Drivers: hv: fcopy: restore correct transfer length

commit 549e658a0919e355a2b2144dc380b3729bef7f3e upstream.

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: 'c7e490fc23eb ("Drivers: hv: fcopy: convert to hv_utils_transport")'
Fixes: '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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/hv/hv_fcopy.c b/drivers/hv/hv_fcopy.c
index e47d8c9..75126e4 100644 (file)
--- a/drivers/hv/hv_fcopy.c
+++ b/drivers/hv/hv_fcopy.c
@@ -161,6 +161,10 @@ 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;