linux/sharedfolders/utils.c

/** @file
 *
 * vboxsf -- VirtualBox Guest Additions for Linux:
 * Utility functions.
 * Mainly conversion from/to VirtualBox/Linux data structures
 */

/*
 * Copyright (C) 2006-2012 Oracle Corporation
 *
 * This file is part of VirtualBox Open Source Edition (OSE), as
 * available from http://www.virtualbox.org. This file is free software;
 * you can redistribute it and/or modify it under the terms of the GNU
 * General Public License (GPL) as published by the Free Software
 * Foundation, in version 2 as it comes in the "COPYING" file of the
 * VirtualBox OSE distribution. VirtualBox OSE is distributed in the
 * hope that it will be useful, but WITHOUT ANY WARRANTY of any kind.
 */

#include "vfsmod.h"
#include <iprt/asm.h>
#include <linux/nfs_fs.h>
#include <linux/vfs.h>

/* #define USE_VMALLOC */

/*
 * sf_reg_aops and sf_backing_dev_info are just quick implementations to make
 * sendfile work. For more information have a look at
 *
 *   http://us1.samba.org/samba/ftp/cifs-cvs/ols2006-fs-tutorial-smf.odp
 *
 * and the sample implementation
 *
 *   http://pserver.samba.org/samba/ftp/cifs-cvs/samplefs.tar.gz
 */

#if LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 0)
static void sf_ftime_from_timespec(time_t *time, RTTIMESPEC *ts)
{
    int64_t t = RTTimeSpecGetNano(ts);

    do_div(t, 1000000000);
    *time = t;
}

static void sf_timespec_from_ftime(RTTIMESPEC *ts, time_t *time)
{
    int64_t t = 1000000000 * *time;
    RTTimeSpecSetNano(ts, t);
}
#else /* >= 2.6.0 */
static void sf_ftime_from_timespec(struct timespec *tv, RTTIMESPEC *ts)
{
    int64_t t = RTTimeSpecGetNano(ts);
    int64_t nsec;

    nsec = do_div(t, 1000000000);
    tv->tv_sec = t;
    tv->tv_nsec = nsec;
}

static void sf_timespec_from_ftime(RTTIMESPEC *ts, struct timespec *tv)
{
    int64_t t = (int64_t)tv->tv_nsec + (int64_t)tv->tv_sec * 1000000000;
    RTTimeSpecSetNano(ts, t);
}
#endif /* >= 2.6.0 */

/* set [inode] attributes based on [info], uid/gid based on [sf_g] */
void sf_init_inode(struct sf_glob_info *sf_g, struct inode *inode,
                   PSHFLFSOBJINFO info)
{
    PSHFLFSOBJATTR attr;
    int mode;

    TRACE();

    attr = &info->Attr;

#define mode_set(r) attr->fMode & (RTFS_UNIX_##r) ? (S_##r) : 0;
    mode  = mode_set(ISUID);
    mode |= mode_set(ISGID);

    mode |= mode_set(IRUSR);
    mode |= mode_set(IWUSR);
    mode |= mode_set(IXUSR);

    mode |= mode_set(IRGRP);
    mode |= mode_set(IWGRP);
    mode |= mode_set(IXGRP);

    mode |= mode_set(IROTH);
    mode |= mode_set(IWOTH);
    mode |= mode_set(IXOTH);

#undef mode_set

#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 0)
    inode->i_mapping->a_ops = &sf_reg_aops;
# if LINUX_VERSION_CODE <= KERNEL_VERSION(3, 19, 0)
    /* XXX Was this ever necessary? */
    inode->i_mapping->backing_dev_info = &sf_g->bdi;
# endif
#endif

