inode.c

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/*
  FUSE: Filesystem in Userspace
  Copyright (C) 2001-2008  Miklos Szeredi <[email protected]>

  This program can be distributed under the terms of the GNU GPL.
  See the file COPYING.
*/

#include "fuse_i.h"

#include <linux/pagemap.h>
#include <linux/slab.h>
#include <linux/file.h>
#include <linux/seq_file.h>
#include <linux/init.h>
#include <linux/module.h>
#include <linux/moduleparam.h>
#include <linux/parser.h>
#include <linux/statfs.h>
#include <linux/random.h>
#include <linux/sched.h>
#include <linux/exportfs.h>

MODULE_AUTHOR("Miklos Szeredi <[email protected]>");
MODULE_DESCRIPTION("Filesystem in Userspace");
MODULE_LICENSE("GPL");

static struct kmem_cache *fuse_inode_cachep;
struct list_head fuse_conn_list;
DEFINE_MUTEX(fuse_mutex);

static int set_global_limit(const char *val, struct kernel_param *kp);

unsigned max_user_bgreq;
module_param_call(max_user_bgreq, set_global_limit, param_get_uint,
          &max_user_bgreq, 0644);
__MODULE_PARM_TYPE(max_user_bgreq, "uint");
MODULE_PARM_DESC(max_user_bgreq,
 "Global limit for the maximum number of backgrounded requests an "
 "unprivileged user can set");

unsigned max_user_congthresh;
module_param_call(max_user_congthresh, set_global_limit, param_get_uint,
          &max_user_congthresh, 0644);
__MODULE_PARM_TYPE(max_user_congthresh, "uint");
MODULE_PARM_DESC(max_user_congthresh,
 "Global limit for the maximum congestion threshold an "
 "unprivileged user can set");

#define FUSE_SUPER_MAGIC 0x65735546

#define FUSE_DEFAULT_BLKSIZE 512

#define FUSE_DEFAULT_MAX_BACKGROUND 12

#define FUSE_DEFAULT_CONGESTION_THRESHOLD (FUSE_DEFAULT_MAX_BACKGROUND * 3 / 4)

struct fuse_mount_data {
    int fd;
    unsigned rootmode;
    unsigned user_id;
    unsigned group_id;
    unsigned fd_present:1;
    unsigned rootmode_present:1;
    unsigned user_id_present:1;
    unsigned group_id_present:1;
    unsigned flags;
    unsigned max_read;
    unsigned blksize;
};

struct fuse_forget_link *fuse_alloc_forget(void)
{
    return kzalloc(sizeof(struct fuse_forget_link), GFP_KERNEL);
}

static struct inode *fuse_alloc_inode(struct super_block *sb)
{
    struct inode *inode;
    struct fuse_inode *fi;

    inode = kmem_cache_alloc(fuse_inode_cachep, GFP_KERNEL);
    if (!inode)
        return NULL;

    fi = get_fuse_inode(inode);
    fi->i_time = 0;
    fi->nodeid = 0;
    fi->nlookup = 0;
    fi->attr_version = 0;
    fi->writectr = 0;
    fi->orig_ino = 0;
    INIT_LIST_HEAD(&fi->write_files);
    INIT_LIST_HEAD(&fi->queued_writes);
    INIT_LIST_HEAD(&fi->writepages);
    init_waitqueue_head(&fi->page_waitq);
    fi->forget = fuse_alloc_forget();
    if (!fi->forget) {
        kmem_cache_free(fuse_inode_cachep, inode);
        return NULL;
    }

    return inode;
}

static void fuse_i_callback(struct rcu_head *head)
{
    struct inode *inode = container_of(head, struct inode, i_rcu);
    kmem_cache_free(fuse_inode_cachep, inode);
}

static void fuse_destroy_inode(struct inode *inode)
{
    struct fuse_inode *fi = get_fuse_inode(inode);
    BUG_ON(!list_empty(&fi->write_files));
    BUG_ON(!list_empty(&fi->queued_writes));
    kfree(fi->forget);
    call_rcu(&inode->i_rcu, fuse_i_callback);
}

static void fuse_evict_inode(struct inode *inode)
{
    truncate_inode_pages(&inode->i_data, 0);
    clear_inode(inode);
    if (inode->i_sb->s_flags & MS_ACTIVE) {
        struct fuse_conn *fc = get_fuse_conn(inode);
        struct fuse_inode *fi = get_fuse_inode(inode);
        fuse_queue_forget(fc, fi->forget, fi->nodeid, fi->nlookup);
        fi->forget = NULL;
    }
}

static int fuse_remount_fs(struct super_block *sb, int *flags, char *data)
{
    if (*flags & MS_MANDLOCK)
        return -EINVAL;

    return 0;
}

/*
 * ino_t is 32-bits on 32-bit arch. We have to squash the 64-bit value down
 * so that it will fit.
 */
static ino_t fuse_squash_ino(u64 ino64)
{
    ino_t ino = (ino_t) ino64;
    if (sizeof(ino_t) < sizeof(u64))
        ino ^= ino64 >> (sizeof(u64) - sizeof(ino_t)) * 8;
    return ino;
}

