[PATCH 16/22] xen-blkfront: Make use of the new sg_map helper function

From: Logan Gunthorpe
Date: Thu Apr 13 2017 - 18:13:32 EST


Straightforward conversion to the new helper, except due to
the lack of error path, we have to warn if unmapable memory
is ever present in the sgl.

Signed-off-by: Logan Gunthorpe <logang@xxxxxxxxxxxx>
---
drivers/block/xen-blkfront.c | 33 +++++++++++++++++++++++++++------
1 file changed, 27 insertions(+), 6 deletions(-)

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 5067a0a..7dcf41d 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -807,8 +807,19 @@ static int blkif_queue_rw_req(struct request *req, struct blkfront_ring_info *ri
BUG_ON(sg->offset + sg->length > PAGE_SIZE);

if (setup.need_copy) {
- setup.bvec_off = sg->offset;
- setup.bvec_data = kmap_atomic(sg_page(sg));
+ setup.bvec_off = 0;
+ setup.bvec_data = sg_map(sg, SG_KMAP_ATOMIC);
+ if (IS_ERR(setup.bvec_data)) {
+ /*
+ * This should really never happen unless
+ * the code is changed to use memory that is
+ * not mappable in the sg. Seeing there is a
+ * questionable error path out of here,
+ * we WARN.
+ */
+ WARN(1, "Non-mappable memory used in sg!");
+ return 1;
+ }
}

gnttab_foreach_grant_in_range(sg_page(sg),
@@ -818,7 +829,7 @@ static int blkif_queue_rw_req(struct request *req, struct blkfront_ring_info *ri
&setup);

if (setup.need_copy)
- kunmap_atomic(setup.bvec_data);
+ sg_unmap(sg, setup.bvec_data, SG_KMAP_ATOMIC);
}
if (setup.segments)
kunmap_atomic(setup.segments);
@@ -1468,8 +1479,18 @@ static bool blkif_completion(unsigned long *id,
for_each_sg(s->sg, sg, num_sg, i) {
BUG_ON(sg->offset + sg->length > PAGE_SIZE);

- data.bvec_offset = sg->offset;
- data.bvec_data = kmap_atomic(sg_page(sg));
+ data.bvec_offset = 0;
+ data.bvec_data = sg_map(sg, SG_KMAP_ATOMIC);
+ if (IS_ERR(data.bvec_data)) {
+ /*
+ * This should really never happen unless
+ * the code is changed to use memory that is
+ * not mappable in the sg. Seeing there is no
+ * clear error path, we WARN.
+ */
+ WARN(1, "Non-mappable memory used in sg!");
+ return 1;
+ }

gnttab_foreach_grant_in_range(sg_page(sg),
sg->offset,
@@ -1477,7 +1498,7 @@ static bool blkif_completion(unsigned long *id,
blkif_copy_from_grant,
&data);

- kunmap_atomic(data.bvec_data);
+ sg_unmap(sg, data.bvec_data, SG_KMAP_ATOMIC);
}
}
/* Add the persistent grant into the list of free grants */
--
2.1.4