Since we split the scsi_request out of struct request, while the
standard prep_rq_fn builds 10 byte cmds, it missed to invoke
scsi_req_init() to initialize certain fields of a scsi_request
structure (.__cmd[], .cmd, .cmd_len and .sense_len but no other
members of struct scsi_request).
An example panic on virtual machines (qemu/virtualbox) to boot
from IDE cdrom:
...
[ 8.754381] Call Trace:
[ 8.755419] blk_peek_request+0x182/0x2e0
[ 8.755863] blk_fetch_request+0x1c/0x40
[ 8.756148] ? ktime_get+0x40/0xa0
[ 8.756385] do_ide_request+0x37d/0x660
[ 8.756704] ? cfq_group_service_tree_add+0x98/0xc0
[ 8.757011] ? cfq_service_tree_add+0x1e5/0x2c0
[ 8.757313] ? ktime_get+0x40/0xa0
[ 8.757544] __blk_run_queue+0x3d/0x60
[ 8.757837] queue_unplugged+0x2f/0xc0
[ 8.758088] blk_flush_plug_list+0x1f4/0x240
[ 8.758362] blk_finish_plug+0x2c/0x40
...
[ 8.770906] RIP: ide_cdrom_prep_fn+0x63/0x180 RSP: ffff92aec018bae8
[ 8.772329] ---[ end trace 6408481e551a85c9 ]---
...
Fixes: 82ed4db499 ("block: split scsi_request out of struct request")
Signed-off-by: Hongxu Jia <hongxu.jia@windriver.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
79d73346ac