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Date:   Wed, 13 Dec 2023 14:02:31 +0100
From:   Christian Brauner <brauner@kernel.org>
To:     John Garry <john.g.garry@oracle.com>
Cc:     axboe@kernel.dk, kbusch@kernel.org, hch@lst.de, sagi@grimberg.me,
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Subject: Re: [PATCH v2 04/16] fs: Increase fmode_t size
Message-ID: <20231213-gurte-beeren-e71ff21c3c03@brauner>
References: <20231212110844.19698-1-john.g.garry@oracle.com>
 <20231212110844.19698-5-john.g.garry@oracle.com>
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On Tue, Dec 12, 2023 at 11:08:32AM +0000, John Garry wrote:
> Currently all bits are being used in fmode_t.
> 
> To allow for further expansion, increase from unsigned int to unsigned
> long.
> 
> Since the dma-buf driver prints the file->f_mode member, change the print
> as necessary to deal with the larger size.
> 
> Signed-off-by: John Garry <john.g.garry@oracle.com>
> ---
>  drivers/dma-buf/dma-buf.c | 2 +-
>  include/linux/types.h     | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/dma-buf/dma-buf.c b/drivers/dma-buf/dma-buf.c
> index 21916bba77d5..a5227ae3d637 100644
> --- a/drivers/dma-buf/dma-buf.c
> +++ b/drivers/dma-buf/dma-buf.c
> @@ -1628,7 +1628,7 @@ static int dma_buf_debug_show(struct seq_file *s, void *unused)
>  
>  
>  		spin_lock(&buf_obj->name_lock);
> -		seq_printf(s, "%08zu\t%08x\t%08x\t%08ld\t%s\t%08lu\t%s\n",
> +		seq_printf(s, "%08zu\t%08x\t%08lx\t%08ld\t%s\t%08lu\t%s\n",
>  				buf_obj->size,
>  				buf_obj->file->f_flags, buf_obj->file->f_mode,
>  				file_count(buf_obj->file),
> diff --git a/include/linux/types.h b/include/linux/types.h
> index 253168bb3fe1..49c754fde1d6 100644
> --- a/include/linux/types.h
> +++ b/include/linux/types.h
> @@ -153,7 +153,7 @@ typedef u32 dma_addr_t;
>  
>  typedef unsigned int __bitwise gfp_t;
>  typedef unsigned int __bitwise slab_flags_t;
> -typedef unsigned int __bitwise fmode_t;
> +typedef unsigned long __bitwise fmode_t;

As Jan said, that's likely a bad idea. There's a bunch of places that
assume fmode_t is 32bit. So not really a change we want to make if we
can avoid it.