Patch "IB/rxe: Don't clamp residual length to mtu" has been added to the 4.9-stable tree

This is a note to let you know that I've just added the patch titled

IB/rxe: Don't clamp residual length to mtu

to the 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
ib-rxe-don-t-clamp-residual-length-to-mtu.patch
and it can be found in the queue-4.9 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Johannes Thumshirn <[email protected]>
Date: Thu, 6 Apr 2017 14:49:44 +0200
Subject: IB/rxe: Don't clamp residual length to mtu

From: Johannes Thumshirn <[email protected]>

[ Upstream commit d52418502e288b5c7e9e2e6cf1de5f1d3d79d2e1 ]

When reading a RDMA WRITE FIRST packet we copy the DMA length from the RDMA header into the qp->resp.resid variable for later use. Later in check_rkey() we clamp it to the MTU if the packet is an RDMA WRITE packet and has a residual length bigger than the MTU. Later in write_data_in() we subtract the payload of the packet from the residual length. If the packet happens to have a payload of exactly the MTU size we end up with a residual length of 0 despite the packet not being the last in the conversation. When the next packet in the conversation arrives, we don't have any residual length left and thus set the QP into an error state.

This broke NVMe over Fabrics functionality over rdma_rxe.ko

The patch was verified using the following test.

 # echo eth0 > /sys/module/rdma_rxe/parameters/add
 # nvme connect -t rdma -a 192.168.155.101 -s 1023 -n nvmf-test
 # mkfs.xfs -fK /dev/nvme0n1
 meta-data=/dev/nvme0n1           isize=256    agcount=4, agsize=65536 blks
          =                       sectsz=4096  attr=2, projid32bit=1
          =                       crc=0        finobt=0, sparse=0
 data     =                       bsize=4096   blocks=262144, imaxpct=25
          =                       sunit=0      swidth=0 blks
 naming   =version 2              bsize=4096   ascii-ci=0 ftype=1
 log      =internal log           bsize=4096   blocks=2560, version=2
          =                       sectsz=4096  sunit=1 blks, lazy-count=1
 realtime =none                   extsz=4096   blocks=0, rtextents=0
 # mount /dev/nvme0n1 /tmp/
 [  148.923263] XFS (nvme0n1): Mounting V4 Filesystem
 [  148.961196] XFS (nvme0n1): Ending clean mount
 # dd if=/dev/urandom of=test.bin bs=1M count=128
 128+0 records in
 128+0 records out
 134217728 bytes (134 MB, 128 MiB) copied, 0.437991 s, 306 MB/s
 # sha256sum test.bin
 cde42941f045efa8c4f0f157ab6f29741753cdd8d1cff93a6b03649d83c4129a  test.bin
 # cp test.bin /tmp/
 sha256sum /tmp/test.bin
 cde42941f045efa8c4f0f157ab6f29741753cdd8d1cff93a6b03649d83c4129a  /tmp/test.bin

---
 drivers/infiniband/sw/rxe/rxe_resp.c |    2 --
 1 file changed, 2 deletions(-)

@@ -471,8 +471,6 @@ static enum resp_states check_rkey(struc
 				state = RESPST_ERR_LENGTH;
 				goto err;
 			}
-
-			qp->resp.resid = mtu;
 		} else {
 			if (pktlen != resid) {
 				state = RESPST_ERR_LENGTH;

Patches currently in stable-queue which might be from [email protected] are

queue-4.9/fix-driver-usage-of-128b-wqes-when-wq_create-is-v1.patch queue-4.9/fix-express-lane-queue-creation.patch queue-4.9/ib-rxe-don-t-clamp-residual-length-to-mtu.patch