On 09/13/2017 11:54 AM, Jens Axboe wrote: > On 09/12/2017 09:39 PM, jianchao.wang wrote: >>> Exactly, and especially the readability is the key element here. It's >>> just not worth it to try and be too clever, especially not for >>> something like this. When you read the above, you immediately know >>> what the code does without needing a comment. That's not true for the >>> other construct. You both have to read other parts of the function >>> to figure out what it does, AND read the entire function to ensure it >>> always does the right thing. Fragile. >> >> Thanks for your comments , jens and ming. I＇m really appreciative of >> that. About the fragility, do you mean the possibility that may >> release the tag of the next rq which has a driver tag itself (maybe a >> flush) ? > > I mean that if you do: > > if (!list_empty(list)) > blk_mq_put_driver_tag(nxt); > > it's fragile code in the sense that changes elsewhere in the function > are harder to validate and/or can impact the functionality of that > simple if and tag put. > > The actual release must always be safe, of course. > Got it, thanks a lot.
