ipr crashes due to NULL dma_need_drain since cc97923a5bcc ("block: move dma drain handling to scsi")

[Michael Ellerman]

Christoph Hellwig <hch at lst.de> writes:
> Can you try this patch?
>
> ---
> From 1c9913360a0494375c5655b133899cb4323bceb4 Mon Sep 17 00:00:00 2001
> From: Christoph Hellwig <hch at lst.de>
> Date: Tue, 9 Jun 2020 14:07:31 +0200
> Subject: scsi: wire up ata_scsi_dma_need_drain for SAS HBA drivers
>
> We need ata_scsi_dma_need_drain for all drivers wired up to drive ATAPI
> devices through libata.  That also includes the SAS HBA drivers in
> addition to native libata HBA drivers.
>
> Fixes: cc97923a5bcc ("block: move dma drain handling to scsi")
> Reported-by: Michael Ellerman <mpe at ellerman.id.au>
> Signed-off-by: Christoph Hellwig <hch at lst.de>

Yep that works for me here with ipr.

Tested-by: Michael Ellerman <mpe at ellerman.id.au>

cheers