Re: [LTP] [PATCH/RFC] aiodio: make read_sparse use same mode as writers

[chrubis@suse.cz]

Hi!
> Starting with 3.10 dio_sparse sporadically fails, because
> read() in read_sparse returns garbage and dio_sparse testcase
> fails with:
>   dio_sparse    0  TINFO  :  Dirtying free blocks
>   dio_sparse    0  TINFO  :  Starting I/O tests
>   non zero buffer at buf[0] => 0xffffffaa,ffffffaa,ffffffaa,ffffffaa
>   non-zero read at offset 0
>   dio_sparse    0  TINFO  :  Killing childrens(s)
>   dio_sparse    1  TFAIL  :  1 children(s) exited abnormally
> 
> Issue is that we have parent opening file as O_DIRECT and
> children trying to read from it without O_DIRECT, which is
> discouraged in man pages.
> 
> open(2) says:
> "Applications should avoid mixing O_DIRECT and normal I/O to the same
> file, and especially to overlapping byte regions in the same file."
> 
> Signed-off-by: Jan Stancek <jstancek@redhat.com>
> ---

The README in the testcases directory says that the tests explicitly
tests for consistency between buffered I/O and O_DIRECT.

I will consult some kernel guys if this was ever supported and we will
either remove the tests or try to find a bug in the kernel.

-- 
Cyril Hrubis
chrubis@suse.cz

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