fscrypt: introduce fscrypt_decrypt_block_inplace()

Currently fscrypt_decrypt_page() does one of two logically distinct
things depending on whether FS_CFLG_OWN_PAGES is set in the filesystem's
fscrypt_operations: decrypt a pagecache page in-place, or decrypt a
filesystem block in-place in any page.  Currently these happen to share
the same implementation, but this conflates the notion of blocks and
pages.  It also makes it so that all callers have to provide inode and
lblk_num, when fscrypt could determine these itself for pagecache pages.

Therefore, move the FS_CFLG_OWN_PAGES behavior into a new function
fscrypt_decrypt_block_inplace().  This mirrors
fscrypt_encrypt_block_inplace().

This is in preparation for allowing encryption on ext4 filesystems with
blocksize != PAGE_SIZE.

Reviewed-by: Chandan Rajendra <chandan@linux.ibm.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>

1 files changed, 11 insertions, 0 deletions

diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h
index c7e16bd16a6c..315affc99b05 100644
--- a/include/linux/fscrypt.h
+++ b/include/linux/fscrypt.h
@@ -114,6 +114,9 @@ extern int fscrypt_encrypt_block_inplace(const struct inode *inode,
 					 gfp_t gfp_flags);
 extern int fscrypt_decrypt_page(const struct inode *, struct page *, unsigned int,
 				unsigned int, u64);
+extern int fscrypt_decrypt_block_inplace(const struct inode *inode,
+					 struct page *page, unsigned int len,
+					 unsigned int offs, u64 lblk_num);
 
 static inline bool fscrypt_is_bounce_page(struct page *page)
 {
@@ -315,6 +318,14 @@ static inline int fscrypt_decrypt_page(const struct inode *inode,
 	return -EOPNOTSUPP;
 }
 
+static inline int fscrypt_decrypt_block_inplace(const struct inode *inode,
+						struct page *page,
+						unsigned int len,
+						unsigned int offs, u64 lblk_num)
+{
+	return -EOPNOTSUPP;
+}
+
 static inline bool fscrypt_is_bounce_page(struct page *page)
 {
 	return false;