RE: FAILED: patch "[PATCH] svcrdma: handle rdma read with a non-zero initial page offset" failed to apply to 4.1-stable tree

["Steve Wise" <swise@opengridcomputing.com>]

> -----Original Message-----
> From: gregkh@linuxfoundation.org [mailto:gregkh@linuxfoundation.org]
> Sent: Saturday, October 17, 2015 7:27 PM
> To: swise@opengridcomputing.com; bfields@redhat.com; chuck.lever@oracle.com
> Cc: stable@vger.kernel.org
> Subject: FAILED: patch "[PATCH] svcrdma: handle rdma read with a non-zero initial page offset" failed to apply to 4.1-stable tree
> 
> 
> The patch below does not apply to the 4.1-stable tree.
> If someone wants it applied there, or to any other stable or longterm
> tree, then please email the backport, including the original git commit
> id to <stable@vger.kernel.org>.
> 
> thanks,
> 
> greg k-h
> 

Hey Greg, I submitted the backport patch to linux-stable. 

Thanks,

Steve.

> ------------------ original commit in Linus's tree ------------------
> 
> >From c91aed9896946721bb30705ea2904edb3725dd61 Mon Sep 17 00:00:00 2001
> From: Steve Wise <swise@opengridcomputing.com>
> Date: Mon, 28 Sep 2015 16:46:06 -0500
> Subject: [PATCH] svcrdma: handle rdma read with a non-zero initial page offset
> 
> The server rdma_read_chunk_lcl() and rdma_read_chunk_frmr() functions
> were not taking into account the initial page_offset when determining
> the rdma read length.  This resulted in a read who's starting address
> and length exceeded the base/bounds of the frmr.
> 
> The server gets an async error from the rdma device and kills the
> connection, and the client then reconnects and resends.  This repeats
> indefinitely, and the application hangs.
> 
> Most work loads don't tickle this bug apparently, but one test hit it
> every time: building the linux kernel on a 16 core node with 'make -j
> 16 O=/mnt/0' where /mnt/0 is a ramdisk mounted via NFSRDMA.
> 
> This bug seems to only be tripped with devices having small fastreg page
> list depths.  I didn't see it with mlx4, for instance.
> 
> Fixes: 0bf4828983df ('svcrdma: refactor marshalling logic')
> Signed-off-by: Steve Wise <swise@opengridcomputing.com>
> Tested-by: Chuck Lever <chuck.lever@oracle.com>
> Cc: stable@vger.kernel.org
> Signed-off-by: J. Bruce Fields <bfields@redhat.com>
> 
> diff --git a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
> index cb5174284074..5f6ca47092b0 100644
> --- a/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
> +++ b/net/sunrpc/xprtrdma/svc_rdma_recvfrom.c
> @@ -136,7 +136,8 @@ int rdma_read_chunk_lcl(struct svcxprt_rdma *xprt,
>  	ctxt->direction = DMA_FROM_DEVICE;
>  	ctxt->read_hdr = head;
>  	pages_needed = min_t(int, pages_needed, xprt->sc_max_sge_rd);
> -	read = min_t(int, pages_needed << PAGE_SHIFT, rs_length);
> +	read = min_t(int, (pages_needed << PAGE_SHIFT) - *page_offset,
> +		     rs_length);
> 
>  	for (pno = 0; pno < pages_needed; pno++) {
>  		int len = min_t(int, rs_length, PAGE_SIZE - pg_off);
> @@ -235,7 +236,8 @@ int rdma_read_chunk_frmr(struct svcxprt_rdma *xprt,
>  	ctxt->direction = DMA_FROM_DEVICE;
>  	ctxt->frmr = frmr;
>  	pages_needed = min_t(int, pages_needed, xprt->sc_frmr_pg_list_len);
> -	read = min_t(int, pages_needed << PAGE_SHIFT, rs_length);
> +	read = min_t(int, (pages_needed << PAGE_SHIFT) - *page_offset,
> +		     rs_length);
> 
>  	frmr->kva = page_address(rqstp->rq_arg.pages[pg_no]);
>  	frmr->direction = DMA_FROM_DEVICE;