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From:   Tong Zhang <ztong0001@gmail.com>
Date:   Tue, 3 Nov 2020 08:52:32 -0500
Message-ID: <CAA5qM4C+UGB_SXW5OeWKPtNkXyVCfwwB_ct9wps0Lj6VhvTawg@mail.gmail.com>
Subject: Re: [PATCH v3] qnx4: qnx4_block_map error handling
To:     David Laight <David.Laight@aculab.com>
Cc:     Anders Larsen <al@alarsen.net>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
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Precedence: bulk

On Tue, Nov 3, 2020 at 5:54 AM David Laight <David.Laight@aculab.com> wrote:
>
> From: Tong Zhang
> > Sent: 02 November 2020 23:14
> >
> > qnx4_block_map() may return -EIO on funny qnx4 fs image, in this case do
> > not interpret -EIO as a correct block number
>
> That commit message is now wrong.
ouch -- what would you suggest here?

> Also 'blknum' is only 'unsigned long' so ~0ull is wrong.
> It can be worth injecting an error and checking the error
> propagation works.
>
> What is the actual maximum file size?
The maximum file size is 2GB-1, but from my understanding
qnx4_block_map() returns
a physical block number. The max disk size supported is 2**64 bytes, however
it is limited to unsigned long (2**32)
-- so I am actually very hesitant to encode an error code in the return value
without changing the function return type, which will introduce more
changes I don't like.
The original -EIO in qnx4_block_map() is also dodgy btw.
> Is there actually an 'out of range' blknum value
> that can be used to signify an error without
> changing the return value to 'long long'.
>
>         David
>
> -
> Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK
> Registration No: 1397386 (Wales)
>