block: add bdrv_write_zeroes()

Signed-off-by: Peter Lieven <pl@kamp.de>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

block.c

diff --git a/block.c b/block.c
index b560241..b05e2d6 100644
--- a/block.c
+++ b/block.c
@@ -2162,6 +2162,7 @@
     QEMUIOVector *qiov;
     bool is_write;
     int ret;
+    BdrvRequestFlags flags;
 } RwCo;
 
 static void coroutine_fn bdrv_rw_co_entry(void *opaque)
@@ -2170,10 +2171,12 @@
 
     if (!rwco->is_write) {
         rwco->ret = bdrv_co_do_readv(rwco->bs, rwco->sector_num,
-                                     rwco->nb_sectors, rwco->qiov, 0);
+                                     rwco->nb_sectors, rwco->qiov,
+                                     rwco->flags);
     } else {
         rwco->ret = bdrv_co_do_writev(rwco->bs, rwco->sector_num,
-                                      rwco->nb_sectors, rwco->qiov, 0);
+                                      rwco->nb_sectors, rwco->qiov,
+                                      rwco->flags);
     }
 }
 
@@ -2181,7 +2184,8 @@
  * Process a vectored synchronous request using coroutines
  */
 static int bdrv_rwv_co(BlockDriverState *bs, int64_t sector_num,
-                       QEMUIOVector *qiov, bool is_write)
+                       QEMUIOVector *qiov, bool is_write,
+                       BdrvRequestFlags flags)
 {
     Coroutine *co;
     RwCo rwco = {
@@ -2191,6 +2195,7 @@
         .qiov = qiov,
         .is_write = is_write,
         .ret = NOT_DONE,
+        .flags = flags,
     };
     assert((qiov->size & (BDRV_SECTOR_SIZE - 1)) == 0);
 
@@ -2222,7 +2227,7 @@
  * Process a synchronous request using coroutines
  */
 static int bdrv_rw_co(BlockDriverState *bs, int64_t sector_num, uint8_t *buf,
-                      int nb_sectors, bool is_write)
+                      int nb_sectors, bool is_write, BdrvRequestFlags flags)
 {
     QEMUIOVector qiov;
     struct iovec iov = {
@@ -2231,14 +2236,14 @@
     };
 
     qemu_iovec_init_external(&qiov, &iov, 1);
-    return bdrv_rwv_co(bs, sector_num, &qiov, is_write);
+    return bdrv_rwv_co(bs, sector_num, &qiov, is_write, flags);
 }
 
 /* return < 0 if error. See bdrv_write() for the return codes */
 int bdrv_read(BlockDriverState *bs, int64_t sector_num,
               uint8_t *buf, int nb_sectors)
 {
-    return bdrv_rw_co(bs, sector_num, buf, nb_sectors, false);
+    return bdrv_rw_co(bs, sector_num, buf, nb_sectors, false, 0);
 }
 
 /* Just like bdrv_read(), but with I/O throttling temporarily disabled */
@@ -2264,12 +2269,18 @@
 int bdrv_write(BlockDriverState *bs, int64_t sector_num,
                const uint8_t *buf, int nb_sectors)
 {
-    return bdrv_rw_co(bs, sector_num, (uint8_t *)buf, nb_sectors, true);
+    return bdrv_rw_co(bs, sector_num, (uint8_t *)buf, nb_sectors, true, 0);
 }
 
 int bdrv_writev(BlockDriverState *bs, int64_t sector_num, QEMUIOVector *qiov)
 {
-    return bdrv_rwv_co(bs, sector_num, qiov, true);
+    return bdrv_rwv_co(bs, sector_num, qiov, true, 0);
+}
+
+int bdrv_write_zeroes(BlockDriverState *bs, int64_t sector_num, int nb_sectors)
+{
+    return bdrv_rw_co(bs, sector_num, NULL, nb_sectors, true,
+                      BDRV_REQ_ZERO_WRITE);
 }
 
 int bdrv_pread(BlockDriverState *bs, int64_t offset,

include/block/block.h

diff --git a/include/block/block.h b/include/block/block.h
index b6b9014..742fce5 100644
--- a/include/block/block.h
+++ b/include/block/block.h
@@ -157,6 +157,8 @@
                           uint8_t *buf, int nb_sectors);
 int bdrv_write(BlockDriverState *bs, int64_t sector_num,
                const uint8_t *buf, int nb_sectors);
+int bdrv_write_zeroes(BlockDriverState *bs, int64_t sector_num,
+               int nb_sectors);
 int bdrv_writev(BlockDriverState *bs, int64_t sector_num, QEMUIOVector *qiov);
 int bdrv_pread(BlockDriverState *bs, int64_t offset,
                void *buf, int count);