[PATCH] Block layer stuff/DIO rewrite prep for 3.14

Kent Overstreet
2013-11-04T23:36:40Z

Now that immutable biovecs is in, these are the remaining patches required for
my DIO rewrite, along with some related cleanup/refactoring.

The key enabler is patch 4 - making generic_make_request() handle arbitary sized
bios. This takes what was once bio_add_page()'s responsibility and pushes it
down; long term plan is to hopefully push this down to the driver level, which
should simplify a lot of code (a lot of it very fragile code!) and improve
performance at the same time.

The DIO rewrite needs some more work before it'll be ready, but I wanted to get
this patch series out because this stuff should all be ready and it's useful for
other reasons - I think this stuff will make it a lot easier for the btrfs
people to do what they need with their DIO code.

Other stuff enabled by this:

* With this and the bio_split() rewrite already in, we can just delete
merge_bvec_fn. I have patches for this, but they'll need more testing.

* Multipage bvecs - bvecs pointing to an arbitrary amount of contiguous
physical memory. I have this working but it'll need more testing and code
auditing - this is what lets us kill bi_seg_front_size and bi_seg_back_size
though.

Patch series is based on Jens' for-next tree, and it's available in my git
repository - git://evilpiepirate.org/~kent/linux-bcache.git for-jens