Hello, Asias.
On Mon, Jun 18, 2012 at 02:53:08PM +0800, Asias He wrote:
> Split the mapping code in blk_rq_map_sg() to a helper
> __blk_segment_map_sg(), so that other mapping function, e.g.
> blk_bio_map_sg(), can share the code.
>
> Cc: Jens Axboe <axboe@xxxxxxxxx>
> Cc: Tejun Heo <tj@xxxxxxxxxx>
> Cc: Shaohua Li <shli@xxxxxxxxxx>
> Cc: linux-kernel@xxxxxxxxxxxxxxx
> Suggested-by: Tejun Heo <tj@xxxxxxxxxx>
> Suggested-by: Jens Axboe <axboe@xxxxxxxxx>
> Signed-off-by: Asias He <asias@xxxxxxxxxx>
> ---
> block/blk-merge.c | 80 ++++++++++++++++++++++++++++++-----------------------
> 1 file changed, 45 insertions(+), 35 deletions(-)
>
> diff --git a/block/blk-merge.c b/block/blk-merge.c
> index 160035f..576b68e 100644
> --- a/block/blk-merge.c
> +++ b/block/blk-merge.c
> @@ -110,6 +110,49 @@ static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio,
> return 0;
> }
>
> +static void
> +__blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec,
> + struct scatterlist *sglist, struct bio_vec **bvprv,
> + struct scatterlist **sg, int *nsegs, int *cluster)
> +{
> +
> + int nbytes = bvec->bv_len;
> +
> + if (*bvprv && *cluster) {
> + if ((*sg)->length + nbytes > queue_max_segment_size(q))
> + goto new_segment;
> +
> + if (!BIOVEC_PHYS_MERGEABLE(*bvprv, bvec))
> + goto new_segment;
> + if (!BIOVEC_SEG_BOUNDARY(q, *bvprv, bvec))
> + goto new_segment;
> +
> + (*sg)->length += nbytes;
> + } else {
> +new_segment:
> + if (!*sg)
> + *sg = sglist;
> + else {
> + /*
> + * If the driver previously mapped a shorter
> + * list, we could see a termination bit
> + * prematurely unless it fully inits the sg
> + * table on each mapping. We KNOW that there
> + * must be more entries here or the driver
> + * would be buggy, so force clear the
> + * termination bit to avoid doing a full
> + * sg_init_table() in drivers for each command.
> + */
> + (*sg)->page_link &= ~0x02;
> + *sg = sg_next(*sg);
> + }
> +
> + sg_set_page(*sg, bvec->bv_page, nbytes, bvec->bv_offset);
> + (*nsegs)++;
> + }
> + *bvprv = bvec;
> +}
I *hope* this is a bit prettier. e.g. Do we really need to pass in
@sglist and keep using "goto new_segment"?
Thanks.
--
tejun
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