On Wed, 29 Jul 2015 04:23:38 -0500, mchristi@xxxxxxxxxx wrote:
> From: Mike Christie <michaelc@xxxxxxxxxxx>
>
> LIO uses scatterlist for its page/data management. This patch
> adds a scatterlist messenger data type, so LIO can pass its sg
> down directly to rbd.
>
> Signed-off-by: Mike Christie <michaelc@xxxxxxxxxxx>
...
> /*
> + * For a sg data item, a piece is whatever remains of the next
> + * entry in the current sg entry, or the first entry in the next
> + * sg in the list.
> + */
> +static void ceph_msg_data_sg_cursor_init(struct ceph_msg_data_cursor *cursor,
> + size_t length)
> +{
> + struct ceph_msg_data *data = cursor->data;
> + struct scatterlist *sg;
> +
> + BUG_ON(data->type != CEPH_MSG_DATA_SG);
> +
> + sg = data->sgl;
> + BUG_ON(!sg);
> +
> + cursor->resid = min_t(u64, length, data->sgl_length);
> + cursor->sg = sg;
> + cursor->sg_consumed = data->sgl_init_offset;
> + cursor->last_piece = cursor->resid <= sg->length;
> +}
Just in case the CEPH_MSG_DATA_SG changes are picked up, the
cursor->last_piece calculation here needs to take into account the
data->sgl_init_offset:
if (cursor->resid <= (sg->length - data->sgl_init_offset))
cursor->last_piece = true;
...
Cheers, David
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