Version 0.8 uploaded

I've just pushed out version 0.8 of the driver. Here's the shortlog:

Matthew Wilcox (13):
NVMe: Implement doorbell stride capability
NVMe: Update Identify Controller data structure
NVMe: Simplify completion handling
NVMe: Change get_nvmeq to take a dev instead of a namespace
NVMe: Change nvme_completion_fn to take a dev
NVMe: Merge the nvme_bio and nvme_prp data structures
NVMe: Rename IO_TIMEOUT to NVME_IO_TIMEOUT
NVMe: Fix DMA mapping for admin commands
NVMe: Mark the end of the sg list
NVMe: Simplify nvme_unmap_user_pages
NVMe: Set queue flags correctly
NVMe: Version 0.8
NVMe: Set number of queues correctly

Mostly bugfixes, but the big change is merging the nvme_bio and nvme_prp data structures. I've been made aware that certain applications mostly send I/Os larger than a single page; in particular MySQL uses 16k I/Os. That was probably the pessimal size for the NVMe driver; just large enough to cause it to allocate an nvme_prp data structure and small enough that per-I/O overhead is still meaningful.

So I merged the nvme_bio and nvme_prp data structures into the new nvme_iod data structure. This was a bit of a challenge since it needs to contain two variable-length arrays, which C does not permit you to express neatly. I hope the comments around the data structure make it clear what I'm doing. I saw noticable reductions in per-I/O CPU overhead with the new scheme, so I think it's worthwhile. Also, the additional overhead for 512-byte I/Os was down in the noise and it was completely unmeasurable for 4k I/Os.

I plan to ask Linus to merge this version of the driver for Linux 3.3. I know there's still a lot on the TODO list, but we'll have a chance to merge more patches in April. I have a couple of patches from Keith Busch still to review (adding a character device to represent the controller and the beginnings of an error handler), but I'd rather get what we have merged now than wait for the next merge window.