SG: audit of drivers that use blk_rq_map_sg()

They need to properly init the sg table, or blk_rq_map_sg() will
complain if CONFIG_DEBUG_SG is set.
Signed-off-by: Jens Axboe <jens.axboe@oracle.com>

drivers/block/virtio_blk.c

@@ -4,7 +4,9 @@
 #include <linux/hdreg.h>
 #include <linux/virtio.h>
 #include <linux/virtio_blk.h>
-#include <linux/virtio_blk.h>
+#include <linux/scatterlist.h>
+
+#define VIRTIO_MAX_SG	(3+MAX_PHYS_SEGMENTS)
 
 static unsigned char virtblk_index = 'a';
 struct virtio_blk
@@ -23,7 +25,7 @@ struct virtio_blk
 	mempool_t *pool;
 
 	/* Scatterlist: can be too big for stack. */
-	struct scatterlist sg[3+MAX_PHYS_SEGMENTS];
+	struct scatterlist sg[VIRTIO_MAX_SG];
 };
 
 struct virtblk_req
@@ -94,8 +96,8 @@ static bool do_req(struct request_queue *q, struct virtio_blk *vblk,
 	if (blk_barrier_rq(vbr->req))
 		vbr->out_hdr.type |= VIRTIO_BLK_T_BARRIER;
 
-	/* We have to zero this, otherwise blk_rq_map_sg gets upset. */
-	memset(vblk->sg, 0, sizeof(vblk->sg));
+	/* This init could be done at vblk creation time */
+	sg_init_table(vblk->sg, VIRTIO_MAX_SG);
 	sg_set_buf(&vblk->sg[0], &vbr->out_hdr, sizeof(vbr->out_hdr));
 	num = blk_rq_map_sg(q, vbr->req, vblk->sg+1);
 	sg_set_buf(&vblk->sg[num+1], &vbr->in_hdr, sizeof(vbr->in_hdr));

drivers/cdrom/viocd.c

@@ -41,9 +41,9 @@
 #include <linux/completion.h>
 #include <linux/proc_fs.h>
 #include <linux/seq_file.h>
+#include <linux/scatterlist.h>
 
 #include <asm/vio.h>
-#include <asm/scatterlist.h>
 #include <asm/iseries/hv_types.h>
 #include <asm/iseries/hv_lp_event.h>
 #include <asm/iseries/vio.h>
@@ -258,6 +258,7 @@ static int send_request(struct request *req)
 		cmd = viomajorsubtype_cdio | viocdwrite;
 	}
 
+	sg_init_table(&sg, 1);
         if (blk_rq_map_sg(req->q, req, &sg) == 0) {
 		printk(VIOCD_KERN_WARNING
 				"error setting up scatter/gather list\n");

drivers/message/i2o/i2o_block.c

@@ -284,6 +284,7 @@ static inline struct i2o_block_request *i2o_block_request_alloc(void)
 		return ERR_PTR(-ENOMEM);
 
 	INIT_LIST_HEAD(&ireq->queue);
+	sg_init_table(ireq->sg_table, I2O_MAX_PHYS_SEGMENTS);
 
 	return ireq;
 };