diff mbox

[v2,02/24] block: Inherit opt_transfer_length

Message ID 1386940979-3824-3-git-send-email-kwolf@redhat.com
State New
Headers show

Commit Message

Kevin Wolf Dec. 13, 2013, 1:22 p.m. UTC 
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>
---
 block.c | 20 +++++++++++++++++++-
 1 file changed, 19 insertions(+), 1 deletion(-)

Comments

Max Reitz Jan. 11, 2014, 10:24 p.m. UTC | #1 
On 13.12.2013 14:22, Kevin Wolf wrote:
> 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>
> ---
>   block.c | 20 +++++++++++++++++++-
>   1 file changed, 19 insertions(+), 1 deletion(-)

Reviewed-by: Max Reitz <mreitz@redhat.com>
diff mbox

Patch

diff --git a/block.c b/block.c
index 3bbcad4..79a325f 100644
--- a/block.c
+++ b/block.c
@@ -485,7 +485,25 @@  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);
     }