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block: move drain outside of bdrv_root_unref_child()

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This is part of resolving the deadlock mentioned in commit "block:
move draining out of bdrv_change_aio_context() and mark GRAPH_RDLOCK".

bdrv_root_unref_child() is called by:
1. blk_remove_bs(), where a drained section is introduced.
2. bdrv_unref_child(), which runs under the graph lock, so the drain
   will be moved further up to its callers.
3. block_job_remove_all_bdrv(), where a drained section is introduced.

For all callers of bdrv_unref_child() and its generated
bdrv_co_unref_child() coroutine variant, a drained section is
introduced, they are not explicilty listed here. The caller
quorum_del_child() holds the graph lock, so it is not actually allowed
to drain. This will be addressed in the next commit.

Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
Message-ID: <20250530151125.955508-16-f.ebner@proxmox.com>
Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Fiona Ebner 2025-05-30 17:10:52 +02:00 • committed by Kevin Wolf
parent 0414930d3a
commit b13f546545
11 changed files with 52 additions and 4 deletions
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2
blockjob.c
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@ -198,6 +198,7 @@ void block_job_remove_all_bdrv(BlockJob *job)
* one to make sure that such a concurrent access does not attempt
* to process an already freed BdrvChild.
*/
bdrv_drain_all_begin();
bdrv_graph_wrlock();
while (job->nodes) {
GSList *l = job->nodes;
@ -211,6 +212,7 @@ void block_job_remove_all_bdrv(BlockJob *job)
g_slist_free_1(l);
}
bdrv_graph_wrunlock();
bdrv_drain_all_end();
}
bool block_job_has_bdrv(BlockJob *job, BlockDriverState *bs)