MFC:

>r268205 | imp | 2014-07-02 23:22:13 -0600 (Wed, 02 Jul 2014) | 9 lines
>Rework the BIO_DELETE code slightly. Always queue the BIO_DELETE
>requests on the trim_queue, even for the CFA ERASE. This allows us, in
>the future, to collapse adjacent requests. Since CFA ERASE is only for
>CF cards, and it is so restrictive in what it can do, the collapse
>code is not presently here. This also brings the ada driver more in
>line with the da driver's treatment of BIO_DELETEs.
MFC:

>r267118 | imp | 2014-06-05 11:13:42 -0600 (Thu, 05 Jun 2014) | 9 lines
>The code that combines adjacent ranges for BIO_DELETEs to optimize
>trims to the device assumes the list is sorted. Don't apply the
>optimization of not sorting the queue when we have SSDs to the
>delete_queue, since it causes more discard traffic to the drive. While
>one could argue that the higher levels should coalesce the trims,
>that's not done today, so some optimization at this level is needed.
>CR: https://phabric.freebsd.org/D142