Subject: Re: letting userland issue FUA writes
To: None <>
From: Christos Zoulas <>
List: tech-kern
Date: 03/16/2006 00:37:00
In article <>,
Bill Studenmund  <> wrote:
>On Wed, Mar 15, 2006 at 05:23:51PM +0100, Pavel Cahyna wrote:
>> On Tue, Mar 14, 2006 at 06:35:46PM -0800, Bill Studenmund wrote:
>> > I'm interested in adding infrastructure so that applications can issue 
>> > writes that have the FUA (Force Unit Access) bit set. SCSI CDBs handle 
>> > this, as do some RAID cards.
>> > 
>> > The main question I have is what kind of user-level interfaces exist for 
>> > this? I certainly could cook up a new system call, but I would much rather 
>> > use prior art. My simplistic attempt at googling for this failed. Does 
>> > anyone else have suggestions?
>> O_DSYNC is documented as: "each write will wait for the file data 
>> to be committed to stable storage."
>> Is this semantics different from FUA?
>Not really. However I really want a system call where I can request this 
>on a per-call basis. Otherwise I have to have two open file descriptors, 
>one with and one without this flag set. That seems kinda silly.

Can't you use fcntl for this?