From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from userp1040.oracle.com ([156.151.31.81]:32499 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752710AbdBVAIO (ORCPT ); Tue, 21 Feb 2017 19:08:14 -0500 Date: Tue, 21 Feb 2017 16:07:56 -0800 From: Liu Bo To: fdmanana@kernel.org Cc: linux-btrfs@vger.kernel.org Subject: Re: [PATCH] Btrfs: try harder to migrate items to left sibling before splitting a leaf Message-ID: <20170222000756.GD32725@lim.localdomain> Reply-To: bo.li.liu@oracle.com References: <1487537799-17570-1-git-send-email-fdmanana@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <1487537799-17570-1-git-send-email-fdmanana@kernel.org> Sender: linux-btrfs-owner@vger.kernel.org List-ID: On Sun, Feb 19, 2017 at 08:56:39PM +0000, fdmanana@kernel.org wrote: > From: Filipe Manana > > Before attempting to split a leaf we try to migrate items from the leaf to > its right and left siblings. We start by trying to move items into the > rigth sibling and, if the new item is meant to be inserted at the end of > our leaf, we try to free from our leaf an amount of bytes equal to the > number of bytes used by the new item, by setting the variable space_needed > to the byte size of that new item. However if we fail to move enough items > to the right sibling due to lack of space in that sibling, we then try > to move items into the left sibling, and in that case we try to free > an amount equal to the size of the new item from our leaf, when we need > only to free an amount corresponding to the size of the new item minus > the current free space of our leaf. So make sure that before we try to > move items to the left sibling we do set the variable space_needed with > a value corresponding to the new item's size minus the leaf's current > free space. > > Signed-off-by: Filipe Manana > --- > fs/btrfs/ctree.c | 7 +++++++ > 1 file changed, 7 insertions(+) > > diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c > index a426dc8..1d66761 100644 > --- a/fs/btrfs/ctree.c > +++ b/fs/btrfs/ctree.c > @@ -4160,6 +4160,9 @@ static noinline int push_for_double_split(struct btrfs_trans_handle *trans, > > /* try to push all the items before our slot into the next leaf */ > slot = path->slots[0]; > + space_needed = data_size; > + if (slot > 0) > + space_needed -= btrfs_leaf_free_space(fs_info, path->nodes[0]); Good point. > ret = push_leaf_left(trans, root, path, 1, space_needed, 0, slot); > if (ret < 0) > return ret; > @@ -4215,6 +4218,10 @@ static noinline int split_leaf(struct btrfs_trans_handle *trans, > if (wret < 0) > return wret; > if (wret) { > + space_needed = data_size; > + if (slot > 0) > + space_needed -= btrfs_leaf_free_space(fs_info, > + l); Not sure if we need this, the above push_leaf_right() was called with @min_data_size == space_needed, thus if @wret == 1, no items have been moved in push_leaf_right() so that leaf 'l' remains unchanged. Thanks, -liubo > wret = push_leaf_left(trans, root, path, space_needed, > space_needed, 0, (u32)-1); > if (wret < 0) > -- > 2.7.0.rc3 > > -- > 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