    if (RTFS_IS_DIRECTORY(attr->fMode))
    {
        inode->i_mode  = sf_g->dmode != ~0 ? (sf_g->dmode & 0777) : mode;
        inode->i_mode &= ~sf_g->dmask;
        inode->i_mode |= S_IFDIR;
        inode->i_op    = &sf_dir_iops;
        inode->i_fop   = &sf_dir_fops;
        /* XXX: this probably should be set to the number of entries
           in the directory plus two (. ..) */
#if LINUX_VERSION_CODE >= KERNEL_VERSION(3, 2, 0)
        set_nlink(inode, 1);
#else
        inode->i_nlink = 1;
#endif
    }
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 0)
    else if (RTFS_IS_SYMLINK(attr->fMode))
    {
        inode->i_mode  = sf_g->fmode != ~0 ? (sf_g->fmode & 0777): mode;
        inode->i_mode &= ~sf_g->fmask;
        inode->i_mode |= S_IFLNK;
        inode->i_op    = &sf_lnk_iops;
# if LINUX_VERSION_CODE >= KERNEL_VERSION(3, 2, 0)
        set_nlink(inode, 1);
# else
        inode->i_nlink = 1;
# endif
    }
#endif
    else
    {
        inode->i_mode  = sf_g->fmode != ~0 ? (sf_g->fmode & 0777): mode;
        inode->i_mode &= ~sf_g->fmask;
        inode->i_mode |= S_IFREG;
        inode->i_op    = &sf_reg_iops;
        inode->i_fop   = &sf_reg_fops;
#if LINUX_VERSION_CODE >= KERNEL_VERSION(3, 2, 0)
        set_nlink(inode, 1);
#else
        inode->i_nlink = 1;
#endif
    }

#if LINUX_VERSION_CODE >= KERNEL_VERSION(3, 5, 0)
    inode->i_uid = make_kuid(current_user_ns(), sf_g->uid);
    inode->i_gid = make_kgid(current_user_ns(), sf_g->gid);
#else
    inode->i_uid = sf_g->uid;
    inode->i_gid = sf_g->gid;
#endif

    inode->i_size = info->cbObject;
#if LINUX_VERSION_CODE < KERNEL_VERSION(2, 6, 19) && !defined(KERNEL_FC6)
    inode->i_blksize = 4096;
#endif
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 4, 11)
    inode->i_blkbits = 12;
#endif
    /* i_blocks always in units of 512 bytes! */
    inode->i_blocks = (info->cbAllocated + 511) / 512;

    sf_ftime_from_timespec(&inode->i_atime, &info->AccessTime);
    sf_ftime_from_timespec(&inode->i_ctime, &info->ChangeTime);
    sf_ftime_from_timespec(&inode->i_mtime, &info->ModificationTime);
}

int sf_stat(const char *caller, struct sf_glob_info *sf_g,
            SHFLSTRING *path, PSHFLFSOBJINFO result, int ok_to_fail)
{
    int rc;
    SHFLCREATEPARMS params;
    NOREF(caller);

    TRACE();

    RT_ZERO(params);
    params.Handle = SHFL_HANDLE_NIL;
    params.CreateFlags = SHFL_CF_LOOKUP | SHFL_CF_ACT_FAIL_IF_NEW;
    LogFunc(("sf_stat: calling vboxCallCreate, file %s, flags %#x\n",
             path->String.utf8, params.CreateFlags));
    rc = vboxCallCreate(&client_handle, &sf_g->map, path, &params);
    if (rc == VERR_INVALID_NAME)
    {
        /* this can happen for names like 'foo*' on a Windows host */
        return -ENOENT;
    }
    if (RT_FAILURE(rc))
    {
        LogFunc(("vboxCallCreate(%s) failed.  caller=%s, rc=%Rrc\n",
                    path->String.utf8, rc, caller));
        return -EPROTO;
    }
    if (params.Result != SHFL_FILE_EXISTS)
    {
        if (!ok_to_fail)
            LogFunc(("vboxCallCreate(%s) file does not exist.  caller=%s, result=%d\n",
                        path->String.utf8, params.Result, caller));
        return -ENOENT;
    }

    *result = params.Info;
    return 0;
}

/* this is called directly as iop on 2.4, indirectly as dop
   [sf_dentry_revalidate] on 2.4/2.6, indirectly as iop through
   [sf_getattr] on 2.6. the job is to find out whether dentry/inode is
   still valid. the test is failed if [dentry] does not have an inode
   or [sf_stat] is unsuccessful, otherwise we return success and
   update inode attributes */
int sf_inode_revalidate(struct dentry *dentry)
{
    int err;
    struct sf_glob_info *sf_g;
    struct sf_inode_info *sf_i;
    SHFLFSOBJINFO info;

    TRACE();
    if (!dentry || !dentry->d_inode)
    {
        LogFunc(("no dentry(%p) or inode(%p)\n", dentry, dentry->d_inode));
        return -EINVAL;
    }

    sf_g = GET_GLOB_INFO(dentry->d_inode->i_sb);
    sf_i = GET_INODE_INFO(dentry->d_inode);

