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block: move drain outside of quorum_add_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".

The quorum_add_child() callback runs under the graph lock, so it is
not allowed to drain. It is only called as the .bdrv_add_child()
callback, which is only called in the bdrv_add_child() function, which
also runs under the graph lock.

The bdrv_add_child() function is called by qmp_x_blockdev_change(),
where a drained section is introduced.

Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>
Message-ID: <20250530151125.955508-15-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 17:10:51 +02:00 • committed by Kevin Wolf
parent 77f3965ba7
commit 0414930d3a
4 changed files with 17 additions and 4 deletions
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10
block.c
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@ -8220,8 +8220,10 @@ char *bdrv_dirname(BlockDriverState *bs, Error **errp)
}
/*
* Hot add/remove a BDS's child. So the user can take a child offline when
* it is broken and take a new child online
* Hot add a BDS's child. Used in combination with bdrv_del_child, so the user
* can take a child offline when it is broken and take a new child online.
*
* All block nodes must be drained.
*/
void bdrv_add_child(BlockDriverState *parent_bs, BlockDriverState *child_bs,
Error **errp)
@ -8261,6 +8263,10 @@ void bdrv_add_child(BlockDriverState *parent_bs, BlockDriverState *child_bs,
parent_bs->drv->bdrv_add_child(parent_bs, child_bs, errp);
}
/*
* Hot remove a BDS's child. Used in combination with bdrv_add_child, so the
* user can take a child offline when it is broken and take a new child online.
*/
void bdrv_del_child(BlockDriverState *parent_bs, BdrvChild *child, Error **errp)
{
BdrvChild *tmp;