On Fri, Aug 11, 2017 at 06:01:42PM +0200, Benjamin Block wrote: > When the BSG interface is used with bsg-lib, and the user sends a > Bidirectional command - so when he gives an input- and output-buffer > (most users of our interface will likely do that, if they wanna get the > transport-level response data) - bsg will allocate two requests from the > queue. The first request's bio is used to map the input and the second > request's bio for the output (see bsg_map_hdr() in the if-statement with > (op == REQ_OP_SCSI_OUT && hdr->din_xfer_len)). > > When we now allocate the full space of bsg_job, sense, dd_data for each > request, these will be wasted on the (linked) second request. They will > go unused all the time, as only the first request's bsg_job, sense and > dd_data is used by the LLDs and BSG itself. > > Right now, because we don't allocate this on each request, those spaces > are only allocated for the first request in bsg-lib. > > Maybe we can ignore this, if it gets to complicated, I don't wanne > prolong this unnecessary. We have the same 'issue' with bidirection scsi commands - it's a side effect of having two request structures for these commands, and the only real fix would be to have a single request structure, which would be nice especially if we can't do it without growing struct request.
