block: use fallocate(FALLOC_FL_ZERO_RANGE) in handle_aiocb_write_zeroes

This efficiently writes zeroes on Linux if the kernel is capable enough.
FALLOC_FL_ZERO_RANGE correctly handles all cases, including and not
including file expansion.

CC: Kevin Wolf <kwolf@redhat.com>
CC: Stefan Hajnoczi <stefanha@redhat.com>
CC: Peter Lieven <pl@kamp.de>
CC: Fam Zheng <famz@redhat.com>
Signed-off-by: Denis V. Lunev <den@openvz.org>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

1 files changed, 19 insertions, 0 deletions

diff --git a/configure b/configure
index f185dd0..e00e03a 100755
--- a/configure
+++ b/configure
@@ -3335,6 +3335,22 @@ if compile_prog "" "" ; then
   fallocate_punch_hole=yes
 fi
 
+# check that fallocate supports range zeroing inside the file
+fallocate_zero_range=no
+cat > $TMPC << EOF
+#include <fcntl.h>
+#include <linux/falloc.h>
+
+int main(void)
+{
+    fallocate(0, FALLOC_FL_ZERO_RANGE, 0, 0);
+    return 0;
+}
+EOF
+if compile_prog "" "" ; then
+  fallocate_zero_range=yes
+fi
+
 # check for posix_fallocate
 posix_fallocate=no
 cat > $TMPC << EOF
@@ -4567,6 +4583,9 @@ fi
 if test "$fallocate_punch_hole" = "yes" ; then
   echo "CONFIG_FALLOCATE_PUNCH_HOLE=y" >> $config_host_mak
 fi
+if test "$fallocate_zero_range" = "yes" ; then
+  echo "CONFIG_FALLOCATE_ZERO_RANGE=y" >> $config_host_mak
+fi
 if test "$posix_fallocate" = "yes" ; then
   echo "CONFIG_POSIX_FALLOCATE=y" >> $config_host_mak
 fi