This v2 follows Keith's suggestion to only add a 'failover_rq_fn' to the request_queue (rather than both the bio and request structs).
Jens or Christoph, provided review is favorable, I'd very much appreciate it you'd pick up patches 1 - 3 for 4.16. 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 request_queue's 'failover_rq_fn' established by Patch 1. Patch 3 moves the nvme_req_needs_failover() from NVMe multipath to core. Which allows stacked devices (like DM multipath) to make use of NVMe's enhanced error handling. Patch 4 updates DM multipath to also make use of the request_queue's 'failover_rq_fn' 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 (James Smart has since sent a fix for commit a0b69cc8) Thanks, Mike Mike Snitzer (5): block: establish request failover callback nvme: use request_queue's failover_rq_fn 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 drivers/md/dm-mpath.c | 87 +++++++++++++++++++++++++++++++++++++++++-- drivers/md/dm-rq.c | 8 ++-- drivers/md/dm-table.c | 2 + drivers/md/dm.c | 7 ++-- drivers/nvme/host/core.c | 51 ++++++++++++++++++++++++- drivers/nvme/host/multipath.c | 48 ------------------------ drivers/nvme/host/nvme.h | 10 ----- include/linux/blkdev.h | 6 +++ include/linux/device-mapper.h | 9 +++++ 9 files changed, 158 insertions(+), 70 deletions(-) -- 2.15.0 -- dm-devel mailing list dm-devel@redhat.com https://www.redhat.com/mailman/listinfo/dm-devel
