badblocks: return error if any badblock set fails

badblocks: return error if any badblock set fails

_badblocks_set() returns success if at least one badblock is set
successfully, even if others fail. This can lead to data inconsistencies
in raid, where a failed badblock set should trigger the disk to be kicked
out to prevent future reads from failed write areas.

_badblocks_set() should return error if any badblock set fails. Instead
of relying on 'rv', directly returning 'sectors' for clearer logic. If all
badblocks are successfully set, 'sectors' will be 0, otherwise it
indicates the number of badblocks that have not been set yet, thus
signaling failure.

By the way, it can also fix an issue: when a newly set unack badblock is
included in an existing ack badblock, the setting will return an error.
···
  echo "0 100" /sys/block/md0/md/dev-loop1/bad_blocks
  echo "0 100" /sys/block/md0/md/dev-loop1/unacknowledged_bad_blocks
  -bash: echo: write error: No space left on device
```
After fix, it will return success.

Fixes: aa511ff8218b ("badblocks: switch to the improved badblock handling code")
Signed-off-by: Li Nan <linan122@huawei.com>
Reviewed-by: Yu Kuai <yukuai3@huawei.com>
Acked-by: Coly Li <colyli@kernel.org>
Link: https://lore.kernel.org/r/20250227075507.151331-6-zhengqixing@huaweicloud.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>