Commit 1de6b45f authored by Kevin Wolf's avatar Kevin Wolf
Browse files

block: bdrv_reopen() with backing file in different AioContext 



This patch allows bdrv_reopen() (and therefore the x-blockdev-reopen QMP
command) to attach a node as the new backing file even if the node is in
a different AioContext than the parent if one of both nodes can be moved
to the AioContext of the other node.

Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
Tested-by: default avatarPeter Krempa <pkrempa@redhat.com>
Message-Id: <20200306141413.30705-3-kwolf@redhat.com>
Reviewed-by: default avatarAlberto Garcia <berto@igalia.com>
Signed-off-by: default avatarKevin Wolf <kwolf@redhat.com>
parent 97518e11

block.c

+26 −6
Original line number Diff line number Diff line
@@ -3787,6 +3787,29 @@ static void bdrv_reopen_perm(BlockReopenQueue *q, BlockDriverState *bs, 
    *shared = cumulative_shared_perms;

}



static bool bdrv_reopen_can_attach(BlockDriverState *parent,

                                   BdrvChild *child,

                                   BlockDriverState *new_child,

                                   Error **errp)

{

    AioContext *parent_ctx = bdrv_get_aio_context(parent);

    AioContext *child_ctx = bdrv_get_aio_context(new_child);

    GSList *ignore;

    bool ret;



    ignore = g_slist_prepend(NULL, child);

    ret = bdrv_can_set_aio_context(new_child, parent_ctx, &ignore, NULL);

    g_slist_free(ignore);

    if (ret) {

        return ret;

    }



    ignore = g_slist_prepend(NULL, child);

    ret = bdrv_can_set_aio_context(parent, child_ctx, &ignore, errp);

    g_slist_free(ignore);

    return ret;

}



/*

 * Take a BDRVReopenState and check if the value of 'backing' in the

 * reopen_state->options QDict is valid or not.
@@ -3838,14 +3861,11 @@ static int bdrv_reopen_parse_backing(BDRVReopenState *reopen_state, 
    }



    /*

     * TODO: before removing the x- prefix from x-blockdev-reopen we

     * should move the new backing file into the right AioContext

     * instead of returning an error.

     * Check AioContext compatibility so that the bdrv_set_backing_hd() call in

     * bdrv_reopen_commit() won't fail.

     */

    if (new_backing_bs) {

        if (bdrv_get_aio_context(new_backing_bs) != bdrv_get_aio_context(bs)) {

            error_setg(errp, "Cannot use a new backing file "

                       "with a different AioContext");

        if (!bdrv_reopen_can_attach(bs, bs->backing, new_backing_bs, errp)) {

            return -EINVAL;

        }

    }

tests/qemu-iotests/245

+3 −5
Original line number Diff line number Diff line
@@ -1015,18 +1015,16 @@ class TestBlockdevReopen(iotests.QMPTestCase): 
    # neither of them can switch to the other AioContext

    def test_iothreads_error(self):

        self.run_test_iothreads('iothread0', 'iothread1',

                                "Cannot use a new backing file with a different AioContext")

                                "Cannot change iothread of active block backend")



    def test_iothreads_compatible_users(self):

        self.run_test_iothreads('iothread0', 'iothread0')



    def test_iothreads_switch_backing(self):

        self.run_test_iothreads('iothread0', None,

                                "Cannot use a new backing file with a different AioContext")

        self.run_test_iothreads('iothread0', None)



    def test_iothreads_switch_overlay(self):

        self.run_test_iothreads(None, 'iothread0',

                                "Cannot use a new backing file with a different AioContext")

        self.run_test_iothreads(None, 'iothread0')



if __name__ == '__main__':

    iotests.main(supported_fmts=["qcow2"],