When there is a format driver between the backend, it's not guaranteed
that exposing the opt_transfer_length for the format driver results in
the optimal requests (because of fragmentation etc.), but it can't make
things worse, so let's just do it.
Signed-off-by: Kevin Wolf <kw...@redhat.com>
---
block.c | 18 +++++++++++++++++-
1 file changed, 17 insertions(+), 1 deletion(-)
diff --git a/block.c b/block.c
index c32d856..79a325f 100644
--- a/block.c
+++ b/block.c
@@ -487,7 +487,23 @@ static int bdrv_refresh_limits(BlockDriverState *bs)
if (!drv) {
return 0;
- } else if (drv->bdrv_refresh_limits) {
+ }
+
+ /* Take some limits from the children as a default */
+ if (bs->file) {
+ bdrv_refresh_limits(bs->file);
+ bs->bl.opt_transfer_length = bs->file->bl.opt_transfer_length;
+ }
+
+ if (bs->backing_hd) {
+ bdrv_refresh_limits(bs->backing_hd);
+ bs->bl.opt_transfer_length =
+ MAX(bs->bl.opt_transfer_length,
+ bs->backing_hd->bl.opt_transfer_length);
+ }
+
+ /* Then let the driver override it */
+ if (drv->bdrv_refresh_limits) {
return drv->bdrv_refresh_limits(bs);
}
--
1.8.1.4
