From: Corinna Vinschen <corinna-cygwin@cygwin.com>
To: cygwin@cygwin.com
Subject: Re: Win32 FILE_BASIC_INFORMATION.*Time.QuadPart - which value should be used if filesystem does not support it, so Cygwin /usr/bin/stat lists the value as '-'?
Date: Wed, 10 Apr 2024 09:59:41 +0200 [thread overview]
Message-ID: <ZhZG7TqOlelPUhlC@calimero.vinschen.de> (raw)
In-Reply-To: <5f0672aa-a33b-45fb-8ec6-826ad586bb66@SystematicSW.ab.ca>
On Apr 9 22:30, Brian Inglis via Cygwin wrote:
> On 2024-04-09 15:14, Corinna Vinschen via Cygwin wrote:
> > On Apr 5 04:26, Martin Wege via Cygwin wrote:
> > > On Fri, Apr 5, 2024 at 2:05 AM Martin Wege <martin.l.wege@gmail.com> wrote:
> > > > I have problems with debugging, so a quick help would be appreciated,
> > > > as I cannot figure this out after several hours of digging.
> > > >
> > > > Cygwin /usr/bin/stat returns "Birth: -" for some files. Which value
> > > > must the CreationTime member of FILE_BASIC_INFORMATION have to cause
> > > > /usr/bin/stat ti return "-"? 0, -1, or something else?
> > >
> > > In a related matter:
> > > The Win32 FILE_BASIC_INFORMATION structure defines four time values:
> > >
> > > LARGE_INTEGER CreationTime;
> > > LARGE_INTEGER LastAccessTime;
> > > LARGE_INTEGER LastWriteTime;
> > > LARGE_INTEGER ChangeTime;
> > >
> > > How can a filesystem indicate if it does not support a particular
> > > timestamp, such as ChangeTime? Should ChangeTime.QuadPart then be -1,
> > > -2 or 0, or another value?
> >
> > I'm not aware of a filesystem not supporting ChangeTime, that is,
> > st_ctime. Usually only CreationTime (st_birthtime) is missing.
>
> R/O media like CD/DVD-R or FS w/o write support?
Oh yes, that makes sense, CDFS and the likes of them.
> > I think setting the timestamp to 0 works for indicating that this kind
> > of timestamp is not supported. Cygwin is handling Windows timestamps
> > this way, but I can't find this in documentation ATM.
>
> See upthread?:
>
> Caller or application can set 0 to mean keep/return current value, caller or
> driver can set -1 to mean don't update/return current value:
>
> https://learn.microsoft.com/en-us/windows-hardware/drivers/ddi/wdm/ns-wdm-_file_basic_information#remarks
I'm aware of that. This remarks session is copy/pasted in other MSFT
articles, too. But it doesn't really answer Martin's question.
It describes what a consumer (application or driver) is supposed to set
the timestamps to when passing timestamps to a filesystem driver via
ZwSetInformationFile (or its friends on the lower OS levels).
It does *not* describe the other direction of the call stack, i. e.,
what a filesystem driver is supposed to set a timestamp to, if its
underlying filesystem doesn't support this kind of timestamp.
And that's the direction Martin is asking about.
Corinna
prev parent reply other threads:[~2024-04-10 7:59 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-05 0:05 Cygwin /usr/bin/stat returns "Birth: -", which value in FILE_BASIC_INFORMATION.CreationTime causes that? Martin Wege
2024-04-05 0:54 ` Brian Inglis
2024-04-05 1:08 ` Martin Wege
2024-04-05 15:51 ` Brian Inglis
2024-04-05 2:26 ` Win32 FILE_BASIC_INFORMATION.*Time.QuadPart - which value should be used if filesystem does not support it, so Cygwin /usr/bin/stat lists the value as '-'? Martin Wege
2024-04-09 21:14 ` Corinna Vinschen
2024-04-10 4:30 ` Brian Inglis
2024-04-10 7:59 ` Corinna Vinschen [this message]
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