From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-11.2 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1917FC43461 for ; Wed, 16 Sep 2020 21:05:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C23E7206BE for ; Wed, 16 Sep 2020 21:05:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726477AbgIPQO5 (ORCPT ); Wed, 16 Sep 2020 12:14:57 -0400 Received: from mx2.suse.de ([195.135.220.15]:60118 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726467AbgIPQOc (ORCPT ); Wed, 16 Sep 2020 12:14:32 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.221.27]) by mx2.suse.de (Postfix) with ESMTP id 4F0F8AFEA; Wed, 16 Sep 2020 16:02:43 +0000 (UTC) Received: by ds.suse.cz (Postfix, from userid 10065) id E0339DA7C7; Wed, 16 Sep 2020 18:01:15 +0200 (CEST) Date: Wed, 16 Sep 2020 18:01:15 +0200 From: David Sterba To: Qu Wenruo Cc: linux-btrfs@vger.kernel.org Subject: Re: [PATCH v2 04/19] btrfs: remove the open-code to read disk-key Message-ID: <20200916160115.GN1791@twin.jikos.cz> Reply-To: dsterba@suse.cz Mail-Followup-To: dsterba@suse.cz, Qu Wenruo , linux-btrfs@vger.kernel.org References: <20200915053532.63279-1-wqu@suse.com> <20200915053532.63279-5-wqu@suse.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200915053532.63279-5-wqu@suse.com> User-Agent: Mutt/1.5.23.1-rc1 (2014-03-12) Sender: linux-btrfs-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-btrfs@vger.kernel.org On Tue, Sep 15, 2020 at 01:35:17PM +0800, Qu Wenruo wrote: > generic_bin_search() distinguishes between reading a key which doesn't > cross a page and one which does. However this distinction is not > necessary since read_extent_buffer handles both cases transparently. > > Just use read_extent_buffer to streamline the code. > > Signed-off-by: Qu Wenruo > --- > fs/btrfs/ctree.c | 13 ++----------- > 1 file changed, 2 insertions(+), 11 deletions(-) > > diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c > index cd1cd673bc0b..e204e1320745 100644 > --- a/fs/btrfs/ctree.c > +++ b/fs/btrfs/ctree.c > @@ -1697,7 +1697,6 @@ static noinline int generic_bin_search(struct extent_buffer *eb, > } > > while (low < high) { > - unsigned long oip; > unsigned long offset; > struct btrfs_disk_key *tmp; > struct btrfs_disk_key unaligned; > @@ -1705,17 +1704,9 @@ static noinline int generic_bin_search(struct extent_buffer *eb, > > mid = (low + high) / 2; > offset = p + mid * item_size; > - oip = offset_in_page(offset); > > - if (oip + key_size <= PAGE_SIZE) { > - const unsigned long idx = offset >> PAGE_SHIFT; > - char *kaddr = page_address(eb->pages[idx]); > - > - tmp = (struct btrfs_disk_key *)(kaddr + oip); > - } else { > - read_extent_buffer(eb, &unaligned, offset, key_size); > - tmp = &unaligned; > - } > + read_extent_buffer(eb, &unaligned, offset, key_size); > + tmp = &unaligned; Reading from the first page is a performance optimization on systems with 4K pages, ie. the majority. I'm not in favor removing it just to make the code look nicer.