block/iscsi: allow fall back to WRITE SAME without UNMAP

if the iscsi driver receives a write zeroes request with
the BDRV_REQ_MAY_UNMAP flag set it fails with -ENOTSUP
if the iscsi target does not support WRITE SAME with
UNMAP. However, the BDRV_REQ_MAY_UNMAP is only a hint
and writing zeroes with WRITE SAME will still be
better than falling back to writing zeroes with WRITE16.

Signed-off-by: Peter Lieven <pl@kamp.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/block/iscsi.c b/block/iscsi.c
index a636ea4f53f4ddc6d60d1c85160dfb69cca1f6e8..56f54193c8f6343e9ca1b987cbdb139106da7bef 100644 (file)
--- a/block/iscsi.c
+++ b/block/iscsi.c
@@ -809,13 +809,14 @@ coroutine_fn iscsi_co_write_zeroes(BlockDriverState *bs, int64_t sector_num,
         return -EINVAL;
     }
 
-    if (!(flags & BDRV_REQ_MAY_UNMAP) && !iscsilun->has_write_same) {
-        /* WRITE SAME without UNMAP is not supported by the target */
-        return -ENOTSUP;
+    if ((flags & BDRV_REQ_MAY_UNMAP) && !iscsilun->lbp.lbpws) {
+        /* WRITE SAME with UNMAP is not supported by the target,
+         * fall back and try WRITE SAME without UNMAP */
+        flags &= ~BDRV_REQ_MAY_UNMAP;
     }
 
-    if ((flags & BDRV_REQ_MAY_UNMAP) && !iscsilun->lbp.lbpws) {
-        /* WRITE SAME with UNMAP is not supported by the target */
+    if (!(flags & BDRV_REQ_MAY_UNMAP) && !iscsilun->has_write_same) {
+        /* WRITE SAME without UNMAP is not supported by the target */
         return -ENOTSUP;
     }