Commit d30b8e64 authored by Kevin Wolf's avatar Kevin Wolf
Browse files

block: Remove bdrv_drain_recurse() 



For bdrv_drain(), recursively waiting for child node requests is
pointless because we didn't quiesce their parents, so new requests could
come in anyway. Letting the function work only on a single node makes it
more consistent.

For subtree drains and drain_all, we already have the recursion in
bdrv_do_drained_begin(), so the extra recursion doesn't add anything
either.

Remove the useless code.

Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
Reviewed-by: default avatarStefan Hajnoczi <stefanha@redhat.com>
parent 89bd0305

block/io.c

+3 −33
Original line number Diff line number Diff line
@@ -219,38 +219,6 @@ static bool bdrv_drain_poll_top_level(BlockDriverState *bs, 
    return bdrv_drain_poll(bs, ignore_parent);

}



static bool bdrv_drain_recurse(BlockDriverState *bs, BdrvChild *parent)

{

    BdrvChild *child, *tmp;

    bool waited;



    /* Wait for drained requests to finish */

    waited = BDRV_POLL_WHILE(bs, bdrv_drain_poll_top_level(bs, parent));



    QLIST_FOREACH_SAFE(child, &bs->children, next, tmp) {

        BlockDriverState *bs = child->bs;

        bool in_main_loop =

            qemu_get_current_aio_context() == qemu_get_aio_context();

        assert(bs->refcnt > 0);

        if (in_main_loop) {

            /* In case the recursive bdrv_drain_recurse processes a

             * block_job_defer_to_main_loop BH and modifies the graph,

             * let's hold a reference to bs until we are done.

             *

             * IOThread doesn't have such a BH, and it is not safe to call

             * bdrv_unref without BQL, so skip doing it there.

             */

            bdrv_ref(bs);

        }

        waited |= bdrv_drain_recurse(bs, child);

        if (in_main_loop) {

            bdrv_unref(bs);

        }

    }



    return waited;

}



static void bdrv_do_drained_begin(BlockDriverState *bs, bool recursive,

                                  BdrvChild *parent);

static void bdrv_do_drained_end(BlockDriverState *bs, bool recursive,
@@ -318,7 +286,9 @@ void bdrv_do_drained_begin(BlockDriverState *bs, bool recursive, 


    bdrv_parent_drained_begin(bs, parent);

    bdrv_drain_invoke(bs, true);

    bdrv_drain_recurse(bs, parent);



    /* Wait for drained requests to finish */

    BDRV_POLL_WHILE(bs, bdrv_drain_poll_top_level(bs, parent));



    if (recursive) {

        bs->recursive_quiesce_counter++;