Messages in this thread | | | Date | Sat, 05 Oct 2013 15:20:05 -0500 | From | Mike Christie <> | Subject | Re: [PATCH 2/5] [PATCH 2/5] revert: "blk-mq: blk-mq should free bios in pass through case" |
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On 10/05/2013 05:50 AM, Christoph Hellwig wrote: > On Fri, Oct 04, 2013 at 12:39:33PM -0500, Mike Christie wrote: >> Sorry, messed up function name. I meant blk_end_request*. >> >> For blk_execute_rq_nowait/blk_execute_rq and normal request use, the >> lower levels free the bios as they are completed by one of the >> blk_finish_request* calls. The caller of of >> blk_execute_rq_nowait/blk_execute_rq does not have to worry about >> freeing bios. It just frees the request when it is done with it. > > Are you talking about bios or requests? All these functions deal with > requests, so the talk of bios really confuses me.
The functions take in requests as the argument, but they end up operating on bios too. The scsi layer does scsi_io_completion->scsi_end_request-> blk_end_request -> blk_end_bidi_request -> blk_update_bidi_request -> blk_update_request. That function will then complete bios on the request passed in. It does not matter if the request is a REQ_TYPE_FS or REQ_TYPE_BLOCK_PC.
With my patch I was trying to make the block layer do the same for mq REQ_TYPE_BLOCK_PC requests inserted into the queue with blk_execute_rq_nowait (Nick's patch had support for something like that) by having the block mq layer call blk_mq_finish_request instead of making the code that calls blk_execute_rq_nowait do it.
> > That beeing said the old ones all require the caller to free the > request, and complicate that with the useless refcounting that my patch > 3 removes. Take a look at the other patches how all the calling > conventions can be nicely unified.
I agree. I like them. I am saying though it could be better because even with your patches the rq->end_io functions need to have the mq_ops check like the flush_end_io does. If my patch worked as intended we would have your improvements and we would not need the rq->end_io functions to have that check and call blk_mq_finish_request because the blk mq layer was doing it for them.
That is all I am saying. I would like to be able to remove that check and blk_mq_finish_request call from the rq->end_io callouts.
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