[PATCH] USB Storage: retry hard errors

This patch started life as as527, and was rediffed by me.

Since the IDE interface doesn't convey much information about types of
errors, many USB-IDE adapters report all low-level errors with SK = 0x04,
which is supposed to be used only for non-recoverable errors.  As a result
the SCSI midlayer doesn't retry the command.  But quite often a retry
would succeed, whereas an unnecessary retry doesn't really hurt anything.

This patch uses a recently-implemented flag to tell the SCSI midlayer that
such hardware errors should be retried.
Signed-off-by: NAlan Stern <stern@rowland.harvard.edu>
Signed-off-by: NMatthew Dharm <mdharm-usb@one-eyed-alien.net>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>

drivers/usb/storage/scsiglue.c

@@ -155,6 +155,15 @@ static int slave_configure(struct scsi_device *sdev)
 		 * If this device makes that mistake, tell the sd driver. */
 		if (us->flags & US_FL_FIX_CAPACITY)
 			sdev->fix_capacity = 1;
+
+		/* USB-IDE bridges tend to report SK = 0x04 (Non-recoverable
+		 * Hardware Error) when any low-level error occurs,
+		 * recoverable or not.  Setting this flag tells the SCSI
+		 * midlayer to retry such commands, which frequently will
+		 * succeed and fix the error.  The worst this can lead to
+		 * is an occasional series of retries that will all fail. */
+		sdev->retry_hwerror = 1;
+
 	} else {
 
 		/* Non-disk-type devices don't need to blacklist any pages