From 4be6a6d118123340f16fb8b3bf45220d0f8ed6d4 Mon Sep 17 00:00:00 2001 From: Kevin Wolf Date: Fri, 29 Jun 2018 18:01:31 +0200 Subject: block: Poll after drain on attaching a node Commit dcf94a23b1 ('block: Don't poll in parent drain callbacks') removed polling in bdrv_child_cb_drained_begin() on the grounds that the original bdrv_drain() already will poll and BdrvChildRole.drained_begin calls must not cause graph changes (and therefore must not call aio_poll() or the recursion through the graph will break. This reasoning is correct for calls through bdrv_do_drained_begin(). However, BdrvChildRole.drained_begin is also called when a node that is already in a drained section (i.e. bdrv_do_drained_begin() has already returned and therefore can't poll any more) is attached to a new parent. In this case, we must explicitly poll to have all requests completed before the drained new child can be attached to the parent. In bdrv_replace_child_noperm(), we know that we're not inside the recursion of bdrv_do_drained_begin() because graph changes are not allowed there, and bdrv_replace_child_noperm() is a graph change. The call of BdrvChildRole.drained_begin() must therefore be followed by a BDRV_POLL_WHILE() that waits for the completion of requests. Reported-by: Max Reitz Signed-off-by: Kevin Wolf --- block.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'block.c') diff --git a/block.c b/block.c index ac8b3a3511..a2fe05ea96 100644 --- a/block.c +++ b/block.c @@ -2066,7 +2066,7 @@ static void bdrv_replace_child_noperm(BdrvChild *child, } assert(num >= 0); for (i = 0; i < num; i++) { - child->role->drained_begin(child); + bdrv_parent_drained_begin_single(child, true); } } -- cgit v1.2.3-55-g7522