dlmfs_file_operations = {
        .open           = dlmfs_file_open,
        .release        = dlmfs_file_release,
        .read           = dlmfs_file_read,
        .write          = dlmfs_file_write,
};

static const struct inode_operations dlmfs_dir_inode_operations = {
        .create         = dlmfs_create,
        .lookup         = simple_lookup,
        .unlink         = dlmfs_unlink,
};

/* this way we can restrict mkdir to only the toplevel of the fs. */
static const struct inode_operations dlmfs_root_inode_operations = {
        .lookup         = simple_lookup,
        .mkdir          = dlmfs_mkdir,
        .rmdir          = simple_rmdir,
};

static const struct super_operations dlmfs_ops = {
        .statfs         = simple_statfs,
        .alloc_inode    = dlmfs_alloc_inode,
        .destroy_inode  = dlmfs_destroy_inode,
        .clear_inode    = dlmfs_clear_inode,
        .drop_inode     = generic_delete_inode,
};

static const struct inode_operations dlmfs_file_inode_operations = {
        .getattr        = simple_getattr,
};

static int dlmfs_get_sb(struct file_system_type *fs_type,
        int flags, const char *dev_name, void *data, struct vfsmount *mnt)
{
        return get_sb_nodev(fs_type, flags, data, dlmfs_fill_super, mnt);
}

static struct file_system_type dlmfs_fs_type = {
        .owner          = THIS_MODULE,
        .name           = "ocfs2_dlmfs",
        .get_sb         = dlmfs_get_sb,
        .kill_sb        = kill_litter_super,
};

static int __init init_dlmfs_fs(void)
{
        int status;
        int cleanup_inode = 0, cleanup_worker = 0;

        dlmfs_print_version();

        status = bdi_init(&dlmfs_backing_dev_info);
        if (status)
                return status;

        dlmfs_inode_cache = kmem_cache_create("dlmfs_inode_cache",
                                sizeof(struct dlmfs_inode_private),
                                0, (SLAB_HWCACHE_ALIGN|SLAB_RECLAIM_ACCOUNT|
                                        SLAB_MEM_SPREAD),
                                dlmfs_init_once);
        if (!dlmfs_inode_cache)
                goto bail;
        cleanup_inode = 1;

        user_dlm_worker = create_singlethread_workqueue("user_dlm");
        if (!user_dlm_worker) {
                status = -ENOMEM;
                goto bail;
        }
        cleanup_worker = 1;

        status = register_filesystem(&dlmfs_fs_type);
bail:
        if (status) {
                if (cleanup_inode)
                        kmem_cache_destroy(dlmfs_inode_cache);
                if (cleanup_worker)
                        destroy_workqueue(user_dlm_worker);
                bdi_destroy(&dlmfs_backing_dev_info);
        } else
                printk("OCFS2 User DLM kernel interface loaded\n");
        return status;
}

static void __exit exit_dlmfs_fs(void)
{
        unregister_filesystem(&dlmfs_fs_type);

        flush_workqueue(user_dlm_worker);
        destroy_workqueue(user_dlm_worker);

        kmem_cache_destroy(dlmfs_inode_cache);

        bdi_destroy(&dlmfs_backing_dev_info);
}

MODULE_AUTHOR("Oracle");
MODULE_LICENSE("GPL");

module_init(init_dlmfs_fs)
module_exit(exit_dlmfs_fs)