dlmfs.c

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/* -*- 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 <linux/poll.h>

#include <asm/uaccess.h>

#include "stackglue.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;



/*
 * These are the ABI capabilities of dlmfs.
 *
 * Over time, dlmfs has added some features that were not part of the
 * initial ABI.  Unfortunately, some of these features are not detectable
 * via standard usage.  For example, Linux's default poll always returns
 * POLLIN, so there is no way for a caller of poll(2) to know when dlmfs
 * added poll support.  Instead, we provide this list of new capabilities.
 *
 * Capabilities is a read-only attribute.  We do it as a module parameter
 * so we can discover it whether dlmfs is built in, loaded, or even not
 * loaded.
 *
 * The ABI features are local to this machine's dlmfs mount.  This is
 * distinct from the locking protocol, which is concerned with inter-node
 * interaction.
 *
 * Capabilities:
 * - bast   : POLLIN against the file descriptor of a held lock
 *        signifies a bast fired on the lock.
 */
#define DLMFS_CAPABILITIES "bast stackglue"
static int param_set_dlmfs_capabilities(const char *val,
                    struct kernel_param *kp)
{
    printk(KERN_ERR "%s: readonly parameter\n", kp->name);
    return -EINVAL;
}
static int param_get_dlmfs_capabilities(char *buffer,
                    struct kernel_param *kp)
{
    return strlcpy(buffer, DLMFS_CAPABILITIES,
               strlen(DLMFS_CAPABILITIES) + 1);
}
module_param_call(capabilities, param_set_dlmfs_capabilities,
          param_get_dlmfs_capabilities, NULL, 0444);
MODULE_PARM_DESC(capabilities, DLMFS_CAPABILITIES);


/*
 * 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 -> NOQUEUE
 */
static int dlmfs_decode_open_flags(int open_flags,
                   int *level,
                   int *flags)
{
    if (open_flags & (O_WRONLY|O_RDWR))
        *level = DLM_LOCK_EX;
    else
        *level = DLM_LOCK_PR;

    *flags = 0;
    if (open_flags & O_NONBLOCK)
        *flags |= DLM_LKF_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 & DLM_LKF_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 = 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 != DLM_LOCK_IV)
            user_dlm_cluster_unlock(&ip->ip_lockres, level);

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

    return 0;
}

/*
 * We do ->setattr() just to override size changes.  Our size is the size
 * of the LVB and nothing else.
 */
static int dlmfs_file_setattr(struct dentry *dentry, struct iattr *attr)
{
    int error;
    struct inode *inode = dentry->d_inode;

    attr->ia_valid &= ~ATTR_SIZE;
    error = inode_change_ok(inode, attr);
    if (error)
        return error;

    setattr_copy(inode, attr);
    mark_inode_dirty(inode);
    return 0;
}

static unsigned int dlmfs_file_poll(struct file *file, poll_table *wait)
{
    int event = 0;
    struct inode *inode = file->f_path.dentry->d_inode;
    struct dlmfs_inode_private *ip = DLMFS_I(inode);

    poll_wait(file, &ip->ip_lockres.l_event, wait);

    spin_lock(&ip->ip_lockres.l_lock);
    if (ip->ip_lockres.l_flags & USER_LOCK_BLOCKED)
        event = POLLIN | POLLRDNORM;
    spin_unlock(&ip->ip_lockres.l_lock);

    return event;
}

static ssize_t dlmfs_file_read(struct file *filp,
                   char __user *buf,
                   size_t count,
                   loff_t *ppos)
{
    int bytes_left;
    ssize_t readlen, got;
    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;

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

    got = user_dlm_read_lvb(inode, lvb_buf, readlen);
    if (got) {
        BUG_ON(got != readlen);
        bytes_left = __copy_to_user(buf, lvb_buf, readlen);
        readlen -= bytes_left;
    } else
        readlen = 0;

    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(void *foo)
{
    struct dlmfs_inode_private *ip =
        (struct dlmfs_inode_private *) foo;

    ip->ip_conn = 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_i_callback(struct rcu_head *head)
{
    struct inode *inode = container_of(head, struct inode, i_rcu);
    kmem_cache_free(dlmfs_inode_cache, DLMFS_I(inode));
}

static void dlmfs_destroy_inode(struct inode *inode)
{
    call_rcu(&inode->i_rcu, dlmfs_i_callback);
}

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

    clear_inode(inode);

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

static struct backing_dev_info dlmfs_backing_dev_info = {
    .name       = "ocfs2-dlmfs",
    .ra_pages   = 0,    /* No readahead */
    .capabilities   = BDI_CAP_NO_ACCT_AND_WRITEBACK,
};

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

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

        inode->i_ino = get_next_ino();
        inode_init_owner(inode, NULL, mode);
        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,
                     umode_t 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_ino = get_next_ino();
    inode_init_owner(inode, parent, mode);
    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_conn = DLMFS_I(parent)->ip_conn;

    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;
    }
    return inode;
}

/*
 * File creation. Allocate an inode, and we're done..
 */
/* SMP-safe */
static int dlmfs_mkdir(struct inode * dir,
               struct dentry * dentry,
               umode_t mode)
{
    int status;
    struct inode *inode = NULL;
    struct qstr *domain = &dentry->d_name;
    struct dlmfs_inode_private *ip;
    struct ocfs2_cluster_connection *conn;

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

    /* verify that we have a proper domain */
    if (domain->len >= GROUP_NAME_MAX) {
        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);

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

    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,
            umode_t mode,
            bool excl)
{
    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)
{
    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;
    sb->s_root = d_make_root(dlmfs_get_root_inode(sb));
    if (!sb->s_root)
        return -ENOMEM;
    return 0;
}

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

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,
    .evict_inode    = dlmfs_evict_inode,
    .drop_inode = generic_delete_inode,
};

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

static struct dentry *dlmfs_mount(struct file_system_type *fs_type,
    int flags, const char *dev_name, void *data)
{
    return mount_nodev(fs_type, flags, data, dlmfs_fill_super);
}

static struct file_system_type dlmfs_fs_type = {
    .owner      = THIS_MODULE,
    .name       = "ocfs2_dlmfs",
    .mount      = dlmfs_mount,
    .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) {
        status = -ENOMEM;
        goto bail;
    }
    cleanup_inode = 1;

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

    user_dlm_set_locking_protocol();
    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);

    /*
     * Make sure all delayed rcu free inodes are flushed before we
     * destroy cache.
     */
    rcu_barrier();
    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)