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>

1 files changed, 6 insertions, 4 deletions

diff --git a/drivers/block/virtio_blk.c b/drivers/block/virtio_blk.c
index a901eee64ba5..3cf7129d83e6 100644
--- a/drivers/block/virtio_blk.c
+++ b/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));