[Xen-devel] [PATCH 03/12] xen: make use of xenbus_read_unsigned() in xen-blkfront

[Juergen Gross <jgross@xxxxxxxx>]

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@xxxxxxxxxx
Cc: roger.pau@xxxxxxxxxx

Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
---
 drivers/block/xen-blkfront.c | 81 ++++++++++++++------------------------------
 1 file changed, 26 insertions(+), 55 deletions(-)

diff --git a/drivers/block/xen-blkfront.c b/drivers/block/xen-blkfront.c
index 9908597..2ee9646 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 @@ static int talk_to_blkback(struct xenbus_device *dev,
 
 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 @@ static int blkfront_setup_indirect(struct 
blkfront_ring_info *rinfo)
  */
 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]);
-- 
2.6.6


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