Re: [PATCH] sd: preserve sysfs updates to max_sectors_kb

[Bart Van Assche <Bart.VanAssche@wdc.com>]

On Tue, 2017-08-29 at 17:42 +0000, Don Brace wrote:
> From: Don Brace
> > [ ... ]
> > Hello Don,
> > 
> > Can you have another look at the udev rules on your test system? The last
> > rule in 60-block.rules looks like a watch rule to me. The same holds for the
> > upstream version of that file
> > (https://github.com/systemd/systemd/blob/maste
> > r/rules/60-block.rules).
> > 
> > Bart.
> 
> It is a watch rule.
> 
> systemd/src/udev/udevd.c
>    manager_new
>        manager->fd_inotify = udev_watch_init(manager->udev);
>        sd_event_add_io(manager->event, &manager->inotify_event, manager->fd_inotify, EPOLLIN, on_inotify, manager);
>            on_inotify (systemd source code: src/udev/udevd.c)
>               synthesize_change
>                     ioctl --> BLKRRPART
> 
> This rule ends up calling BLKRRPART.

Hello Don,

Sorry if I'm slow today, but it's not clear to me how the BLKRRPART ioctl
triggers a change of max_sectors_kb? And even if it really is this ioctl that
triggers a change of max_sectors_kb, should the kernel code that handles
max_sectors_kb writes be modified or should rather a udev rule be added that
sets max_sectors_kb to the desired value after each partition rescan?

Thanks,

Bart.