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

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



________________________________________
From: Bart Van Assche [Bart.VanAssche@xxxxxxx]
Sent: Tuesday, August 29, 2017 11:13 AM
To: hch@xxxxxxxxxxxxx; Viswas G; Gerry Morong; Mahesh Rajashekhara; POSWALD@xxxxxxxx; Scott Benesh; Don Brace; Bader Ali - Saleh; Kevin Barnett; joseph.szczypek@xxxxxxx; Scott Teel; jejb@xxxxxxxxxxxxxxxxxx; Justin Lindley; John Hall
Cc: linux-scsi@xxxxxxxxxxxxxxx
Subject: Re: [PATCH] sd: preserve sysfs updates to max_sectors_kb

EXTERNAL EMAIL


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.

----
BLKRRPART ends up in the sd driver function sd_revalidate_disk, which resets 
        q->limits.max_sectors = min(rw_max, queue_max_hw_sectors(q));
back to the value from VPD page 0xb0.

When you cat out max_sectors_kb, it obtains it's valuse from q->limits.max_sectors

Adding a udev rule... Will there be a delay between the watch rule and the new rule?

Thanks,
Don Brace




[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[Index of Archives]     [SCSI Target Devel]     [Linux SCSI Target Infrastructure]     [Kernel Newbies]     [IDE]     [Security]     [Git]     [Netfilter]     [Bugtraq]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux RAID]     [Linux ATA RAID]     [Linux IIO]     [Samba]     [Device Mapper]

  Powered by Linux