On Wed, 11 Feb 2009 16:52:37 +0200 Boaz Harrosh <bharrosh@xxxxxxxxxxx> wrote: > FUJITA Tomonori wrote: > > On Wed, 11 Feb 2009 11:15:53 +0200 > > Boaz Harrosh <bharrosh@xxxxxxxxxxx> wrote: > > > >> I spoke too soon. There is one more place that uses blk_rq_append_bio, that is > >> the place that adds the read/write bio that is received in osd_req_write/read. > >> The reason I receive a bio at these is because mainly I need a way to > >> accept struct page* arrays, as well as kernel & user pointers. A bio is a nice > > > > The API using an array of pointers to page can handle everything. So > > why do the users of ULD (some rare file systems, I guess), osd > > initiator, need to build bios and pass them? > > > > > >> general carrier for any type of memory. Given a bio at hand there are no ways > >> left to prepare a request from it save the FS generic_make_request() route. > >> > >> I was thinking of using struct sg_iovec* at one stage but they look very > >> scary when used with page*, and mapping a page to a pointer but not doing > >> cache sync and all that jazz. A bio is a very nice carrier of a scatter-gather > >> list of memory. It has all the API for any needs. blk_rq_append_bio() was the last > >> way to associate a bio with a request. (except for privileged block-filesystems) > > > > We need to remove the usage of blk_rq_append_bio() in scsi. > > > > > >> So the first thing we have to decide is what API we need at read/write > >> today there is: > > > > You are talking about the API for osd file systems (or something > > related with osd), right? If so, I think that you can do whatever you > > want to do now. You can make a mistake since it's in-kernel API. > > > > > >> void osd_req_read(struct osd_request *or, > >> const struct osd_obj_id *, struct bio *data_in, u64 offset); > >> > >> in exofs I use these two: > >> > >> int osd_req_read_kern(struct osd_request *or, > >> const struct osd_obj_id *obj, u64 offset, void *buff, u64 len); > >> int osd_req_read_pages(struct osd_request *or, > >> const struct osd_obj_id *, u64 offset, u64 length, > >> struct page **pages, int page_count); > >> > > > > As I wrote above, if you have an interface handling 'struct page > > **pages', then there should be ok. > > Sorry you miss understand me, I did not explain well. > > int osd_req_read_pages(,,,, struct page **pages, int page_count); > > Is in exofs.ko. It builds a bio out of **pages then calls > osd_req_read(,,bio,) which will then call blk_rq_append_bio() As I wrote in the previous mail, why does exofs need to build a bio? Why can exofs pass pages to osd ULD? > So for exofs (filesystem) and pNFS-objects layout driver (Also part of filesystem) > I currently need blk_rq_append_bio(), unless we want to do something new for > these people. -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
