On 09/02/13 15:11, Hannes Reinecke wrote:
On 09/02/2013 02:45 PM, Bart Van Assche wrote:
This patch adds several new calls to LLD EH handlers. Is it
guaranteed that these will only be invoked before scsi_remove_host()
has finished ? For more background information, see also "[PATCH]
Make scsi_remove_host() wait until error handling finished"
(http://thread.gmane.org/gmane.linux.scsi/82572/focus=82779).
Well, that depends how scsi_remove_host() handles outstanding
commands. What happens if you call scsi_remove_host() and there is
still I/O in flight? I would assume that any HBA would have to kill
any outstanding I/O prior to calling scsi_remove_host() (FC most
certainly does this).
Which would mean that it'll have to wait for scsi_put_command() to
be called for all outstanding commands. And as scsi_put_command()
will be called only _after_ our routine runs (see the reasoning
above) we should be safe.
Hello Hannes,
Since fc_remove_host() has to be invoked before scsi_remove_host() and
since fc_remove_host() changes the port state into FC_PORTSTATE_DELETED
this means that fc_remote_port_chkready() will return DID_NO_CONNECT
while scsi_remove_host() is in progress. I think this prevents that the
SYNCHRONIZE CACHE command submitted by sd_remove() reaches SCSI disks
over FC since sd_remove() is invoked from inside scsi_remove_host(). The
SRP transport patch I had posted recently makes sure that the
SYNCHRONIZE CACHE command submitted by sd_remove() reaches the target
SCSI disk. This makes me wonder what the correct behavior is for SCSI
transport drivers - disabling I/O before scsi_remove_host() starts or
ensuring that I/O is still possible while scsi_remove_host() is in
progress ? I think the call chain is as follows: scsi_remove_host() ->
device_del() -> bus_remove_device() -> device_release_driver() ->
__device_release_driver() -> sd_remove() -> sd_shutdown() ->
sd_sync_cache().
Bart.
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