void fuse_change_attributes_common(struct inode *inode, struct fuse_attr *attr,
                   u64 attr_valid)
{
    struct fuse_conn *fc = get_fuse_conn(inode);
    struct fuse_inode *fi = get_fuse_inode(inode);

    fi->attr_version = ++fc->attr_version;
    fi->i_time = attr_valid;

    inode->i_ino     = fuse_squash_ino(attr->ino);
    inode->i_mode    = (inode->i_mode & S_IFMT) | (attr->mode & 07777);
    set_nlink(inode, attr->nlink);
    inode->i_uid     = attr->uid;
    inode->i_gid     = attr->gid;
    inode->i_blocks  = attr->blocks;
    inode->i_atime.tv_sec   = attr->atime;
    inode->i_atime.tv_nsec  = attr->atimensec;
    inode->i_mtime.tv_sec   = attr->mtime;
    inode->i_mtime.tv_nsec  = attr->mtimensec;
    inode->i_ctime.tv_sec   = attr->ctime;
    inode->i_ctime.tv_nsec  = attr->ctimensec;

    if (attr->blksize != 0)
        inode->i_blkbits = ilog2(attr->blksize);
    else
        inode->i_blkbits = inode->i_sb->s_blocksize_bits;

    /*
     * Don't set the sticky bit in i_mode, unless we want the VFS
     * to check permissions.  This prevents failures due to the
     * check in may_delete().
     */
    fi->orig_i_mode = inode->i_mode;
    if (!(fc->flags & FUSE_DEFAULT_PERMISSIONS))
        inode->i_mode &= ~S_ISVTX;

    fi->orig_ino = attr->ino;
}

void fuse_change_attributes(struct inode *inode, struct fuse_attr *attr,
                u64 attr_valid, u64 attr_version)
{
    struct fuse_conn *fc = get_fuse_conn(inode);
    struct fuse_inode *fi = get_fuse_inode(inode);
    loff_t oldsize;
    struct timespec old_mtime;

    spin_lock(&fc->lock);
    if (attr_version != 0 && fi->attr_version > attr_version) {
        spin_unlock(&fc->lock);
        return;
    }

    old_mtime = inode->i_mtime;
    fuse_change_attributes_common(inode, attr, attr_valid);

    oldsize = inode->i_size;
    i_size_write(inode, attr->size);
    spin_unlock(&fc->lock);

    if (S_ISREG(inode->i_mode)) {
        bool inval = false;

        if (oldsize != attr->size) {
            truncate_pagecache(inode, oldsize, attr->size);
            inval = true;
        } else if (fc->auto_inval_data) {
            struct timespec new_mtime = {
                .tv_sec = attr->mtime,
                .tv_nsec = attr->mtimensec,
            };

            /*
             * Auto inval mode also checks and invalidates if mtime
             * has changed.
             */
            if (!timespec_equal(&old_mtime, &new_mtime))
                inval = true;
        }

        if (inval)
            invalidate_inode_pages2(inode->i_mapping);
    }
}

static void fuse_init_inode(struct inode *inode, struct fuse_attr *attr)
{
    inode->i_mode = attr->mode & S_IFMT;
    inode->i_size = attr->size;
    if (S_ISREG(inode->i_mode)) {
        fuse_init_common(inode);
        fuse_init_file_inode(inode);
    } else if (S_ISDIR(inode->i_mode))
        fuse_init_dir(inode);
    else if (S_ISLNK(inode->i_mode))
        fuse_init_symlink(inode);
    else if (S_ISCHR(inode->i_mode) || S_ISBLK(inode->i_mode) ||
         S_ISFIFO(inode->i_mode) || S_ISSOCK(inode->i_mode)) {
        fuse_init_common(inode);
        init_special_inode(inode, inode->i_mode,
                   new_decode_dev(attr->rdev));
    } else
        BUG();
}

int fuse_inode_eq(struct inode *inode, void *_nodeidp)
{
    u64 nodeid = *(u64 *) _nodeidp;
    if (get_node_id(inode) == nodeid)
        return 1;
    else
        return 0;
}

static int fuse_inode_set(struct inode *inode, void *_nodeidp)
{
    u64 nodeid = *(u64 *) _nodeidp;
    get_fuse_inode(inode)->nodeid = nodeid;
    return 0;
}

struct inode *fuse_iget(struct super_block *sb, u64 nodeid,
            int generation, struct fuse_attr *attr,
            u64 attr_valid, u64 attr_version)
{
    struct inode *inode;
    struct fuse_inode *fi;
    struct fuse_conn *fc = get_fuse_conn_super(sb);

 retry:
    inode = iget5_locked(sb, nodeid, fuse_inode_eq, fuse_inode_set, &nodeid);
    if (!inode)
        return NULL;

    if ((inode->i_state & I_NEW)) {
        inode->i_flags |= S_NOATIME|S_NOCMTIME;
        inode->i_generation = generation;
        inode->i_data.backing_dev_info = &fc->bdi;
        fuse_init_inode(inode, attr);
        unlock_new_inode(inode);
    } else if ((inode->i_mode ^ attr->mode) & S_IFMT) {
        /* Inode has changed type, any I/O on the old should fail */
        make_bad_inode(inode);
        iput(inode);
        goto retry;
    }

