usb-storage: add last-sector hacks

usb-storage: add last-sector hacks

commit 25ff1c316f6a763f1eefe7f8984b2d8c03888432 upstream.

This patch (as1189d) adds some hacks to usb-storage for dealing with
the growing problems involving bad capacity values and last-sector
accesses:

	A new flag, US_FL_CAPACITY_OK, is created to indicate that
	the device is known to report its capacity correctly.  An
	unusual_devs entry for Linux's own File-backed Storage Gadget
	is added with this flag set, since g_file_storage always
	reports the correct capacity and since the capacity need
	not be even (it is determined by the size of the backing
	file).

	An entry in unusual_devs.h which has only the CAPACITY_OK
	flag set shouldn't prejudice libusual, since the device will
	work perfectly well with either usb-storage or ub.  So a
	new macro, COMPLIANT_DEV, is added to let libusual know
	about these entries.

	When a last-sector access fails three times in a row and
	neither the FIX_CAPACITY nor the CAPACITY_OK flag is set,
	we assume the last-sector bug is present.  We replace the
	existing status and sense data with values that will cause
	the SCSI core to fail the access immediately rather than
	retry indefinitely.  This should fix the difficulties
	people have been having with Nokia phones.

This version of the patch differs from the version accepted into the
mainline only in that it does not trigger a WARN() when an
odd-numbered last-sector access succeeds.  In a stable kernel series
we don't want to go around spamming users' logs and consoles for no
good reason.

Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>