xen: make use of xenbus_read_unsigned() in xen-blkfront

Use xenbus_read_unsigned() instead of xenbus_scanf() when possible.
This requires to change the type of some reads from int to unsigned,
but these cases have been wrong before: negative values are not allowed
for the modified cases.

Cc: konrad.wilk@oracle.com
Cc: roger.pau@citrix.com

Signed-off-by: Juergen Gross <jgross@suse.com>
Acked-by: David Vrabel <david.vrabel@citrix.com>

1 files changed, 26 insertions, 55 deletions

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 9908597c5209..2ee9646d8a5f 100644
--- a/drivers/block/xen-blkfront.c
+++ b/drivers/block/xen-blkfront.c
@@ -1758,17 +1758,13 @@ static int talk_to_blkback(struct xenbus_device *dev,
         const char *message = NULL;
         struct xenbus_transaction xbt;
         int err;
-        unsigned int i, max_page_order = 0;
-        unsigned int ring_page_order = 0;
+        unsigned int i, max_page_order;
+        unsigned int ring_page_order;
 
-        err = xenbus_scanf(XBT_NIL, info->xbdev->otherend,
-                           "max-ring-page-order", "%u", &max_page_order);
-        if (err != 1)
-                info->nr_ring_pages = 1;
-        else {
-                ring_page_order = min(xen_blkif_max_ring_order, max_page_order);
-                info->nr_ring_pages = 1 << ring_page_order;
-        }
+        max_page_order = xenbus_read_unsigned(info->xbdev->otherend,
+                                              "max-ring-page-order", 0);
+        ring_page_order = min(xen_blkif_max_ring_order, max_page_order);
+        info->nr_ring_pages = 1 << ring_page_order;
 
         for (i = 0; i < info->nr_rings; i++) {
                 struct blkfront_ring_info *rinfo = &info->rinfo[i];
@@ -1877,18 +1873,14 @@ again:
 
 static int negotiate_mq(struct blkfront_info *info)
 {
-        unsigned int backend_max_queues = 0;
-        int err;
+        unsigned int backend_max_queues;
         unsigned int i;
 
         BUG_ON(info->nr_rings);
 
         /* Check if backend supports multiple queues. */
-        err = xenbus_scanf(XBT_NIL, info->xbdev->otherend,
-                           "multi-queue-max-queues", "%u", &backend_max_queues);
-        if (err < 0)
-                backend_max_queues = 1;
-
+        backend_max_queues = xenbus_read_unsigned(info->xbdev->otherend,
+                                                  "multi-queue-max-queues", 1);
         info->nr_rings = min(backend_max_queues, xen_blkif_max_queues);
         /* We need at least one ring. */
         if (!info->nr_rings)
@@ -2195,7 +2187,6 @@ static void blkfront_setup_discard(struct blkfront_info *info)
         int err;
         unsigned int discard_granularity;
         unsigned int discard_alignment;
-        unsigned int discard_secure;
 
         info->feature_discard = 1;
         err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
@@ -2206,10 +2197,9 @@ static void blkfront_setup_discard(struct blkfront_info *info)
                 info->discard_granularity = discard_granularity;
                 info->discard_alignment = discard_alignment;
         }
-        err = xenbus_scanf(XBT_NIL, info->xbdev->otherend,
-                           "discard-secure", "%u", &discard_secure);
-        if (err > 0)
-                info->feature_secdiscard = !!discard_secure;
+        info->feature_secdiscard =
+                !!xenbus_read_unsigned(info->xbdev->otherend, "discard-secure",
+                                       0);
 }
 
 static int blkfront_setup_indirect(struct blkfront_ring_info *rinfo)
@@ -2301,16 +2291,11 @@ out_of_memory:
  */
 static void blkfront_gather_backend_features(struct blkfront_info *info)
 {
-        int err;
-        int barrier, flush, discard, persistent;
         unsigned int indirect_segments;
 
         info->feature_flush = 0;
         info->feature_fua = 0;
 
-        err = xenbus_scanf(XBT_NIL, info->xbdev->otherend,
-                           "feature-barrier", "%d", &barrier);
-
         /*
          * If there's no "feature-barrier" defined, then it means
          * we're dealing with a very old backend which writes
@@ -2318,7 +2303,7 @@ static void blkfront_gather_backend_features(struct blkfront_info *info)
          *
          * If there are barriers, then we use flush.
          */
-        if (err > 0 && barrier) {
+        if (xenbus_read_unsigned(info->xbdev->otherend, "feature-barrier", 0)) {
                 info->feature_flush = 1;
                 info->feature_fua = 1;
         }
@@ -2327,35 +2312,23 @@ static void blkfront_gather_backend_features(struct blkfront_info *info)
          * And if there is "feature-flush-cache" use that above
          * barriers.
          */
-        err = xenbus_scanf(XBT_NIL, info->xbdev->otherend,
-                           "feature-flush-cache", "%d", &flush);
-
-        if (err > 0 && flush) {
+        if (xenbus_read_unsigned(info->xbdev->otherend, "feature-flush-cache",
+                                 0)) {
                 info->feature_flush = 1;
                 info->feature_fua = 0;
         }
 
-        err = xenbus_scanf(XBT_NIL, info->xbdev->otherend,
-                           "feature-discard", "%d", &discard);
-
-        if (err > 0 && discard)
+        if (xenbus_read_unsigned(info->xbdev->otherend, "feature-discard", 0))
                 blkfront_setup_discard(info);
 
-        err = xenbus_scanf(XBT_NIL, info->xbdev->otherend,
-                           "feature-persistent", "%d", &persistent);
-        if (err <= 0)
-                info->feature_persistent = 0;
-        else
-                info->feature_persistent = persistent;
+        info->feature_persistent =
+                xenbus_read_unsigned(info->xbdev->otherend,
+                                     "feature-persistent", 0);
 
-        err = xenbus_scanf(XBT_NIL, info->xbdev->otherend,
-                           "feature-max-indirect-segments", "%u",
-                           &indirect_segments);
-        if (err <= 0)
-                info->max_indirect_segments = 0;
-        else
-                info->max_indirect_segments = min(indirect_segments,
-                                                  xen_blkif_max_segments);
+        indirect_segments = xenbus_read_unsigned(info->xbdev->otherend,
+                                        "feature-max-indirect-segments", 0);
+        info->max_indirect_segments = min(indirect_segments,
+                                          xen_blkif_max_segments);
 }
 
 /*
@@ -2420,11 +2393,9 @@ static void blkfront_connect(struct blkfront_info *info)
          * provide this. Assume physical sector size to be the same as
          * sector_size in that case.
          */
-        err = xenbus_scanf(XBT_NIL, info->xbdev->otherend,
-                           "physical-sector-size", "%u", &physical_sector_size);
-        if (err != 1)
-                physical_sector_size = sector_size;
-
+        physical_sector_size = xenbus_read_unsigned(info->xbdev->otherend,
+                                                    "physical-sector-size",
+                                                    sector_size);
         blkfront_gather_backend_features(info);
         for (i = 0; i < info->nr_rings; i++) {
                 err = blkfront_setup_indirect(&info->rinfo[i]);