#include <linux/fs.h>
#include <linux/magic.h>
#include <linux/module.h>
#include <linux/mm.h>
#include <linux/pagemap.h>
#include <linux/statfs.h>
#include <linux/slab.h>
#include <linux/seq_file.h>
#include <linux/writeback.h>
#include <linux/mount.h>
#include <linux/fs_context.h>
#include <linux/fs_parser.h>
#include <linux/namei.h>
#include "hostfs.h"
#include <init.h>
#include <kern.h>
struct hostfs_fs_info {
char *host_root_path;
};
struct hostfs_inode_info {
int fd;
fmode_t mode;
struct inode vfs_inode;
struct mutex open_mutex;
dev_t dev;
struct hostfs_timespec btime;
};
static inline struct hostfs_inode_info *HOSTFS_I(struct inode *inode)
{
return list_entry(inode, struct hostfs_inode_info, vfs_inode);
}
#define FILE_HOSTFS_I(file) HOSTFS_I(file_inode(file))
static struct kmem_cache *hostfs_inode_cache;
static char *root_ino = "";
static int append = 0;
static const struct inode_operations hostfs_iops;
static const struct inode_operations hostfs_dir_iops;
static const struct inode_operations hostfs_link_iops;
#ifndef MODULE
static int __init hostfs_args(char *options, int *add)
{
char *ptr;
*add = 0;
ptr = strchr(options, ',');
if (ptr != NULL)
*ptr++ = '\0';
if (*options != '\0')
root_ino = options;
options = ptr;
while (options) {
ptr = strchr(options, ',');
if (ptr != NULL)
*ptr++ = '\0';
if (*options != '\0') {
if (!strcmp(options, "append"))
append = 1;
else printf("hostfs_args - unsupported option - %s\n",
options);
}
options = ptr;
}
return 0;
}
__uml_setup("hostfs=", hostfs_args,
"hostfs=<root dir>,<flags>,...\n"
" This is used to set hostfs parameters. The root directory argument\n"
" is used to confine all hostfs mounts to within the specified directory\n"
" tree on the host. If this isn't specified, then a user inside UML can\n"
" mount anything on the host that's accessible to the user that's running\n"
" it.\n"
" The only flag currently supported is 'append', which specifies that all\n"
" files opened by hostfs will be opened in append mode.\n\n"
);
#endif
static char *__dentry_name(struct dentry *dentry, char *name)
{
char *p = dentry_path_raw(dentry, name, PATH_MAX);
struct hostfs_fs_info *fsi = dentry->d_sb->s_fs_info;
char *root = fsi->host_root_path;
size_t len = strlen(root);
if (IS_ERR(p) || len > p - name) {
__putname(name);
return NULL;
}
memcpy(name, root, len);
memmove(name + len, p, name + PATH_MAX - p);
return name;
}
static char *dentry_name(struct dentry *dentry)
{
char *name = __getname();
if (!name)
return NULL;
return __dentry_name(dentry, name);
}
static char *inode_name(struct inode *ino)
{
struct dentry *dentry;
char *name;
dentry = d_find_alias(ino);
if (!dentry)
return NULL;
name = dentry_name(dentry);
dput(dentry);
return name;
}
static char *follow_link(char *link)
{
char *name, *resolved, *end;
int n;
name = kmalloc(PATH_MAX, GFP_KERNEL);
if (!name) {
n = -ENOMEM;
goto out_free;
}
n = hostfs_do_readlink(link, name, PATH_MAX);
if (n < 0)
goto out_free;
else if (n == PATH_MAX) {
n = -E2BIG;
goto out_free;
}
if (*name == '/')
return name;
end = strrchr(link, '/');
if (end == NULL)
return name;
*(end + 1) = '\0';
resolved = kasprintf(GFP_KERNEL, "%s%s", link, name);
if (resolved == NULL) {
