ext4 crypto: ext4_page_crypto() doesn't need a encryption context

Since ext4_page_crypto() doesn't need an encryption context (at least
not any more), this allows us to simplify a number function signature
and also allows us to avoid needing to allocate a context in
ext4_block_write_begin().  It also means we no longer need a separate
ext4_decrypt_one() function.

Signed-off-by: Theodore Ts'o <tytso@mit.edu>
diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index c95d406..ae52e32 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -965,7 +965,7 @@
 	if (unlikely(err))
 		page_zero_new_buffers(page, from, to);
 	else if (decrypt)
-		err = ext4_decrypt_one(inode, page);
+		err = ext4_decrypt(page);
 	return err;
 }
 #endif
@@ -3404,7 +3404,7 @@
 			/* We expect the key to be set. */
 			BUG_ON(!ext4_has_encryption_key(inode));
 			BUG_ON(blocksize != PAGE_CACHE_SIZE);
-			WARN_ON_ONCE(ext4_decrypt_one(inode, page));
+			WARN_ON_ONCE(ext4_decrypt(page));
 		}
 	}
 	if (ext4_should_journal_data(inode)) {