Messages in this thread | | | Date | Wed, 1 Apr 2009 22:22:10 +0900 | Subject | Re: [PATCH 8/8] blk-map: reimplement blk_rq_map_user() using blk_rq_map_user_iov() | From | FUJITA Tomonori <> |
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On Wed, 01 Apr 2009 22:17:05 +0900 Tejun Heo <tj@kernel.org> wrote:
> Hello, > > FUJITA Tomonori wrote: > > On Wed, 01 Apr 2009 22:03:39 +0900 > > Tejun Heo <tj@kernel.org> wrote: > > > >> FUJITA Tomonori wrote: > >>> No, we are not talking about blk_rq_append_bio(). > >>> > >>> We are talking about the multiple bio handling in blk_rq_map_user, > >>> which is the feature that Mike added long time ago. The feature is > >>> surely necessary for some users. So you can't remote it. > >> How would someone use that without blk_rq_append_bio()? The only > > > > Hmm, I'm not sure what you are talking about. > > > > Why do we need to live without blk_rq_append_bio()? > > > > You want to remove blk_rq_append_bio()? Please make your goal clear. > > Yeah, I'm writing header message for the next patchset. It will go > out in a few minutes. With the bogus fix part removed, this patch > (and related earlier ones) should have been part of the next set. > And, yes, the goal is removing blk_rq_append_bio() and any and all > request/bio internal meddling with further patchsets.
Sounds a good idea. But I need to review that.
But 7/8 and 8/8 patches are not bug fixes at all (as I wrote, your descriptions about checking is untrue). It can't be for 2.6.30. So put them to the next patchset.
> >> reason blk_rq_map_user() had multiple bio chaining was to work around > >> BIO_MAX_SIZE. blk_rq_map_user_iov() doesn't support multiple bio > >> chaining, so sans blk_rq_append_bio() or playing with rq/bio internals > >> directly, there's no way to use or even know about multiple bios. > > > > Yes, only non iovec interface of SG_IO supports large data > > transfer. Users have been lived with that. > > This patch doesn't remove any feature. You don't lose anything. What > used to be done with multiple bios is now done with single bio. The > implementation is simpler and shorter. Using or not using multiple > bios doesn't (and shouldn't) make any difference to blk_map_*() users.
Hmm, with your change, blk_rq_map_user can't handle larger than BIO_MAX_SIZE, right?
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