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    SubjectRe: [PATCH 14/17] scsi: replace custom rq mapping with blk_rq_map_kern_sgl()
    On 04/01/2009 04:44 PM, Tejun Heo wrote:
    > Impact: hack removal
    >
    > SCSI needs to map sgl into rq for kernel PC requests; however, block
    > API didn't have such feature so it used its own rq mapping function
    > which hooked into block/bio internals and is generally considered an
    > ugly hack. The private function may also produce requests which are
    > bigger than queue per-rq limits.
    >
    > Block blk_rq_map_kern_sgl(). Kill the private implementation and use
    > it.
    >
    > Signed-off-by: Tejun Heo <tj@kernel.org>

    James, TOMO

    what happened to Tomo's patches that removes all this after fixing up
    all users (sg.c)?

    I thought that was agreed and done? What is left to do for that to go
    in.

    Thanks Boaz

    > ---
    > drivers/scsi/scsi_lib.c | 108 +----------------------------------------------
    > 1 files changed, 1 insertions(+), 107 deletions(-)
    >
    > diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
    > index 3196c83..3fa5589 100644
    > --- a/drivers/scsi/scsi_lib.c
    > +++ b/drivers/scsi/scsi_lib.c
    > @@ -296,112 +296,6 @@ static void scsi_end_async(struct request *req, int uptodate)
    > __blk_put_request(req->q, req);
    > }
    >
    > -static int scsi_merge_bio(struct request *rq, struct bio *bio)
    > -{
    > - struct request_queue *q = rq->q;
    > -
    > - bio->bi_flags &= ~(1 << BIO_SEG_VALID);
    > - if (rq_data_dir(rq) == WRITE)
    > - bio->bi_rw |= (1 << BIO_RW);
    > - blk_queue_bounce(q, &bio);
    > -
    > - return blk_rq_append_bio(q, rq, bio);
    > -}
    > -
    > -static void scsi_bi_endio(struct bio *bio, int error)
    > -{
    > - bio_put(bio);
    > -}
    > -
    > -/**
    > - * scsi_req_map_sg - map a scatterlist into a request
    > - * @rq: request to fill
    > - * @sgl: scatterlist
    > - * @nsegs: number of elements
    > - * @bufflen: len of buffer
    > - * @gfp: memory allocation flags
    > - *
    > - * scsi_req_map_sg maps a scatterlist into a request so that the
    > - * request can be sent to the block layer. We do not trust the scatterlist
    > - * sent to use, as some ULDs use that struct to only organize the pages.
    > - */
    > -static int scsi_req_map_sg(struct request *rq, struct scatterlist *sgl,
    > - int nsegs, unsigned bufflen, gfp_t gfp)
    > -{
    > - struct request_queue *q = rq->q;
    > - int nr_pages = (bufflen + sgl[0].offset + PAGE_SIZE - 1) >> PAGE_SHIFT;
    > - unsigned int data_len = bufflen, len, bytes, off;
    > - struct scatterlist *sg;
    > - struct page *page;
    > - struct bio *bio = NULL;
    > - int i, err, nr_vecs = 0;
    > -
    > - for_each_sg(sgl, sg, nsegs, i) {
    > - page = sg_page(sg);
    > - off = sg->offset;
    > - len = sg->length;
    > -
    > - while (len > 0 && data_len > 0) {
    > - /*
    > - * sg sends a scatterlist that is larger than
    > - * the data_len it wants transferred for certain
    > - * IO sizes
    > - */
    > - bytes = min_t(unsigned int, len, PAGE_SIZE - off);
    > - bytes = min(bytes, data_len);
    > -
    > - if (!bio) {
    > - nr_vecs = min_t(int, BIO_GUARANTEED_PAGES,
    > - nr_pages);
    > - nr_pages -= nr_vecs;
    > -
    > - bio = bio_alloc(gfp, nr_vecs);
    > - if (!bio) {
    > - err = -ENOMEM;
    > - goto free_bios;
    > - }
    > - bio->bi_end_io = scsi_bi_endio;
    > - }
    > -
    > - if (bio_add_pc_page(q, bio, page, bytes, off) !=
    > - bytes) {
    > - bio_put(bio);
    > - err = -EINVAL;
    > - goto free_bios;
    > - }
    > -
    > - if (bio->bi_vcnt >= nr_vecs) {
    > - err = scsi_merge_bio(rq, bio);
    > - if (err) {
    > - bio_endio(bio, 0);
    > - goto free_bios;
    > - }
    > - bio = NULL;
    > - }
    > -
    > - page++;
    > - len -= bytes;
    > - data_len -=bytes;
    > - off = 0;
    > - }
    > - }
    > -
    > - rq->buffer = rq->data = NULL;
    > - rq->data_len = bufflen;
    > - return 0;
    > -
    > -free_bios:
    > - while ((bio = rq->bio) != NULL) {
    > - rq->bio = bio->bi_next;
    > - /*
    > - * call endio instead of bio_put incase it was bounced
    > - */
    > - bio_endio(bio, 0);
    > - }
    > -
    > - return err;
    > -}
    > -
    > /**
    > * scsi_execute_async - insert request
    > * @sdev: scsi device
    > @@ -438,7 +332,7 @@ int scsi_execute_async(struct scsi_device *sdev, const unsigned char *cmd,
    > req->cmd_flags |= REQ_QUIET;
    >
    > if (use_sg)
    > - err = scsi_req_map_sg(req, buffer, use_sg, bufflen, gfp);
    > + err = blk_rq_map_kern_sg(req->q, req, buffer, use_sg, gfp);
    > else if (bufflen)
    > err = blk_rq_map_kern(req->q, req, buffer, bufflen, gfp);
    >



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