Re: [PATCH] io_uring/rsrc: remove registered buffer 1GB limit

["Clément Léger" <cleger@meta.com>]

On 5/5/26 12:09, Jens Axboe wrote:
> > 
> On 5/5/26 1:39 AM, Jens Axboe wrote:
>> There's no real reason to have a limit, as the memory is accounted by
>> the lockmem limits anyway, if any exist. io_pin_pages() will still
>> restrict the maximum allowed limit per buffer, which is INT_MAX
>> number of pages. For a 4kb page size system, the limit is 8TB.
>>
>> Reported-by: Andres Freund <andres@anarazel.de>
>> Signed-off-by: Jens Axboe <axboe@kernel.dk>
> 
> Forgot that I had a prep patch for this one... The branch is here:
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/axboe/linux.git/log/?h=io_uring-reg-buffers
> 
> and notably the patch before this one is below, which bumps the ->len
> size of the io_mapped_ubuf. I'll send this out as a proper series later
> this week, this is 7.2 material obviously.
> 
> commit 381e736515173a1fb78d2a86983d3ebfcf263597
> Author: Jens Axboe <axboe@kernel.dk>
> Date:   Mon May 4 05:40:16 2026 -0600
> 
>      io_uring/rsrc: bump struct io_mapped_ubuf length field to size_t
>      
>      In preparation for supporting bigger individual buffers, bump the length
>      field to a full 8-bytes with size_t rather than an unsigned int.
>      
>      Signed-off-by: Jens Axboe <axboe@kernel.dk>
> 
> diff --git a/io_uring/fdinfo.c b/io_uring/fdinfo.c
> index c2d3e45544bb..f0ff4bd01b6d 100644
> --- a/io_uring/fdinfo.c
> +++ b/io_uring/fdinfo.c
> @@ -223,7 +223,7 @@ static void __io_uring_show_fdinfo(struct io_ring_ctx *ctx, struct seq_file *m)
>   		if (ctx->buf_table.nodes[i])
>   			buf = ctx->buf_table.nodes[i]->buf;
>   		if (buf)
> -			seq_printf(m, "%5u: 0x%llx/%u\n", i, buf->ubuf, buf->len);
> +			seq_printf(m, "%5u: 0x%llx/%zu\n", i, buf->ubuf, buf->len);
>   		else
>   			seq_printf(m, "%5u: <none>\n", i);
>   	}
> diff --git a/io_uring/rsrc.h b/io_uring/rsrc.h
> index 44e3386f7c1c..03521b50926c 100644
> --- a/io_uring/rsrc.h
> +++ b/io_uring/rsrc.h
> @@ -34,15 +34,15 @@ enum {
>   
>   struct io_mapped_ubuf {
>   	u64		ubuf;
> -	unsigned int	len;
> +	size_t		len;
>   	unsigned int	nr_bvecs;
>   	unsigned int    folio_shift;
>   	refcount_t	refs;
> +	u8		flags;
> +	u8		dir;
>   	unsigned long	acct_pages;
>   	void		(*release)(void *);
>   	void		*priv;
> -	u8		flags;
> -	u8		dir;

Hi Jens,

This seems like an unrelated change.

Thanks,

Clément

>   	struct bio_vec	bvec[] __counted_by(nr_bvecs);
>   };
>   
>