n = -ENOMEM;
goto out_free;
}
kfree(name);
return resolved;
out_free:
kfree(name);
return ERR_PTR(n);
}
static int hostfs_statfs(struct dentry *dentry, struct kstatfs *sf)
{
int err;
long long f_blocks;
long long f_bfree;
long long f_bavail;
long long f_files;
long long f_ffree;
struct hostfs_fs_info *fsi;
fsi = dentry->d_sb->s_fs_info;
err = do_statfs(fsi->host_root_path,
&sf->f_bsize, &f_blocks, &f_bfree, &f_bavail, &f_files,
&f_ffree, &sf->f_fsid, sizeof(sf->f_fsid),
&sf->f_namelen);
if (err)
return err;
sf->f_blocks = f_blocks;
sf->f_bfree = f_bfree;
sf->f_bavail = f_bavail;
sf->f_files = f_files;
sf->f_ffree = f_ffree;
sf->f_type = HOSTFS_SUPER_MAGIC;
return 0;
}
static struct inode *hostfs_alloc_inode(struct super_block *sb)
{
struct hostfs_inode_info *hi;
hi = alloc_inode_sb(sb, hostfs_inode_cache, GFP_KERNEL_ACCOUNT);
if (hi == NULL)
return NULL;
hi->fd = -1;
hi->mode = 0;
hi->dev = 0;
inode_init_once(&hi->vfs_inode);
mutex_init(&hi->open_mutex);
return &hi->vfs_inode;
}
static void hostfs_evict_inode(struct inode *inode)
{
truncate_inode_pages_final(&inode->i_data);
clear_inode(inode);
if (HOSTFS_I(inode)->fd != -1) {
close_file(&HOSTFS_I(inode)->fd);
HOSTFS_I(inode)->fd = -1;
HOSTFS_I(inode)->dev = 0;
}
}
static void hostfs_free_inode(struct inode *inode)
{
kmem_cache_free(hostfs_inode_cache, HOSTFS_I(inode));
}
static int hostfs_show_options(struct seq_file *seq, struct dentry *root)
{
struct hostfs_fs_info *fsi;
const char *root_path;
fsi = root->d_sb->s_fs_info;
root_path = fsi->host_root_path;
size_t offset = strlen(root_ino) + 1;
if (strlen(root_path) > offset)
seq_show_option(seq, root_path + offset, NULL);
if (append)
seq_puts(seq, ",append");
return 0;
}
static const struct super_operations hostfs_sbops = {
.alloc_inode = hostfs_alloc_inode,
.free_inode = hostfs_free_inode,
.drop_inode = inode_just_drop,
.evict_inode = hostfs_evict_inode,
.statfs = hostfs_statfs,
.show_options = hostfs_show_options,
};
static int hostfs_readdir(struct file *file, struct dir_context *ctx)
{
void *dir;
char *name;
unsigned long long next, ino;
int error, len;
unsigned int type;
name = dentry_name(file->f_path.dentry);
if (name == NULL)
return -ENOMEM;
dir = open_dir(name, &error);
__putname(name);
if (dir == NULL)
return -error;
next = ctx->pos;
seek_dir(dir, next);
while ((name = read_dir(dir, &next, &ino, &len, &type)) != NULL) {
if (!dir_emit(ctx, name, len, ino, type))
break;
ctx->pos = next;
}
close_dir(dir);
return 0;
}
static int hostfs_open(struct inode *ino, struct file *file)
{
char *name;
fmode_t mode;
int err;
int r, w, fd;
mode = file->f_mode & (FMODE_READ | FMODE_WRITE);
if ((mode & HOSTFS_I(ino)->mode) == mode)
return 0;
mode |= HOSTFS_I(ino)->mode;
retry:
r = w = 0;
if (mode & FMODE_READ)
r = 1;
if (mode & FMODE_WRITE)
r = w = 1;
name = dentry_name(file_dentry(file));
if (name == NULL)
return -ENOMEM;
fd = open_file(name, r, w, append);
__putname(name);
if (fd < 0)
return fd;
mutex_lock(&HOSTFS_I(ino)->open_mutex);
if ((mode & HOSTFS_I(ino)->mode) == mode) {
mutex_unlock(&HOSTFS_I(ino)->open_mutex);
close_file(&fd);
return 0;
}
if ((mode | HOSTFS_I(ino)->mode) != mode) {
mode |= HOSTFS_I(ino)->mode;
