[parted-devel] [PATCH 0/5] Add --readonly flag to parted

[Brian C. Lane]

On Mon, Feb 13, 2023 at 08:41:35AM +0000, Arvin Schnell wrote:
> On Thu, Feb 09, 2023 at 05:18:56PM -0800, Brian C. Lane wrote:
> 
> > The benefit of this is that you can now easily read the device without
> > triggering any udev events with:
> > 
> > parted --script --readonly /dev/sda u s p free
> 
> This does not work on Linux if there are partitions that are not
> mounted. In that case _flush_cache still opens the partitions in
> WRONLY mode thus triggering udev. The problem seems to be that
> while _device_open gets the flags correctly (from
> _device_open_ro), _flush_cache looks at dev->read_only.

Good catch. I was testing it on a disk.img file and a disk with mounted
partitions and didn't see that.

It looks like the path there is through the initial probe, using
_device_open_ro(), and the reason the _flush_cache is there is because
of commit fb99ba5e which says it was sometimes mis-identifying a
new filesystem because the cache hadn't been flushed yet.

So I don't think there is any way to prevent that, it needs to flush it
to make sure it has the latest data.

I think this patchset is an improvement over the other options, but I'm
not totally convinced it matters if it can't keep all the events from
happening.

Brian

-- 
Brian C. Lane (PST8PDT) - weldr.io - lorax - parted - pykickstart