Subject: Re: Extension of fsync_range() to permit forcing disk cache flushing
To: YAMAMOTO Takashi <>
From: Bill Studenmund <>
List: tech-kern
Date: 12/16/2004 19:16:17
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On Fri, Dec 17, 2004 at 11:20:51AM +0900, YAMAMOTO Takashi wrote:
> hi,
> > Also, you're implicitly assuming that disks don't fail. If an admin has
> > taken steps, either in configuration or product choice (good UPS or RAID
> > box w/ battery backup for cache), to ensure that writing to the disk dr=
> > is as good as writing to the media, why penalize him or her by forcing
> > cache flushing. And since disks fail (even in RAID), all we have to do =
> > make sure that the cache failure probability is less than the disk drive
> > failure probability, and then the cache doesn't matter.
> while you says "permanent storage" is device and environment dependent,
> why do you think flushing disk cache is always needed for your applicatio=

My application needs to be able to ensure that data have reached the disk
under certain circumstances. The requirements implied by the SCSI
SYNCHRONIZE CACHE command meet the requirements I wish to satisfy. Thus a=
clean way to issue a DIOCCACHESYNC ioctl is in order, and fsync_range()=20
seems the best way.

While I believe that few other applications will need this level of=20
control, I think there may be a few. Thus I propose this change.

Take care,


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