There is an error with the medium access timeout feature of the sd driver. The sdkp->medium_access_timed_out value is set to zero in sd_done() in the wrong place. It is set to zero only if a command returns sense data. If an I/O command times out, error handling succeeds, and the I/O commands complete, the value won't be reset if nothing responds with a sense buffer. Then, another timeout (no matter how far in the future) can increment it again, causing the device to be errantly set offline.
The resetting of sdkp->medium_access_timed_out should occur before the check for sense data. Signed-off-by: David Jeffery <[email protected]> --- It can be reproduced using scsi_debug and using SCSI_DEBUG_OPT_MAC_TIMEOUT to force some I/O to timeout once. This small script assumes /dev/sdb as scsi_debug's disk, causes a timeout, completes 2MB of I/O successfully including the timed out I/O command, then repeats. Without the patch, the device is offlined on the second loop. All loops will successfully complete I/O with the patch. echo "-1" >/sys/bus/pseudo/drivers/scsi_debug/every_nth for i in `seq 1 4`; do echo starting loop $i echo "128" >/sys/bus/pseudo/drivers/scsi_debug/opts dd if=/dev/sdb of=/dev/null bs=1M iflag=direct count=1 & sleep 5 echo "0" >/sys/bus/pseudo/drivers/scsi_debug/opts wait dd if=/dev/sdb of=/dev/null bs=1M iflag=direct count=1 echo ending loop $i done diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c index 86fcf2c..2779e6b 100644 --- a/drivers/scsi/sd.c +++ b/drivers/scsi/sd.c @@ -1669,12 +1669,12 @@ static int sd_done(struct scsi_cmnd *SCpnt) sshdr.ascq)); } #endif + sdkp->medium_access_timed_out = 0; + if (driver_byte(result) != DRIVER_SENSE && (!sense_valid || sense_deferred)) goto out; - sdkp->medium_access_timed_out = 0; - switch (sshdr.sense_key) { case HARDWARE_ERROR: case MEDIUM_ERROR: -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