    fi = get_fuse_inode(inode);
    spin_lock(&fc->lock);
    fi->nlookup++;
    spin_unlock(&fc->lock);
    fuse_change_attributes(inode, attr, attr_valid, attr_version);

    return inode;
}

int fuse_reverse_inval_inode(struct super_block *sb, u64 nodeid,
                 loff_t offset, loff_t len)
{
    struct inode *inode;
    pgoff_t pg_start;
    pgoff_t pg_end;

    inode = ilookup5(sb, nodeid, fuse_inode_eq, &nodeid);
    if (!inode)
        return -ENOENT;

    fuse_invalidate_attr(inode);
    if (offset >= 0) {
        pg_start = offset >> PAGE_CACHE_SHIFT;
        if (len <= 0)
            pg_end = -1;
        else
            pg_end = (offset + len - 1) >> PAGE_CACHE_SHIFT;
        invalidate_inode_pages2_range(inode->i_mapping,
                          pg_start, pg_end);
    }
    iput(inode);
    return 0;
}

static void fuse_umount_begin(struct super_block *sb)
{
    fuse_abort_conn(get_fuse_conn_super(sb));
}

static void fuse_send_destroy(struct fuse_conn *fc)
{
    struct fuse_req *req = fc->destroy_req;
    if (req && fc->conn_init) {
        fc->destroy_req = NULL;
        req->in.h.opcode = FUSE_DESTROY;
        req->force = 1;
        fuse_request_send(fc, req);
        fuse_put_request(fc, req);
    }
}

static void fuse_bdi_destroy(struct fuse_conn *fc)
{
    if (fc->bdi_initialized)
        bdi_destroy(&fc->bdi);
}

void fuse_conn_kill(struct fuse_conn *fc)
{
    spin_lock(&fc->lock);
    fc->connected = 0;
    fc->blocked = 0;
    spin_unlock(&fc->lock);
    /* Flush all readers on this fs */
    kill_fasync(&fc->fasync, SIGIO, POLL_IN);
    wake_up_all(&fc->waitq);
    wake_up_all(&fc->blocked_waitq);
    wake_up_all(&fc->reserved_req_waitq);
}
EXPORT_SYMBOL_GPL(fuse_conn_kill);

static void fuse_put_super(struct super_block *sb)
{
    struct fuse_conn *fc = get_fuse_conn_super(sb);

    fuse_send_destroy(fc);

    fuse_conn_kill(fc);
    mutex_lock(&fuse_mutex);
    list_del(&fc->entry);
    fuse_ctl_remove_conn(fc);
    mutex_unlock(&fuse_mutex);
    fuse_bdi_destroy(fc);

    fuse_conn_put(fc);
}

static void convert_fuse_statfs(struct kstatfs *stbuf, struct fuse_kstatfs *attr)
{
    stbuf->f_type    = FUSE_SUPER_MAGIC;
    stbuf->f_bsize   = attr->bsize;
    stbuf->f_frsize  = attr->frsize;
    stbuf->f_blocks  = attr->blocks;
    stbuf->f_bfree   = attr->bfree;
    stbuf->f_bavail  = attr->bavail;
    stbuf->f_files   = attr->files;
    stbuf->f_ffree   = attr->ffree;
    stbuf->f_namelen = attr->namelen;
    /* fsid is left zero */
}

static int fuse_statfs(struct dentry *dentry, struct kstatfs *buf)
{
    struct super_block *sb = dentry->d_sb;
    struct fuse_conn *fc = get_fuse_conn_super(sb);
    struct fuse_req *req;
    struct fuse_statfs_out outarg;
    int err;

    if (!fuse_allow_task(fc, current)) {
        buf->f_type = FUSE_SUPER_MAGIC;
        return 0;
    }

    req = fuse_get_req(fc);
    if (IS_ERR(req))
        return PTR_ERR(req);

    memset(&outarg, 0, sizeof(outarg));
    req->in.numargs = 0;
    req->in.h.opcode = FUSE_STATFS;
    req->in.h.nodeid = get_node_id(dentry->d_inode);
    req->out.numargs = 1;
    req->out.args[0].size =
        fc->minor < 4 ? FUSE_COMPAT_STATFS_SIZE : sizeof(outarg);
    req->out.args[0].value = &outarg;
    fuse_request_send(fc, req);
    err = req->out.h.error;
    if (!err)
        convert_fuse_statfs(buf, &outarg.st);
    fuse_put_request(fc, req);
    return err;
}

enum {
    OPT_FD,
    OPT_ROOTMODE,
    OPT_USER_ID,
    OPT_GROUP_ID,
    OPT_DEFAULT_PERMISSIONS,
    OPT_ALLOW_OTHER,
    OPT_MAX_READ,
    OPT_BLKSIZE,
    OPT_ERR
};

