I don't need these, but I thought that they might be helpful routines. With the normal write_sg/read_sg routines if the data on the caller side is scattered, the caller has to copy the scattered data into/from a single bio buffer. With the _kern API the caller could instead let these routines set up the bios from a pointer list without a copy.
John.
On Oct 19, 2010, at 8:22 AM, Boaz Harrosh wrote:
> From: John A. Chandy <john.chandy@xxxxxxxxx>
>
> This is a trivial addition to the SG API that can receive kernel
> pointers. It is only used by the out-of-tree test module. So
> it's immediate need is questionable. For maintenance ease it might
> just get in, as it's very small.
>
> John.
> do you need this in the Kernel, or is it only for osd_ktest.ko?
>
> Signed-off-by: John A. Chandy <john.chandy@xxxxxxxxx>
> Signed-off-by: Boaz Harrosh <bharrosh@xxxxxxxxxxx>
> ---
> drivers/scsi/osd/osd_initiator.c | 71 ++++++++++++++++++++++++++++++++++++++
> 1 files changed, 71 insertions(+), 0 deletions(-)
>
> diff --git a/drivers/scsi/osd/osd_initiator.c b/drivers/scsi/osd/osd_initiator.c
> index f5b5735..0433ea6 100644
> --- a/drivers/scsi/osd/osd_initiator.c
> +++ b/drivers/scsi/osd/osd_initiator.c
> @@ -1015,6 +1015,77 @@ int osd_req_read_sg(struct osd_request *or,
> }
> EXPORT_SYMBOL(osd_req_read_sg);
>
> +/* SG-list write/read Kern API
> + *
> + * osd_req_{write,read}_sg_kern takes an array of @buff pointers and an array
> + * of sg_entries. @numentries indicates how many pointers and sg_entries there
> + * are. By requiring an array of buff pointers. This allows a caller to do a
> + * single write/read and scatter into multiple buffers.
> + * NOTE: Each buffer + len should not cross a page boundary.
> + */
> +static struct bio *_create_sg_bios(struct osd_request *or,
> + void **buff, const struct osd_sg_entry *sglist, unsigned numentries)
> +{
> + struct request_queue *q = osd_request_queue(or->osd_dev);
> + struct bio *bio;
> + unsigned i;
> +
> + bio = bio_kmalloc(GFP_KERNEL, numentries);
> + if (unlikely(!bio)) {
> + OSD_DEBUG("Faild to allocate BIO size=%u\n", numentries);
> + return ERR_PTR(-ENOMEM);
> + }
> +
> + for (i = 0; i < numentries; i++) {
> + unsigned offset = offset_in_page(buff[i]);
> + struct page *page = virt_to_page(buff[i]);
> + unsigned len = sglist[i].len;
> + unsigned added_len;
> +
> + BUG_ON(offset + len > PAGE_SIZE);
> + added_len = bio_add_pc_page(q, bio, page, len, offset);
> + if (unlikely(len != added_len)) {
> + OSD_DEBUG("bio_add_pc_page len(%d) != added_len(%d)\n",
> + len, added_len);
> + bio_put(bio);
> + return ERR_PTR(-ENOMEM);
> + }
> + }
> +
> + return bio;
> +}
> +
> +int osd_req_write_sg_kern(struct osd_request *or,
> + const struct osd_obj_id *obj, void **buff,
> + const struct osd_sg_entry *sglist, unsigned numentries)
> +{
> + struct bio *bio = _create_sg_bios(or, buff, sglist, numentries);
> + if (IS_ERR(bio))
> + return PTR_ERR(bio);
> +
> + bio->bi_rw |= REQ_WRITE;
> + osd_req_write_sg(or, obj, bio, sglist, numentries);
> +
> + return 0;
> +}
> +EXPORT_SYMBOL(osd_req_write_sg_kern);
> +
> +int osd_req_read_sg_kern(struct osd_request *or,
> + const struct osd_obj_id *obj, void **buff,
> + const struct osd_sg_entry *sglist, unsigned numentries)
> +{
> + struct bio *bio = _create_sg_bios(or, buff, sglist, numentries);
> + if (IS_ERR(bio))
> + return PTR_ERR(bio);
> +
> + osd_req_read_sg(or, obj, bio, sglist, numentries);
> +
> + return 0;
> +}
> +EXPORT_SYMBOL(osd_req_read_sg_kern);
> +
> +
> +
> void osd_req_get_attributes(struct osd_request *or,
> const struct osd_obj_id *obj)
> {
> --
> 1.7.2.3
>
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