Re: Race between vmtruncate and mapped areas?

Dave McCracken
2003-05-14T15:25:26Z

--On Wednesday, May 14, 2003 08:06:53 -0700 William Lee Irwin III
<wli@holomorphy.com> wrote:

>> Which the application thinks is still part of the file, and will expect
>> its changes to be written back. Granted, if the page fault occurred
>> just after the truncate it'd get SIGBUS, so it's clearly not a robust
>> assumption, but it will result in unexpected behavior. Note that if the
>> application later extends the file to include this page it could result
>> in a corrupted file, since all the pages around it will be written
>> properly.
>
> Well, for this one I'd say the app loses; it was its own failure to
> synchronize truncation vs. access, at least given that the kernel
> doesn't oops.

I think allowing a race condition that can randomly leave corrupted files
is a really bad idea, even if the app is doing something stupid. We know
what the race is. We should be able to prevent it.

Dave

======================================================================
Dave McCracken IBM Linux Base Kernel Team 1-512-838-3059
dmccr@us.ibm.com T/L 678-3059