Re: [PATCH 1/2] pm-hibernate: flush disk cache when suspending

[Mikulas Patocka <mpatocka@redhat.com>]

On Sun, 23 Nov 2025, Askar Safin wrote:

> Mikulas Patocka <mpatocka@redhat.com>:
> > [PATCH 1/2] pm-hibernate: flush disk cache when suspending
> > 
> > There was reported failure that suspend doesn't work with dm-integrity.
> > The reason for the failure is that the suspend code doesn't issue the
> > FLUSH bio - the data still sits in the dm-integrity cache and they are
> > lost when poweroff happens.
> 
> I tested this patchset (in Qemu). It works.
> 
> Here is script I used for testing:
> 
> https://zerobin.net/?66669be7d2404586#xWufhCq7zCoOk3LJcJCj7W4k3vYT3U4vhGutTN3p8m0=
> 
> Here are logs:
> 
> https://zerobin.net/?5d4a2abbad751890#WMcQl4FAZC9KqcAuJU3TSVr7wuVnPFwI7dlinA9QHOo=
> 
> Tested-By: Askar Safin <safinaskar@gmail.com>
> 
> There was no any reason to wait for me. You could easily test using script above.
> 
> Also: Linux shows this scary message when booting in Qemu:
> 
> [    0.512581] sd 0:0:0:0: [sda] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
> 
> So, FUA is not supported? Does it mean that this patch is wrong, and works purely
> by chance?

If FUA is not supported by a disk, the kernel would send a flush request 
after the write request with the FUA flag. There's no problem with that - 
the cache will be flushed correctly.

Mikulas

> -- 
> Askar Safin
>