[Qemu-devel] [PATCH 5/5] vmdk: add bdrv_co_write_zeroes

[Fam Zheng]

From: Feiran Zheng <address@hidden>

Use special offset to write zeroes efficiently, when zeroed-grain GTE is
available. If zero-write an allocated cluster, cluster is leaked because
its offset pointer is overwritten by "0x1".

Signed-off-by: Fam Zheng <address@hidden>
---
 block/vmdk.c | 63 +++++++++++++++++++++++++++++++++++++++++++++++-------------
 1 file changed, 50 insertions(+), 13 deletions(-)

diff --git a/block/vmdk.c b/block/vmdk.c
index 5daa9f2..3055847 100644
--- a/block/vmdk.c
+++ b/block/vmdk.c
@@ -1163,8 +1163,16 @@ static coroutine_fn int vmdk_co_read(BlockDriverState 
*bs, int64_t sector_num,
     return ret;
 }
 
+/**
+ * params:
+ *  - zeroed:       buf is ignored (data is zero), use zeroed_grain GTE
+ *                  feature if possible, otherwise return -ENOTSUP.
+ *  - zero_dry_run: used for zeroed == true only, don't update L2 table, just
+ *                  try if it's supported
+ */
 static int vmdk_write(BlockDriverState *bs, int64_t sector_num,
-                     const uint8_t *buf, int nb_sectors)
+                      const uint8_t *buf, int nb_sectors,
+                      bool zeroed, bool zero_dry_run)
 {
     BDRVVmdkState *s = bs->opaque;
     VmdkExtent *extent = NULL;
@@ -1220,17 +1228,30 @@ static int vmdk_write(BlockDriverState *bs, int64_t 
sector_num,
         if (n > nb_sectors) {
             n = nb_sectors;
         }
-
-        ret = vmdk_write_extent(extent,
-                        cluster_offset, index_in_cluster * 512,
-                        buf, n, sector_num);
-        if (ret) {
-            return ret;
-        }
-        if (m_data.valid) {
-            /* update L2 tables */
-            if (vmdk_L2update(extent, &m_data) == -1) {
-                return -EIO;
+        if (zeroed) {
+            /* Do zeroed write, buf is ignored */
+            if (extent->has_zero_grain &&
+                    index_in_cluster == 0 &&
+                    n >= extent->cluster_sectors) {
+                n = extent->cluster_sectors;
+                if (!zero_dry_run) {
+                    m_data.offset = VMDK_GTE_ZEROED;
+                }
+            } else {
+                return -ENOTSUP;
+            }
+        } else {
+            ret = vmdk_write_extent(extent,
+                            cluster_offset, index_in_cluster * 512,
+                            buf, n, sector_num);
+            if (ret) {
+                return ret;
+            }
+            if (m_data.valid) {
+                /* update L2 tables */
+                if (vmdk_L2update(extent, &m_data) == -1) {
+                    return -EIO;
+                }
             }
         }
         nb_sectors -= n;
@@ -1256,7 +1277,22 @@ static coroutine_fn int vmdk_co_write(BlockDriverState 
*bs, int64_t sector_num,
     int ret;
     BDRVVmdkState *s = bs->opaque;
     qemu_co_mutex_lock(&s->lock);
-    ret = vmdk_write(bs, sector_num, buf, nb_sectors);
+    ret = vmdk_write(bs, sector_num, buf, nb_sectors, false, false);
+    qemu_co_mutex_unlock(&s->lock);
+    return ret;
+}
+
+static int coroutine_fn vmdk_co_write_zeroes(BlockDriverState *bs,
+                                             int64_t sector_num,
+                                             int nb_sectors)
+{
+    int ret;
+    BDRVVmdkState *s = bs->opaque;
+    qemu_co_mutex_lock(&s->lock);
+    ret = vmdk_write(bs, sector_num, NULL, nb_sectors, true, true);
+    if (!ret) {
+        ret = vmdk_write(bs, sector_num, NULL, nb_sectors, true, false);
+    }
     qemu_co_mutex_unlock(&s->lock);
     return ret;
 }
@@ -1736,6 +1772,7 @@ static BlockDriver bdrv_vmdk = {
     .bdrv_reopen_prepare = vmdk_reopen_prepare,
     .bdrv_read      = vmdk_co_read,
     .bdrv_write     = vmdk_co_write,
+    .bdrv_co_write_zeroes = vmdk_co_write_zeroes,
     .bdrv_close     = vmdk_close,
     .bdrv_create    = vmdk_create,
     .bdrv_co_flush_to_disk  = vmdk_co_flush,
-- 
1.8.1.4