On 6/1/18 8:36 PM, Ming Lei wrote: >> clear the bit when we need to, potentially even adding a debug check to >> blk_queue_enter_live() that complains if the ref was not already >> elevated. Though that would be expensive, compared to the percpu inc >> now. Not saying the bit is necessarily the best way forward, but I do >> like it a LOT more than adding an argument to generic_make_request. > > We may introduce generic_make_request_with_ref() for blk_queue_split(), > what do you think of the following patch? Functionally it'll work as well. > In DM or MD, there is the following use case: > > 1) bio comes from fs, then one clone is made from this bio > > 2) the cloned bio is submitted via generic_make_request() from > another context, such as wq. > > 3) then the flag of BIO_QUEUE_ENTERED is inherited and causes > the queue usage counter isn't held. We don't copy flags on a clone. -- Jens Axboe
