target: Do memory allocation for bidi commands using target_alloc_sgl
This patch updates transport_generic_new_cmd() to call target_alloc_sgl()
for SGL + page memory allocation for se_cmd->t_bidi_data_sg.
It also adds the special case for SCF_COMPARE_AND_WRITE to calculate a
different bidi_length based upon se_cmd->t_task_nolb.
Reported-by: Christoph Hellwig <hch@lst.de> Cc: Christoph Hellwig <hch@lst.de> Cc: Hannes Reinecke <hare@suse.de> Cc: Martin Petersen <martin.petersen@oracle.com> Cc: Chris Mason <chris.mason@fusionio.com> Cc: James Bottomley <JBottomley@Parallels.com> Cc: Nicholas Bellinger <nab@linux-iscsi.org> Signed-off-by: Nicholas Bellinger <nab@daterainc.com>