On 06/19/2012 05:31 AM, Tejun Heo wrote:
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"?
I think this deserves another patch on top of this splitting one. I'd like to clean this up later.
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