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    Subject[PATCH V2 2/4] Drivers: hv: fcopy: restore correct transfer length
    Date
    From: Olaf Hering <olaf@aepfle.de>

    Till recently the expected length of bytes read by the
    daemon did depend on the context. It was either hv_start_fcopy or
    hv_do_fcopy. The daemon had a buffer size of two pages, which was much
    larger than needed.

    Now the expected length of bytes read by the
    daemon changed slightly. For START_FILE_COPY it is still the size of
    hv_start_fcopy. But for WRITE_TO_FILE and the other operations it is as
    large as the buffer that arrived via vmbus. In case of WRITE_TO_FILE
    that is slightly larger than a struct hv_do_fcopy. Since the buffer in
    the daemon was still larger everything was fine.

    Currently, the daemon reads only what is actually needed.
    The new buffer layout is as large as a struct hv_do_fcopy, for the
    WRITE_TO_FILE operation. Since the kernel expects a slightly larger
    size, hvt_op_read will return -EINVAL because the daemon will read
    slightly less than expected. Address this by restoring the expected
    buffer size in case of WRITE_TO_FILE.

    Fixes: 'commit c7e490fc23eb ("Drivers: hv: fcopy: convert to hv_utils_transport")'
    Fixes: 'commit 3f2baa8a7d2e ("Tools: hv: update buffer handling in hv_fcopy_daemon")'

    Signed-off-by: Olaf Hering <olaf@aepfle.de>
    Signed-off-by: K. Y. Srinivasan <kys@microsoft.com>
    ---
    drivers/hv/hv_fcopy.c | 4 ++++
    1 file changed, 4 insertions(+)

    diff --git a/drivers/hv/hv_fcopy.c b/drivers/hv/hv_fcopy.c
    index daa75bd41f86..2364281d8593 100644
    --- a/drivers/hv/hv_fcopy.c
    +++ b/drivers/hv/hv_fcopy.c
    @@ -170,6 +170,10 @@ static void fcopy_send_data(struct work_struct *dummy)
    out_src = smsg_out;
    break;

    + case WRITE_TO_FILE:
    + out_src = fcopy_transaction.fcopy_msg;
    + out_len = sizeof(struct hv_do_fcopy);
    + break;
    default:
    out_src = fcopy_transaction.fcopy_msg;
    out_len = fcopy_transaction.recv_len;
    --
    2.14.1
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