static const match_table_t tokens = {
    {OPT_FD,            "fd=%u"},
    {OPT_ROOTMODE,          "rootmode=%o"},
    {OPT_USER_ID,           "user_id=%u"},
    {OPT_GROUP_ID,          "group_id=%u"},
    {OPT_DEFAULT_PERMISSIONS,   "default_permissions"},
    {OPT_ALLOW_OTHER,       "allow_other"},
    {OPT_MAX_READ,          "max_read=%u"},
    {OPT_BLKSIZE,           "blksize=%u"},
    {OPT_ERR,           NULL}
};

static int parse_fuse_opt(char *opt, struct fuse_mount_data *d, int is_bdev)
{
    char *p;
    memset(d, 0, sizeof(struct fuse_mount_data));
    d->max_read = ~0;
    d->blksize = FUSE_DEFAULT_BLKSIZE;

    while ((p = strsep(&opt, ",")) != NULL) {
        int token;
        int value;
        substring_t args[MAX_OPT_ARGS];
        if (!*p)
            continue;

        token = match_token(p, tokens, args);
        switch (token) {
        case OPT_FD:
            if (match_int(&args[0], &value))
                return 0;
            d->fd = value;
            d->fd_present = 1;
            break;

        case OPT_ROOTMODE:
            if (match_octal(&args[0], &value))
                return 0;
            if (!fuse_valid_type(value))
                return 0;
            d->rootmode = value;
            d->rootmode_present = 1;
            break;

        case OPT_USER_ID:
            if (match_int(&args[0], &value))
                return 0;
            d->user_id = value;
            d->user_id_present = 1;
            break;

        case OPT_GROUP_ID:
            if (match_int(&args[0], &value))
                return 0;
            d->group_id = value;
            d->group_id_present = 1;
            break;

        case OPT_DEFAULT_PERMISSIONS:
            d->flags |= FUSE_DEFAULT_PERMISSIONS;
            break;

        case OPT_ALLOW_OTHER:
            d->flags |= FUSE_ALLOW_OTHER;
            break;

        case OPT_MAX_READ:
            if (match_int(&args[0], &value))
                return 0;
            d->max_read = value;
            break;

        case OPT_BLKSIZE:
            if (!is_bdev || match_int(&args[0], &value))
                return 0;
            d->blksize = value;
            break;

        default:
            return 0;
        }
    }

    if (!d->fd_present || !d->rootmode_present ||
        !d->user_id_present || !d->group_id_present)
        return 0;

    return 1;
}

static int fuse_show_options(struct seq_file *m, struct dentry *root)
{
    struct super_block *sb = root->d_sb;
    struct fuse_conn *fc = get_fuse_conn_super(sb);

    seq_printf(m, ",user_id=%u", fc->user_id);
    seq_printf(m, ",group_id=%u", fc->group_id);
    if (fc->flags & FUSE_DEFAULT_PERMISSIONS)
        seq_puts(m, ",default_permissions");
    if (fc->flags & FUSE_ALLOW_OTHER)
        seq_puts(m, ",allow_other");
    if (fc->max_read != ~0)
        seq_printf(m, ",max_read=%u", fc->max_read);
    if (sb->s_bdev && sb->s_blocksize != FUSE_DEFAULT_BLKSIZE)
        seq_printf(m, ",blksize=%lu", sb->s_blocksize);
    return 0;
}

void fuse_conn_init(struct fuse_conn *fc)
{
    memset(fc, 0, sizeof(*fc));
    spin_lock_init(&fc->lock);
    mutex_init(&fc->inst_mutex);
    init_rwsem(&fc->killsb);
    atomic_set(&fc->count, 1);
    init_waitqueue_head(&fc->waitq);
    init_waitqueue_head(&fc->blocked_waitq);
    init_waitqueue_head(&fc->reserved_req_waitq);
    INIT_LIST_HEAD(&fc->pending);
    INIT_LIST_HEAD(&fc->processing);
    INIT_LIST_HEAD(&fc->io);
    INIT_LIST_HEAD(&fc->interrupts);
    INIT_LIST_HEAD(&fc->bg_queue);
    INIT_LIST_HEAD(&fc->entry);
    fc->forget_list_tail = &fc->forget_list_head;
    atomic_set(&fc->num_waiting, 0);
    fc->max_background = FUSE_DEFAULT_MAX_BACKGROUND;
    fc->congestion_threshold = FUSE_DEFAULT_CONGESTION_THRESHOLD;
    fc->khctr = 0;
    fc->polled_files = RB_ROOT;
    fc->reqctr = 0;
    fc->blocked = 1;
    fc->attr_version = 1;
    get_random_bytes(&fc->scramble_key, sizeof(fc->scramble_key));
}
EXPORT_SYMBOL_GPL(fuse_conn_init);

void fuse_conn_put(struct fuse_conn *fc)
{
    if (atomic_dec_and_test(&fc->count)) {
        if (fc->destroy_req)
            fuse_request_free(fc->destroy_req);
        mutex_destroy(&fc->inst_mutex);
        fc->release(fc);
    }
}
EXPORT_SYMBOL_GPL(fuse_conn_put);

struct fuse_conn *fuse_conn_get(struct fuse_conn *fc)
{
    atomic_inc(&fc->count);
    return fc;
}
EXPORT_SYMBOL_GPL(fuse_conn_get);