mutex_unlock(&HOSTFS_I(ino)->open_mutex);
close_file(&fd);
goto retry;
}
if (HOSTFS_I(ino)->fd == -1) {
HOSTFS_I(ino)->fd = fd;
} else {
err = replace_file(fd, HOSTFS_I(ino)->fd);
close_file(&fd);
if (err < 0) {
mutex_unlock(&HOSTFS_I(ino)->open_mutex);
return err;
}
}
HOSTFS_I(ino)->mode = mode;
mutex_unlock(&HOSTFS_I(ino)->open_mutex);
return 0;
}
static int hostfs_file_release(struct inode *inode, struct file *file)
{
filemap_write_and_wait(inode->i_mapping);
return 0;
}
static int hostfs_fsync(struct file *file, loff_t start, loff_t end,
int datasync)
{
struct inode *inode = file->f_mapping->host;
int ret;
ret = file_write_and_wait_range(file, start, end);
if (ret)
return ret;
inode_lock(inode);
ret = fsync_file(HOSTFS_I(inode)->fd, datasync);
inode_unlock(inode);
return ret;
}
static const struct file_operations hostfs_file_fops = {
.llseek = generic_file_llseek,
.splice_read = filemap_splice_read,
.splice_write = iter_file_splice_write,
.read_iter = generic_file_read_iter,
.write_iter = generic_file_write_iter,
.mmap_prepare = generic_file_mmap_prepare,
.open = hostfs_open,
.release = hostfs_file_release,
.fsync = hostfs_fsync,
};
static const struct file_operations hostfs_dir_fops = {
.llseek = generic_file_llseek,
.iterate_shared = hostfs_readdir,
.read = generic_read_dir,
.open = hostfs_open,
.fsync = hostfs_fsync,
};
static int hostfs_writepages(struct address_space *mapping,
struct writeback_control *wbc)
{
struct inode *inode = mapping->host;
struct folio *folio = NULL;
loff_t i_size = i_size_read(inode);
int err = 0;
while ((folio = writeback_iter(mapping, wbc, folio, &err))) {
loff_t pos = folio_pos(folio);
size_t count = folio_size(folio);
char *buffer;
int ret;
if (count > i_size - pos)
count = i_size - pos;
buffer = kmap_local_folio(folio, 0);
ret = write_file(HOSTFS_I(inode)->fd, &pos, buffer, count);
kunmap_local(buffer);
folio_unlock(folio);
if (ret != count) {
err = ret < 0 ? ret : -EIO;
mapping_set_error(mapping, err);
}
}
return err;
}
static int hostfs_read_folio(struct file *file, struct folio *folio)
{
char *buffer;
loff_t start = folio_pos(folio);
int bytes_read, ret = 0;
buffer = kmap_local_folio(folio, 0);
bytes_read = read_file(FILE_HOSTFS_I(file)->fd, &start, buffer,
PAGE_SIZE);
if (bytes_read < 0)
ret = bytes_read;
else
buffer = folio_zero_tail(folio, bytes_read, buffer + bytes_read);
kunmap_local(buffer);
folio_end_read(folio, ret == 0);
return ret;
}
static int hostfs_write_begin(const struct kiocb *iocb,
struct address_space *mapping,
loff_t pos, unsigned len,
struct folio **foliop, void **fsdata)
{
pgoff_t index = pos >> PAGE_SHIFT;
*foliop = __filemap_get_folio(mapping, index, FGP_WRITEBEGIN,
mapping_gfp_mask(mapping));
if (IS_ERR(*foliop))
return PTR_ERR(*foliop);
return 0;
}
static int hostfs_write_end(const struct kiocb *iocb,
struct address_space *mapping,
loff_t pos, unsigned len, unsigned copied,
struct folio *folio, void *fsdata)
{
struct inode *inode = mapping->host;
void *buffer;
size_t from = offset_in_folio(folio, pos);
int err;
buffer = kmap_local_folio(folio, from);
err = write_file(FILE_HOSTFS_I(iocb->ki_filp)->fd, &pos, buffer, copied);
kunmap_local(buffer);
if (!folio_test_uptodate(folio) && err == folio_size(folio))
