On 07/18/2013 01:14 PM, Nicholas A. Bellinger wrote: > On Thu, 2013-07-18 at 11:51 -0700, Nicholas A. Bellinger wrote: >> On Wed, 2013-07-17 at 18:19 +0200, Alexander Gordeev wrote: >>> On Tue, Jul 16, 2013 at 02:38:03PM -0700, Nicholas A. Bellinger wrote: >>>> [ 7.927818] scsi_execute(): Calling blk_mq_free_request >>> >>>> [ 7.927826] scsi 0:0:0:0: Direct-Access ATA ST9500530NS CC03 PQ: 0 ANSI: 5 >>>> >>>> OK, so INQUIRY response payload is looking as expected here. >>> >>> Yep. It is not on the top of my head, but I remember something like INQUIRYs >>> are emulated and thus do not have payload. >>> >>>> [ 7.927960] sd 0:0:0:0: [sda] Sector size 0 reported, assuming 512. >>>> [ 7.927964] sd 0:0:0:0: [sda] 1 512-byte logical blocks: (512 B/512 B) >>>> [ 7.927965] sd 0:0:0:0: [sda] 0-byte physical blocks >>>> >>>> Strange.. READ_CAPACITY appears to be returning a payload as zeros..? >>> >>> Yep. Because blk_execute_rq() does not put the proper callback and data do >>> not get copied from sg's to bounce buffer. That is why I tried to use >>> blk_mq_execute_rq() instead. Once I do that, data start getting read and >>> booting stops elsewhere. >> >> Mmmmmm. >> >> The call to blk_queue_bounce() exists within blk_mq_make_request(), but >> AFAICT this should still be getting invoked regardless of if the struct >> request is dispatched into blk-mq via the modified blk_execute_rq() -> >> blk_execute_rq_nowait() -> blk_mq_insert_request() codepath, or directly >> via blk_mq_execute_rq().. >> >> Jens..? >> > > Actually sorry, your right. A call to blk_mq_insert_request() for > REQ_TYPE_BLOCK_PC will not invoke blk_queue_bounce() located near the > top of blk_mq_execute_rq(), which means that only REQ_TYPE_FS is > currently using bounce buffers, if required. > > Need to think a bit more about what to do here for REQ_TYPE_BLOCK_PC > bounce buffer special case with blk_execute_rq(), but I'm thinking that > blk_mq_execute_rq() should really not be used here.. > > Jens..? It needs to be pre-bounced, blk-mq will only bounce incoming bios and not requests merely added to the queue(s). Might be useful to add an equiv blk_mq_make_request() for this. -- Jens Axboe -- To unsubscribe from this list: send the line "unsubscribe linux-ide" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