static struct inode *fuse_get_root_inode(struct super_block *sb, unsigned mode)
{
    struct fuse_attr attr;
    memset(&attr, 0, sizeof(attr));

    attr.mode = mode;
    attr.ino = FUSE_ROOT_ID;
    attr.nlink = 1;
    return fuse_iget(sb, 1, 0, &attr, 0, 0);
}

struct fuse_inode_handle {
    u64 nodeid;
    u32 generation;
};

static struct dentry *fuse_get_dentry(struct super_block *sb,
                      struct fuse_inode_handle *handle)
{
    struct fuse_conn *fc = get_fuse_conn_super(sb);
    struct inode *inode;
    struct dentry *entry;
    int err = -ESTALE;

    if (handle->nodeid == 0)
        goto out_err;

    inode = ilookup5(sb, handle->nodeid, fuse_inode_eq, &handle->nodeid);
    if (!inode) {
        struct fuse_entry_out outarg;
        struct qstr name;

        if (!fc->export_support)
            goto out_err;

        name.len = 1;
        name.name = ".";
        err = fuse_lookup_name(sb, handle->nodeid, &name, &outarg,
                       &inode);
        if (err && err != -ENOENT)
            goto out_err;
        if (err || !inode) {
            err = -ESTALE;
            goto out_err;
        }
        err = -EIO;
        if (get_node_id(inode) != handle->nodeid)
            goto out_iput;
    }
    err = -ESTALE;
    if (inode->i_generation != handle->generation)
        goto out_iput;

    entry = d_obtain_alias(inode);
    if (!IS_ERR(entry) && get_node_id(inode) != FUSE_ROOT_ID)
        fuse_invalidate_entry_cache(entry);

    return entry;

 out_iput:
    iput(inode);
 out_err:
    return ERR_PTR(err);
}

static int fuse_encode_fh(struct inode *inode, u32 *fh, int *max_len,
               struct inode *parent)
{
    int len = parent ? 6 : 3;
    u64 nodeid;
    u32 generation;

    if (*max_len < len) {
        *max_len = len;
        return  255;
    }

    nodeid = get_fuse_inode(inode)->nodeid;
    generation = inode->i_generation;

    fh[0] = (u32)(nodeid >> 32);
    fh[1] = (u32)(nodeid & 0xffffffff);
    fh[2] = generation;

    if (parent) {
        nodeid = get_fuse_inode(parent)->nodeid;
        generation = parent->i_generation;

        fh[3] = (u32)(nodeid >> 32);
        fh[4] = (u32)(nodeid & 0xffffffff);
        fh[5] = generation;
    }

    *max_len = len;
    return parent ? 0x82 : 0x81;
}

static struct dentry *fuse_fh_to_dentry(struct super_block *sb,
        struct fid *fid, int fh_len, int fh_type)
{
    struct fuse_inode_handle handle;

    if ((fh_type != 0x81 && fh_type != 0x82) || fh_len < 3)
        return NULL;

    handle.nodeid = (u64) fid->raw[0] << 32;
    handle.nodeid |= (u64) fid->raw[1];
    handle.generation = fid->raw[2];
    return fuse_get_dentry(sb, &handle);
}

static struct dentry *fuse_fh_to_parent(struct super_block *sb,
        struct fid *fid, int fh_len, int fh_type)
{
    struct fuse_inode_handle parent;

    if (fh_type != 0x82 || fh_len < 6)
        return NULL;

    parent.nodeid = (u64) fid->raw[3] << 32;
    parent.nodeid |= (u64) fid->raw[4];
    parent.generation = fid->raw[5];
    return fuse_get_dentry(sb, &parent);
}

static struct dentry *fuse_get_parent(struct dentry *child)
{
    struct inode *child_inode = child->d_inode;
    struct fuse_conn *fc = get_fuse_conn(child_inode);
    struct inode *inode;
    struct dentry *parent;
    struct fuse_entry_out outarg;
    struct qstr name;
    int err;

    if (!fc->export_support)
        return ERR_PTR(-ESTALE);

    name.len = 2;
    name.name = "..";
    err = fuse_lookup_name(child_inode->i_sb, get_node_id(child_inode),
                   &name, &outarg, &inode);
    if (err) {
        if (err == -ENOENT)
            return ERR_PTR(-ESTALE);
        return ERR_PTR(err);
    }

    parent = d_obtain_alias(inode);
    if (!IS_ERR(parent) && get_node_id(inode) != FUSE_ROOT_ID)
        fuse_invalidate_entry_cache(parent);

    return parent;
}

static const struct export_operations fuse_export_operations = {
    .fh_to_dentry   = fuse_fh_to_dentry,
    .fh_to_parent   = fuse_fh_to_parent,
    .encode_fh  = fuse_encode_fh,
    .get_parent = fuse_get_parent,
};

