On 10/23/19 12:42 PM, Jeff Moyer wrote:
> Jackie Liu <liuyun01@xxxxxxxxxx> writes:
>
>> If cq_entries is smaller than sq_entries, it will cause a lot of overflow
>> to appear. when customizing cq_entries, at least let him be no smaller than
>> sq_entries.
>>
>> Fixes: 95d8765bd9f2 ("io_uring: allow application controlled CQ ring size")
>> Signed-off-by: Jackie Liu <liuyun01@xxxxxxxxxx>
>> ---
>> fs/io_uring.c | 2 +-
>> 1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/fs/io_uring.c b/fs/io_uring.c
>> index b64cd2c..dfa9731 100644
>> --- a/fs/io_uring.c
>> +++ b/fs/io_uring.c
>> @@ -3784,7 +3784,7 @@ static int io_uring_create(unsigned entries, struct io_uring_params *p)
>> * to a power-of-two, if it isn't already. We do NOT impose
>> * any cq vs sq ring sizing.
>> */
>> - if (!p->cq_entries || p->cq_entries > IORING_MAX_CQ_ENTRIES)
>> + if (p->cq_entries < p->sq_entries || p->cq_entries > IORING_MAX_CQ_ENTRIES)
>
> What if they're both zero? I think you want to keep that check.
sq_entries being zero is already checked and failed at this point.
So I think the patch looks fine from that perspective.
Is there really a strong reason to disallow this? Yes, it could
cause overflows, but it's just doing what was asked for. The
normal case is of course cq_entries being much larger than
sq_entries.
--
Jens Axboe
