PATCH V4 0/5 nvme-pci: fixes on nvme_timeout and nvme_dev_disable

[Jianchao Wang <jianchao.w.wang@oracle.com>]

Firstly, really appreciate Keith and Sagi's precious advice on previous versions.
And this is the version 4.

Some patches of the previous patchset have been submitted and the left is this patchset
which has been refactored. Please consider it for 4.17.

The target of this patchset is to avoid nvme_dev_disable to be invoked by nvme_timeout.
As we know, nvme_dev_disable will issue commands on adminq, if the controller no response,
it has to depend on timeout path. However, nvme_timeout will also need to invoke
nvme_dev_disable. This will introduce dangerous circular dependence. Moreover,
nvme_dev_disable is under the shutdown_lock, even when it go to sleep, this makes things
worse.

The basic idea of this patchset is:
 - When need to schedule reset_work, hand over expired requests to nvme_dev_disable. They
   will be completed after the controller is disabled/shtudown.

 - When requests from nvme_dev_disable and nvme_reset_work expires, disable the controller
   directly then the request could be completed to wakeup the waiter. 

The 'disable the controller directly' here means that it doesn't send commands on adminq.
A new interface is introduced for this, nvme_pci_disable_ctrl_directly. More details,
please refer to the comment of the function.

Then nvme_timeout doesn't depends on nvme_dev_disable any more.

Because there is big difference from previous version, and some relatively independent patches
have been submitted, so I just reserve the key part of previous version change log following.

Change V3->V4
 - refactor the interfaces flushing in-flight requests and add them to nvme core.
 - refactor the nvme_timeout to make it more clearly

Change V2->V3:
 - discard the patch which unfreeze the queue after nvme_dev_disable

Changes V1->V2:
 - disable PCI controller bus master in nvme_pci_disable_ctrl_directly

There are 5 patches:
1st one is to change the operations on nvme_request->flags to atomic operations, then we could introduce
another NVME_REQ_ABORTED next.
2nd patch introduce two new interfaces to flush in-flight requests in nvme core.
3rd patch is to avoid the nvme_dev_disable in nvme_timeout, it introduce new interface nvme_pci_disable_ctrl_directly
and refactor the nvme_timeout
4th~5th is to fix issues introduced after 3rd patch.

Jianchao Wang (5)
0001-nvme-do-atomically-bit-operations-on-nvme_request.fl.patch
0002-nvme-add-helper-interface-to-flush-in-flight-request.patch
0003-nvme-pci-avoid-nvme_dev_disable-to-be-invoked-in-nvm.patch
0004-nvme-pci-discard-wait-timeout-when-delete-cq-sq.patch
0005-nvme-pci-add-the-timeout-case-for-DELETEING-state.patch

diff stat
 drivers/nvme/host/core.c |  96 +++++++++++++++++++++++++++++++++++++++++++++++
 drivers/nvme/host/nvme.h |   4 +-
 drivers/nvme/host/pci.c  | 224 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++-----------------------------------
 
 Thanks
 Jianchao