static const struct super_operations fuse_super_operations = {
    .alloc_inode    = fuse_alloc_inode,
    .destroy_inode  = fuse_destroy_inode,
    .evict_inode    = fuse_evict_inode,
    .drop_inode = generic_delete_inode,
    .remount_fs = fuse_remount_fs,
    .put_super  = fuse_put_super,
    .umount_begin   = fuse_umount_begin,
    .statfs     = fuse_statfs,
    .show_options   = fuse_show_options,
};

static void sanitize_global_limit(unsigned *limit)
{
    if (*limit == 0)
        *limit = ((num_physpages << PAGE_SHIFT) >> 13) /
             sizeof(struct fuse_req);

    if (*limit >= 1 << 16)
        *limit = (1 << 16) - 1;
}

static int set_global_limit(const char *val, struct kernel_param *kp)
{
    int rv;

    rv = param_set_uint(val, kp);
    if (rv)
        return rv;

    sanitize_global_limit((unsigned *)kp->arg);

    return 0;
}

static void process_init_limits(struct fuse_conn *fc, struct fuse_init_out *arg)
{
    int cap_sys_admin = capable(CAP_SYS_ADMIN);

    if (arg->minor < 13)
        return;

    sanitize_global_limit(&max_user_bgreq);
    sanitize_global_limit(&max_user_congthresh);

    if (arg->max_background) {
        fc->max_background = arg->max_background;

        if (!cap_sys_admin && fc->max_background > max_user_bgreq)
            fc->max_background = max_user_bgreq;
    }
    if (arg->congestion_threshold) {
        fc->congestion_threshold = arg->congestion_threshold;

        if (!cap_sys_admin &&
            fc->congestion_threshold > max_user_congthresh)
            fc->congestion_threshold = max_user_congthresh;
    }
}

static void process_init_reply(struct fuse_conn *fc, struct fuse_req *req)
{
    struct fuse_init_out *arg = &req->misc.init_out;

    if (req->out.h.error || arg->major != FUSE_KERNEL_VERSION)
        fc->conn_error = 1;
    else {
        unsigned long ra_pages;

        process_init_limits(fc, arg);

        if (arg->minor >= 6) {
            ra_pages = arg->max_readahead / PAGE_CACHE_SIZE;
            if (arg->flags & FUSE_ASYNC_READ)
                fc->async_read = 1;
            if (!(arg->flags & FUSE_POSIX_LOCKS))
                fc->no_lock = 1;
            if (arg->minor >= 17) {
                if (!(arg->flags & FUSE_FLOCK_LOCKS))
                    fc->no_flock = 1;
            } else {
                if (!(arg->flags & FUSE_POSIX_LOCKS))
                    fc->no_flock = 1;
            }
            if (arg->flags & FUSE_ATOMIC_O_TRUNC)
                fc->atomic_o_trunc = 1;
            if (arg->minor >= 9) {
                /* LOOKUP has dependency on proto version */
                if (arg->flags & FUSE_EXPORT_SUPPORT)
                    fc->export_support = 1;
            }
            if (arg->flags & FUSE_BIG_WRITES)
                fc->big_writes = 1;
            if (arg->flags & FUSE_DONT_MASK)
                fc->dont_mask = 1;
            if (arg->flags & FUSE_AUTO_INVAL_DATA)
                fc->auto_inval_data = 1;
        } else {
            ra_pages = fc->max_read / PAGE_CACHE_SIZE;
            fc->no_lock = 1;
            fc->no_flock = 1;
        }

        fc->bdi.ra_pages = min(fc->bdi.ra_pages, ra_pages);
        fc->minor = arg->minor;
        fc->max_write = arg->minor < 5 ? 4096 : arg->max_write;
        fc->max_write = max_t(unsigned, 4096, fc->max_write);
        fc->conn_init = 1;
    }
    fc->blocked = 0;
    wake_up_all(&fc->blocked_waitq);
}

static void fuse_send_init(struct fuse_conn *fc, struct fuse_req *req)
{
    struct fuse_init_in *arg = &req->misc.init_in;

    arg->major = FUSE_KERNEL_VERSION;
    arg->minor = FUSE_KERNEL_MINOR_VERSION;
    arg->max_readahead = fc->bdi.ra_pages * PAGE_CACHE_SIZE;
    arg->flags |= FUSE_ASYNC_READ | FUSE_POSIX_LOCKS | FUSE_ATOMIC_O_TRUNC |
        FUSE_EXPORT_SUPPORT | FUSE_BIG_WRITES | FUSE_DONT_MASK |
        FUSE_SPLICE_WRITE | FUSE_SPLICE_MOVE | FUSE_SPLICE_READ |
        FUSE_FLOCK_LOCKS | FUSE_IOCTL_DIR | FUSE_AUTO_INVAL_DATA;
    req->in.h.opcode = FUSE_INIT;
    req->in.numargs = 1;
    req->in.args[0].size = sizeof(*arg);
    req->in.args[0].value = arg;
    req->out.numargs = 1;
    /* Variable length argument used for backward compatibility
       with interface version < 7.5.  Rest of init_out is zeroed
       by do_get_request(), so a short reply is not a problem */
    req->out.argvar = 1;
    req->out.args[0].size = sizeof(struct fuse_init_out);
    req->out.args[0].value = &req->misc.init_out;
    req->end = process_init_reply;
    fuse_request_send_background(fc, req);
}

