On Thu, 2014-06-19 at 09:33 +0000, Cox, Alan wrote:
> On Thu, 2014-06-19 at 10:30 +0100, Alan Cox wrote:
> > The block code has 32bit cleanness problems with the iterator. This
> > prevents things like partitioning a 32GB volume on a 32bit system.
> >
> > I hit this with a volume of exactly 32GB in size (easy to duplicate with
> > virtual machines). Tracing at step by step through the kernel I found
> > the problem lines in blkdev_read_iter which truncates the size value
> > into a 32bit value when setting up the iterator.
> >
> > The hack below if applied "fixes" this and I think demonstrates that
> > this is the problem spot.
> >
> > What I'm less clear on is what the correct fix for this should be.
>
> block: fix inability to partition large volumes
>
> From: Alan <alan@xxxxxxxxxxxxxxx>
>
> The block code has 32bit cleanness problems with the iterator. This
> prevents things like partitioning a 32GB volume on a 32bit system.
>
> This is a simple initial "fix" that clips the problem cases so get
> behaviour that is at least sane and trivially backportable.
>
> Signed-off-by: Alan Cox <alan@xxxxxxxxxxxxxxx>
> ---
> fs/block_dev.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/fs/block_dev.c b/fs/block_dev.c
> index 6d72746..bef2414 100644
> --- a/fs/block_dev.c
> +++ b/fs/block_dev.c
> @@ -1603,6 +1603,9 @@ static ssize_t blkdev_read_iter(struct kiocb
> *iocb, struct iov_iter *to)
>
> size -= pos;
> iov_iter_truncate(to, size);
> + /* Fix up for 32bit boxes for now */
> + if (to->count < size)
> + to->count = 0xFFFFFFFF;
> return generic_file_read_iter(iocb, to);
> }
>
>
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> NrybXǧv^){.n+{~^b^nrzh& Gh(階ݢj"mzޖfh~m
Wow that's junk issued by an Exchange server ... Alan, really ...
Do you have CONFIG_LBD turned on? That's supposed to let us go up to
about 16TB before we run out of page index bits. If you do, we might
have a variable that's int but should be sector_t somewhere.
James
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