Re: [BISECTED] Re: [BUG] Linux-2.6.31-rc1 Fails To Recognize Some USB Disks

Matthew Wilcox
2009-07-27T02:06:13Z

On Sun, Jul 26, 2009 at 09:28:15PM -0400, Martin K. Petersen wrote:
> sd: Avoid sending extended inquiry to legacy/broken devices
>
> Our existing check for VPD page validity does not handle devices that
> refuse to respond to INQUIRY with the EVPD bit set.

But ... why doesn't it?

we do:

result = scsi_execute_req(sdev, cmd, DMA_FROM_DEVICE, buffer,
len + 4, NULL, 30 * HZ, 3, NULL);
if (result)
return result;

so that should return some error code. And that's called from here:

/* Ask for all the pages supported by this device */
result = scsi_vpd_inquiry(sdev, buf, 0, 255);
if (result)
goto fail;

which goes to:

fail:
kfree(buf);
return NULL;

and the sd code seems to check for that. So what bug are you papering
over here?

> Restrict extended inquiry to devices reporting SBC2/SPC3 or higher.
>
> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
>
> ---
>
> diff --git a/drivers/scsi/sd.c b/drivers/scsi/sd.c
> index 5616cd7..9b703fd 100644
> --- a/drivers/scsi/sd.c
> +++ b/drivers/scsi/sd.c
> @@ -1840,6 +1840,13 @@ static void sd_read_block_characteristics(struct scsi_disk *sdkp)
> kfree(buffer);
> }
>
> +static int sd_try_extended_inquiry(struct scsi_device *sdp)
> +{
> + if (sdp->scsi_level > SCSI_SPC_2)
> + return 1;
> + return 0;
> +}
> +
> /**
> * sd_revalidate_disk - called the first time a new disk is seen,
> * performs disk spin up, read_capacity, etc.
> @@ -1877,8 +1884,12 @@ static int sd_revalidate_disk(struct gendisk *disk)
> */
> if (sdkp->media_present) {
> sd_read_capacity(sdkp, buffer);
> - sd_read_block_limits(sdkp);
> - sd_read_block_characteristics(sdkp);
> +
> + if (sd_try_extended_inquiry(sdp)) {
> + sd_read_block_limits(sdkp);
> + sd_read_block_characteristics(sdkp);
> + }
> +
> sd_read_write_protect_flag(sdkp, buffer);
> sd_read_cache_type(sdkp, buffer);
> sd_read_app_tag_own(sdkp, buffer);
> --
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--
Matthew Wilcox Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours. We can't possibly take such
a retrograde step."