static void fuse_free_conn(struct fuse_conn *fc)
{
    kfree(fc);
}

static int fuse_bdi_init(struct fuse_conn *fc, struct super_block *sb)
{
    int err;

    fc->bdi.name = "fuse";
    fc->bdi.ra_pages = (VM_MAX_READAHEAD * 1024) / PAGE_CACHE_SIZE;
    /* fuse does it's own writeback accounting */
    fc->bdi.capabilities = BDI_CAP_NO_ACCT_WB;

    err = bdi_init(&fc->bdi);
    if (err)
        return err;

    fc->bdi_initialized = 1;

    if (sb->s_bdev) {
        err =  bdi_register(&fc->bdi, NULL, "%u:%u-fuseblk",
                    MAJOR(fc->dev), MINOR(fc->dev));
    } else {
        err = bdi_register_dev(&fc->bdi, fc->dev);
    }

    if (err)
        return err;

    /*
     * For a single fuse filesystem use max 1% of dirty +
     * writeback threshold.
     *
     * This gives about 1M of write buffer for memory maps on a
     * machine with 1G and 10% dirty_ratio, which should be more
     * than enough.
     *
     * Privileged users can raise it by writing to
     *
     *    /sys/class/bdi/<bdi>/max_ratio
     */
    bdi_set_max_ratio(&fc->bdi, 1);

    return 0;
}

static int fuse_fill_super(struct super_block *sb, void *data, int silent)
{
    struct fuse_conn *fc;
    struct inode *root;
    struct fuse_mount_data d;
    struct file *file;
    struct dentry *root_dentry;
    struct fuse_req *init_req;
    int err;
    int is_bdev = sb->s_bdev != NULL;

    err = -EINVAL;
    if (sb->s_flags & MS_MANDLOCK)
        goto err;

    sb->s_flags &= ~MS_NOSEC;

    if (!parse_fuse_opt((char *) data, &d, is_bdev))
        goto err;

    if (is_bdev) {
#ifdef CONFIG_BLOCK
        err = -EINVAL;
        if (!sb_set_blocksize(sb, d.blksize))
            goto err;
#endif
    } else {
        sb->s_blocksize = PAGE_CACHE_SIZE;
        sb->s_blocksize_bits = PAGE_CACHE_SHIFT;
    }
    sb->s_magic = FUSE_SUPER_MAGIC;
    sb->s_op = &fuse_super_operations;
    sb->s_maxbytes = MAX_LFS_FILESIZE;
    sb->s_time_gran = 1;
    sb->s_export_op = &fuse_export_operations;

    file = fget(d.fd);
    err = -EINVAL;
    if (!file)
        goto err;

    if (file->f_op != &fuse_dev_operations)
        goto err_fput;

    fc = kmalloc(sizeof(*fc), GFP_KERNEL);
    err = -ENOMEM;
    if (!fc)
        goto err_fput;

    fuse_conn_init(fc);

    fc->dev = sb->s_dev;
    fc->sb = sb;
    err = fuse_bdi_init(fc, sb);
    if (err)
        goto err_put_conn;

    sb->s_bdi = &fc->bdi;

    /* Handle umasking inside the fuse code */
    if (sb->s_flags & MS_POSIXACL)
        fc->dont_mask = 1;
    sb->s_flags |= MS_POSIXACL;

    fc->release = fuse_free_conn;
    fc->flags = d.flags;
    fc->user_id = d.user_id;
    fc->group_id = d.group_id;
    fc->max_read = max_t(unsigned, 4096, d.max_read);

    /* Used by get_root_inode() */
    sb->s_fs_info = fc;

    err = -ENOMEM;
    root = fuse_get_root_inode(sb, d.rootmode);
    root_dentry = d_make_root(root);
    if (!root_dentry)
        goto err_put_conn;
    /* only now - we want root dentry with NULL ->d_op */
    sb->s_d_op = &fuse_dentry_operations;

    init_req = fuse_request_alloc();
    if (!init_req)
        goto err_put_root;

    if (is_bdev) {
        fc->destroy_req = fuse_request_alloc();
        if (!fc->destroy_req)
            goto err_free_init_req;
    }

    mutex_lock(&fuse_mutex);
    err = -EINVAL;
    if (file->private_data)
        goto err_unlock;

    err = fuse_ctl_add_conn(fc);
    if (err)
        goto err_unlock;

    list_add_tail(&fc->entry, &fuse_conn_list);
    sb->s_root = root_dentry;
    fc->connected = 1;
    file->private_data = fuse_conn_get(fc);
    mutex_unlock(&fuse_mutex);
    /*
     * atomic_dec_and_test() in fput() provides the necessary
     * memory barrier for file->private_data to be visible on all
     * CPUs after this
     */
    fput(file);

    fuse_send_init(fc, init_req);

    return 0;

 err_unlock:
    mutex_unlock(&fuse_mutex);
 err_free_init_req:
    fuse_request_free(init_req);
 err_put_root:
    dput(root_dentry);
 err_put_conn:
    fuse_bdi_destroy(fc);
    fuse_conn_put(fc);
 err_fput:
    fput(file);
 err:
    return err;
}

