/*
* devpts_mount()
*
* If the '-o newinstance' mount option was specified, mount a new
* (private) instance of devpts. PTYs created in this instance are
* independent of the PTYs in other devpts instances.
*
* If the '-o newinstance' option was not specified, mount/remount the
* initial kernel mount of devpts. This type of mount gives the
* legacy, single-instance semantics.
*
* The 'newinstance' option is needed to support multiple namespace
* semantics in devpts while preserving backward compatibility of the
* current 'single-namespace' semantics. i.e all mounts of devpts
* without the 'newinstance' mount option should bind to the initial
* kernel mount, like mount_single().
*
* Mounts with 'newinstance' option create a new, private namespace.
*
* NOTE:
*
* For single-mount semantics, devpts cannot use mount_single(),
* because mount_single()/sget() find and use the super-block from
* the most recent mount of devpts. But that recent mount may be a
* 'newinstance' mount and mount_single() would pick the newinstance
* super-block instead of the initial super-block.
*/
static struct dentry *devpts_mount(struct file_system_type *fs_type,
int flags, const char *dev_name, void *data)
{
int error;
struct pts_mount_opts opts;
struct super_block *s;
error = parse_mount_options(data, PARSE_MOUNT, &opts);
if (error)
return ERR_PTR(error);
/* Require newinstance for all user namespace mounts to ensure
* the mount options are not changed.
*/
if ((current_user_ns() != &init_user_ns) && !opts.newinstance)
return ERR_PTR(-EINVAL);
if (opts.newinstance)
s = sget(fs_type, NULL, set_anon_super, flags, NULL);
else
s = sget(fs_type, compare_init_pts_sb, set_anon_super, flags,
NULL);
if (IS_ERR(s))
return ERR_CAST(s);
if (!s->s_root) {
error = devpts_fill_super(s, data, flags & MS_SILENT ? 1 : 0);
if (error)
goto out_undo_sget;
s->s_flags |= MS_ACTIVE;
}
memcpy(&(DEVPTS_SB(s))->mount_opts, &opts, sizeof(opts));
error = mknod_ptmx(s);
if (error)
goto out_undo_sget;
return dget(s->s_root);
out_undo_sget:
deactivate_locked_super(s);
return ERR_PTR(error);
}
/*
* devpts_get_sb()
*
* If the '-o newinstance' mount option was specified, mount a new
* (private) instance of devpts. PTYs created in this instance are
* independent of the PTYs in other devpts instances.
*
* If the '-o newinstance' option was not specified, mount/remount the
* initial kernel mount of devpts. This type of mount gives the
* legacy, single-instance semantics.
*
* The 'newinstance' option is needed to support multiple namespace
* semantics in devpts while preserving backward compatibility of the
* current 'single-namespace' semantics. i.e all mounts of devpts
* without the 'newinstance' mount option should bind to the initial
* kernel mount, like get_sb_single().
*
* Mounts with 'newinstance' option create a new, private namespace.
*
* NOTE:
*
* For single-mount semantics, devpts cannot use get_sb_single(),
* because get_sb_single()/sget() find and use the super-block from
* the most recent mount of devpts. But that recent mount may be a
* 'newinstance' mount and get_sb_single() would pick the newinstance
* super-block instead of the initial super-block.
*/
static int devpts_get_sb(struct file_system_type *fs_type,
int flags, const char *dev_name, void *data, struct vfsmount *mnt)
{
int error;
struct pts_mount_opts opts;
struct super_block *s;
error = parse_mount_options(data, PARSE_MOUNT, &opts);
if (error)
return error;
if (opts.newinstance)
s = sget(fs_type, NULL, set_anon_super, NULL);
else
s = sget(fs_type, compare_init_pts_sb, set_anon_super, NULL);
if (IS_ERR(s))
return PTR_ERR(s);
if (!s->s_root) {
s->s_flags = flags;
error = devpts_fill_super(s, data, flags & MS_SILENT ? 1 : 0);
if (error)
goto out_undo_sget;
s->s_flags |= MS_ACTIVE;
}
simple_set_mnt(mnt, s);
memcpy(&(DEVPTS_SB(s))->mount_opts, &opts, sizeof(opts));
error = mknod_ptmx(s);
if (error)
goto out_dput;
return 0;
out_dput:
dput(s->s_root); /* undo dget() in simple_set_mnt() */
out_undo_sget:
deactivate_locked_super(s);
return error;
}