These patches enable DM multipath to work well on NVMe over Fabrics devices. Currently that implies CONFIG_NVME_MULTIPATH is _not_ set. But follow-on work will be to make it so that native NVMe multipath and DM multipath can be made to co-exist (e.g. blacklisting certain NVMe devices from being consumed by native NVMe multipath?) Patch 1 updates block core to formalize a recent construct that Christoph embeedded into NVMe core (and native NVMe multipath): callback into a bio-based driver from the blk-mq driver's .complete hook to blk_steal_bios() a request's bios. Patch 2 switches NVMe over to using the block infrastructure established by Patch 1. Patch 3 moves the nvme_req_needs_failover() from NVMe multipath to core. Which allow sstacked devices (like DM multipath) to make use of NVMe's enhanced error handling. Patch 4 updates DM multipath to also make use of the block infrastructure established by Patch 1. Patch 5 can be largely ignored.. but it illustrates that Patch 1 - 4 enable DM multipath to avoid extra DM endio callbacks. These patches have been developed ontop of numerous DM changes I've staged for 4.16, see: https://git.kernel.org/pub/scm/linux/kernel/git/device-mapper/linux-dm.git/log/?h=dm-4.16 (which happens to include these 5 patches at the end, purely for interim linux-next coverage purposes as these changes land in the appropriate maintainer tree). I've updated the "mptest" DM multipath testsuite to provide NVMe test coverage (using NVMe fcloop), see: https://github.com/snitm/mptest The tree I've been testing includes all of 'dm-4.16' and all but one of the commits from 'nvme-4.16', see: https://git.kernel.org/pub/scm/linux/kernel/git/snitzer/linux.git/log/?h=dm-4.16_nvme-4.16 (I've let James Smart know that commit a0b69cc8 causes "nvme connect" to not work on my fcloop testbed). Jens, provided review is favorable, I'd very much appreciate it you'd pick up patches 1 - 3 for 4.16. Thanks, Mike Mike Snitzer (5): block: establish request failover callback infrastructure nvme: use request's failover callback for multipath failover nvme: move nvme_req_needs_failover() from multipath to core dm mpath: use NVMe error handling to know when an error is retryable dm mpath: skip calls to end_io_bio if using NVMe bio-based and round-robin block/blk-core.c | 2 ++ block/blk-mq.c | 1 + drivers/md/dm-mpath.c | 68 ++++++++++++++++++++++++++++++++++++++++++- drivers/md/dm-rq.c | 8 ++--- drivers/md/dm.c | 7 +++-- drivers/nvme/host/core.c | 50 +++++++++++++++++++++++++++++-- drivers/nvme/host/multipath.c | 52 ++------------------------------- drivers/nvme/host/nvme.h | 14 --------- include/linux/blk_types.h | 4 +++ include/linux/blkdev.h | 6 ++++ include/linux/device-mapper.h | 6 ++++ 11 files changed, 145 insertions(+), 73 deletions(-) -- 2.15.0