static struct dentry *fuse_mount(struct file_system_type *fs_type,
               int flags, const char *dev_name,
               void *raw_data)
{
    return mount_nodev(fs_type, flags, raw_data, fuse_fill_super);
}

static void fuse_kill_sb_anon(struct super_block *sb)
{
    struct fuse_conn *fc = get_fuse_conn_super(sb);

    if (fc) {
        down_write(&fc->killsb);
        fc->sb = NULL;
        up_write(&fc->killsb);
    }

    kill_anon_super(sb);
}

static struct file_system_type fuse_fs_type = {
    .owner      = THIS_MODULE,
    .name       = "fuse",
    .fs_flags   = FS_HAS_SUBTYPE,
    .mount      = fuse_mount,
    .kill_sb    = fuse_kill_sb_anon,
};

#ifdef CONFIG_BLOCK
static struct dentry *fuse_mount_blk(struct file_system_type *fs_type,
               int flags, const char *dev_name,
               void *raw_data)
{
    return mount_bdev(fs_type, flags, dev_name, raw_data, fuse_fill_super);
}

static void fuse_kill_sb_blk(struct super_block *sb)
{
    struct fuse_conn *fc = get_fuse_conn_super(sb);

    if (fc) {
        down_write(&fc->killsb);
        fc->sb = NULL;
        up_write(&fc->killsb);
    }

    kill_block_super(sb);
}

static struct file_system_type fuseblk_fs_type = {
    .owner      = THIS_MODULE,
    .name       = "fuseblk",
    .mount      = fuse_mount_blk,
    .kill_sb    = fuse_kill_sb_blk,
    .fs_flags   = FS_REQUIRES_DEV | FS_HAS_SUBTYPE,
};

static inline int register_fuseblk(void)
{
    return register_filesystem(&fuseblk_fs_type);
}

static inline void unregister_fuseblk(void)
{
    unregister_filesystem(&fuseblk_fs_type);
}
#else
static inline int register_fuseblk(void)
{
    return 0;
}

static inline void unregister_fuseblk(void)
{
}
#endif

static void fuse_inode_init_once(void *foo)
{
    struct inode *inode = foo;

    inode_init_once(inode);
}

static int __init fuse_fs_init(void)
{
    int err;

    fuse_inode_cachep = kmem_cache_create("fuse_inode",
                          sizeof(struct fuse_inode),
                          0, SLAB_HWCACHE_ALIGN,
                          fuse_inode_init_once);
    err = -ENOMEM;
    if (!fuse_inode_cachep)
        goto out;

    err = register_fuseblk();
    if (err)
        goto out2;

    err = register_filesystem(&fuse_fs_type);
    if (err)
        goto out3;

    return 0;

 out3:
    unregister_fuseblk();
 out2:
    kmem_cache_destroy(fuse_inode_cachep);
 out:
    return err;
}

static void fuse_fs_cleanup(void)
{
    unregister_filesystem(&fuse_fs_type);
    unregister_fuseblk();

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

static struct kobject *fuse_kobj;
static struct kobject *connections_kobj;

static int fuse_sysfs_init(void)
{
    int err;

    fuse_kobj = kobject_create_and_add("fuse", fs_kobj);
    if (!fuse_kobj) {
        err = -ENOMEM;
        goto out_err;
    }

    connections_kobj = kobject_create_and_add("connections", fuse_kobj);
    if (!connections_kobj) {
        err = -ENOMEM;
        goto out_fuse_unregister;
    }

    return 0;

 out_fuse_unregister:
    kobject_put(fuse_kobj);
 out_err:
    return err;
}

static void fuse_sysfs_cleanup(void)
{
    kobject_put(connections_kobj);
    kobject_put(fuse_kobj);
}

static int __init fuse_init(void)
{
    int res;

    printk(KERN_INFO "fuse init (API version %i.%i)\n",
           FUSE_KERNEL_VERSION, FUSE_KERNEL_MINOR_VERSION);

    INIT_LIST_HEAD(&fuse_conn_list);
    res = fuse_fs_init();
    if (res)
        goto err;

    res = fuse_dev_init();
    if (res)
        goto err_fs_cleanup;

    res = fuse_sysfs_init();
    if (res)
        goto err_dev_cleanup;

    res = fuse_ctl_init();
    if (res)
        goto err_sysfs_cleanup;

    sanitize_global_limit(&max_user_bgreq);
    sanitize_global_limit(&max_user_congthresh);

    return 0;

 err_sysfs_cleanup:
    fuse_sysfs_cleanup();
 err_dev_cleanup:
    fuse_dev_cleanup();
 err_fs_cleanup:
    fuse_fs_cleanup();
 err:
    return res;
}

static void __exit fuse_exit(void)
{
    printk(KERN_DEBUG "fuse exit\n");

    fuse_ctl_cleanup();
    fuse_sysfs_cleanup();
    fuse_fs_cleanup();
    fuse_dev_cleanup();
}

module_init(fuse_init);
module_exit(fuse_exit);