xprtrdma: Fix DMAR failure in frwr_op_map() after reconnect

xprtrdma: Fix DMAR failure in frwr_op_map() after reconnect

commit 62bdf94a2049822ef8c6d4b0e83cd9c3a1663ab4 upstream.

When a LOCALINV WR is flushed, the frmr is marked STALE, then
frwr_op_unmap_sync DMA-unmaps the frmr's SGL. These STALE frmrs
are then recovered when frwr_op_map hunts for an INVALID frmr to
use.

All other cases that need frmr recovery leave that SGL DMA-mapped.
The FRMR recovery path unconditionally DMA-unmaps the frmr's SGL.

To avoid DMA unmapping the SGL twice for flushed LOCAL_INV WRs,
alter the recovery logic (rather than the hot frwr_op_unmap_sync
path) to distinguish among these cases. This solution also takes
care of the case where multiple LOCAL_INV WRs are issued for the
same rpcrdma_req, some complete successfully, but some are flushed.

Reported-by: Vasco Steinmetz <linux@kyberraum.net>
Signed-off-by: Chuck Lever <chuck.lever@oracle.com>
Tested-by: Vasco Steinmetz <linux@kyberraum.net>
Signed-off-by: Anna Schumaker <Anna.Schumaker@Netapp.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>