ext4 crypto: migrate into vfs's crypto engine

This patch removes the most parts of internal crypto codes.
And then, it modifies and adds some ext4-specific crypt codes to use the generic
facility.

Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
diff --git a/fs/ext4/ialloc.c b/fs/ext4/ialloc.c
index 3da4cf8..35f3518 100644
--- a/fs/ext4/ialloc.c
+++ b/fs/ext4/ialloc.c
@@ -767,10 +767,10 @@
 	if ((ext4_encrypted_inode(dir) ||
 	     DUMMY_ENCRYPTION_ENABLED(EXT4_SB(dir->i_sb))) &&
 	    (S_ISREG(mode) || S_ISDIR(mode) || S_ISLNK(mode))) {
-		err = ext4_get_encryption_info(dir);
+		err = fscrypt_get_encryption_info(dir);
 		if (err)
 			return ERR_PTR(err);
-		if (ext4_encryption_info(dir) == NULL)
+		if (!fscrypt_has_encryption_key(dir))
 			return ERR_PTR(-EPERM);
 		if (!handle)
 			nblocks += EXT4_DATA_TRANS_BLOCKS(dir->i_sb);
@@ -1115,7 +1115,8 @@
 	}
 
 	if (encrypt) {
-		err = ext4_inherit_context(dir, inode);
+		/* give pointer to avoid set_context with journal ops. */
+		err = fscrypt_inherit_context(dir, inode, &encrypt, true);
 		if (err)
 			goto fail_free_drop;
 	}