#if 0
    printk("%s called by %p:%p\n",
            sf_i->path->String.utf8,
            __builtin_return_address (0),
            __builtin_return_address (1));
#endif

    BUG_ON(!sf_g);
    BUG_ON(!sf_i);

    if (!sf_i->force_restat)
    {
        if (jiffies - dentry->d_time < sf_g->ttl)
            return 0;
    }

    err = sf_stat(__func__, sf_g, sf_i->path, &info, 1);
    if (err)
        return err;

    dentry->d_time = jiffies;
    sf_init_inode(sf_g, dentry->d_inode, &info);
    return 0;
}

/* this is called during name resolution/lookup to check if the
   [dentry] in the cache is still valid. the job is handled by
   [sf_inode_revalidate] */
static int
#if LINUX_VERSION_CODE >= KERNEL_VERSION(3, 6, 0)
sf_dentry_revalidate(struct dentry *dentry, unsigned flags)
#elif LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 0)
sf_dentry_revalidate(struct dentry *dentry, struct nameidata *nd)
#else
sf_dentry_revalidate(struct dentry *dentry, int flags)
#endif
{
    TRACE();

#if LINUX_VERSION_CODE >= KERNEL_VERSION(3, 6, 0)
    if (flags & LOOKUP_RCU)
        return -ECHILD;
#elif LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 38)
    /* see Documentation/filesystems/vfs.txt */
    if (nd && nd->flags & LOOKUP_RCU)
        return -ECHILD;
#endif

    if (sf_inode_revalidate(dentry))
        return 0;

    return 1;
}

/* on 2.6 this is a proxy for [sf_inode_revalidate] which (as a side
   effect) updates inode attributes for [dentry] (given that [dentry]
   has inode at all) from these new attributes we derive [kstat] via
   [generic_fillattr] */
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 0)
int sf_getattr(struct vfsmount *mnt, struct dentry *dentry, struct kstat *kstat)
{
    int err;

    TRACE();
    err = sf_inode_revalidate(dentry);
    if (err)
        return err;

    generic_fillattr(dentry->d_inode, kstat);
    return 0;
}

int sf_setattr(struct dentry *dentry, struct iattr *iattr)
{
    struct sf_glob_info *sf_g;
    struct sf_inode_info *sf_i;
    SHFLCREATEPARMS params;
    SHFLFSOBJINFO info;
    uint32_t cbBuffer;
    int rc, err;

    TRACE();

    sf_g = GET_GLOB_INFO(dentry->d_inode->i_sb);
    sf_i = GET_INODE_INFO(dentry->d_inode);
    err  = 0;

    RT_ZERO(params);
    params.Handle = SHFL_HANDLE_NIL;
    params.CreateFlags = SHFL_CF_ACT_OPEN_IF_EXISTS
                       | SHFL_CF_ACT_FAIL_IF_NEW
                       | SHFL_CF_ACCESS_ATTR_WRITE;

    /* this is at least required for Posix hosts */
    if (iattr->ia_valid & ATTR_SIZE)
        params.CreateFlags |= SHFL_CF_ACCESS_WRITE;

    rc = vboxCallCreate(&client_handle, &sf_g->map, sf_i->path, &params);
    if (RT_FAILURE(rc))
    {
        LogFunc(("vboxCallCreate(%s) failed rc=%Rrc\n",
                 sf_i->path->String.utf8, rc));
        err = -RTErrConvertToErrno(rc);
        goto fail2;
    }
    if (params.Result != SHFL_FILE_EXISTS)
    {
        LogFunc(("file %s does not exist\n", sf_i->path->String.utf8));
        err = -ENOENT;
        goto fail1;
    }

    /* Setting the file size and setting the other attributes has to be
     * handled separately, see implementation of vbsfSetFSInfo() in
     * vbsf.cpp */
    if (iattr->ia_valid & (ATTR_MODE | ATTR_ATIME | ATTR_MTIME))
    {
#define mode_set(r) ((iattr->ia_mode & (S_##r)) ? RTFS_UNIX_##r : 0)

