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    SubjectRe: [RFC PATCH 1/6] bsg: fix kernel panic resulting from missing allocation of a reply-buffer
    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.

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