On 3/29/22 14:40, Wenchao Hao wrote:
On 2022/3/29 18:56, Steffen Maier wrote:
On 3/29/22 11:06, Wenchao Hao wrote:
SCSI timeout would call scsi_eh_scmd_add() on some conditions, host
would be set
to SHOST_RECOVERY state. Once host enter SHOST_RECOVERY, IOs
submitted to all
devices in this host would not succeed until the scsi_error_handler()
finished.
The scsi_error_handler() might takes long time to be done, it's
unbearable when
host has massive devices.
I want to ask is anyone applying another error handler flow to
address this
phenomenon?
I think we can move some operations(like scsi get sense, scsi send
startunit
and scsi device reset) out of scsi_unjam_host(), to perform these
operations
without setting host to SHOST_RECOVERY? It would reduce the time of
block the
whole host.
Waiting for your discussion.
We already have "async" aborts before even entering scsi_eh. So your
use case seems to imply that those aborts fail and we enter scsi_eh?
Yes, I mean when scsi_abort_command() failed and scsi_eh_scmd_add() is
called.
There's eh_deadline for limiting the time spent in escalation of
scsi_eh, and instead directly go to host reset. Would this help?
The deadline seems not helpful. What we want to see is a single LUN's
command error
would not stop other LUNs which share the same host. So my plan is to
move reset LUN out
from scsi_unjam_host() which run with host set to SHOST_RECOVERY.
Nope. One of the key points of scsi_unjam_host() is that is has to stop
all I/O before proceeding. Without doing so basically all SCSI parallel
HBAs will fail EH as they _require_ I/O to be stopped.
And even on modern HBAs we have the challenge that 99% of every EH
invocation is triggered by command timeouts, where 'LUN reset' is only
of limited usability.
Cheers,
Hannes
