diff options
| author | Asias He <asias@redhat.com> | 2012-08-02 23:42:03 +0200 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2012-08-02 23:42:03 +0200 |
| commit | 963ab9e5da95c654bb3ab937cc478de4f7088a96 (patch) | |
| tree | 644caf1f513e1f206d4c732044b943c276af9f8d /block | |
| parent | fs/block-dev.c:fix performance regression in O_DIRECT writes to md block devices (diff) | |
| download | linux-963ab9e5da95c654bb3ab937cc478de4f7088a96.tar.xz linux-963ab9e5da95c654bb3ab937cc478de4f7088a96.zip | |
block: Introduce __blk_segment_map_sg() helper
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: Rusty Russell <rusty@rustcorp.com.au>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Tejun Heo <tj@kernel.org>
Cc: Shaohua Li <shli@kernel.org>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: kvm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Cc: virtualization@lists.linux-foundation.org
Suggested-by: Jens Axboe <axboe@kernel.dk>
Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Asias He <asias@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block')
| -rw-r--r-- | block/blk-merge.c | 80 |
1 files changed, 45 insertions, 35 deletions
diff --git a/block/blk-merge.c b/block/blk-merge.c index 160035f54882..576b68e79248 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; +} + /* * map a request to scatterlist, return number of sg entries setup. Caller * must make sure sg can hold rq->nr_phys_segments entries @@ -131,41 +174,8 @@ int blk_rq_map_sg(struct request_queue *q, struct request *rq, bvprv = NULL; sg = NULL; rq_for_each_segment(bvec, rq, iter) { - 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; + __blk_segment_map_sg(q, bvec, sglist, &bvprv, &sg, + &nsegs, &cluster); } /* segments in rq */ |