Re: [PATCH v3 00/11] Add RDMA support to the pNFS file+flexfiles data channels

[Trond Myklebust <trondmy@hammerspace.com>]

On Sat, 2020-11-14 at 00:46 +0100, Mkrtchyan, Tigran wrote:
> 
> 
> ----- Original Message -----
> > From: "trondmy" <trondmy@hammerspace.com>
> > To: "Tigran Mkrtchyan" <tigran.mkrtchyan@desy.de>
> > Cc: "linux-nfs" <linux-nfs@vger.kernel.org>
> > Sent: Friday, 13 November, 2020 23:45:00
> > Subject: Re: [PATCH v3 00/11] Add RDMA support to the pNFS
> > file+flexfiles data channels
> 
> > On Fri, 2020-11-13 at 22:30 +0100, Mkrtchyan, Tigran wrote:
> > > 
> > > After more testing, it looks like that client doesn't like
> > > notification bitmap:
> > > 
> > > 
> > > [31576.789492] --> _nfs4_proc_getdeviceinfo
> > > [31576.789503] --> nfs41_call_sync_prepare data->seq_server
> > > 000000001d17c43e
> > > [31576.789507] --> nfs4_alloc_slot used_slots=0000
> > > highest_used=4294967295 max_slots=16
> > > [31576.789510] <-- nfs4_alloc_slot used_slots=0001 highest_used=0
> > > slotid=0
> > > [31576.789527] encode_sequence:
> > > sessionid=2910695007:150995712:0:16777216 seqid=92462 slotid=0
> > > max_slotid=0 cache_this=0
> > > [31576.789991] decode_getdeviceinfo: unsupported notification
> > 
> > According to this, you appear to be returning a deviceinfo bitmap
> > with
> > at least one non-zero entry that is not in the first 32-bit word.
> > We
> > only ask for notifications for NOTIFY_DEVICEID4_CHANGE and
> > NOTIFY_DEVICEID4_DELETE, so we only expect bitmap[0] to have non-
> > zero
> > entries.
> 
> 
> according to packet capture only bitmap[0] has non zero bits set.
> This is the reply of compound starting from nfs staus code, tag
> length and so on.
> 
> 
> 0000   00 00 00 00 00 00 00 00 00 00 00 02 00 00 00 35
> 0010   00 00 00 00 5f ae 7d ad 00 03 00 09 00 00 00 00
> 0020   00 00 00 01 00 00 00 4c 00 00 00 00 00 00 00 0f
> 0030   00 00 00 0f 00 00 00 00 00 00 00 2f 00 00 00 00
> 0040   00 00 00 04 00 00 00 40 00 00 00 01 00 00 00 03
> 0050   74 63 70 00 00 00 00 16 31 33 31 2e 31 36 39 2e
> 0060   31 39 31 2e 31 34 33 2e 31 32 35 2e 34 39 00 00
> 0070   00 00 00 01 00 00 00 04 00 00 00 01 00 10 00 00
> 0080   00 10 00 00 00 00 00 01 00 00 00 02 00 00 00 06
> 0090   00 00 00 00
> 
> 
> the last 12 bytes : bitmap size, bitmap[0], bitmap[1]
> 
> 
> This part of code in the didn't change since 2010, and I
> have no issues to use 5.8 kernel. I am pretty sure, that
> tests with 5.9 did pass as expected. I will try to bisec it.

I don't think I've introduced this bug. I did not touch anything in the
getdeviceinfo proc or XDR code.
Does the following patch help?

8<-------------------------------------------------------
From e92b2d4e39e91d379ec1147115820ab5dfe4c89a Mon Sep 17 00:00:00 2001
From: Trond Myklebust <trond.myklebust@hammerspace.com>
Date: Fri, 13 Nov 2020 21:42:16 -0500
Subject: [PATCH] NFSv4: Fix the alignment of page data in the getdeviceinfo
 reply

We can fit the device_addr4 opaque data padding in the pages.

Fixes: cf500bac8fd4 ("SUNRPC: Introduce rpc_prepare_reply_pages()")
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
---
 fs/nfs/nfs4xdr.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
index c6dbfcae7517..c8714381d511 100644
--- a/fs/nfs/nfs4xdr.c
+++ b/fs/nfs/nfs4xdr.c
@@ -3009,15 +3009,19 @@ static void nfs4_xdr_enc_getdeviceinfo(struct rpc_rqst *req,
 	struct compound_hdr hdr = {
 		.minorversion = nfs4_xdr_minorversion(&args->seq_args),
 	};
+	uint32_t replen;
 
 	encode_compound_hdr(xdr, req, &hdr);
 	encode_sequence(xdr, &args->seq_args, &hdr);
+
+	replen = hdr.replen + op_decode_hdr_maxsz;
+
 	encode_getdeviceinfo(xdr, args, &hdr);
 
-	/* set up reply kvec. Subtract notification bitmap max size (2)
-	 * so that notification bitmap is put in xdr_buf tail */
+	/* set up reply kvec. device_addr4 opaque data is read into the
+	 * pages */
 	rpc_prepare_reply_pages(req, args->pdev->pages, args->pdev->pgbase,
-				args->pdev->pglen, hdr.replen - 2);
+				args->pdev->pglen, replen + 2);
 	encode_nops(&hdr);
 }
 
@@ -5848,7 +5852,9 @@ static int decode_getdeviceinfo(struct xdr_stream *xdr,
 	 * and places the remaining xdr data in xdr_buf->tail
 	 */
 	pdev->mincount = be32_to_cpup(p);
-	if (xdr_read_pages(xdr, pdev->mincount) != pdev->mincount)
+	/* Calculate padding */
+	len = xdr_align_size(pdev->mincount);
+	if (xdr_read_pages(xdr, len) != len)
 		return -EIO;
 
 	/* Parse notification bitmap, verifying that it is zero. */
-- 
2.28.0



-- 
Trond Myklebust
Linux NFS client maintainer, Hammerspace
trond.myklebust@hammerspace.com