        RT_ZERO(info);
        if (iattr->ia_valid & ATTR_MODE)
        {
            info.Attr.fMode  = mode_set(ISUID);
            info.Attr.fMode |= mode_set(ISGID);
            info.Attr.fMode |= mode_set(IRUSR);
            info.Attr.fMode |= mode_set(IWUSR);
            info.Attr.fMode |= mode_set(IXUSR);
            info.Attr.fMode |= mode_set(IRGRP);
            info.Attr.fMode |= mode_set(IWGRP);
            info.Attr.fMode |= mode_set(IXGRP);
            info.Attr.fMode |= mode_set(IROTH);
            info.Attr.fMode |= mode_set(IWOTH);
            info.Attr.fMode |= mode_set(IXOTH);

            if (iattr->ia_mode & S_IFDIR)
                info.Attr.fMode |= RTFS_TYPE_DIRECTORY;
            else
                info.Attr.fMode |= RTFS_TYPE_FILE;
        }

        if (iattr->ia_valid & ATTR_ATIME)
            sf_timespec_from_ftime(&info.AccessTime, &iattr->ia_atime);
        if (iattr->ia_valid & ATTR_MTIME)
            sf_timespec_from_ftime(&info.ModificationTime, &iattr->ia_mtime);
        /* ignore ctime (inode change time) as it can't be set from userland anyway */

        cbBuffer = sizeof(info);
        rc = vboxCallFSInfo(&client_handle, &sf_g->map, params.Handle,
                SHFL_INFO_SET | SHFL_INFO_FILE, &cbBuffer,
                (PSHFLDIRINFO)&info);
        if (RT_FAILURE(rc))
        {
            LogFunc(("vboxCallFSInfo(%s, FILE) failed rc=%Rrc\n",
                        sf_i->path->String.utf8, rc));
            err = -RTErrConvertToErrno(rc);
            goto fail1;
        }
    }

    if (iattr->ia_valid & ATTR_SIZE)
    {
        RT_ZERO(info);
        info.cbObject = iattr->ia_size;
        cbBuffer = sizeof(info);
        rc = vboxCallFSInfo(&client_handle, &sf_g->map, params.Handle,
                            SHFL_INFO_SET | SHFL_INFO_SIZE, &cbBuffer,
                            (PSHFLDIRINFO)&info);
        if (RT_FAILURE(rc))
        {
            LogFunc(("vboxCallFSInfo(%s, SIZE) failed rc=%Rrc\n",
                        sf_i->path->String.utf8, rc));
            err = -RTErrConvertToErrno(rc);
            goto fail1;
        }
    }

    rc = vboxCallClose(&client_handle, &sf_g->map, params.Handle);
    if (RT_FAILURE(rc))
        LogFunc(("vboxCallClose(%s) failed rc=%Rrc\n", sf_i->path->String.utf8, rc));

    return sf_inode_revalidate(dentry);

fail1:
    rc = vboxCallClose(&client_handle, &sf_g->map, params.Handle);
    if (RT_FAILURE(rc))
        LogFunc(("vboxCallClose(%s) failed rc=%Rrc\n", sf_i->path->String.utf8, rc));

fail2:
    return err;
}
#endif /* >= 2.6.0 */

static int sf_make_path(const char *caller, struct sf_inode_info *sf_i,
                        const char *d_name, size_t d_len, SHFLSTRING **result)
{
    size_t path_len, shflstring_len;
    SHFLSTRING *tmp;
    uint16_t p_len;
    uint8_t *p_name;
    int fRoot = 0;

    TRACE();
    p_len = sf_i->path->u16Length;
    p_name = sf_i->path->String.utf8;

    if (p_len == 1 && *p_name == '/')
    {
        path_len = d_len + 1;
        fRoot = 1;
    }
    else
    {
        /* lengths of constituents plus terminating zero plus slash  */
        path_len = p_len + d_len + 2;
        if (path_len > 0xffff)
        {
            LogFunc(("path too long.  caller=%s, path_len=%zu\n", caller, path_len));
            return -ENAMETOOLONG;
        }
    }

    shflstring_len = offsetof(SHFLSTRING, String.utf8) + path_len;
    tmp = kmalloc(shflstring_len, GFP_KERNEL);
    if (!tmp)
    {
        LogRelFunc(("kmalloc failed, caller=%s\n", caller));
        return -ENOMEM;
    }
    tmp->u16Length = path_len - 1;
    tmp->u16Size = path_len;

    if (fRoot)
        memcpy(&tmp->String.utf8[0], d_name, d_len + 1);
    else
    {
        memcpy(&tmp->String.utf8[0], p_name, p_len);
        tmp->String.utf8[p_len] = '/';
        memcpy(&tmp->String.utf8[p_len + 1], d_name, d_len);
        tmp->String.utf8[p_len + 1 + d_len] = '\0';
    }

