tree 3a32d4c377b5e919f6718d3733434558407a5f6f
parent a78868497c2e4858e2c73818eed7b4877ab2316d
author Chuck Lever <chuck.lever@oracle.com> 1545235136 -0500
committer Anna Schumaker <Anna.Schumaker@Netapp.com> 1546448717 -0500

xprtrdma: Remove support for FMR memory registration

FMR is not supported on most recent RDMA devices. It is also less
secure than FRWR because an FMR memory registration can expose
adjacent bytes to remote reading or writing. As discussed during the
RDMA BoF at LPC 2018, it is time to remove support for FMR in the
NFS/RDMA client stack.

Note that NFS/RDMA server-side uses either local memory registration
or FRWR. FMR is not used.

There are a few Infiniband/RoCE devices in the kernel tree that do
not appear to support MEM_MGT_EXTENSIONS (FRWR), and therefore will
not support client-side NFS/RDMA after this patch. These are:

 - mthca
 - qib
 - hns (RoCE)

Users of these devices can use NFS/TCP on IPoIB instead.

Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>