Commit 38475269 authored by Kevin Wolf's avatar Kevin Wolf
Browse files

block: Implement .(can_)set_aio_ctx for BlockBackend 



bdrv_try_set_aio_context() currently fails if a BlockBackend is attached
to a node because it doesn't implement the BdrvChildRole callbacks for
AioContext management.

We can allow changing the AioContext of monitor-owned BlockBackends as
long as no device is attached to them.

When setting the AioContext of the root node of a BlockBackend, we now
need to pass blk->root as an ignored child because we don't want the
root node to recursively call back into BlockBackend and execute
blk_do_set_aio_context() a second time.

Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
parent 7e2f096a

block/block-backend.c

+43 −2
Original line number Diff line number Diff line
@@ -124,6 +124,11 @@ static void blk_root_drained_end(BdrvChild *child); 
static void blk_root_change_media(BdrvChild *child, bool load);

static void blk_root_resize(BdrvChild *child);



static bool blk_root_can_set_aio_ctx(BdrvChild *child, AioContext *ctx,

                                     GSList **ignore, Error **errp);

static void blk_root_set_aio_ctx(BdrvChild *child, AioContext *ctx,

                                 GSList **ignore);



static char *blk_root_get_parent_desc(BdrvChild *child)

{

    BlockBackend *blk = child->opaque;
@@ -300,6 +305,9 @@ static const BdrvChildRole child_root = { 


    .attach             = blk_root_attach,

    .detach             = blk_root_detach,



    .can_set_aio_ctx    = blk_root_can_set_aio_ctx,

    .set_aio_ctx        = blk_root_set_aio_ctx,

};



/*
@@ -1852,7 +1860,8 @@ static AioContext *blk_aiocb_get_aio_context(BlockAIOCB *acb) 
    return blk_get_aio_context(blk_acb->blk);

}



void blk_set_aio_context(BlockBackend *blk, AioContext *new_context)

static void blk_do_set_aio_context(BlockBackend *blk, AioContext *new_context,

                                   bool update_root_node)

{

    BlockDriverState *bs = blk_bs(blk);

    ThrottleGroupMember *tgm = &blk->public.throttle_group_member;
@@ -1864,9 +1873,41 @@ void blk_set_aio_context(BlockBackend *blk, AioContext *new_context) 
            throttle_group_attach_aio_context(tgm, new_context);

            bdrv_drained_end(bs);

        }

        bdrv_set_aio_context(bs, new_context);

        if (update_root_node) {

            GSList *ignore = g_slist_prepend(NULL, blk->root);

            bdrv_set_aio_context_ignore(bs, new_context, &ignore);

            g_slist_free(ignore);

        }

    }

}



void blk_set_aio_context(BlockBackend *blk, AioContext *new_context)

{

    blk_do_set_aio_context(blk, new_context, true);

}



static bool blk_root_can_set_aio_ctx(BdrvChild *child, AioContext *ctx,

                                     GSList **ignore, Error **errp)

{

    BlockBackend *blk = child->opaque;



    /* Only manually created BlockBackends that are not attached to anything

     * can change their AioContext without updating their user. */

    if (!blk->name || blk->dev) {

        /* TODO Add BB name/QOM path */

        error_setg(errp, "Cannot change iothread of active block backend");

        return false;

    }



    return true;

}



static void blk_root_set_aio_ctx(BdrvChild *child, AioContext *ctx,

                                 GSList **ignore)

{

    BlockBackend *blk = child->opaque;

    blk_do_set_aio_context(blk, ctx, false);

}



void blk_add_aio_context_notifier(BlockBackend *blk,

        void (*attached_aio_context)(AioContext *new_context, void *opaque),