info: Keep request within 4G bound

Otherwise, we get a failure due to Numerical result out of range.

And for safety's sake, we are best capping our request to an aligned
value, if the server insists on minimum alignment.

Maybe nbdinfo should consolidate adjacent lines with identical status,
but that's a different patch.

Fixes: f3fd935

info/Makefile.am

@@ -31,6 +31,7 @@ info_sh_files = \
 	info-description-qemu.sh \
 	info-map-base-allocation.sh \
 	info-map-base-allocation-json.sh \
+	info-map-base-allocation-large.sh \
 	info-map-qemu-dirty-bitmap.sh \
 	info-atomic-output.sh \
 	$(NULL)

info/info-map-base-allocation-large.sh

@@ -0,0 +1,50 @@
+#!/usr/bin/env bash
+# nbd client library in userspace
+# Copyright (C) 2020 Red Hat Inc.
+#
+# This library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2 of the License, or (at your option) any later version.
+#
+# This library is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this library; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+
+. ../tests/functions.sh
+
+set -e
+set -x
+
+requires nbdkit --version
+requires nbdsh --version
+requires tr --version
+
+out=info-base-allocation.out
+cleanup_fn rm -f $out
+rm -f $out
+
+# Note the memory plugin uses a 32K page size, and extents
+# are always aligned with this.
+nbdkit -U - memory 6G --run '
+    nbdsh -u "$uri" \
+          -c "h.pwrite(b\"\\x01\"*131072, 0)" \
+          -c "h.pwrite(b\"\\x02\"*131072, 320*1024)" &&
+    $VG nbdinfo --map "$uri"
+' > $out
+
+cat $out
+
+if [ "$(tr -s ' ' < $out)" != " 0 131072 0 allocated
+ 131072 196608 3 hole,zero
+ 327680 131072 0 allocated
+ 458752 4294508544 3 hole,zero
+4294967296 2147483648 3 hole,zero" ]; then
+    echo "$0: unexpected output from nbdinfo --map"
+    exit 1
+fi

info/nbdinfo.c

@@ -31,6 +31,8 @@
 
 #include <libnbd.h>
 
+#define MIN(a,b) ((a) < (b) ? (a) : (b))
+
 static const char *progname;
 static FILE *fp;
 static bool list_all = false;
@@ -267,7 +269,7 @@ main (int argc, char *argv[])
     fprintf (fp, "%" PRIi64 "\n", size);
   }
   else if (map) {               /* --map (!list_all) */
-    uint64_t offset, prev_offset;
+    uint64_t offset, prev_offset, align, max_len;
 
     /* Did we get the requested map? */
     if (!nbd_can_meta_context (nbd, map)) {
@@ -276,6 +278,8 @@ main (int argc, char *argv[])
                progname, map);
       exit (EXIT_FAILURE);
     }
+    align = nbd_get_block_size (nbd, LIBNBD_SIZE_MINIMUM) ?: 512;
+    max_len = UINT32_MAX - align + 1;
 
     size = nbd_get_size (nbd);
     if (size == -1) {
@@ -286,7 +290,7 @@ main (int argc, char *argv[])
     if (json_output) fprintf (fp, "[\n");
     for (offset = 0; offset < size;) {
       prev_offset = offset;
-      if (nbd_block_status (nbd, size - offset, offset,
+      if (nbd_block_status (nbd, MIN (size - offset, max_len), offset,
                             (nbd_extent_callback) { .callback = extent_callback,
                                                     .user_data = &offset },
                             0) == -1) {