I understand this for the case of RECOVERED_ERROR. But for the case of NO_SENSE the driver didn't supply any extra information with the failure. Why does this code assume the request completed okay? good_bytes is set to 0 based on the non-zero result in the scsi_cmnd result field. Then its reset based on NO_SENSE. Not returning more sense information would be poor driver behavior but changing result to 0 seems dangerous. Laurie ----- Original Message ---- From: Douglas Gilbert <dougg@xxxxxxxxxx> To: Laurie Costello <lmcostello@xxxxxxxxx> Cc: linux-scsi@xxxxxxxxxxxxxxx Sent: Thursday, November 2, 2006 10:10:16 AM Subject: Re: non-zero result with NO_SENSE Laurie Costello wrote: > I'm researching a problem with data corruption on linux 2.6.9. > > I'm seeing results of scsi_print_sense() in the system log, which brought me > > to this chunk of code. Is it correct to process a non-zero result with > > NO_SENSE as if an error didn't occur or was recovered? Laurie, Well it isn't ideal obviously. The problem is that sd sits between a SCSI direct access device and the SCSI block subsystem. SCSI devices try and be helpful and tell the application client things like: the data was read but required 3 retries and ECC. The block layer is only interested in errors that impact the current IO, so sd has no slot to file these warnings in, apart from the system log. There was some proposal about logging such errors and warning (but where to store the log :-) ) and disks already do a fair amount of logging themselves. Even more worrying are deferred errors. Something like a cached write that at some later time gets an IO error when the disk tries to write its cache to the media. This should become a more interesting area as disks get larger non-volatile caches. There are tools such as smartmontools that can monitor the health of disks. Doug Gilbert - To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
