raw-posix: Fix build without posix_fallocate()

Check for the presence of posix_fallocate() in configure and only
compile in support for PREALLOC_MODE_FALLOC when it's there.
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
Signed-off-by: NPeter Maydell <peter.maydell@linaro.org>

block/raw-posix.c

@@ -1416,16 +1416,21 @@ static int raw_create(const char *filename, QemuOpts *opts, Error **errp)
         goto out_close;
     }
 
-    if (prealloc == PREALLOC_MODE_FALLOC) {
+    switch (prealloc) {
+#ifdef CONFIG_POSIX_FALLOCATE
+    case PREALLOC_MODE_FALLOC:
         /* posix_fallocate() doesn't set errno. */
         result = -posix_fallocate(fd, 0, total_size);
         if (result != 0) {
             error_setg_errno(errp, -result,
                              "Could not preallocate data for the new file");
         }
-    } else if (prealloc == PREALLOC_MODE_FULL) {
-        buf = g_malloc0(65536);
+        break;
+#endif
+    case PREALLOC_MODE_FULL:
+    {
         int64_t num = 0, left = total_size;
+        buf = g_malloc0(65536);
 
         while (left > 0) {
             num = MIN(left, 65536);
@@ -1440,10 +1445,15 @@ static int raw_create(const char *filename, QemuOpts *opts, Error **errp)
         }
         fsync(fd);
         g_free(buf);
-    } else if (prealloc != PREALLOC_MODE_OFF) {
+        break;
+    }
+    case PREALLOC_MODE_OFF:
+        break;
+    default:
         result = -EINVAL;
         error_setg(errp, "Unsupported preallocation mode: %s",
                    PreallocMode_lookup[prealloc]);
+        break;
     }
 
 out_close:

configure

@@ -3308,6 +3308,21 @@ if compile_prog "" "" ; then
   fallocate_punch_hole=yes
 fi
 
+# check for posix_fallocate
+posix_fallocate=no
+cat > $TMPC << EOF
+#include <fcntl.h>
+
+int main(void)
+{
+    posix_fallocate(0, 0, 0);
+    return 0;
+}
+EOF
+if compile_prog "" "" ; then
+    posix_fallocate=yes
+fi
+
 # check for sync_file_range
 sync_file_range=no
 cat > $TMPC << EOF
@@ -4522,6 +4537,9 @@ fi
 if test "$fallocate_punch_hole" = "yes" ; then
   echo "CONFIG_FALLOCATE_PUNCH_HOLE=y" >> $config_host_mak
 fi
+if test "$posix_fallocate" = "yes" ; then
+  echo "CONFIG_POSIX_FALLOCATE=y" >> $config_host_mak
+fi
 if test "$sync_file_range" = "yes" ; then
   echo "CONFIG_SYNC_FILE_RANGE=y" >> $config_host_mak
 fi