Re: no hotplugging support (FIXME)

[Robert Hancock <hancockrwd@gmail.com>]

Todd and Margo Chester wrote:
> Robert Hancock wrote:
>> Todd and Margo Chester wrote:
>>> Robert Hancock wrote:
>>>> Todd and Margo Chester wrote:
>>>>> Hi Jeff,
>>>>>
>>>>> I am having a nasty problem with hot swapping a removable (not
>>>>> eSATA) drive I use for backup on several servers.  It is reported
>>>>> over on
>>>>> http://bugs.centos.org/view.php?id=3391
>>>>>
>>>>> Trying to help me find a work around to the problem at
>>>>> http://www.centos.org/modules/newbb/viewtopic.php?topic_id=18608&start=0#forumpost68783 
>>>>>
>>>>> Alan posted your ata_piix.c code at
>>>>> http://centos.toracat.org/ajb/tmp/toddandmargo/ata_piix.c
>>>>> He pointed out
>>>>>
>>>>> 1483 /* no hotplugging support (FIXME) */
>>>>> 1484 if (!in_module_init)
>>>>> 1485 return -ENODEV;
>>>>>
>>>>> What do you mean by the comment in line 1483?  Is there some
>>>>> know issue with hot swapping SATA drives?
>>>>
>>>> If you're using the ata_piix driver then it means your motherboard 
>>>> is not in AHCI mode, so hotplugging is not supported by either the 
>>>> driver or controller. You have to enable AHCI for SATA hotplug to 
>>>> work on Intel controllers.
>>>>
>>>
>>> Hi Robers,
>>>
>>>    As far as I can tell, ACHI is turned on on my motherboard.
>>> I have tried all variation in bios (one of them turns /dev/sdb
>>> into /dev/hda).   Does not mean ACHI is working right.
>>>
>>>    Do you know of any reason why my kernel
>>> (CentOS 5.2: 2.6.18-92.1.22.el5) would not support
>>> (bugs, etc.) hotplugging?
>>>
>>>    Also, do you know of a utility that I can use to
>>> ask ACHI what is has for me (give me a report)?
>>>
>>> Many thanks,
>>> -T
>>
>> If the device is in AHCI mode then the ata_piix driver won't load for 
>> it - at least it won't in current kernels, I can't say for sure that 
>> it won't in the CentOS 5 version.. You do need to get it using the 
>> ahci driver instead of ata_piix or hotplug definitely won't work.
>>
>> You can try changing the boot initrd to try to load the AHCI driver 
>> instead by changing the scsi_hostadapter entry in /etc/modprobe.conf 
>> to be ahci instead of ata_piix, then rebuilding the initrd or 
>> reinstalling the kernel RPM. However, if the BIOS isn't set up 
>> properly for AHCI mode to work, you'll have to either boot up in 
>> rescue mode and fix it, or boot up from a different kernel entry in grub.
>>
> 
> Hi Robert,
> 
> I have
> 
> $ modprobe --dry-run -v ahci
> insmod /lib/modules/2.6.18-92.1.22.el5/kernel/drivers/ata/ahci.ko
> 
> in my system.  Do I just use "modprobe" to install the module
> and go edit /etc/modprobe.conf?
> 
> And, does the modprobe insertion stay permanent (survives a reboot)?

Running modprobe only loads the module for the current session. You have 
to edit /etc/modprobe.conf to get it to be loaded on boot-up. Also, 
since this driver is needed to mount the root filesystem, you have to 
rebuild the initrd afterwards so that it will contain that driver - you 
should be able to do:

mkinird -f /boot/initrd-2.6.18-92.1.22.el5.img 2.6.18-92.1.22.el5

> 
> I am confused   :-[   Can you point me to a link that gives the
> directions?
> 
> -T