Re: Race between vmtruncate and mapped areas?

[Dave McCracken <dmccr@us.ibm.com>]

--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

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