Shenghui Wang <shhuiw@xxxxxxxxxxx> writes:
> This issue is found by running liburing/test/io_uring_setup test.
>
> When test run, the testcase "attempt to bind to invalid cpu" would not
> pass with messages like:
> io_uring_setup(1, 0xbfc2f7c8), \
> flags: IORING_SETUP_SQPOLL|IORING_SETUP_SQ_AFF, \
> resv: 0x00000000 0x00000000 0x00000000 0x00000000 0x00000000, \
> sq_thread_cpu: 2
> expected -1, got 3
> FAIL
>
> On my system, there is:
> CPU(s) possible : 0-3
> CPU(s) online : 0-1
> CPU(s) offline : 2-3
> CPU(s) present : 0-1
>
> The sq_thread_cpu 2 is offline on my system, so the bind should fail.
> But cpu_possible() will pass the check. We shouldn't be able to bind
> to an offline cpu. Use cpu_online() to do the check.
>
> After the change, the testcase run as expected: EINVAL will be returned
> for cpu offlined.
>
> Signed-off-by: Shenghui Wang <shhuiw@xxxxxxxxxxx>
> ---
> fs/io_uring.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/fs/io_uring.c b/fs/io_uring.c
> index 0e9fb2cb1984..aa3d39860a1c 100644
> --- a/fs/io_uring.c
> +++ b/fs/io_uring.c
> @@ -2241,7 +2241,7 @@ static int io_sq_offload_start(struct io_ring_ctx *ctx,
> ctx->sqo_mm = current->mm;
>
> ret = -EINVAL;
> - if (!cpu_possible(p->sq_thread_cpu))
> + if (!cpu_online(p->sq_thread_cpu))
> goto err;
>
> if (ctx->flags & IORING_SETUP_SQPOLL) {
> @@ -2258,7 +2258,7 @@ static int io_sq_offload_start(struct io_ring_ctx *ctx,
>
> cpu = array_index_nospec(p->sq_thread_cpu, NR_CPUS);
> ret = -EINVAL;
> - if (!cpu_possible(p->sq_thread_cpu))
> + if (!cpu_online(p->sq_thread_cpu))
> goto err;
>
> ctx->sqo_thread = kthread_create_on_cpu(io_sq_thread,
Hmm. Why are we doing this check twice? Oh... Jens, I think you
braino'd commit 917257daa0fea. Have a look. You probably wanted to get
rid of the first check for cpu_possible.
-Jeff
