nvme-pci: handle completions outside of the queue lock

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Split the completion of events into a two part process:

1) Reap the events inside the queue lock
2) Complete the events outside the queue lock

Since we never wrap the queue, we can access it locklessly after we've
updated the completion queue head. This patch started off with batching
events on the stack, but with this trick we don't have to. Keith Busch
<keith.busch@intel.com> came up with that idea.

Note that this kills the ->cqe_seen as well. I haven't been able to
trigger any ill effects of this. If we do race with polling every so
often, it should be rare enough NOT to trigger any issues.

Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Keith Busch <keith.busch@intel.com>
[hch: refactored, restored poll early exit optimization]
Signed-off-by: Christoph Hellwig <hch@lst.de>

...

This commit is contained in:

Jens Axboe 2018-05-17 18:31:50 +02:00 • committed by Keith Busch

parent d1f06f4ae0

commit 5cb525c831

1 changed files with 45 additions and 42 deletions

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drivers/nvme/host/pci.c

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