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Date:   Sat, 22 Aug 2020 14:13:12 +0100
From:   Christoph Hellwig <hch@infradead.org>
To:     Dave Chinner <david@fromorbit.com>
Cc:     Ritesh Harjani <riteshh@linux.ibm.com>,
        Anju T Sudhakar <anju@linux.vnet.ibm.com>, hch@infradead.org,
        darrick.wong@oracle.com, linux-xfs@vger.kernel.org,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        willy@infradead.org
Subject: Re: [PATCH] iomap: Fix the write_count in iomap_add_to_ioend().
Message-ID: <20200822131312.GA17997@infradead.org>
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On Sat, Aug 22, 2020 at 07:53:58AM +1000, Dave Chinner wrote:
> but iomap only allows BIO_MAX_PAGES when creating the bio. And:
> 
> #define BIO_MAX_PAGES 256
> 
> So even on a 64k page machine, we should not be building a bio with
> more than 16MB of data in it. So how are we getting 4GB of data into
> it?

BIO_MAX_PAGES is the number of bio_vecs in the bio, it has no
direct implication on the size, as each entry can fit up to UINT_MAX
bytes.