block: properly handle REQ_OP_ZONE_APPEND in __bio_split_to_limits

Currently REQ_OP_ZONE_APPEND is handled by the bio_split_rw case in
__bio_split_to_limits.  This is harmful because REQ_OP_ZONE_APPEND
bios do not adhere to the soft max_limits value but instead use their
own capped version of max_hw_sectors, leading to incorrect splits that
later blow up in bio_split.

We still need the bio_split_rw logic to count nr_segs for blk-mq code,
so add a new wrapper that passes in the right limit, and turns any bio
that would need a split into an error as an additional debugging aid.

Signed-off-by: Christoph Hellwig <[email protected]>
Reviewed-by: Damien Le Moal <[email protected]>
Tested-by: Hans Holmberg <[email protected]>
Reviewed-by: Hans Holmberg <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>

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