On 5/1/19 5:56 AM, Jeff Moyer wrote:
> 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.
Added a fixup patch the other day:
http://git.kernel.dk/cgit/linux-block/commit/?h=for-linus&id=362bf8670efccebca22efda1ee5a5ee831ec5efb
--
Jens Axboe
