From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-oi0-f72.google.com (mail-oi0-f72.google.com [209.85.218.72]) by kanga.kvack.org (Postfix) with ESMTP id E16FC6B0038 for ; Tue, 18 Oct 2016 03:50:42 -0400 (EDT) Received: by mail-oi0-f72.google.com with SMTP id e200so416091912oig.4 for ; Tue, 18 Oct 2016 00:50:42 -0700 (PDT) Received: from szxga03-in.huawei.com (szxga03-in.huawei.com. [119.145.14.66]) by mx.google.com with ESMTPS id l125si13429689oia.86.2016.10.18.00.50.41 for (version=TLS1 cipher=AES128-SHA bits=128/128); Tue, 18 Oct 2016 00:50:42 -0700 (PDT) From: zhongjiang Subject: [PATCH] z3fold: limit first_num to the actual range of possible buddy indexes Date: Tue, 18 Oct 2016 15:42:49 +0800 Message-ID: <1476776569-29504-1-git-send-email-zhongjiang@huawei.com> MIME-Version: 1.0 Content-Type: text/plain Sender: owner-linux-mm@kvack.org List-ID: To: ddstreet@ieee.org, akpm@linux-foundation.org, david@fromorbit.com Cc: vitalywool@gmail.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org From: zhong jiang At present, Tying the first_num size to NCHUNKS_ORDER is confusing. the number of chunks is completely unrelated to the number of buddies. The patch limit the first_num to actual range of possible buddy indexes. and that is more reasonable and obvious without functional change. Suggested-by: Dan Streetman Signed-off-by: zhong jiang --- mm/z3fold.c | 10 +++++++--- 1 file changed, 7 insertions(+), 3 deletions(-) diff --git a/mm/z3fold.c b/mm/z3fold.c index 8f9e89c..207e5dd 100644 --- a/mm/z3fold.c +++ b/mm/z3fold.c @@ -50,7 +50,7 @@ #define ZHDR_SIZE_ALIGNED CHUNK_SIZE #define NCHUNKS ((PAGE_SIZE - ZHDR_SIZE_ALIGNED) >> CHUNK_SHIFT) -#define BUDDY_MASK ((1 << NCHUNKS_ORDER) - 1) +#define BUDDY_MASK (0x3) struct z3fold_pool; struct z3fold_ops { @@ -109,7 +109,7 @@ struct z3fold_header { unsigned short middle_chunks; unsigned short last_chunks; unsigned short start_middle; - unsigned short first_num:NCHUNKS_ORDER; + unsigned short first_num:2; }; /* @@ -179,7 +179,11 @@ static struct z3fold_header *handle_to_z3fold_header(unsigned long handle) return (struct z3fold_header *)(handle & PAGE_MASK); } -/* Returns buddy number */ +/* + * (handle & BUDDY_MASK) < zhdr->first_num is possible in encode_handle + * but that doesn't matter. because the masking will result in the + * correct buddy number. + */ static enum buddy handle_to_buddy(unsigned long handle) { struct z3fold_header *zhdr = handle_to_z3fold_header(handle); -- 1.8.3.1 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org