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block-backend: Update ctx immediately after root 

blk_get_aio_context() asserts that blk->ctx is always equal to the root
BDS's context (if there is a root BDS).  Therefore,
blk_do_set_aio_context() must update blk->ctx immediately after the root
BDS's context has changed.

Without this patch, the next patch would break iotest 238, because
bdrv_drained_begin() (called by blk_do_set_aio_context()) may then
invoke bdrv_child_get_parent_aio_context() on the root child, i.e.
blk_get_aio_context().  However, by this point, blk->ctx would not have
been updated and thus differ from the root node's context.  This patch
fixes that.

Reviewed-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Hanna Reitz <hreitz@redhat.com>
Message-Id: <20221107151321.211175-3-hreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
master
Hanna Reitz 2022-11-07 16:13:20 +01:00 committed by Kevin Wolf
parent d5f8d79c2f
commit af5b6ebe5b
1 changed files with 7 additions and 1 deletions
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8
block/block-backend.c
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@ -2158,6 +2158,11 @@ static int blk_do_set_aio_context(BlockBackend *blk, AioContext *new_context,
return ret;
}
}
/*
* Make blk->ctx consistent with the root node before we invoke any
* other operations like drain that might inquire blk->ctx
*/
blk->ctx = new_context;
if (tgm->throttle_state) {
bdrv_drained_begin(bs);
throttle_group_detach_aio_context(tgm);
@ -2166,9 +2171,10 @@ static int blk_do_set_aio_context(BlockBackend *blk, AioContext *new_context,
}
bdrv_unref(bs);
} else {
blk->ctx = new_context;
}
blk->ctx = new_context;
return 0;
}