Jens Axboe <axboe@xxxxxxxxx> writes:
> Rather than use remap_pfn_range() for this and manually free later,
> switch to using vm_insert_pages() and have it Just Work.
>
> If possible, allocate a single compound page that covers the range that
> is needed. If that works, then we can just use page_address() on that
> page. If we fail to get a compound page, allocate single pages and use
> vmap() to map them into the kernel virtual address space.
>
> This just covers the rings/sqes, the other remaining user of the mmap
> remap_pfn_range() user will be converted separately. Once that is done,
> we can kill the old alloc/free code.
>
> Signed-off-by: Jens Axboe <axboe@xxxxxxxxx>
> ---
> io_uring/io_uring.c | 136 +++++++++++++++++++++++++++++++++++++++++---
> io_uring/io_uring.h | 2 +
> 2 files changed, 130 insertions(+), 8 deletions(-)
>
> diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
> index 104899522bc5..982545ca23f9 100644
> --- a/io_uring/io_uring.c
> +++ b/io_uring/io_uring.c
> @@ -2594,6 +2594,33 @@ static int io_cqring_wait(struct io_ring_ctx *ctx, int min_events,
> return READ_ONCE(rings->cq.head) == READ_ONCE(rings->cq.tail) ? ret : 0;
> }
>
> +static void io_pages_unmap(void *ptr, struct page ***pages,
> + unsigned short *npages)
> +{
> + bool do_vunmap = false;
> +
> + if (*npages) {
> + struct page **to_free = *pages;
> + int i;
> +
> + /*
> + * Only did vmap for the non-compound multiple page case.
> + * For the compound page, we just need to put the head.
> + */
> + if (PageCompound(to_free[0]))
> + *npages = 1;
> + else if (*npages > 1)
> + do_vunmap = true;
> + for (i = 0; i < *npages; i++)
> + put_page(to_free[i]);
> + }
Hi Jens,
wouldn't it be simpler to handle the compound case separately as a
folio? Then you folio_put the compound page here and just handle the
non-continuous case after.
--
Gabriel Krisman Bertazi
