4.15-stable review patch. If anyone has any objections, please let me know.
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From: Chuck Lever chuck.lever@oracle.com
commit 1179e2c27efe21167ec9d882b14becefba2ee990 upstream.
Commit 16f906d66cd7 ("xprtrdma: Reduce required number of send SGEs") introduced the rpcrdma_ia::ri_max_send_sges field. This fixes a problem where xprtrdma would not work if the device's max_sge capability was small (low single digits).
At least RPCRDMA_MIN_SEND_SGES are needed for the inline parts of each RPC. ri_max_send_sges is set to this value:
ia->ri_max_send_sges = max_sge - RPCRDMA_MIN_SEND_SGES;
Then when marshaling each RPC, rpcrdma_args_inline uses that value to determine whether the device has enough Send SGEs to convey an NFS WRITE payload inline, or whether instead a Read chunk is required.
More recently, commit ae72950abf99 ("xprtrdma: Add data structure to manage RDMA Send arguments") used the ri_max_send_sges value to calculate the size of an array, but that commit erroneously assumed ri_max_send_sges contains a value similar to the device's max_sge, and not one that was reduced by the minimum SGE count.
This assumption results in the calculated size of the sendctx's Send SGE array to be too small. When the array is used to marshal an RPC, the code can write Send SGEs into the following sendctx element in that array, corrupting it. When the device's max_sge is large, this issue is entirely harmless; but it results in an oops in the provider's post_send method, if dev.attrs.max_sge is small.
So let's straighten this out: ri_max_send_sges will now contain a value with the same meaning as dev.attrs.max_sge, which makes the code easier to understand, and enables rpcrdma_sendctx_create to calculate the size of the SGE array correctly.
Reported-by: Michal Kalderon Michal.Kalderon@cavium.com Fixes: 16f906d66cd7 ("xprtrdma: Reduce required number of send SGEs") Signed-off-by: Chuck Lever chuck.lever@oracle.com Tested-by: Michal Kalderon Michal.Kalderon@cavium.com Cc: stable@vger.kernel.org # v4.10+ Signed-off-by: Anna Schumaker Anna.Schumaker@Netapp.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org
--- net/sunrpc/xprtrdma/rpc_rdma.c | 2 +- net/sunrpc/xprtrdma/verbs.c | 2 +- 2 files changed, 2 insertions(+), 2 deletions(-)
--- a/net/sunrpc/xprtrdma/rpc_rdma.c +++ b/net/sunrpc/xprtrdma/rpc_rdma.c @@ -143,7 +143,7 @@ static bool rpcrdma_args_inline(struct r if (xdr->page_len) { remaining = xdr->page_len; offset = offset_in_page(xdr->page_base); - count = 0; + count = RPCRDMA_MIN_SEND_SGES; while (remaining) { remaining -= min_t(unsigned int, PAGE_SIZE - offset, remaining); --- a/net/sunrpc/xprtrdma/verbs.c +++ b/net/sunrpc/xprtrdma/verbs.c @@ -509,7 +509,7 @@ rpcrdma_ep_create(struct rpcrdma_ep *ep, pr_warn("rpcrdma: HCA provides only %d send SGEs\n", max_sge); return -ENOMEM; } - ia->ri_max_send_sges = max_sge - RPCRDMA_MIN_SEND_SGES; + ia->ri_max_send_sges = max_sge;
if (ia->ri_device->attrs.max_qp_wr <= RPCRDMA_BACKWARD_WRS) { dprintk("RPC: %s: insufficient wqe's available\n",