On 1/29/15, 1:38 PM, Mike Christie wrote:
On 1/29/15, 7:02 AM, Bart Van Assche wrote:Delay REQ_PREEMPT requests submitted against a blocked device until the device is unblocked by returning SCSI_MLQUEUE_HOST_BUSY to the SCSI mid-layer. This avoids that a rescan shortly after a cable pull sporadically triggers the following kernel oops: BUG: unable to handle kernel paging request at ffffc9001a6bc084 IP: [<ffffffffa04e08f2>] mlx4_ib_post_send+0xd2/0xb30 [mlx4_ib] Process rescan-scsi-bus (pid: 9241, threadinfo ffff88053484a000, task ffff880534aae100) Call Trace: [<ffffffffa0718135>] srp_post_send+0x65/0x70 [ib_srp] [<ffffffffa071b9df>] srp_queuecommand+0x1cf/0x3e0 [ib_srp] [<ffffffffa0001ff1>] scsi_dispatch_cmd+0x101/0x280 [scsi_mod] [<ffffffffa0009ad1>] scsi_request_fn+0x411/0x4d0 [scsi_mod] [<ffffffff81223b37>] __blk_run_queue+0x27/0x30 [<ffffffff8122a8d2>] blk_execute_rq_nowait+0x82/0x110 [<ffffffff8122a9c2>] blk_execute_rq+0x62/0xf0 [<ffffffffa000b0e8>] scsi_execute+0xe8/0x190 [scsi_mod] [<ffffffffa000b2f3>] scsi_execute_req+0xa3/0x130 [scsi_mod] [<ffffffffa000c1aa>] scsi_probe_lun+0x17a/0x450 [scsi_mod] [<ffffffffa000ce86>] scsi_probe_and_add_lun+0x156/0x480 [scsi_mod] [<ffffffffa000dc2f>] __scsi_scan_target+0xdf/0x1f0 [scsi_mod] [<ffffffffa000dfa3>] scsi_scan_host_selected+0x183/0x1c0 [scsi_mod] [<ffffffffa000edfb>] scsi_scan+0xdb/0xe0 [scsi_mod] [<ffffffffa000ee13>] store_scan+0x13/0x20 [scsi_mod] [<ffffffff811c8d9b>] sysfs_write_file+0xcb/0x160 [<ffffffff811589de>] vfs_write+0xce/0x140 [<ffffffff81158b53>] sys_write+0x53/0xa0 [<ffffffff81464592>] system_call_fastpath+0x16/0x1b [<00007f611c9d9300>] 0x7f611c9d92ff Reported-by: Max Gurtuvoy <maxg@xxxxxxxxxxxx> Signed-off-by: Bart Van Assche <bart.vanassche@xxxxxxxxxxx> Cc: Sagi Grimberg <sagig@xxxxxxxxxxxx> Cc: <stable@xxxxxxxxxxxxxxx> --- drivers/infiniband/ulp/srp/ib_srp.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/drivers/infiniband/ulp/srp/ib_srp.c b/drivers/infiniband/ulp/srp/ib_srp.c index 0747c05..77a7a2f 100644 --- a/drivers/infiniband/ulp/srp/ib_srp.c +++ b/drivers/infiniband/ulp/srp/ib_srp.c @@ -2003,8 +2003,13 @@ static int srp_queuecommand(struct Scsi_Host *shost, struct scsi_cmnd *scmnd) if (in_scsi_eh) mutex_lock(&rport->mutex); + /* + * The "blocked" state of SCSI devices is ignored by the SCSI core for + * REQ_PREEMPT requests. Hence the explicit check below for the SCSI + * device state. + */ scmnd->result = srp_chkready(target->rport); - if (unlikely(scmnd->result)) + if (unlikely(scmnd->result != 0 || scsi_device_blocked(scmnd->device))) goto err; WARN_ON_ONCE(scmnd->request->tag < 0);What is the case where a driver blocks the device and can handle or wants commands? iSCSI and FC also do not want commands, even PREEMPT ones, at this time. It looks like they have been hitting internal checks to prevent hitting similar issues.
I think I figured this out. I think we want to change the scsi_prep_state_check check instead of each driver/class.
It looks like for the SDEV_QUIESCE state we want to allow REQ_PREEMPT commands. James would know best, but I think SPI needs that ability.
For SDEV_BLOCK/SDEV_CREATED_BLOCK, it looks like drivers/classes that use that state do not want any commands to be queued at that time, because the transport is normally down.
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