[SCSI] scsi_eh_prep_cmnd should save scmd->underflow

This patch (as1116) fixes a bug in scsi_eh_prep_cmnd() and
scsi_eh_restore_cmnd(). These routines are supposed to save any
values they change and restore them later, but someone forgot to
save & restore scmd->underflow.

This fixes part of the problem reported in Bugzilla #9638.

[jejb: fix up rejections around DIF/DIX]
Signed-off-by: Alan Stern <[e-mail]>
Signed-off-by: James Bottomley <[e-mail]>

drivers/scsi/scsi_error.c

···
 	ses->sdb = scmd->sdb;
 	ses->next_rq = scmd->request->next_rq;
 	ses->result = scmd->result;
+	ses->underflow = scmd->underflow;
 	ses->prot_op = scmd->prot_op;
 
 	scmd->prot_op = SCSI_PROT_NORMAL;
···
 	scmd->sdb = ses->sdb;
 	scmd->request->next_rq = ses->next_rq;
 	scmd->result = ses->result;
+	scmd->underflow = ses->underflow;
 	scmd->prot_op = ses->prot_op;
 }
 EXPORT_SYMBOL(scsi_eh_restore_cmnd);

include/scsi/scsi_eh.h

···
 	/* saved state */
 	int result;
 	enum dma_data_direction data_direction;
+	unsigned underflow;
 	unsigned char cmd_len;
 	unsigned char prot_op;
 	unsigned char *cmnd;