From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from acsinet15.oracle.com ([141.146.126.227]:38562 "EHLO acsinet15.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754624Ab2JRIrs (ORCPT ); Thu, 18 Oct 2012 04:47:48 -0400 Message-ID: <507FC228.4050400@oracle.com> Date: Thu, 18 Oct 2012 16:47:36 +0800 From: Liu Bo MIME-Version: 1.0 To: miaox@cn.fujitsu.com CC: Linux Btrfs Subject: Re: [PATCH V2] Btrfs: fix unnecessary while loop when search the free space, cache References: <507FB7A6.70805@cn.fujitsu.com> <507FBB39.5090603@cn.fujitsu.com> In-Reply-To: <507FBB39.5090603@cn.fujitsu.com> Content-Type: text/plain; charset=UTF-8 Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 10/18/2012 04:18 PM, Miao Xie wrote: > When we find a bitmap free space entry, we may check the previous extent > entry covers the offset or not. But if we find this entry is also a bitmap > entry, we will continue to check the previous entry of the current one by > a while loop. It is unnecessary because it is impossible that the extent > entry which is in front of a bitmap entry can cover the offset of the entry > after that bitmap entry. > Looks good to me. Reviewed-by: Liu Bo > Signed-off-by: Miao Xie > --- > Changelog v1 -> v2: > - fix the same problem in the other place > --- > fs/btrfs/free-space-cache.c | 30 ++++++++++-------------------- > 1 files changed, 10 insertions(+), 20 deletions(-) > > diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c > index 1027b85..557502c 100644 > --- a/fs/btrfs/free-space-cache.c > +++ b/fs/btrfs/free-space-cache.c > @@ -1250,18 +1250,13 @@ tree_search_offset(struct btrfs_free_space_ctl *ctl, > * if previous extent entry covers the offset, > * we should return it instead of the bitmap entry > */ > - n = &entry->offset_index; > - while (1) { > - n = rb_prev(n); > - if (!n) > - break; > + n = rb_prev(&entry->offset_index); > + if (n) { > prev = rb_entry(n, struct btrfs_free_space, > offset_index); > - if (!prev->bitmap) { > - if (prev->offset + prev->bytes > offset) > - entry = prev; > - break; > - } > + if (!prev->bitmap && > + prev->offset + prev->bytes > offset) > + entry = prev; > } > } > return entry; > @@ -1287,18 +1282,13 @@ tree_search_offset(struct btrfs_free_space_ctl *ctl, > } > > if (entry->bitmap) { > - n = &entry->offset_index; > - while (1) { > - n = rb_prev(n); > - if (!n) > - break; > + n = rb_prev(&entry->offset_index); > + if (n) { > prev = rb_entry(n, struct btrfs_free_space, > offset_index); > - if (!prev->bitmap) { > - if (prev->offset + prev->bytes > offset) > - return prev; > - break; > - } > + if (!prev->bitmap && > + prev->offset + prev->bytes > offset) > + return prev; > } > if (entry->offset + BITS_PER_BITMAP * ctl->unit > offset) > return entry; >