Hi, Jens, On 2016/7/6 1:33, Jens Axboe wrote: > On 07/04/2016 07:03 AM, Wei Fang wrote: >> Theoretically, request only flags in enum rq_flag_bits can bigger >> than 31 after we add some new flags in the future, so we can't >> store REQ_IO_STAT in op_flags which is a int type in __get_request(). >> Actually, when REQ_IO_STAT become 31, the most-significant bit of >> op_flags will be 1, and OR it to ->cmd_flags will cause the top 32 >> bits of ->cmd_flags become 1. >> >> Fix it by using a u64-type object to store flags. > > Why not change op_flags to a 64-bit type, if the flags are already overflowing? > > Either that, or we need a BUILD_BUG_ON() for the flags not being > 32 bit. > op_flags passed into __get_request() is used to store bio flags which won't be > 31 bit, so it can not be overflowing when it passed in. But request only flags, e.g. REQ_IO_STAT, that op_flags try to store in __get_request() may be > 31 bit in the future, so op_flags will be overflowing in that case. (I already met that problem after I added some new common flags.) Converting int to u64 can be problematic when the most-significant bit of op_flags is 1 when it passed in (it may happen theoretically?), so I add a explicit cast between op_flags and cmd_flags. Thanks, Wei -- To unsubscribe from this list: send the line "unsubscribe linux-block" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
