You may remember the unfortunately named "last_sector_bug" workaround. It was applied to the SCSI SD driver to handle certain USB cardreaders. Unfortunately it introduced a regression by breaking certain other buggy USB cardreaders. I ended up driving this fix, as the sucker who bought the second lot of buggy hardware. Alan Stern from USB-land said that he's happy to see this patch merged (after fixing my logic and critiquing the patch description). I'm grateful for his help and everyone else who chimed in on the usb-storage mailing list. The patch description goes into detail. Here's a less formal description - The original bug causes multi-sector accesses which include the last sector of the device to fail. The workaround was to split such accesses in two, so that the last sector is accessed on it's own. The overhead is minimal and so it was applied to all USB storage devices. Perversely, this revealed a second bug in a different set of card readers. This time, failure is caused by multi-sector accesses which stop just short of the last sector. This suggests a systemic failure in the design/testing of USB cardreaders, where multi-sector accesses to the last sectors are overlooked, and fencepost errors may be common. What follows is a general workaround to prevent multi-sector accesses touching any of the last 8 hardware sectors. Thanks Alan -- 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
