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Original Message
From: Corinna Vinschen - [email protected]
Sent: Thursday, April 23, 2015 9:25 AM
To: [email protected]
Reply To: [email protected]
Subject: Re: Deleting files with open handles on subst'd drives
On Apr 23 10:15, Corinna Vinschen wrote:
> On Apr 23 01:44, David Macek wrote:
> > Hello everyone.
> >
> > Some time ago, I encountered a problem in a script when run on
> > Cygwin/MSYS2. To add some drama, I'll mention that the problem caused some
> > data loss (nothing important though). The problem is that some operations
> > on open files seem to fail on subst'd drives (but not on regular ones).
> >
> > To reproduce the problem, choose some writable directory and run:
> > $ subst X: C:/somesubdir
> > $ cd /cygdrive/x/
> > $ touch foo
> > $ { rm foo; touch foo; } <foo
> > touch: cannot touch 'foo': Permission denied
> >
> > (Do not subst to just C:/, because that somehow doesn't lead to the error.)
> >
> > There's also a C program that does essentially the same thing:
> > <https://gist.github.com/elieux/6463521192baed613099>
> >
> > I compared this with the same operations running on a regular drive,
> > but I couldn't find any difference in how `rm` deletes the file nor in
> > how `touch` creates the file. Just the result of the last NtCreateFile
> > is different (STATUS_SUCCESS vs. STATUS_DELETE_PENDING).
>
> It's a result of how Cygwin tries to workaround the weird Windows
> behaviour that a deleted, but still opened file is not invisible in the
> filesystem, as desired per POSIX. Cygwin then tries to move the
> file out of the way, on local drives into the recycler. This fails
> on a subst drive pointing to some subdir apparently, so Cygwin just
> falls back to what Windows does.
>
> I have no simple workaround for that. In theory there should be a
> way to check the drive for being a virtual drive and then using the
> recycler of the drive it's pointing to for the aforementioned operation.
I hacked a bit on that and it seems the solution was easier than I thought.
I uploaded new developer snaphshots to https://cygwin.com/snapshots/
Replacing the Cygwin DLL alone is sufficient for testing. Please give it
a try.
Thanks,
Corinna
--
Corinna Vinschen Please, send mails regarding Cygwin to
Cygwin Maintainer cygwin AT cygwin DOT com
Red Hat
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