On Fri, Feb 17, 2017 at 07:16:04PM +0000, fdmanana@xxxxxxxxxx wrote:
> From: Filipe Manana <fdmanana@xxxxxxxx>
>
> If we want to append an item to a leaf we were trying to move off from the
> leaf into its neighbors an amount of space corresponding to the item's
> size. That amount of space is too much and can be reduced to the item's
> size minus the amount of free space in the leaf, like we do for all the
> other cases (item inserted at the beginning or somewhere in the middle of
> the leaf).
>
> Signed-off-by: Filipe Manana <fdmanana@xxxxxxxx>
> ---
> fs/btrfs/ctree.c | 12 +++++-------
> 1 file changed, 5 insertions(+), 7 deletions(-)
>
> diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c
> index a426dc8..86be619 100644
> --- a/fs/btrfs/ctree.c
> +++ b/fs/btrfs/ctree.c
> @@ -4130,11 +4130,11 @@ static noinline int push_for_double_split(struct btrfs_trans_handle *trans,
> int progress = 0;
> int slot;
> u32 nritems;
> - int space_needed = data_size;
> + int space_needed;
>
> slot = path->slots[0];
> - if (slot < btrfs_header_nritems(path->nodes[0]))
> - space_needed -= btrfs_leaf_free_space(fs_info, path->nodes[0]);
> + space_needed = data_size -
> + btrfs_leaf_free_space(fs_info, path->nodes[0]);
>
> /*
> * try to push all the items after our slot into the
> @@ -4205,11 +4205,9 @@ static noinline int split_leaf(struct btrfs_trans_handle *trans,
>
> /* first try to make some room by pushing left and right */
> if (data_size && path->nodes[1]) {
> - int space_needed = data_size;
> -
> - if (slot < btrfs_header_nritems(l))
> - space_needed -= btrfs_leaf_free_space(fs_info, l);
> + int space_needed;
One doubt, if (slot == nritems(l)), and push_leaf_right() is with @emtpy == 0,
so it is possible to use the right sibling as the node for the new item, so if
we minus l's free space from space_needed, then it's possible that
(the original space_needed) > (free space of right node) > (the subtracted space_needed)
in that case, we're going to use right node as path->nodes[0] while right node
doesn't have enough space.
Thanks,
-liubo
>
> + space_needed = data_size - btrfs_leaf_free_space(fs_info, l);
> wret = push_leaf_right(trans, root, path, space_needed,
> space_needed, 0, 0);
> if (wret < 0)
> --
> 2.7.0.rc3
>
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