On 28/05/15 13:49, Dietmar Maurer wrote:
I'm not kernel/IO expert in any way, but I think this test program has a
race condition, so it is not helping us diagnose the problem.
We're writing to buffer x while it is in use by write syscall. This is
plainly wrong on userspace.
For this test, we do not care about userspace semantics. The point is
that it results in damaged RAID, which should never! happen.
I don't think the kernel can do anything if you're not complying with
calling conventions.
If you provide a buffer to the kernel, that you change while it is
working with it, I don't know why you expect a reliable/predictable
result? Specially (but not only) if you tell it not to make a copy!!
Note that without O_DIRECT you won't get a "correct" result either; disk
may end not containing the data in the buffer when write was called.
Softmirror data will be identically uncertain :)
Cheers
Eneko
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Zuzendari Teknikoa / Director Técnico
Binovo IT Human Project, S.L.
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