dvfs api and toolkits

Nate Nielsen nielsen-list at memberwebs.com
Sat Apr 9 22:21:56 EEST 2005

Sean Middleditch wrote:
> On Sat, 2005-04-09 at 18:05 +0000, Nate Nielsen wrote:
>>Sean Middleditch wrote:
>>>Would there be a problem with the
>>>file possibly changing under us?  Could we potentially detect that?
>>Yes, in HTTP you use ETag, Modified-Date and perhaps other lesser known
> OK.  And once we detect it, what are we supposed to do about it?  Return
> an error?  Just ignore it and let the developer get what is essentially
> going to be corrupted data?

This isn't a particularly new problem. Your OS doesn't give you an error
 in this case. It's up to the application to be aware of multiple users,
and use some sort of locking. [1]

Basically almost every single method of accessing files system has this
problem. Sure some support locking (like smb and nfs) but even then it's
up to the application to be aware and use it. FTP, HTTP, all currently
have this problem even without bringing a VFS into the picture.

It's admirable to try and take on this ubiquitous problem. But if DVFS
feels it should address it, then I think it should do so in a competent
and complete manner and not just toss out 'seeking' (on reads, no less)
because of these already present issues.


[1] Most "serious" network file systems support locking (ie: smb,
webdav, nfs, afs). And apparently DVFS aims to support this in some form
(as per the wiki page).

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