fscrypt: introduce fscrypt_encrypt_block_inplace()

fscrypt_encrypt_page() behaves very differently depending on whether the
filesystem set FS_CFLG_OWN_PAGES in its fscrypt_operations.  This makes
the function difficult to understand and document.  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_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, 13 insertions, 0 deletions

diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h
index 1c7287f146a9..a9b2d26e615d 100644
--- a/include/linux/fscrypt.h
+++ b/include/linux/fscrypt.h
@@ -106,6 +106,10 @@ extern void fscrypt_release_ctx(struct fscrypt_ctx *);
 extern struct page *fscrypt_encrypt_page(const struct inode *, struct page *,
 						unsigned int, unsigned int,
 						u64, gfp_t);
+extern int fscrypt_encrypt_block_inplace(const struct inode *inode,
+					 struct page *page, unsigned int len,
+					 unsigned int offs, u64 lblk_num,
+					 gfp_t gfp_flags);
 extern int fscrypt_decrypt_page(const struct inode *, struct page *, unsigned int,
 				unsigned int, u64);
 
@@ -293,6 +297,15 @@ static inline struct page *fscrypt_encrypt_page(const struct inode *inode,
 	return ERR_PTR(-EOPNOTSUPP);
 }
 
+static inline int fscrypt_encrypt_block_inplace(const struct inode *inode,
+						struct page *page,
+						unsigned int len,
+						unsigned int offs, u64 lblk_num,
+						gfp_t gfp_flags)
+{
+	return -EOPNOTSUPP;
+}
+
 static inline int fscrypt_decrypt_page(const struct inode *inode,
 				       struct page *page,
 				       unsigned int len, unsigned int offs,