From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from userp1040.oracle.com ([156.151.31.81]:38997 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751773AbbHGIux (ORCPT ); Fri, 7 Aug 2015 04:50:53 -0400 Received: from userv0022.oracle.com (userv0022.oracle.com [156.151.31.74]) by userp1040.oracle.com (Sentrion-MTA-4.3.2/Sentrion-MTA-4.3.2) with ESMTP id t778oqT4019821 (version=TLSv1 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Fri, 7 Aug 2015 08:50:52 GMT Received: from userv0121.oracle.com (userv0121.oracle.com [156.151.31.72]) by userv0022.oracle.com (8.13.8/8.13.8) with ESMTP id t778oql6024274 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=FAIL) for ; Fri, 7 Aug 2015 08:50:52 GMT Received: from abhmp0017.oracle.com (abhmp0017.oracle.com [141.146.116.23]) by userv0121.oracle.com (8.13.8/8.13.8) with ESMTP id t778opVx026725 for ; Fri, 7 Aug 2015 08:50:52 GMT Date: Fri, 7 Aug 2015 16:50:45 +0800 From: Liu Bo To: linux-btrfs@vger.kernel.org Subject: Re: [PATCH] Btrfs: fix defrag to merge tail file extent Message-ID: <20150807085045.GB8887@localhost.localdomain> Reply-To: bo.li.liu@oracle.com References: <1438937321-19042-1-git-send-email-bo.li.liu@oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <1438937321-19042-1-git-send-email-bo.li.liu@oracle.com> Sender: linux-btrfs-owner@vger.kernel.org List-ID: Writing a xfstests case for this, will come soon. Thanks, -liubo On Fri, Aug 07, 2015 at 04:48:41PM +0800, Liu Bo wrote: > The file layout is > > [extent 1]...[extent n][4k extent][HOLE][extent x] > > extent 1~n and 4k extent can be merged during defrag, and the whole > defrag bytes is larger than our defrag thresh(256k), 4k extent as a > tail is left unmerged since we check if its next extent can be merged > (the next one is a hole, so the check will fail), the layout thus can > be > > [new extent][4k extent][HOLE][extent x] > (1~n) > > To fix it, beside looking at the next one, this also looks at the > previous one by checking @defrag_end, which is set to 0 when we > decide to stop merging contiguous extents, otherwise, we can merge > the previous one with our extent. > > Also, this makes btrfs behave consistent with how xfs and ext4 do. > > Signed-off-by: Liu Bo > --- > fs/btrfs/ioctl.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) > > diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c > index 0770c91..0691b2b 100644 > --- a/fs/btrfs/ioctl.c > +++ b/fs/btrfs/ioctl.c > @@ -1030,6 +1030,7 @@ static int should_defrag_range(struct inode *inode, u64 start, u32 thresh, > struct extent_map *em; > int ret = 1; > bool next_mergeable = true; > + bool prev_mergeable = true; > > /* > * make sure that once we start defragging an extent, we keep on > @@ -1050,13 +1051,16 @@ static int should_defrag_range(struct inode *inode, u64 start, u32 thresh, > goto out; > } > > + if (!*defrag_end) > + prev_mergeable = false; > + > next_mergeable = defrag_check_next_extent(inode, em); > /* > * we hit a real extent, if it is big or the next extent is not a > * real extent, don't bother defragging it > */ > if (!compress && (*last_len == 0 || *last_len >= thresh) && > - (em->len >= thresh || !next_mergeable)) > + (em->len >= thresh || (!next_mergeable && !prev_mergeable))) > ret = 0; > out: > /* > -- > 2.1.0 > > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html