Messages in this thread | | | Date | Wed, 14 Sep 2011 20:17:53 +0300 | From | Boaz Harrosh <> | Subject | Re: [PATCH 1/2] block: export __make_request |
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On 9/14/2011 12:19 AM, Christoph Hellwig wrote: > On Mon, Sep 12, 2011 at 08:04:46PM +0200, Jens Axboe wrote: >>> I really hate naming things different from the method they are >>> implementing. I've tried to figure out what the point of the >>> old blk_make_request is - why would we not go through >>> generic_make_request for this? >>> >>> Boaz, any idea? >> >> I tend to agree, we could rename the existing blk_make_request(). It >> could be blk_make_request_from_bio() or something like that, since >> that's what it does. > > It should at very least be renamed. But I still can't figure out what > it is for exactly. > > There are three users: > > (1) virtio_blk::virtblk_get_id(): > This looks like it really should just use blk_rq_map_kern. > (2) osd_initiator::_make_request(): > This one looks like it should just use the same scheme as > sg_io(), as it's doing the same thing.
Good god what sg_io? That broken pointr+length from user-mode that sg.c and bsg.c are using? no can do it's not user-mode pointers, and it's not pointer+length it's pages pointers of a bio. The only other structure that could carry the same information is struct sg, but we work very hard to get rid of this contraption. (scsi_execute_async or something that it was)
blk_make_request() was made to be the parallel of __make_request, to be used from filesystem level users. But with two differences. 1. Mainly support for none-FS BLOCK_PC requests 2. Also support chained bios. (was added later)
> (3) target_core_pscsi::__pscsi_map_SG(): > Same as (2). >
There is no better suitable structure in current Kernel to carry a list of pages, with optional offset and length, then bio struct. Given a bio at hand. how do you make a block request out of it? (If it's not an FS_PC type IO?)
As I remember target_core had their own pages-linked-list structure, and how do you make a request out of that? again best at hand is bio.
bio is for a long time a page-pointers-carrier-structure and is out of private block-level use. The filesystem level is full of it.
Thanks Boaz
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