folio_mark_uptodate(folio);
if (err > 0 && (pos > inode->i_size))
inode->i_size = pos;
folio_unlock(folio);
folio_put(folio);
return err;
}
static const struct address_space_operations hostfs_aops = {
.writepages = hostfs_writepages,
.read_folio = hostfs_read_folio,
.dirty_folio = filemap_dirty_folio,
.write_begin = hostfs_write_begin,
.write_end = hostfs_write_end,
.migrate_folio = filemap_migrate_folio,
};
static int hostfs_inode_update(struct inode *ino, const struct hostfs_stat *st)
{
set_nlink(ino, st->nlink);
i_uid_write(ino, st->uid);
i_gid_write(ino, st->gid);
inode_set_atime_to_ts(ino, (struct timespec64){
st->atime.tv_sec,
st->atime.tv_nsec,
});
inode_set_mtime_to_ts(ino, (struct timespec64){
st->mtime.tv_sec,
st->mtime.tv_nsec,
});
inode_set_ctime(ino, st->ctime.tv_sec, st->ctime.tv_nsec);
ino->i_size = st->size;
ino->i_blocks = st->blocks;
return 0;
}
static int hostfs_inode_set(struct inode *ino, void *data)
{
struct hostfs_stat *st = data;
dev_t dev, rdev;
rdev = MKDEV(st->rdev.maj, st->rdev.min);
dev = MKDEV(st->dev.maj, st->dev.min);
switch (st->mode & S_IFMT) {
case S_IFLNK:
ino->i_op = &hostfs_link_iops;
break;
case S_IFDIR:
ino->i_op = &hostfs_dir_iops;
ino->i_fop = &hostfs_dir_fops;
break;
case S_IFCHR:
case S_IFBLK:
case S_IFIFO:
case S_IFSOCK:
init_special_inode(ino, st->mode & S_IFMT, rdev);
ino->i_op = &hostfs_iops;
break;
case S_IFREG:
ino->i_op = &hostfs_iops;
ino->i_fop = &hostfs_file_fops;
ino->i_mapping->a_ops = &hostfs_aops;
break;
default:
return -EIO;
}
HOSTFS_I(ino)->dev = dev;
HOSTFS_I(ino)->btime = st->btime;
ino->i_ino = st->ino;
ino->i_mode = st->mode;
return hostfs_inode_update(ino, st);
}
static int hostfs_inode_test(struct inode *inode, void *data)
{
const struct hostfs_stat *st = data;
dev_t dev = MKDEV(st->dev.maj, st->dev.min);
return inode->i_ino == st->ino && HOSTFS_I(inode)->dev == dev &&
(inode->i_mode & S_IFMT) == (st->mode & S_IFMT) &&
HOSTFS_I(inode)->btime.tv_sec == st->btime.tv_sec &&
HOSTFS_I(inode)->btime.tv_nsec == st->btime.tv_nsec;
}
static struct inode *hostfs_iget(struct super_block *sb, char *name)
{
struct inode *inode;
struct hostfs_stat st;
int err = stat_file(name, &st, -1);
if (err)
return ERR_PTR(err);
inode = iget5_locked(sb, st.ino, hostfs_inode_test, hostfs_inode_set,
&st);
if (!inode)
return ERR_PTR(-ENOMEM);
if (inode_state_read_once(inode) & I_NEW) {
unlock_new_inode(inode);
} else {
spin_lock(&inode->i_lock);
hostfs_inode_update(inode, &st);
spin_unlock(&inode->i_lock);
}
return inode;
}
static int hostfs_create(struct mnt_idmap *idmap, struct inode *dir,
struct dentry *dentry, umode_t mode, bool excl)
{
struct inode *inode;
char *name;
int fd;
name = dentry_name(dentry);
if (name == NULL)
return -ENOMEM;
fd = file_create(name, mode & 0777);
if (fd < 0) {
__putname(name);
return fd;
}
inode = hostfs_iget(dir->i_sb, name);
__putname(name);
if (IS_ERR(inode))
return PTR_ERR(inode);
HOSTFS_I(inode)->fd = fd;
HOSTFS_I(inode)->mode = FMODE_READ | FMODE_WRITE;
d_instantiate(dentry, inode);
return 0;
}
static struct dentry *hostfs_lookup(struct inode *ino, struct dentry *dentry,
unsigned int flags)
{
struct inode *inode = NULL;
char *name;
