fs-verity: add inode and superblock fields
Analogous to fs/crypto/, add fields to the VFS inode and superblock for
use by the fs/verity/ support layer:
- ->s_vop: points to the fsverity_operations if the filesystem supports
fs-verity, otherwise is NULL.
- ->i_verity_info: points to cached fs-verity information for the inode
after someone opens it, otherwise is NULL.
- S_VERITY: bit in ->i_flags that identifies verity inodes, even when
they haven't been opened yet and thus still have NULL ->i_verity_info.
Reviewed-by: Theodore Ts'o <tytso@mit.edu>
Reviewed-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>