From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-vk0-f70.google.com (mail-vk0-f70.google.com [209.85.213.70]) by kanga.kvack.org (Postfix) with ESMTP id 450A16B0038 for ; Tue, 18 Oct 2016 10:54:50 -0400 (EDT) Received: by mail-vk0-f70.google.com with SMTP id t22so163459413vkb.7 for ; Tue, 18 Oct 2016 07:54:50 -0700 (PDT) Received: from mail-qk0-x244.google.com (mail-qk0-x244.google.com. [2607:f8b0:400d:c09::244]) by mx.google.com with ESMTPS id e70si18049580vkf.89.2016.10.18.07.54.49 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 18 Oct 2016 07:54:49 -0700 (PDT) Received: by mail-qk0-x244.google.com with SMTP id v138so17057921qka.2 for ; Tue, 18 Oct 2016 07:54:49 -0700 (PDT) MIME-Version: 1.0 In-Reply-To: References: <1476776569-29504-1-git-send-email-zhongjiang@huawei.com> From: Vitaly Wool Date: Tue, 18 Oct 2016 16:54:48 +0200 Message-ID: Subject: Re: [PATCH] z3fold: limit first_num to the actual range of possible buddy indexes Content-Type: text/plain; charset=UTF-8 Sender: owner-linux-mm@kvack.org List-ID: To: Dan Streetman Cc: zhongjiang , Andrew Morton , Dave Chinner , linux-kernel , Linux-MM On Tue, Oct 18, 2016 at 3:57 PM, Dan Streetman wrote: > On Tue, Oct 18, 2016 at 3:42 AM, zhongjiang wrote: >> 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 > > Acked-by: Dan Streetman Acked-by: Vitaly Wool >> ---> 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