On 07/18/2013 12:51 PM, 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().. > blk_mq_make_request is not called from the blk insert/execute paths. blk_mq_make_request takes a bio and tries to merge it with a request and adds it to the queue. It is only called when the make_request_fn is called like when generic_make_request is called. blk_mq_insert_request adds a already formed request to the queue. It is already formed so that is why that path does not bounce bios. The bios/pages should already be added within the drivers restrictions. So for the read_cap path, the call to blk_rq_map_kern in scsi_execute does the blk_queue_bounce call. Just saw this while trying out iscsi with the scsi-mq stuff :) -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