name = dentry_name(dentry);
if (name == NULL)
return ERR_PTR(-ENOMEM);
inode = hostfs_iget(ino->i_sb, name);
__putname(name);
if (inode == ERR_PTR(-ENOENT))
inode = NULL;
return d_splice_alias(inode, dentry);
}
static int hostfs_link(struct dentry *to, struct inode *ino,
struct dentry *from)
{
char *from_name, *to_name;
int err;
if ((from_name = dentry_name(from)) == NULL)
return -ENOMEM;
to_name = dentry_name(to);
if (to_name == NULL) {
__putname(from_name);
return -ENOMEM;
}
err = link_file(to_name, from_name);
__putname(from_name);
__putname(to_name);
return err;
}
static int hostfs_unlink(struct inode *ino, struct dentry *dentry)
{
char *file;
int err;
if (append)
return -EPERM;
if ((file = dentry_name(dentry)) == NULL)
return -ENOMEM;
err = unlink_file(file);
__putname(file);
return err;
}
static int hostfs_symlink(struct mnt_idmap *idmap, struct inode *ino,
struct dentry *dentry, const char *to)
{
char *file;
int err;
if ((file = dentry_name(dentry)) == NULL)
return -ENOMEM;
err = make_symlink(file, to);
__putname(file);
return err;
}
static struct dentry *hostfs_mkdir(struct mnt_idmap *idmap, struct inode *ino,
struct dentry *dentry, umode_t mode)
{
struct inode *inode;
char *file;
int err;
if ((file = dentry_name(dentry)) == NULL)
return ERR_PTR(-ENOMEM);
err = do_mkdir(file, mode);
if (err) {
dentry = ERR_PTR(err);
} else {
inode = hostfs_iget(dentry->d_sb, file);
d_drop(dentry);
dentry = d_splice_alias(inode, dentry);
}
__putname(file);
return dentry;
}
static int hostfs_rmdir(struct inode *ino, struct dentry *dentry)
{
char *file;
int err;
if ((file = dentry_name(dentry)) == NULL)
return -ENOMEM;
err = hostfs_do_rmdir(file);
__putname(file);
return err;
}
static int hostfs_mknod(struct mnt_idmap *idmap, struct inode *dir,
struct dentry *dentry, umode_t mode, dev_t dev)
{
struct inode *inode;
char *name;
int err;
name = dentry_name(dentry);
if (name == NULL)
return -ENOMEM;
err = do_mknod(name, mode, MAJOR(dev), MINOR(dev));
if (err) {
__putname(name);
return err;
}
inode = hostfs_iget(dir->i_sb, name);
__putname(name);
if (IS_ERR(inode))
return PTR_ERR(inode);
d_instantiate(dentry, inode);
return 0;
}
static int hostfs_rename2(struct mnt_idmap *idmap,
struct inode *old_dir, struct dentry *old_dentry,
struct inode *new_dir, struct dentry *new_dentry,
unsigned int flags)
{
char *old_name, *new_name;
int err;
if (flags & ~(RENAME_NOREPLACE | RENAME_EXCHANGE))
return -EINVAL;
old_name = dentry_name(old_dentry);
if (old_name == NULL)
return -ENOMEM;
new_name = dentry_name(new_dentry);
if (new_name == NULL) {
__putname(old_name);
return -ENOMEM;
}
if (!flags)
err = rename_file(old_name, new_name);
else
err = rename2_file(old_name, new_name, flags);
__putname(old_name);
__putname(new_name);
return err;
}
static int hostfs_permission(struct mnt_idmap *idmap,
struct inode *ino, int desired)
{
char *name;
int r = 0, w = 0, x = 0, err;
if (desired & MAY_NOT_BLOCK)
return -ECHILD;
if (desired & MAY_READ) r = 1;
if (desired & MAY_WRITE) w = 1;
if (desired & MAY_EXEC) x = 1;
name = inode_name(ino);
if (name == NULL)
return -ENOMEM;
if (S_ISCHR(ino->i_mode) || S_ISBLK(ino->i_mode) ||
S_ISFIFO(ino->i_mode) || S_ISSOCK(ino->i_mode))
err = 0;
else
