Re: [PATCH] io_uring: fix bug of wrong BUILD_BUG_ON check

[Hao Xu <haoxu@linux.alibaba.com>]

在 2021/9/6 下午11:22, Pavel Begunkov 写道:
> On 9/6/21 4:12 PM, Hao Xu wrote:
>> Some check should be large than not equal or large than.
>>
>> Signed-off-by: Hao Xu <haoxu@linux.alibaba.com>
>> ---
>>   fs/io_uring.c | 6 +++---
>>   1 file changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/fs/io_uring.c b/fs/io_uring.c
>> index 2bde732a1183..3a833037af43 100644
>> --- a/fs/io_uring.c
>> +++ b/fs/io_uring.c
>> @@ -10637,13 +10637,13 @@ static int __init io_uring_init(void)
>>   		     sizeof(struct io_uring_rsrc_update2));
>>   
>>   	/* ->buf_index is u16 */
>> -	BUILD_BUG_ON(IORING_MAX_REG_BUFFERS >= (1u << 16));
>> +	BUILD_BUG_ON(IORING_MAX_REG_BUFFERS > (1u << 16));
>>   
>>   	/* should fit into one byte */
>> -	BUILD_BUG_ON(SQE_VALID_FLAGS >= (1 << 8));
>> +	BUILD_BUG_ON(SQE_VALID_FLAGS > (1 << 8));
> 
> 0xff = 255 is the largest number fitting in u8,
> 1<<8 = 256.
> 
> let SQE_VALID_FLAGS = 256,
> (256 > (1<<8)) == (256 > 256) == false,  even though it can't
> be represented by u8.
Isn't SQE_VALID_FLAGS = 256 a valid value for it?
> 
> 
>>   	BUILD_BUG_ON(ARRAY_SIZE(io_op_defs) != IORING_OP_LAST);
>> -	BUILD_BUG_ON(__REQ_F_LAST_BIT >= 8 * sizeof(int));
>> +	BUILD_BUG_ON(__REQ_F_LAST_BIT > 8 * sizeof(int));
>>   
>>   	req_cachep = KMEM_CACHE(io_kiocb, SLAB_HWCACHE_ALIGN | SLAB_PANIC |
>>   				SLAB_ACCOUNT);
>>
>