commit 515c2f431ebe561e69c57371b2c2217792b3b820
author Kevin Wolf <kwolf@redhat.com> Tue Jun 07 15:51:28 2016 +0200
committer Kevin Wolf <kwolf@redhat.com> Wed Jun 08 10:21:09 2016 +0200
tree ba262ff553d5d4430cf29ef972c538151bd66db2
parent bf18bee547d19fde314e7b6b81f21f68b46c8a92

block: Don't emulate natively supported pwritev flags

Drivers that implement .bdrv_co_pwritev() get the flags passed as an
argument to said function, but we also unconditionally emulate the flags
anyway. We shouldn't do that.

Fix this by clearing all flags that the driver supports natively after
it returns from .bdrv_co_pwritev().

Fixes: 4df863f3 ('block: Make supported_write_flags a per-bds property')
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>

block/io.c

diff --git a/block/io.c b/block/io.c
index 9dc265b..fb99a71 100644
--- a/block/io.c
+++ b/block/io.c
@@ -816,7 +816,9 @@
     int ret;
 
     if (drv->bdrv_co_pwritev) {
-        ret = drv->bdrv_co_pwritev(bs, offset, bytes, qiov, flags);
+        ret = drv->bdrv_co_pwritev(bs, offset, bytes, qiov,
+                                   flags & bs->supported_write_flags);
+        flags &= ~bs->supported_write_flags;
         goto emulate_flags;
     }