fscrypt_free_filename() only needs to do a kfree() of crypto_buf.name,
which works well as an inline function.  We can skip setting the various
pointers to NULL, since no user cares about it (the name is always freed
just before it goes out of scope).

Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: David Gstir <david@sigma-star.at>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

As I noted on the mailing list, it's easier than I originally thought to
create intentional collisions in the digested names.  Unfortunately it's
not too easy to solve this, so for now just fix the comment to not lie.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

Introduce a helper function fscrypt_match_name() which tests whether a
fscrypt_name matches a directory entry.  Also clean up the magic numbers
and document things properly.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

Previously, each filesystem configured without encryption support would
define all the public fscrypt functions to their notsupp_* stubs.  This
list of #defines had to be updated in every filesystem whenever a change
was made to the public fscrypt functions.  To make things more
maintainable now that we have three filesystems using fscrypt, split the
old header fscrypto.h into several new headers.  fscrypt_supp.h contains
the real declarations and is included by filesystems when configured
with encryption support, whereas fscrypt_notsupp.h contains the inline
stubs and is included by filesystems when configured without encryption
support.  fscrypt_common.h contains common declarations needed by both.

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>