xprtrdma: Disable pad optimization by default
Commit d5440e27 ("xprtrdma: Enable pad optimization") made the Linux client omit XDR round-up padding in normal Read and Write chunks so that the client doesn't have to register and invalidate 3-byte memory regions that contain no real data. Unfortunately, my cheery 2014 assessment that this optimization "is supported now by both Linux and Solaris servers" was premature. We've found bugs in Solaris in this area since commit d5440e27 ("xprtrdma: Enable pad optimization") was merged (SYMLINK is the main offender). So for maximum interoperability, I'm disabling this optimization again. If a CM private message is exchanged when connecting, the client recognizes that the server is Linux, and enables the optimization for that connection. Until now the Solaris server bugs did not impact common operations, and were thus largely benign. Soon, less capable devices on Linux NFS/RDMA clients will make use of Read chunks more often, and these Solaris bugs will prevent interoperation in more cases. Fixes: 677eb17e ("xprtrdma: Fix XDR tail buffer marshalling") Cc: stable@vger.kernel.org # v4.9+ Signed-off-by: NChuck Lever <chuck.lever@oracle.com> Signed-off-by: NAnna Schumaker <Anna.Schumaker@Netapp.com>
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