[Qemu-devel] [PATCH v3 14/22] block: Set default request_alignment during bdrv_refresh_limits()

[Eric Blake <eblake@redhat.com>]

We want to eventually stick request_alignment alongside other
BlockLimits, but first, we must ensure it is populated at the
same time as all other limits, rather than being a special case
that is set only when a block is first opened.

Now that all drivers have been updated to supply an override
of request_alignment during their .bdrv_refresh_limits(), as
needed, the block layer itself can defer setting the default
alignment until part of the overall bdrv_refresh_limits().

Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Fam Zheng <famz@redhat.com>

---
v3: no change
v2: new patch
---
 block.c    | 1 -
 block/io.c | 3 +++
 2 files changed, 3 insertions(+), 1 deletion(-)

diff --git a/block.c b/block.c
index f4648e9..c2fbf06 100644
--- a/block.c
+++ b/block.c
@@ -937,7 +937,6 @@ static int bdrv_open_common(BlockDriverState *bs, BdrvChild *file,
         goto fail_opts;
     }

-    bs->request_alignment = drv->bdrv_co_preadv ? 1 : 512;
     bs->read_only = !(bs->open_flags & BDRV_O_RDWR);

     if (use_bdrv_whitelist && !bdrv_is_whitelisted(drv, bs->read_only)) {
diff --git a/block/io.c b/block/io.c
index 82c9ff0..323e822 100644
--- a/block/io.c
+++ b/block/io.c
@@ -78,6 +78,9 @@ void bdrv_refresh_limits(BlockDriverState *bs, Error **errp)
         return;
     }

+    /* Default alignment based on whether driver has byte interface */
+    bs->request_alignment = drv->bdrv_co_preadv ? 1 : 512;
+
     /* Take some limits from the children as a default */
     if (bs->file) {
         bdrv_refresh_limits(bs->file->bs, &local_err);
-- 
2.5.5