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.
Signed-off-by: Denis V. Lunev <d...@openvz.org>
CC: Kevin Wolf <kw...@redhat.com>
CC: Stefan Hajnoczi <stefa...@redhat.com>
---
block/raw-posix.c | 13 ++++++++++++-
configure | 19 +++++++++++++++++++
2 files changed, 31 insertions(+), 1 deletion(-)
diff --git a/block/raw-posix.c b/block/raw-posix.c
index e51293a..66ebaab 100644
--- a/block/raw-posix.c
+++ b/block/raw-posix.c
@@ -60,7 +60,7 @@
#define FS_NOCOW_FL 0x00800000 /* Do not cow file */
#endif
#endif
-#ifdef CONFIG_FALLOCATE_PUNCH_HOLE
+#if defined(CONFIG_FALLOCATE_PUNCH_HOLE) ||
defined(CONFIG_FALLOCATE_ZERO_RANGE)
#include <linux/falloc.h>
#endif
#if defined (__FreeBSD__) || defined(__FreeBSD_kernel__)
@@ -919,6 +919,17 @@ static ssize_t handle_aiocb_write_zeroes(RawPosixAIOData
*aiocb)
return xfs_write_zeroes(s, aiocb->aio_offset, aiocb->aio_nbytes);
}
#endif
+
+#ifdef CONFIG_FALLOCATE_ZERO_RANGE
+ do {
+ if (fallocate(s->fd, FALLOC_FL_ZERO_RANGE,
+ aiocb->aio_offset, aiocb->aio_nbytes) == 0) {
+ return 0;
+ }
+ } while (errno == EINTR);
+
+ ret = -errno;
+#endif
}
if (ret == -ENODEV || ret == -ENOSYS || ret == -EOPNOTSUPP ||
diff --git a/configure b/configure
index cae588c..dfcf7b3 100755
--- a/configure
+++ b/configure
@@ -3309,6 +3309,22 @@ 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 > $TMPC << EOF
@@ -4538,6 +4554,9 @@ fi
if test "$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
--
1.9.1
