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Apparently, we have a bug where in mark and sweep while accounting for a
key, a replicas entry isn't found. Change the code to print out the key
we couldn't mark and halt instead of a BUG_ON().
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>