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/io.c | 26 ++++++++++++++++++++------ 1 file changed, 20 insertions(+), 6 deletions(-) (limited to 'block') diff --git a/block/io.c b/block/io.c index 1a2272f..038449f 100644 --- a/block/io.c +++ b/block/io.c @@ -52,9 +52,7 @@ void bdrv_parent_drained_begin(BlockDriverState *bs, BdrvChild *ignore, if (c == ignore || (ignore_bds_parents && c->role->parent_is_bds)) { continue; } - if (c->role->drained_begin) { - c->role->drained_begin(c); - } + bdrv_parent_drained_begin_single(c, false); } } @@ -73,6 +71,14 @@ void bdrv_parent_drained_end(BlockDriverState *bs, BdrvChild *ignore, } } +static bool bdrv_parent_drained_poll_single(BdrvChild *c) +{ + if (c->role->drained_poll) { + return c->role->drained_poll(c); + } + return false; +} + static bool bdrv_parent_drained_poll(BlockDriverState *bs, BdrvChild *ignore, bool ignore_bds_parents) { @@ -83,14 +89,22 @@ static bool bdrv_parent_drained_poll(BlockDriverState *bs, BdrvChild *ignore, if (c == ignore || (ignore_bds_parents && c->role->parent_is_bds)) { continue; } - if (c->role->drained_poll) { - busy |= c->role->drained_poll(c); - } + busy |= bdrv_parent_drained_poll_single(c); } return busy; } +void bdrv_parent_drained_begin_single(BdrvChild *c, bool poll) +{ + if (c->role->drained_begin) { + c->role->drained_begin(c); + } + if (poll) { + BDRV_POLL_WHILE(c->bs, bdrv_parent_drained_poll_single(c)); + } +} + static void bdrv_merge_limits(BlockLimits *dst, const BlockLimits *src) { dst->opt_transfer = MAX(dst->opt_transfer, src->opt_transfer); -- cgit v1.1