From: Kevin Barnett kevin.barnett@microsemi.com
[ Upstream commit 2ba55c9851d74eb015a554ef69ddf2ef061d5780 ]
Problem: The Linux kernel takes a logical volume offline after a LUN reset. This is generally accompanied by this message in the dmesg output:
Device offlined - not ready after error recovery
Root Cause: The root cause is a "quirk" in the timeout handling in the Linux SCSI layer. The Linux kernel places a 30-second timeout on most media access commands (reads and writes) that it send to device drivers. When a media access command times out, the Linux kernel goes into error recovery mode for the LUN that was the target of the command that timed out. Every command that timed out is kept on a list inside of the Linux kernel to be retried later. The kernel attempts to recover the command(s) that timed out by issuing a LUN reset followed by a TEST UNIT READY. If the LUN reset and TEST UNIT READY commands are successful, the kernel retries the command(s) that timed out.
Each SCSI command issued by the kernel has a result field associated with it. This field indicates the final result of the command (success or error). When a command times out, the kernel places a value in this result field indicating that the command timed out.
The "quirk" is that after the LUN reset and TEST UNIT READY commands are completed, the kernel checks each command on the timed-out command list before retrying it. If the result field is still "timed out", the kernel treats that command as not having been successfully recovered for a retry. If the number of commands that are in this state are greater than two, the kernel takes the LUN offline.
Fix: When our RAIDStack receives a LUN reset, it simply waits until all outstanding commands complete. Generally, all of these outstanding commands complete successfully. Therefore, the fix in the smartpqi driver is to always set the command result field to indicate success when a request completes successfully. This normally isn’t necessary because the result field is always initialized to success when the command is submitted to the driver. So when the command completes successfully, the result field is left untouched. But in this case, the kernel changes the result field behind the driver’s back and then expects the field to be changed by the driver as the commands that timed-out complete.
Reviewed-by: Dave Carroll david.carroll@microsemi.com Reviewed-by: Scott Teel scott.teel@microsemi.com Signed-off-by: Kevin Barnett kevin.barnett@microsemi.com Signed-off-by: Don Brace don.brace@microsemi.com Signed-off-by: Martin K. Petersen martin.petersen@oracle.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/scsi/smartpqi/smartpqi_init.c | 3 +++ 1 file changed, 3 insertions(+)
diff --git a/drivers/scsi/smartpqi/smartpqi_init.c b/drivers/scsi/smartpqi/smartpqi_init.c index a25a07a0b7f0..c1efc182f5ea 100644 --- a/drivers/scsi/smartpqi/smartpqi_init.c +++ b/drivers/scsi/smartpqi/smartpqi_init.c @@ -2704,6 +2704,9 @@ static unsigned int pqi_process_io_intr(struct pqi_ctrl_info *ctrl_info, switch (response->header.iu_type) { case PQI_RESPONSE_IU_RAID_PATH_IO_SUCCESS: case PQI_RESPONSE_IU_AIO_PATH_IO_SUCCESS: + if (io_request->scmd) + io_request->scmd->result = 0; + /* fall through */ case PQI_RESPONSE_IU_GENERAL_MANAGEMENT: break; case PQI_RESPONSE_IU_TASK_MANAGEMENT: