fscrypt: make fscrypt_operations.max_namelen an integer

Now ->max_namelen() is only called to limit the filename length when
adding NUL padding, and only for real filenames -- not symlink targets.
It also didn't give the correct length for symlink targets anyway since
it forgot to subtract 'sizeof(struct fscrypt_symlink_data)'.

Thus, change ->max_namelen from a function to a simple 'unsigned int'
that gives the filesystem's maximum filename length.

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

fs/crypto/fname.c

@@ -333,7 +333,7 @@ int fscrypt_setup_filename(struct inode *dir, const struct qstr *iname,
 
 	if (dir->i_crypt_info) {
 		if (!fscrypt_fname_encrypted_size(dir, iname->len,
-						  dir->i_sb->s_cop->max_namelen(dir),
+						  dir->i_sb->s_cop->max_namelen,
 						  &fname->crypto_buf.len))
 			return -ENAMETOOLONG;
 		fname->crypto_buf.name = kmalloc(fname->crypto_buf.len,

fs/f2fs/super.c

@@ -1938,19 +1938,13 @@ static bool f2fs_dummy_context(struct inode *inode)
 	return DUMMY_ENCRYPTION_ENABLED(F2FS_I_SB(inode));
 }
 
-static unsigned f2fs_max_namelen(struct inode *inode)
-{
-	return S_ISLNK(inode->i_mode) ?
-			inode->i_sb->s_blocksize : F2FS_NAME_LEN;
-}
-
 static const struct fscrypt_operations f2fs_cryptops = {
 	.key_prefix	= "f2fs:",
 	.get_context	= f2fs_get_context,
 	.set_context	= f2fs_set_context,
 	.dummy_context	= f2fs_dummy_context,
 	.empty_dir	= f2fs_empty_dir,
-	.max_namelen	= f2fs_max_namelen,
+	.max_namelen	= F2FS_NAME_LEN,
 };
 #endif
 

include/linux/fscrypt_supp.h

@@ -28,7 +28,7 @@ struct fscrypt_operations {
 	int (*set_context)(struct inode *, const void *, size_t, void *);
 	bool (*dummy_context)(struct inode *);
 	bool (*empty_dir)(struct inode *);
-	unsigned (*max_namelen)(struct inode *);
+	unsigned int max_namelen;
 };
 
 struct fscrypt_ctx {