On 25 May 2016 at 16:52, Ming Lei <ming.lei@xxxxxxxxxxxxx> wrote:
>> /*
>> + * map a bio to scatterlist, return number of sg entries setup.
>> + */
>> +int blk_bio_map_sg(struct request_queue *q, struct bio *bio,
>> + struct scatterlist *sglist,
>> + struct scatterlist **sg)
>> +{
>> + struct bio_vec bvec, bvprv = { NULL };
>> + struct bvec_iter iter;
>> + int nsegs, cluster;
>> +
>> + nsegs = 0;
>> + cluster = blk_queue_cluster(q);
>> +
>> + if (bio->bi_rw & REQ_DISCARD) {
>> + /*
>> + * This is a hack - drivers should be neither modifying the
>> + * biovec, nor relying on bi_vcnt - but because of
>> + * blk_add_request_payload(), a discard bio may or may not have
>> + * a payload we need to set up here (thank you Christoph) and
>> + * bi_vcnt is really the only way of telling if we need to.
>> + */
>> +
>> + if (bio->bi_vcnt)
>> + goto single_segment;
>> +
>> + return 0;
>> + }
>> +
>> + if (bio->bi_rw & REQ_WRITE_SAME) {
>> +single_segment:
>> + *sg = sglist;
>> + bvec = bio_iovec(bio);
>> + sg_set_page(*sg, bvec.bv_page, bvec.bv_len, bvec.bv_offset);
>> + return 1;
>> + }
>> +
>> + bio_for_each_segment(bvec, bio, iter)
>> + __blk_segment_map_sg(q, &bvec, sglist, &bvprv, sg,
>> + &nsegs, &cluster);
>> +
>> + return nsegs;
>> +}
>> +EXPORT_SYMBOL(blk_bio_map_sg);
>
> You can use __blk_bios_map_sg() to implement blk_bio_map_sg(),
> then code duplication may be avoided.
OK. I'll re-factor the code to map one bio.
>
>> +
>> +/*
>> * map a request to scatterlist, return number of sg entries setup. Caller
>> * must make sure sg can hold rq->nr_phys_segments entries
>> */
>> diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
>> index 1fd8fdf..e5de4f8 100644
>> --- a/include/linux/blkdev.h
>> +++ b/include/linux/blkdev.h
>> @@ -1013,6 +1013,9 @@ extern void blk_queue_write_cache(struct request_queue *q, bool enabled, bool fu
>> extern struct backing_dev_info *blk_get_backing_dev_info(struct block_device *bdev);
>>
>> extern int blk_rq_map_sg(struct request_queue *, struct request *, struct scatterlist *);
>> +extern int blk_bio_map_sg(struct request_queue *q, struct bio *bio,
>> + struct scatterlist *sglist,
>> + struct scatterlist **sg);
>> extern void blk_dump_rq_flags(struct request *, char *);
>> extern long nr_blockdev_pages(void);
>>
>> --
>> 1.7.9.5
>>
--
Baolin.wang
Best Regards
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