Re: [PATCH] Use direct I/O for loop devices

[Jan Beulich <jbeulich@suse.com>]

On 18.08.2022 16:04, Demi Marie Obenour wrote:
> On Thu, Aug 18, 2022 at 09:02:11AM +0200, Jan Beulich wrote:
>> On 17.08.2022 22:46, Demi Marie Obenour wrote:
>>> --- a/tools/hotplug/Linux/block
>>> +++ b/tools/hotplug/Linux/block
>>> @@ -330,7 +330,7 @@ mount it read-write in a guest domain."
>>>          else
>>>            roflag=''
>>>          fi
>>> -        do_or_die losetup $roflag "$loopdev" "$file"
>>> +        do_or_die losetup --direct-io=on $roflag "$loopdev" "$file"
>>
>> I guess you want to first check (maybe in tools/configure) that losetup
>> actually supports that option. The old-ish one I'm looking at doesn't,
>> according to its --help output at least.
> 
> What version are you referring to?

The tool itself doesn't recognize --version. It originates from
util-linux 2.19.1 from all I can tell.

> In Qubes OS the current plan is to use a block “script” written in C, to
> improve performance and (when combined with kernel patches) eliminate
> race conditions.  This code could be made a wrapper for the C version.

Is this relevant here in some way I don't recognize, or did you say this
only to provide some further background info?

Jan