From bc79c87bcde6587a37347f81332fbb0cd6b14b85 Mon Sep 17 00:00:00 2001 From: Denis Plotnikov Date: Thu, 25 Mar 2021 18:12:16 +0300 Subject: [PATCH] vhost-user-blk: perform immediate cleanup if disconnect on initialization Commit 4bcad76f4c39 ("vhost-user-blk: delay vhost_user_blk_disconnect") introduced postponing vhost_dev cleanup aiming to eliminate qemu aborts because of connection problems with vhost-blk daemon. However, it introdues a new problem. Now, any communication errors during execution of vhost_dev_init() called by vhost_user_blk_device_realize() lead to qemu abort on assert in vhost_dev_get_config(). This happens because vhost_user_blk_disconnect() is postponed but it should have dropped s->connected flag by the time vhost_user_blk_device_realize() performs a new connection opening. On the connection opening, vhost_dev initialization in vhost_user_blk_connect() relies on s->connection flag and if it's not dropped, it skips vhost_dev initialization and returns with success. Then, vhost_user_blk_device_realize()'s execution flow goes to vhost_dev_get_config() where it's aborted on the assert. To fix the problem this patch adds immediate cleanup on device initialization(in vhost_user_blk_device_realize()) using different event handlers for initialization and operation introduced in the previous patch. On initialization (in vhost_user_blk_device_realize()) we fully control the initialization process. At that point, nobody can use the device since it isn't initialized and we don't need to postpone any cleanups, so we can do cleaup right away when there is a communication problem with the vhost-blk daemon. On operation we leave it as is, since the disconnect may happen when the device is in use, so the device users may want to use vhost_dev's data to do rollback before vhost_dev is re-initialized (e.g. in vhost_dev_set_log()). Signed-off-by: Denis Plotnikov Reviewed-by: Raphael Norwitz Message-Id: <20210325151217.262793-3-den-plotnikov@yandex-team.ru> Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin --- hw/block/vhost-user-blk.c | 48 +++++++++++++++++++-------------------- 1 file changed, 24 insertions(+), 24 deletions(-) diff --git a/hw/block/vhost-user-blk.c b/hw/block/vhost-user-blk.c index 1af95ec6aa..4e215f71f1 100644 --- a/hw/block/vhost-user-blk.c +++ b/hw/block/vhost-user-blk.c @@ -402,38 +402,38 @@ static void vhost_user_blk_event(void *opaque, QEMUChrEvent event, break; case CHR_EVENT_CLOSED: /* - * A close event may happen during a read/write, but vhost - * code assumes the vhost_dev remains setup, so delay the - * stop & clear. There are two possible paths to hit this - * disconnect event: - * 1. When VM is in the RUN_STATE_PRELAUNCH state. The - * vhost_user_blk_device_realize() is a caller. - * 2. In tha main loop phase after VM start. - * - * For p2 the disconnect event will be delayed. We can't - * do the same for p1, because we are not running the loop - * at this moment. So just skip this step and perform - * disconnect in the caller function. - * - * TODO: maybe it is a good idea to make the same fix - * for other vhost-user devices. + * Closing the connection should happen differently on device + * initialization and operation stages. + * On initalization, we want to re-start vhost_dev initialization + * from the very beginning right away when the connection is closed, + * so we clean up vhost_dev on each connection closing. + * On operation, we want to postpone vhost_dev cleanup to let the + * other code perform its own cleanup sequence using vhost_dev data + * (e.g. vhost_dev_set_log). */ if (realized) { + /* + * A close event may happen during a read/write, but vhost + * code assumes the vhost_dev remains setup, so delay the + * stop & clear. + */ AioContext *ctx = qemu_get_current_aio_context(); qemu_chr_fe_set_handlers(&s->chardev, NULL, NULL, NULL, NULL, NULL, NULL, false); aio_bh_schedule_oneshot(ctx, vhost_user_blk_chr_closed_bh, opaque); - } - /* - * Move vhost device to the stopped state. The vhost-user device - * will be clean up and disconnected in BH. This can be useful in - * the vhost migration code. If disconnect was caught there is an - * option for the general vhost code to get the dev state without - * knowing its type (in this case vhost-user). - */ - s->dev.started = false; + /* + * Move vhost device to the stopped state. The vhost-user device + * will be clean up and disconnected in BH. This can be useful in + * the vhost migration code. If disconnect was caught there is an + * option for the general vhost code to get the dev state without + * knowing its type (in this case vhost-user). + */ + s->dev.started = false; + } else { + vhost_user_blk_disconnect(dev); + } break; case CHR_EVENT_BREAK: case CHR_EVENT_MUX_IN: