4.14-stable review patch. If anyone has any objections, please let me know.
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From: Chuck Lever chuck.lever@oracle.com
[ Upstream commit 175e03101d36c3034f3c80038d4c28838351a7f2 ]
A single NFSv4 WRITE compound can often have three operations: PUTFH, WRITE, then GETATTR.
When the WRITE payload is sent in a Read chunk, the client places the GETATTR in the inline part of the RPC/RDMA message, just after the WRITE operation (sans payload). The position value in the Read chunk enables the receiver to insert the Read chunk at the correct place in the received XDR stream; that is between the WRITE and GETATTR.
According to RFC 8166, an NFS/RDMA client does not have to add XDR round-up to the Read chunk that carries the WRITE payload. The receiver adds XDR round-up padding if it is absent and the receiver's XDR decoder requires it to be present.
Commit 193bcb7b3719 ("svcrdma: Populate tail iovec when receiving") attempted to add support for receiving such a compound so that just the WRITE payload appears in rq_arg's page list, and the trailing GETATTR is placed in rq_arg's tail iovec. (TCP just strings the whole compound into the head iovec and page list, without regard to the alignment of the WRITE payload).
The server transport logic also had to accommodate the optional XDR round-up of the Read chunk, which it did simply by lengthening the tail iovec when round-up was needed. This approach is adequate for the NFSv2 and NFSv3 WRITE decoders.
Unfortunately it is not sufficient for nfsd4_decode_write. When the Read chunk length is a couple of bytes less than PAGE_SIZE, the computation at the end of nfsd4_decode_write allows argp->pagelen to go negative, which breaks the logic in read_buf that looks for the tail iovec.
The result is that a WRITE operation whose payload length is just less than a multiple of a page succeeds, but the subsequent GETATTR in the same compound fails with NFS4ERR_OP_ILLEGAL because the XDR decoder can't find it. Clients ignore the error, but they must update their attribute cache via a separate round trip.
As nfsd4_decode_write appears to expect the payload itself to always have appropriate XDR round-up, have svc_rdma_build_normal_read_chunk add the Read chunk XDR round-up to the page_len rather than lengthening the tail iovec.
Reported-by: Olga Kornievskaia kolga@netapp.com Fixes: 193bcb7b3719 ("svcrdma: Populate tail iovec when receiving") Signed-off-by: Chuck Lever chuck.lever@oracle.com Tested-by: Olga Kornievskaia kolga@netapp.com Signed-off-by: J. Bruce Fields bfields@redhat.com Signed-off-by: Sasha Levin alexander.levin@microsoft.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- net/sunrpc/xprtrdma/svc_rdma_rw.c | 12 ++++++++---- 1 file changed, 8 insertions(+), 4 deletions(-)
--- a/net/sunrpc/xprtrdma/svc_rdma_rw.c +++ b/net/sunrpc/xprtrdma/svc_rdma_rw.c @@ -727,12 +727,16 @@ static int svc_rdma_build_normal_read_ch head->arg.head[0].iov_len - info->ri_position; head->arg.head[0].iov_len = info->ri_position;
- /* Read chunk may need XDR roundup (see RFC 5666, s. 3.7). + /* Read chunk may need XDR roundup (see RFC 8166, s. 3.4.5.2). * - * NFSv2/3 write decoders need the length of the tail to - * contain the size of the roundup padding. + * If the client already rounded up the chunk length, the + * length does not change. Otherwise, the length of the page + * list is increased to include XDR round-up. + * + * Currently these chunks always start at page offset 0, + * thus the rounded-up length never crosses a page boundary. */ - head->arg.tail[0].iov_len += 4 - (info->ri_chunklen & 3); + info->ri_chunklen = XDR_QUADLEN(info->ri_chunklen) << 2;
head->arg.page_len = info->ri_chunklen; head->arg.len += info->ri_chunklen;