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

[Jens Axboe <axboe@kernel.dk>]

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

-- 
Jens Axboe