err = access_file(name, r, w, x);
__putname(name);
if (!err)
err = generic_permission(&nop_mnt_idmap, ino, desired);
return err;
}
static int hostfs_setattr(struct mnt_idmap *idmap,
struct dentry *dentry, struct iattr *attr)
{
struct inode *inode = d_inode(dentry);
struct hostfs_iattr attrs;
char *name;
int err;
int fd = HOSTFS_I(inode)->fd;
err = setattr_prepare(&nop_mnt_idmap, dentry, attr);
if (err)
return err;
if (append)
attr->ia_valid &= ~ATTR_SIZE;
attrs.ia_valid = 0;
if (attr->ia_valid & ATTR_MODE) {
attrs.ia_valid |= HOSTFS_ATTR_MODE;
attrs.ia_mode = attr->ia_mode;
}
if (attr->ia_valid & ATTR_UID) {
attrs.ia_valid |= HOSTFS_ATTR_UID;
attrs.ia_uid = from_kuid(&init_user_ns, attr->ia_uid);
}
if (attr->ia_valid & ATTR_GID) {
attrs.ia_valid |= HOSTFS_ATTR_GID;
attrs.ia_gid = from_kgid(&init_user_ns, attr->ia_gid);
}
if (attr->ia_valid & ATTR_SIZE) {
attrs.ia_valid |= HOSTFS_ATTR_SIZE;
attrs.ia_size = attr->ia_size;
}
if (attr->ia_valid & ATTR_ATIME) {
attrs.ia_valid |= HOSTFS_ATTR_ATIME;
attrs.ia_atime = (struct hostfs_timespec)
{ attr->ia_atime.tv_sec, attr->ia_atime.tv_nsec };
}
if (attr->ia_valid & ATTR_MTIME) {
attrs.ia_valid |= HOSTFS_ATTR_MTIME;
attrs.ia_mtime = (struct hostfs_timespec)
{ attr->ia_mtime.tv_sec, attr->ia_mtime.tv_nsec };
}
if (attr->ia_valid & ATTR_CTIME) {
attrs.ia_valid |= HOSTFS_ATTR_CTIME;
attrs.ia_ctime = (struct hostfs_timespec)
{ attr->ia_ctime.tv_sec, attr->ia_ctime.tv_nsec };
}
if (attr->ia_valid & ATTR_ATIME_SET) {
attrs.ia_valid |= HOSTFS_ATTR_ATIME_SET;
}
if (attr->ia_valid & ATTR_MTIME_SET) {
attrs.ia_valid |= HOSTFS_ATTR_MTIME_SET;
}
name = dentry_name(dentry);
if (name == NULL)
return -ENOMEM;
err = set_attr(name, &attrs, fd);
__putname(name);
if (err)
return err;
if ((attr->ia_valid & ATTR_SIZE) &&
attr->ia_size != i_size_read(inode))
truncate_setsize(inode, attr->ia_size);
setattr_copy(&nop_mnt_idmap, inode, attr);
mark_inode_dirty(inode);
return 0;
}
static const struct inode_operations hostfs_iops = {
.permission = hostfs_permission,
.setattr = hostfs_setattr,
};
static const struct inode_operations hostfs_dir_iops = {
.create = hostfs_create,
.lookup = hostfs_lookup,
.link = hostfs_link,
.unlink = hostfs_unlink,
.symlink = hostfs_symlink,
.mkdir = hostfs_mkdir,
.rmdir = hostfs_rmdir,
.mknod = hostfs_mknod,
.rename = hostfs_rename2,
.permission = hostfs_permission,
.setattr = hostfs_setattr,
};
static const char *hostfs_get_link(struct dentry *dentry,
struct inode *inode,
struct delayed_call *done)
{
char *link;
if (!dentry)
return ERR_PTR(-ECHILD);
link = kmalloc(PATH_MAX, GFP_KERNEL);
if (link) {
char *path = dentry_name(dentry);
int err = -ENOMEM;
if (path) {
err = hostfs_do_readlink(path, link, PATH_MAX);
if (err == PATH_MAX)
err = -E2BIG;
__putname(path);
}
if (err < 0) {
kfree(link);
return ERR_PTR(err);
}
} else {
return ERR_PTR(-ENOMEM);
}
set_delayed_call(done, kfree_link, link);
return link;
}
static const struct inode_operations hostfs_link_iops = {
.get_link = hostfs_get_link,
};
static int hostfs_fill_super(struct super_block *sb, struct fs_context *fc)
{
struct hostfs_fs_info *fsi = sb->s_fs_info;
struct inode *root_inode;
int err;
sb->s_blocksize = 1024;
sb->s_blocksize_bits = 10;
