eCryptfs: Remove unnecessary grow_file() function

When creating a new eCryptfs file, the crypto metadata is written out
and then the lower file was being "grown" with 4 kB of encrypted zeroes.
I suspect that growing the encrypted file was to prevent an information
leak that the unencrypted file was empty. However, the unencrypted file
size is stored, in plaintext, in the metadata so growing the file is
unnecessary.
Signed-off-by: Tyler Hicks <tyhicks@linux.vnet.ibm.com>

fs/ecryptfs/crypto.c

@@ -1389,6 +1389,7 @@ int ecryptfs_write_metadata(struct dentry *ecryptfs_dentry)
 		rc = -ENOMEM;
 		goto out;
 	}
+	/* Zeroed page ensures the in-header unencrypted i_size is set to 0 */
 	rc = ecryptfs_write_headers_virt(virt, virt_len, &size, crypt_stat,
 					 ecryptfs_dentry);
 	if (unlikely(rc)) {

fs/ecryptfs/inode.c

@@ -142,26 +142,6 @@ ecryptfs_do_create(struct inode *directory_inode,
 	return rc;
 }
 
-/**
- * grow_file
- * @ecryptfs_dentry: the eCryptfs dentry
- *
- * This is the code which will grow the file to its correct size.
- */
-static int grow_file(struct dentry *ecryptfs_dentry)
-{
-	struct inode *ecryptfs_inode = ecryptfs_dentry->d_inode;
-	char zero_virt[] = { 0x00 };
-	int rc = 0;
-
-	rc = ecryptfs_write(ecryptfs_inode, zero_virt, 0, 1);
-	i_size_write(ecryptfs_inode, 0);
-	rc = ecryptfs_write_inode_size_to_metadata(ecryptfs_inode);
-	ecryptfs_inode_to_private(ecryptfs_inode)->crypt_stat.flags |=
-		ECRYPTFS_NEW_FILE;
-	return rc;
-}
-
 /**
  * ecryptfs_initialize_file
  *
@@ -202,9 +182,6 @@ static int ecryptfs_initialize_file(struct dentry *ecryptfs_dentry)
 		printk(KERN_ERR "Error writing headers; rc = [%d]\n", rc);
 		goto out;
 	}
-	rc = grow_file(ecryptfs_dentry);
-	if (rc)
-		printk(KERN_ERR "Error growing file; rc = [%d]\n", rc);
 out:
 	return rc;
 }