    *result = tmp;
    return 0;
}

/**
 * [dentry] contains string encoded in coding system that corresponds
 * to [sf_g]->nls, we must convert it to UTF8 here and pass down to
 * [sf_make_path] which will allocate SHFLSTRING and fill it in
 */
int sf_path_from_dentry(const char *caller, struct sf_glob_info *sf_g,
                        struct sf_inode_info *sf_i, struct dentry *dentry,
                        SHFLSTRING **result)
{
    int err;
    const char *d_name;
    size_t d_len;
    const char *name;
    size_t len = 0;

    TRACE();
    d_name = dentry->d_name.name;
    d_len = dentry->d_name.len;

    if (sf_g->nls)
    {
        size_t in_len, i, out_bound_len;
        const char *in;
        char *out;

        in = d_name;
        in_len = d_len;

        out_bound_len = PATH_MAX;
        out = kmalloc(out_bound_len, GFP_KERNEL);
        name = out;

        for (i = 0; i < d_len; ++i)
        {
            /* We renamed the linux kernel wchar_t type to linux_wchar_t in
               the-linux-kernel.h, as it conflicts with the C++ type of that name. */
            linux_wchar_t uni;
            int nb;

            nb = sf_g->nls->char2uni(in, in_len, &uni);
            if (nb < 0)
            {
                LogFunc(("nls->char2uni failed %x %d\n",
                            *in, in_len));
                err = -EINVAL;
                goto fail1;
            }
            in_len -= nb;
            in += nb;

#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 31)
            nb = utf32_to_utf8(uni, out, out_bound_len);
#else
            nb = utf8_wctomb(out, uni, out_bound_len);
#endif
            if (nb < 0)
            {
                LogFunc(("nls->uni2char failed %x %d\n",
                            uni, out_bound_len));
                err = -EINVAL;
                goto fail1;
            }
            out_bound_len -= nb;
            out += nb;
            len += nb;
        }
        if (len >= PATH_MAX - 1)
        {
            err = -ENAMETOOLONG;
            goto fail1;
        }

        LogFunc(("result(%d) = %.*s\n", len, len, name));
        *out = 0;
    }
    else
    {
        name = d_name;
        len = d_len;
    }

    err = sf_make_path(caller, sf_i, name, len, result);
    if (name != d_name)
        kfree(name);

    return err;

fail1:
    kfree(name);
    return err;
}

int sf_nlscpy(struct sf_glob_info *sf_g,
              char *name, size_t name_bound_len,
              const unsigned char *utf8_name, size_t utf8_len)
{
    if (sf_g->nls)
    {
        const char *in;
        char *out;
        size_t out_len;
        size_t out_bound_len;
        size_t in_bound_len;

        in = utf8_name;
        in_bound_len = utf8_len;

        out = name;
        out_len = 0;
        out_bound_len = name_bound_len;

        while (in_bound_len)
        {
            int nb;
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 31)
            unicode_t uni;

            nb = utf8_to_utf32(in, in_bound_len, &uni);
#else
            linux_wchar_t uni;

            nb = utf8_mbtowc(&uni, in, in_bound_len);
#endif
            if (nb < 0)
            {
                LogFunc(("utf8_mbtowc failed(%s) %x:%d\n",
                            (const char *) utf8_name, *in, in_bound_len));
                return -EINVAL;
            }
            in += nb;
            in_bound_len -= nb;

            nb = sf_g->nls->uni2char(uni, out, out_bound_len);
            if (nb < 0)
            {
                LogFunc(("nls->uni2char failed(%s) %x:%d\n",
                            utf8_name, uni, out_bound_len));
                return nb;
            }
            out += nb;
            out_bound_len -= nb;
            out_len += nb;
        }