sb->s_magic = HOSTFS_SUPER_MAGIC;
sb->s_op = &hostfs_sbops;
sb->s_d_flags = DCACHE_DONTCACHE;
sb->s_maxbytes = MAX_LFS_FILESIZE;
err = super_setup_bdi(sb);
if (err)
return err;
root_inode = hostfs_iget(sb, fsi->host_root_path);
if (IS_ERR(root_inode))
return PTR_ERR(root_inode);
if (S_ISLNK(root_inode->i_mode)) {
char *name;
iput(root_inode);
name = follow_link(fsi->host_root_path);
if (IS_ERR(name))
return PTR_ERR(name);
root_inode = hostfs_iget(sb, name);
kfree(name);
if (IS_ERR(root_inode))
return PTR_ERR(root_inode);
}
sb->s_root = d_make_root(root_inode);
if (sb->s_root == NULL)
return -ENOMEM;
return 0;
}
enum hostfs_parma {
Opt_hostfs,
};
static const struct fs_parameter_spec hostfs_param_specs[] = {
fsparam_string_empty("hostfs", Opt_hostfs),
{}
};
static int hostfs_parse_param(struct fs_context *fc, struct fs_parameter *param)
{
struct hostfs_fs_info *fsi = fc->s_fs_info;
struct fs_parse_result result;
char *host_root, *tmp_root;
int opt;
opt = fs_parse(fc, hostfs_param_specs, param, &result);
if (opt < 0)
return opt;
switch (opt) {
case Opt_hostfs:
host_root = param->string;
if (!*host_root)
break;
tmp_root = kasprintf(GFP_KERNEL, "%s%s",
fsi->host_root_path, host_root);
if (!tmp_root)
return -ENOMEM;
kfree(fsi->host_root_path);
fsi->host_root_path = tmp_root;
break;
}
return 0;
}
static int hostfs_parse_monolithic(struct fs_context *fc, void *data)
{
struct hostfs_fs_info *fsi = fc->s_fs_info;
char *tmp_root, *host_root = (char *)data;
if (host_root == NULL)
return 0;
tmp_root = kasprintf(GFP_KERNEL, "%s%s", fsi->host_root_path, host_root);
if (!tmp_root)
return -ENOMEM;
kfree(fsi->host_root_path);
fsi->host_root_path = tmp_root;
return 0;
}
static int hostfs_fc_get_tree(struct fs_context *fc)
{
return get_tree_nodev(fc, hostfs_fill_super);
}
static void hostfs_fc_free(struct fs_context *fc)
{
struct hostfs_fs_info *fsi = fc->s_fs_info;
if (!fsi)
return;
kfree(fsi->host_root_path);
kfree(fsi);
}
static const struct fs_context_operations hostfs_context_ops = {
.parse_monolithic = hostfs_parse_monolithic,
.parse_param = hostfs_parse_param,
.get_tree = hostfs_fc_get_tree,
.free = hostfs_fc_free,
};
static int hostfs_init_fs_context(struct fs_context *fc)
{
struct hostfs_fs_info *fsi;
fsi = kzalloc_obj(*fsi);
if (!fsi)
return -ENOMEM;
fsi->host_root_path = kasprintf(GFP_KERNEL, "%s/", root_ino);
if (!fsi->host_root_path) {
kfree(fsi);
return -ENOMEM;
}
fc->s_fs_info = fsi;
fc->ops = &hostfs_context_ops;
return 0;
}
static void hostfs_kill_sb(struct super_block *s)
{
kill_anon_super(s);
kfree(s->s_fs_info);
}
static struct file_system_type hostfs_type = {
.owner = THIS_MODULE,
.name = "hostfs",
.init_fs_context = hostfs_init_fs_context,
.kill_sb = hostfs_kill_sb,
.fs_flags = 0,
};
MODULE_ALIAS_FS("hostfs");
static int __init init_hostfs(void)
{
hostfs_inode_cache = KMEM_CACHE(hostfs_inode_info, 0);
if (!hostfs_inode_cache)
return -ENOMEM;
return register_filesystem(&hostfs_type);
}
static void __exit exit_hostfs(void)
{
unregister_filesystem(&hostfs_type);
kmem_cache_destroy(hostfs_inode_cache);
}
module_init(init_hostfs)
module_exit(exit_hostfs)
MODULE_DESCRIPTION("User-Mode Linux Host filesystem");
MODULE_LICENSE("GPL");
