diff options
| -rw-r--r-- | fs/devpts/inode.c | 55 |
1 files changed, 54 insertions, 1 deletions
diff --git a/fs/devpts/inode.c b/fs/devpts/inode.c index 8ee9dc2f9e48..2d0eb2cf99e6 100644 --- a/fs/devpts/inode.c +++ b/fs/devpts/inode.c @@ -305,10 +305,63 @@ fail: return -ENOMEM; } +static int compare_init_pts_sb(struct super_block *s, void *p) +{ + if (devpts_mnt) + return devpts_mnt->mnt_sb == s; + + return 0; +} + +/* + * get_init_pts_sb() + * + * This interface 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. + * + * But 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. + * + * This interface is identical to get_sb_single() except that it + * consistently selects the 'single-namespace' superblock even in the + * presence of the private namespace (i.e 'newinstance') super-blocks. + */ +static int get_init_pts_sb(struct file_system_type *fs_type, int flags, + void *data, struct vfsmount *mnt) +{ + struct super_block *s; + int error; + + 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) { + up_write(&s->s_umount); + deactivate_super(s); + return error; + } + s->s_flags |= MS_ACTIVE; + } + do_remount_sb(s, flags, data, 0); + return simple_set_mnt(mnt, s); +} + static int devpts_get_sb(struct file_system_type *fs_type, int flags, const char *dev_name, void *data, struct vfsmount *mnt) { - return get_sb_single(fs_type, flags, data, devpts_fill_super, mnt); + return get_init_pts_sb(fs_type, flags, data, mnt); } static void devpts_kill_sb(struct super_block *sb) |