Re: [PATCH] io_uring: take page references for NOMMU pbuf_ring mmaps

Jens Axboe
2026-04-21T17:39:51Z

On Tue, 21 Apr 2026 15:46:16 +0200, Greg Kroah-Hartman wrote:
> Under !CONFIG_MMU, io_uring_get_unmapped_area() returns the kernel
> virtual address of the io_mapped_region's backing pages directly;
> the user's VMA aliases the kernel allocation. io_uring_mmap() then
> just returns 0 -- it takes no page references.
>
> The CONFIG_MMU path uses vm_insert_pages(), which takes a reference on
> each inserted page. Those references are released when the VMA is torn
> down (zap_pte_range -> put_page). io_free_region() -> release_pages()
> drops the io_uring-side references, but the pages survive until munmap
> drops the VMA-side references.
>
> [...]

Applied, thanks!

[1/1] io_uring: take page references for NOMMU pbuf_ring mmaps
commit: d9b7b3d9c5286a786c7fe8220c55a6e012088c2e

Best regards,
--
Jens Axboe