[RFC] enable FUA support in libata

[RFC] enable FUA support in libata

[Zheng Liu]

Hi Jeff and list,

Recently I met a problem about FUA support of SATA disk.  In my machine,
it has a SATA disk that supports FUA feature.  But after system starts
up, it displays that the disk cannot support FUA from dmesg.

I notice this commit (c3c013a2).  It disables FUA support in all of SATA
disk.  But the commit log is too simple to know why we should disable
FUA support in libata.  Could you please explain it?  Thank you.

Regards,
Zheng

Re: [RFC] enable FUA support in libata

[Jeff Garzik]

On 04/13/2012 04:11 AM, Zheng Liu wrote:
> Hi Jeff and list,
>
> Recently I met a problem about FUA support of SATA disk.  In my machine,
> it has a SATA disk that supports FUA feature.  But after system starts
> up, it displays that the disk cannot support FUA from dmesg.
>
> I notice this commit (c3c013a2).  It disables FUA support in all of SATA
> disk.  But the commit log is too simple to know why we should disable
> FUA support in libata.  Could you please explain it?  Thank you.

FUA support in the block layer wanted speed and guarantees that early 
FUA drives were simply not providing.

Re: [RFC] enable FUA support in libata

[Zheng Liu]

On Fri, Apr 13, 2012 at 10:18 PM, Jeff Garzik <jeff@garzik.org> wrote:
> On 04/13/2012 04:11 AM, Zheng Liu wrote:
>>
>> Hi Jeff and list,
>>
>> Recently I met a problem about FUA support of SATA disk.  In my machine,
>> it has a SATA disk that supports FUA feature.  But after system starts
>> up, it displays that the disk cannot support FUA from dmesg.
>>
>> I notice this commit (c3c013a2).  It disables FUA support in all of SATA
>> disk.  But the commit log is too simple to know why we should disable
>> FUA support in libata.  Could you please explain it?  Thank you.
>
>
> FUA support in the block layer wanted speed and guarantees that early FUA
> drives were simply not providing.

Hi Jeff,

Thank you for your reply.  I notice that this patch is merged in 2006.
 I don't know whether we can enable it now by default or not.  I read
some specifications of SATA disks.  They support FUA feature.
Although libata_fua variable is a kernel module parameter and we can
enable it when this module is loaded,  it is too complicated because
it needs to be loaded before kernel is loaded.  Thus, we need to set
libata_fua in initrd.  Maybe we can change it into a sysctl parameter.
 Then we can enable it dynamically.  Do you have any suggestions?
Thank you.

Regards,
Zheng

Re: [RFC] enable FUA support in libata

[Zheng Liu]

On Fri, Apr 13, 2012 at 10:18 PM, Jeff Garzik <jeff@garzik.org> wrote:
> On 04/13/2012 04:11 AM, Zheng Liu wrote:
>>
>> Hi Jeff and list,
>>
>> Recently I met a problem about FUA support of SATA disk.  In my machine,
>> it has a SATA disk that supports FUA feature.  But after system starts
>> up, it displays that the disk cannot support FUA from dmesg.
>>
>> I notice this commit (c3c013a2).  It disables FUA support in all of SATA
>> disk.  But the commit log is too simple to know why we should disable
>> FUA support in libata.  Could you please explain it?  Thank you.
>
>
> FUA support in the block layer wanted speed and guarantees that early FUA
> drives were simply not providing.

Hi Jeff,

Thank you for your reply.  I notice that this patch is merged in 2006.
 I don't know whether we can enable it now by default or not.  I read
some specifications of SATA disks.  They support FUA feature.
Although libata_fua variable is a kernel module parameter and we can
enable it when this module is loaded,  it is too complicated because
it needs to be loaded before kernel is loaded.  Thus, we need to set
libata_fua in initrd.  Maybe we can change it into a sysctl parameter.
 Then we can enable it dynamically.  Do you have any suggestions?
Thank you.

Regards,
Zheng