On Sat, Jan 28, 2017 at 06:06:32AM +0000, fdmanana@xxxxxxxxxx wrote:
> From: Filipe Manana <fdmanana@xxxxxxxx>
>
> Very often we have the checksums for an extent spread in multiple items
> in the checksums tree, and currently the algorithm to delete them starts
> by looking for them one by one and then deleting them one by one, which
> is not optimal since each deletion involves shifting all the other items
> in the leaf and when the leaf reaches some low threshold, to move items
> off the leaf into its left and right neighbor leafs. Also, after each
> item deletion we release our search path and start a new search for other
> checksums items.
>
> So optimize this by deleting in bulk all the items in the same leaf that
> contain checksums for the extent being freed.
Looks good.
Reviewed-by: Liu Bo <bo.li.liu@xxxxxxxxxx>
Thanks,
-liubo
>
> Signed-off-by: Filipe Manana <fdmanana@xxxxxxxx>
> ---
> fs/btrfs/file-item.c | 28 +++++++++++++++++++++++++++-
> 1 file changed, 27 insertions(+), 1 deletion(-)
>
> diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
> index e97e322..d7d6d4a 100644
> --- a/fs/btrfs/file-item.c
> +++ b/fs/btrfs/file-item.c
> @@ -643,7 +643,33 @@ int btrfs_del_csums(struct btrfs_trans_handle *trans,
>
> /* delete the entire item, it is inside our range */
> if (key.offset >= bytenr && csum_end <= end_byte) {
> - ret = btrfs_del_item(trans, root, path);
> + int del_nr = 1;
> +
> + /*
> + * Check how many csum items preceding this one in this
> + * leaf correspond to our range and then delete them all
> + * at once.
> + */
> + if (key.offset > bytenr && path->slots[0] > 0) {
> + int slot = path->slots[0] - 1;
> +
> + while (slot >= 0) {
> + struct btrfs_key pk;
> +
> + btrfs_item_key_to_cpu(leaf, &pk, slot);
> + if (pk.offset < bytenr ||
> + pk.type != BTRFS_EXTENT_CSUM_KEY ||
> + pk.objectid !=
> + BTRFS_EXTENT_CSUM_OBJECTID)
> + break;
> + path->slots[0] = slot;
> + del_nr++;
> + key.offset = pk.offset;
> + slot--;
> + }
> + }
> + ret = btrfs_del_items(trans, root, path,
> + path->slots[0], del_nr);
> if (ret)
> goto out;
> if (key.offset == bytenr)
> --
> 2.7.0.rc3
>
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