Merge tag 'fscrypt_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/fscrypt

Pull fscrypt updates from Ted Ts'o:
 "Refactor support for encrypted symlinks to move common code to fscrypt"

Ted also points out about the merge:
 "This makes the f2fs symlink code use the fscrypt_encrypt_symlink()
  from the fscrypt tree. This will end up dropping the kzalloc() ->
  f2fs_kzalloc() change, which means the fscrypt-specific allocation
  won't get tested by f2fs's kmalloc error injection system; which is
  fine"

* tag 'fscrypt_for_linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tytso/fscrypt: (26 commits)
  fscrypt: fix build with pre-4.6 gcc versions
  fscrypt: remove 'ci' parameter from fscrypt_put_encryption_info()
  fscrypt: document symlink length restriction
  fscrypt: fix up fscrypt_fname_encrypted_size() for internal use
  fscrypt: define fscrypt_fname_alloc_buffer() to be for presented names
  fscrypt: calculate NUL-padding length in one place only
  fscrypt: move fscrypt_symlink_data to fscrypt_private.h
  fscrypt: remove fscrypt_fname_usr_to_disk()
  ubifs: switch to fscrypt_get_symlink()
  ubifs: switch to fscrypt ->symlink() helper functions
  ubifs: free the encrypted symlink target
  f2fs: switch to fscrypt_get_symlink()
  f2fs: switch to fscrypt ->symlink() helper functions
  ext4: switch to fscrypt_get_symlink()
  ext4: switch to fscrypt ->symlink() helper functions
  fscrypt: new helper function - fscrypt_get_symlink()
  fscrypt: new helper functions for ->symlink()
  fscrypt: trim down fscrypt.h includes
  fscrypt: move fscrypt_is_dot_dotdot() to fs/crypto/fname.c
  fscrypt: move fscrypt_valid_enc_modes() to fscrypt_private.h
  ...

Documentation/filesystems/fscrypt.rst

@@ -448,8 +448,14 @@ astute users may notice some differences in behavior:
 
 - The st_size of an encrypted symlink will not necessarily give the
   length of the symlink target as required by POSIX.  It will actually
-  give the length of the ciphertext, which may be slightly longer than
-  the plaintext due to the NUL-padding.
+  give the length of the ciphertext, which will be slightly longer
+  than the plaintext due to NUL-padding and an extra 2-byte overhead.
+
+- The maximum length of an encrypted symlink is 2 bytes shorter than
+  the maximum length of an unencrypted symlink.  For example, on an
+  EXT4 filesystem with a 4K block size, unencrypted symlinks can be up
+  to 4095 bytes long, while encrypted symlinks can only be up to 4093
+  bytes long (both lengths excluding the terminating null).
 
 Note that mmap *is* supported.  This is possible because the pagecache
 for an encrypted file contains the plaintext, not the ciphertext.