NFS: Fix NFSv3 exclusive open semantics

[linux-2.6.git] / fs / fuse / inode.c

/*
  FUSE: Filesystem in Userspace
  Copyright (C) 2001-2008  Miklos Szeredi <miklos@szeredi.hu>

  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 <miklos@szeredi.hu>");
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

/** Maximum number of outstanding background requests */
#define FUSE_DEFAULT_MAX_BACKGROUND 12

/** Congestion starts at 75% of maximum */
#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()
{
        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;
        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);
        INIT_LIST_HEAD(&inode->i_dentry);
        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);
        end_writeback(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;
}

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     = attr->ino;
        inode->i_mode    = (inode->i_mode & S_IFMT) | (attr->mode & 07777);
        inode->i_nlink   = 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;
}

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;

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

        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) && oldsize != attr->size) {
                truncate_pagecache(inode, oldsize, attr->size);
                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);
        mutex_lock(&fuse_mutex);
        list_del(&fc->entry);
        fuse_ctl_remove_conn(fc);
        mutex_unlock(&fuse_mutex);
        fuse_bdi_destroy(fc);
}
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);
        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 vfsmount *mnt)
{
        struct fuse_conn *fc = get_fuse_conn_super(mnt->mnt_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 (mnt->mnt_sb->s_bdev &&
            mnt->mnt_sb->s_blocksize != FUSE_DEFAULT_BLKSIZE)
                seq_printf(m, ",blksize=%lu", mnt->mnt_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 dentry *dentry, u32 *fh, int *max_len,
                           int connectable)
{
        struct inode *inode = dentry->d_inode;
        bool encode_parent = connectable && !S_ISDIR(inode->i_mode);
        int len = encode_parent ? 6 : 3;
        u64 nodeid;
        u32 generation;

        if (*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 (encode_parent) {
                struct inode *parent;

                spin_lock(&dentry->d_lock);
                parent = dentry->d_parent->d_inode;
                nodeid = get_fuse_inode(parent)->nodeid;
                generation = parent->i_generation;
                spin_unlock(&dentry->d_lock);

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

        *max_len = len;
        return encode_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->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;
                } else {
                        ra_pages = fc->max_read / PAGE_CACHE_SIZE;
                        fc->no_lock = 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;
        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;
        fc->bdi.unplug_io_fn = default_unplug_io_fn;
        /* 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;

        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_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);
        if (!root)
                goto err_put_conn;

        root_dentry = d_alloc_root(root);
        if (!root_dentry) {
                iput(root);
                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;

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

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

        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_unreg2;

        return 0;

 out_unreg2:
        unregister_fuseblk();
 out_unreg:
        unregister_filesystem(&fuse_fs_type);
 out:
        return err;
}

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