[PATCH] Fix BUG at drivers/scsi/scsi_lib.c:1118 caused by "pktsetup dvd /dev/sr0"

[PATCH] Fix BUG at drivers/scsi/scsi_lib.c:1118 caused by "pktsetup dvd /dev/sr0"

Fix http://bugzilla.kernel.org/show_bug.cgi?id=7667

This is because the packet driver tries to send down read/write BLOCK_PC
commands that don't use a bio and do not use sg lists.

The right fix is to replace all the packet_command stuff in the packet
driver by scsi_execute() which needs to be lifted from scsi code to
the block code for that.

Fix the bug for now.  It's not the full way to a generic execute block pc
infrastcuture but fixes the bug for the time being.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Acked-by: Peter Osterlund <petero2@telia.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>