• James Smart's avatar
    nvme: call nvme_complete_rq when nvmf_check_ready fails for mpath I/O · 783f4a44
    James Smart authored
    When an io is rejected by nvmf_check_ready() due to validation of the
    controller state, the nvmf_fail_nonready_command() will normally return
    BLK_STS_RESOURCE to requeue and retry.  However, if the controller is
    dying or the I/O is marked for NVMe multipath, the I/O is failed so that
    the controller can terminate or so that the io can be issued on a
    different path.  Unfortunately, as this reject point is before the
    transport has accepted the command, blk-mq ends up completing the I/O
    and never calls nvme_complete_rq(), which is where multipath may preserve
    or re-route the I/O. The end result is, the device user ends up seeing an
    EIO error.
    
    Example: single path connectivity, controller is under load, and a reset
    is induced.  An I/O is received:
    
      a) while the reset state has been set but the queues have yet to be
         stopped; or
      b) after queues are started (at end of reset) but before the reconnect
         has completed.
    
    The I/O finishes with an EIO status.
    
    This patch makes the following changes:
    
      - Adds the HOST_PATH_ERROR pathing status from TP4028
      - Modifies the reject point such that it appears to queue successfully,
        but actually completes the io with the new pathing status and calls
        nvme_complete_rq().
      - nvme_complete_rq() recognizes the new status, avoids resetting the
        controller (likely was already done in order to get this new status),
        and calls the multipather to clear the current path that errored.
        This allows the next command (retry or new command) to select a new
        path if there is one.
    Signed-off-by: James Smart's avatarJames Smart <jsmart2021@gmail.com>
    Reviewed-by: Sagi Grimberg's avatarSagi Grimberg <sagi@grimberg.me>
    Signed-off-by: default avatarChristoph Hellwig <hch@lst.de>
    783f4a44
nvme.h 28 KB