        *out = 0;
    }
    else
    {
        if (utf8_len + 1 > name_bound_len)
            return -ENAMETOOLONG;

        memcpy(name, utf8_name, utf8_len + 1);
    }
    return 0;
}

static struct sf_dir_buf *sf_dir_buf_alloc(void)
{
    struct sf_dir_buf *b;

    TRACE();
    b = kmalloc(sizeof(*b), GFP_KERNEL);
    if (!b)
    {
        LogRelFunc(("could not alloc directory buffer\n"));
        return NULL;
    }

#ifdef USE_VMALLOC
    b->buf = vmalloc(DIR_BUFFER_SIZE);
#else
    b->buf = kmalloc(DIR_BUFFER_SIZE, GFP_KERNEL);
#endif
    if (!b->buf)
    {
        kfree(b);
        LogRelFunc(("could not alloc directory buffer storage\n"));
        return NULL;
    }

    INIT_LIST_HEAD(&b->head);
    b->cEntries = 0;
    b->cbUsed   = 0;
    b->cbFree   = DIR_BUFFER_SIZE;
    return b;
}

static void sf_dir_buf_free(struct sf_dir_buf *b)
{
    BUG_ON(!b || !b->buf);

    TRACE();
    list_del(&b->head);
#ifdef USE_VMALLOC
    vfree(b->buf);
#else
    kfree(b->buf);
#endif
    kfree(b);
}

/**
 * Free the directory buffer.
 */
void sf_dir_info_free(struct sf_dir_info *p)
{
    struct list_head *list, *pos, *tmp;

    TRACE();
    list = &p->info_list;
    list_for_each_safe(pos, tmp, list)
    {
        struct sf_dir_buf *b;

        b = list_entry(pos, struct sf_dir_buf, head);
        sf_dir_buf_free(b);
    }
    kfree(p);
}

/**
 * Empty (but not free) the directory buffer.
 */
void sf_dir_info_empty(struct sf_dir_info *p)
{
    struct list_head *list, *pos, *tmp;
    TRACE();
    list = &p->info_list;
    list_for_each_safe(pos, tmp, list)
    {
        struct sf_dir_buf *b;
        b = list_entry(pos, struct sf_dir_buf, head);
        b->cEntries = 0;
        b->cbUsed   = 0;
        b->cbFree = DIR_BUFFER_SIZE;
    }
}

/**
 * Create a new directory buffer descriptor.
 */
struct sf_dir_info *sf_dir_info_alloc(void)
{
    struct sf_dir_info *p;

    TRACE();
    p = kmalloc(sizeof(*p), GFP_KERNEL);
    if (!p)
    {
        LogRelFunc(("could not alloc directory info\n"));
        return NULL;
    }

    INIT_LIST_HEAD(&p->info_list);
    return p;
}

/**
 * Search for an empty directory content buffer.
 */
static struct sf_dir_buf *sf_get_empty_dir_buf(struct sf_dir_info *sf_d)
{
    struct list_head *list, *pos;

    list = &sf_d->info_list;
    list_for_each(pos, list)
    {
        struct sf_dir_buf *b;

        b = list_entry(pos, struct sf_dir_buf, head);
        if (!b)
            return NULL;
        else
        {
            if (b->cbUsed == 0)
                return b;
        }
    }

    return NULL;
}

int sf_dir_read_all(struct sf_glob_info *sf_g, struct sf_inode_info *sf_i,
                    struct sf_dir_info *sf_d, SHFLHANDLE handle)
{
    int err;
    SHFLSTRING *mask;
    struct sf_dir_buf *b;

    TRACE();
    err = sf_make_path(__func__, sf_i, "*", 1, &mask);
    if (err)
        goto fail0;

    for (;;)
    {
        int rc;
        void *buf;
        uint32_t cbSize;
        uint32_t cEntries;

        b = sf_get_empty_dir_buf(sf_d);
        if (!b)
        {
            b = sf_dir_buf_alloc();
            if (!b)
            {
                err = -ENOMEM;
                LogRelFunc(("could not alloc directory buffer\n"));
                goto fail1;
            }
            list_add(&b->head, &sf_d->info_list);
        }

        buf = b->buf;
        cbSize = b->cbFree;

