fscrypt: clean up include file mess

Filesystems have to include different header files based on whether they
are compiled with encryption support or not. That's nasty and messy.

Instead, rationalise the headers so we have a single include fscrypt.h
and let it decide what internal implementation to include based on the
__FS_HAS_ENCRYPTION define.  Filesystems set __FS_HAS_ENCRYPTION to 1
before including linux/fscrypt.h if they are built with encryption
support.  Otherwise, they must set __FS_HAS_ENCRYPTION to 0.

Add guards to prevent fscrypt_supp.h and fscrypt_notsupp.h from being
directly included by filesystems.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
[EB: use 1 and 0 rather than defined/undefined]
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

fs/crypto/fscrypt_private.h

@@ -11,7 +11,8 @@
 #ifndef _FSCRYPT_PRIVATE_H
 #define _FSCRYPT_PRIVATE_H
 
-#include <linux/fscrypt_supp.h>
+#define __FS_HAS_ENCRYPTION 1
+#include <linux/fscrypt.h>
 #include <crypto/hash.h>
 
 /* Encryption parameters */

fs/ext4/ext4.h

@@ -33,17 +33,15 @@
 #include <linux/percpu_counter.h>
 #include <linux/ratelimit.h>
 #include <crypto/hash.h>
-#ifdef CONFIG_EXT4_FS_ENCRYPTION
-#include <linux/fscrypt_supp.h>
-#else
-#include <linux/fscrypt_notsupp.h>
-#endif
 #include <linux/falloc.h>
 #include <linux/percpu-rwsem.h>
 #ifdef __KERNEL__
 #include <linux/compat.h>
 #endif
 
+#define __FS_HAS_ENCRYPTION IS_ENABLED(CONFIG_EXT4_FS_ENCRYPTION)
+#include <linux/fscrypt.h>
+
 /*
  * The fourth extended filesystem constants/structures
  */

fs/f2fs/f2fs.h

@@ -23,13 +23,11 @@
 #include <linux/bio.h>
 #include <linux/blkdev.h>
 #include <linux/quotaops.h>
-#ifdef CONFIG_F2FS_FS_ENCRYPTION
-#include <linux/fscrypt_supp.h>
-#else
-#include <linux/fscrypt_notsupp.h>
-#endif
 #include <crypto/hash.h>
 
+#define __FS_HAS_ENCRYPTION IS_ENABLED(CONFIG_F2FS_FS_ENCRYPTION)
+#include <linux/fscrypt.h>
+
 #ifdef CONFIG_F2FS_CHECK_FS
 #define f2fs_bug_on(sbi, condition)	BUG_ON(condition)
 #else

fs/ubifs/ubifs.h

@@ -38,12 +38,11 @@
 #include <linux/backing-dev.h>
 #include <linux/security.h>
 #include <linux/xattr.h>
-#ifdef CONFIG_UBIFS_FS_ENCRYPTION
-#include <linux/fscrypt_supp.h>
-#else
-#include <linux/fscrypt_notsupp.h>
-#endif
 #include <linux/random.h>
+
+#define __FS_HAS_ENCRYPTION IS_ENABLED(CONFIG_UBIFS_FS_ENCRYPTION)
+#include <linux/fscrypt.h>
+
 #include "ubifs-media.h"
 
 /* Version of this UBIFS implementation */

include/linux/fscrypt_common.h → include/linux/fscrypt.h

@@ -1,14 +1,17 @@
 /*
- * fscrypt_common.h: common declarations for per-file encryption
+ * fscrypt.h: declarations for per-file encryption
+ *
+ * Filesystems that implement per-file encryption include this header
+ * file with the __FS_HAS_ENCRYPTION set according to whether that filesystem
+ * is being built with encryption support or not.
  *
  * Copyright (C) 2015, Google, Inc.
  *
  * Written by Michael Halcrow, 2015.
  * Modified by Jaegeuk Kim, 2015.
  */
-
-#ifndef _LINUX_FSCRYPT_COMMON_H
-#define _LINUX_FSCRYPT_COMMON_H
+#ifndef _LINUX_FSCRYPT_H
+#define _LINUX_FSCRYPT_H
 
 #include <linux/key.h>
 #include <linux/fs.h>
@@ -119,23 +122,35 @@ static inline bool fscrypt_is_dot_dotdot(const struct qstr *str)
 	return false;
 }
 
+#if __FS_HAS_ENCRYPTION
+
 static inline struct page *fscrypt_control_page(struct page *page)
 {
-#if IS_ENABLED(CONFIG_FS_ENCRYPTION)
 	return ((struct fscrypt_ctx *)page_private(page))->w.control_page;
-#else
+}
+
+static inline bool fscrypt_has_encryption_key(const struct inode *inode)
+{
+	return (inode->i_crypt_info != NULL);
+}
+
+#include <linux/fscrypt_supp.h>
+
+#else /* !__FS_HAS_ENCRYPTION */
+
+static inline struct page *fscrypt_control_page(struct page *page)
+{
 	WARN_ON_ONCE(1);
 	return ERR_PTR(-EINVAL);
-#endif
 }
 
-static inline int fscrypt_has_encryption_key(const struct inode *inode)
+static inline bool fscrypt_has_encryption_key(const struct inode *inode)
 {
-#if IS_ENABLED(CONFIG_FS_ENCRYPTION)
-	return (inode->i_crypt_info != NULL);
-#else
 	return 0;
-#endif
 }
 
-#endif	/* _LINUX_FSCRYPT_COMMON_H */
+#include <linux/fscrypt_notsupp.h>
+#endif /* __FS_HAS_ENCRYPTION */
+
+
+#endif	/* _LINUX_FSCRYPT_H */

include/linux/fscrypt_notsupp.h

@@ -3,13 +3,16 @@
  *
  * This stubs out the fscrypt functions for filesystems configured without
  * encryption support.
+ *
+ * Do not include this file directly. Use fscrypt.h instead!
  */
+#ifndef _LINUX_FSCRYPT_H
+#error "Incorrect include of linux/fscrypt_notsupp.h!"
+#endif
 
 #ifndef _LINUX_FSCRYPT_NOTSUPP_H
 #define _LINUX_FSCRYPT_NOTSUPP_H
 
-#include <linux/fscrypt_common.h>
-
 /* crypto.c */
 static inline struct fscrypt_ctx *fscrypt_get_ctx(const struct inode *inode,
 						  gfp_t gfp_flags)

include/linux/fscrypt_supp.h

@@ -1,14 +1,15 @@
 /*
  * fscrypt_supp.h
  *
- * This is included by filesystems configured with encryption support.
+ * Do not include this file directly. Use fscrypt.h instead!
  */
+#ifndef _LINUX_FSCRYPT_H
+#error "Incorrect include of linux/fscrypt_supp.h!"
+#endif
 
 #ifndef _LINUX_FSCRYPT_SUPP_H
 #define _LINUX_FSCRYPT_SUPP_H
 
-#include <linux/fscrypt_common.h>
-
 /* crypto.c */
 extern struct kmem_cache *fscrypt_info_cachep;
 extern struct fscrypt_ctx *fscrypt_get_ctx(const struct inode *, gfp_t);