Re: [PATCH 4/7] btrfs: Switch to iomap_dio_rw() for dio

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On Tue, May 26, 2020 at 5:47 PM Goldwyn Rodrigues <rgoldwyn@xxxxxxx> wrote:
>
> On 15:03 26/05, Johannes Thumshirn wrote:
> > Just as a heads up, this one gives me lot's of Page cache invalidation
> > failure prints from dio_warn_stale_pagecache() on btrfs/004 with
> > current misc-next:
> >
> <snip>
>
> > [   23.696400] Page cache invalidation failure on direct I/O.  Possible data corruption due to collision with buffered I/O!
> > [   23.698115] File: /mnt/scratch/bgnoise/p0/f0 PID: 6562 Comm: fsstress
> >
> > I have no idea yet why but I'm investigating.
>
> This is caused because we are trying to release a page when the extent
> has locked the page and release page returns false.

By "we" you mean what exaclty, a direct IO read, a direct IO write?

And who locked the extent range before?

That seems alarming to me, specially if it's a direct IO write failing
to invalidate the page cache, since a subsequent buffered read could
get stale data (what's in the page cache), and not what the direct IO
write wrote.

Can you elaborate more on all those details?

Thanks.


> To minimize the
> effect, I had proposed a patch [1] in v6. However, this created
> more extent locking issues and so was dropped.
>
> [1] https://patchwork.kernel.org/patch/11275063/
>
> --
> Goldwyn



-- 
Filipe David Manana,

“Whether you think you can, or you think you can't — you're right.”




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