        rc = vboxCallDirInfo(&client_handle, &sf_g->map, handle, mask,
                             0, 0, &cbSize, buf, &cEntries);
        switch (rc)
        {
            case VINF_SUCCESS:
                /* fallthrough */
            case VERR_NO_MORE_FILES:
                break;
            case VERR_NO_TRANSLATION:
                LogFunc(("host could not translate entry\n"));
                /* XXX */
                break;
            default:
                err = -RTErrConvertToErrno(rc);
                LogFunc(("vboxCallDirInfo failed rc=%Rrc\n", rc));
                goto fail1;
        }

        b->cEntries += cEntries;
        b->cbFree   -= cbSize;
        b->cbUsed   += cbSize;

        if (RT_FAILURE(rc))
            break;
    }
    err = 0;

fail1:
    kfree(mask);

fail0:
    return err;
}

int sf_get_volume_info(struct super_block *sb, STRUCT_STATFS *stat)
{
    struct sf_glob_info *sf_g;
    SHFLVOLINFO SHFLVolumeInfo;
    uint32_t cbBuffer;
    int rc;

    sf_g = GET_GLOB_INFO(sb);
    cbBuffer = sizeof(SHFLVolumeInfo);
    rc = vboxCallFSInfo(&client_handle, &sf_g->map, 0, SHFL_INFO_GET | SHFL_INFO_VOLUME,
                        &cbBuffer, (PSHFLDIRINFO)&SHFLVolumeInfo);
    if (RT_FAILURE(rc))
        return -RTErrConvertToErrno(rc);

    stat->f_type        = NFS_SUPER_MAGIC; /* XXX vboxsf type? */
    stat->f_bsize       = SHFLVolumeInfo.ulBytesPerAllocationUnit;
    stat->f_blocks      = SHFLVolumeInfo.ullTotalAllocationBytes
                        / SHFLVolumeInfo.ulBytesPerAllocationUnit;
    stat->f_bfree       = SHFLVolumeInfo.ullAvailableAllocationBytes
                        / SHFLVolumeInfo.ulBytesPerAllocationUnit;
    stat->f_bavail      = SHFLVolumeInfo.ullAvailableAllocationBytes
                        / SHFLVolumeInfo.ulBytesPerAllocationUnit;
    stat->f_files       = 1000;
    stat->f_ffree       = 1000; /* don't return 0 here since the guest may think
                                 * that it is not possible to create any more files */
    stat->f_fsid.val[0] = 0;
    stat->f_fsid.val[1] = 0;
    stat->f_namelen     = 255;
    return 0;
}

struct dentry_operations sf_dentry_ops =
{
    .d_revalidate = sf_dentry_revalidate
};

int sf_init_backing_dev(struct sf_glob_info *sf_g)
{
    int rc = 0;
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 0) && LINUX_VERSION_CODE <= KERNEL_VERSION(3, 19, 0)
    /* Each new shared folder map gets a new uint64_t identifier,
     * allocated in sequence.  We ASSUME the sequence will not wrap. */
    static uint64_t s_u64Sequence = 0;
    uint64_t u64CurrentSequence = ASMAtomicIncU64(&s_u64Sequence);

    sf_g->bdi.ra_pages = 0; /* No readahead */
# if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 12)
    sf_g->bdi.capabilities  = BDI_CAP_MAP_DIRECT    /* MAP_SHARED */
                            | BDI_CAP_MAP_COPY      /* MAP_PRIVATE */
                            | BDI_CAP_READ_MAP      /* can be mapped for reading */
                            | BDI_CAP_WRITE_MAP     /* can be mapped for writing */
                            | BDI_CAP_EXEC_MAP;     /* can be mapped for execution */
# endif /* >= 2.6.12 */
# if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 24)
    rc = bdi_init(&sf_g->bdi);
#  if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 26)
    if (!rc)
        rc = bdi_register(&sf_g->bdi, NULL, "vboxsf-%llu",
                          (unsigned long long)u64CurrentSequence);
#  endif /* >= 2.6.26 */
# endif /* >= 2.6.24 */
#endif /* >= 2.6.0 && <= 3.19.0 */
    return rc;
}

void sf_done_backing_dev(struct sf_glob_info *sf_g)
{
#if LINUX_VERSION_CODE >= KERNEL_VERSION(2, 6, 24) && LINUX_VERSION_CODE <= KERNEL_VERSION(3, 19, 0)
    bdi_destroy(&sf_g->bdi); /* includes bdi_unregister() */
#endif
}