On 2022-04-22 00:36, Sam Li wrote:
> Linux recently added a new io_uring(7) optimization API that QEMU
> doesn't take advantage of yet. The liburing library that QEMU uses
> has added a corresponding new API calling io_uring_register_ring_fd().
> When this API is called after creating the ring, the io_uring_submit()
> library function passes a flag to the io_uring_enter(2) syscall
> allowing it to skip the ring file descriptor fdget()/fdput()
> operations. This saves some CPU cycles.
>
> Signed-off-by: Sam Li <faithilike...@gmail.com>
> ---
> block/io_uring.c | 10 +++++++++-
> 1 file changed, 9 insertions(+), 1 deletion(-)
>
> diff --git a/block/io_uring.c b/block/io_uring.c
> index 782afdb433..5247fb79e2 100644
> --- a/block/io_uring.c
> +++ b/block/io_uring.c
> @@ -435,8 +435,16 @@ LuringState *luring_init(Error **errp)
> }
>
> ioq_init(&s->io_q);
> - return s;
> + if (io_uring_register_ring_fd(&s->ring) < 0) {
> + /*
> + * Only warn about this error: we will fallback to the non-optimized
> + * io_uring operations.
> + */
> + error_reportf_err(*errp,
> + "failed to register linux io_uring ring file
> descriptor");
IIUC errp can be NULL, so let's not dereference it without checking. So, just
use error_report?
Fam
> + }
>
> + return s;
> }
>
> void luring_cleanup(LuringState *s)
> --
> Use error_reportf_err to avoid memory leak due to not freeing error
> object.
> --
> 2.35.1
>
>
