On Tue, Nov 19, 2013 at 03:01:47AM -0800, Christoph Hellwig wrote:
> On Tue, Nov 19, 2013 at 06:45:08PM +0800, Zheng Liu wrote:
> > BTW, that would be great if you could give me some comments about this
> > problem itself. Is it a generic problem in vfs? Or just a feature by
> > design?
>
> It seems like a fundamental issue with ext4 (and most older Linux
> filesystems) trying to do dio reads without locking out writers.
Ah, that is a long story for me. Anyway, thanks for your comment.
>
> If you have a shared/exclusive lock to protect dio reads against
> buffered or appending writers like XFS does this issue is properly
> prevented.
Yes, I know that XFS has a shared/exclusive lock. I guess that is why
it can pass the test. But another question is why xfs fails when we do
some append dio writes with doing buffered read.
Regards,
- Zheng
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