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    SubjectRe: [PATCH] [Target_Core_Mod/pSCSI]: Add optional legacy scsi_execute_async() usage for Linux/SCSI passthrough
    On 04/20/2009 11:36 PM, Nicholas A. Bellinger wrote:
    > On Sun, 2009-04-19 at 13:56 +0300, Boaz Harrosh wrote:
    >> Are you aware that scsi_execute_async() has gone in 2.6.30-rc1?
    >>
    >> I'm not sure what would be the best alternative for you. I would say
    >> a bio, but it is still being debated. Your current options are:
    >>
    >> 1. bio_alloc then loop () bio_add_pc_page, and finally blk_rq_append_bio
    >> (Which block people don't like)
    >> 2. sglist => page-pointers-array translation and blk_rq_map_user with
    >> struct rq_map_data mode. (not possible with all kind of sglists)
    >> 2. sglist => iovec translation and blk_rq_map_user_iov()
    >> (Very very ugly mapping of pages to virtual pointers)
    >>
    >> I have a similar situation with my OSD code.
    >>
    >
    > Hey,
    >
    > Thanks for the pointers on this.. Yeah, I knew it was going away soon,
    > but needed it for some legacy drivers..:-)
    >
    > Anyways, I will drop this patch for scsi_execute_async() when I branch
    > for v2.6.30-rcX and look and updating target_core_mod/pSCSI to one of
    > the listed methods to get up and running. From the looks of it however
    > we might want something slightly better than blk_rq_map_user() for the
    > kernel space pages attached to struct scatterlist and page_links..
    >
    > Just FYI, the target_core_mod struct scatterlist memory will be in
    > struct list_head with struct page for allocated se_cmd_t (received CDB),
    > so it will be pretty easy from the target_core_mod+subsystem plugin side
    > side to put something that along the lines of list =>
    > page-pointers-array translation and blk_rq_map_user() into a new
    > function..

    Be ware that page-pointers-array mean that only first/last page can be
    incomplete and all middle pages must be full PAGE_SIZE. As I recall this
    might not be the case for network sglists.

    >
    > lio-core-2.6.git/drivers/target/target_core_transport.c is using
    > include/linux/scatterlist.h macros when interacting with struct
    > scatterlist allocated for each subsystem plugin (from the linked list
    > struct page memory) I will have a look and see what would need to be
    > down to allow all kinds of sglists with something new..
    >

    right, in the general sglist model, only linked-bios will fit one-to-one.

    You should look into something like Tejun's RFCed blk_rq_map_kern_sgl()
    (Which was not yet accepted)

    > Thanks for your comments!
    >
    > --nab
    >
    >

    We'll see what comes up
    Boaz


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