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authorKevin Wolf <kwolf@redhat.com>2013-12-11 19:50:32 +0100
committerKevin Wolf <kwolf@redhat.com>2014-01-24 17:40:01 +0100
commit466ad822deef3a03757d505218a52993c5d56b5d (patch)
treeb92cdf86a640a7c972ba6172fe7cc4895eb9caa4 /block.c
parentd34682cd4a06efe9ee3fc8cb7e8a0ea445299989 (diff)
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block: Inherit opt_transfer_length
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 <kwolf@redhat.com> Reviewed-by: Wenchao Xia <xiawenc@linux.vnet.ibm.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Reviewed-by: BenoƮt Canet <benoit@irqsave.net>
Diffstat (limited to 'block.c')
-rw-r--r--block.c20
1 files changed, 19 insertions, 1 deletions
diff --git a/block.c b/block.c
index 0a3d12c..8a66927 100644
--- a/block.c
+++ b/block.c
@@ -489,7 +489,25 @@ static int bdrv_refresh_limits(BlockDriverState *bs)
memset(&bs->bl, 0, sizeof(bs->bl));
- if (drv && drv->bdrv_refresh_limits) {
+ if (!drv) {
+ return 0;
+ }
+
+ /* 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);
}