[RFC PATCH v1 5/8] nfs: tag READ/WRITE RPCs carrying P2PDMA pages

[Pranjal Shrivastava <praan@google.com>]

A transport must know when an RPC's payload pages are P2PDMA memory,
so it can move them by DMA or refuse the RPC.

Check each page as nfs_generic_pgio() builds the page array, and
record the result in nfs_pgio_args. The READ and WRITE encoders of
every NFS version then set XDRBUF_P2PDMA on the buffer holding the
payload.

Additionally, avoid using READ_PLUS when the pages are P2PDMA memory.

Signed-off-by: Pranjal Shrivastava <praan@google.com>
---
 fs/nfs/nfs2xdr.c        | 4 ++++
 fs/nfs/nfs3xdr.c        | 4 ++++
 fs/nfs/nfs4proc.c       | 3 +++
 fs/nfs/nfs4xdr.c        | 4 ++++
 fs/nfs/pagelist.c       | 2 ++
 include/linux/nfs_xdr.h | 1 +
 6 files changed, 18 insertions(+)

diff --git a/fs/nfs/nfs2xdr.c b/fs/nfs/nfs2xdr.c
index 9eff09158518..5a8f2eccd068 100644
--- a/fs/nfs/nfs2xdr.c
+++ b/fs/nfs/nfs2xdr.c
@@ -628,6 +628,8 @@ static void nfs2_xdr_enc_readargs(struct rpc_rqst *req,
 	rpc_prepare_reply_pages(req, args->pages, args->pgbase, args->count,
 				NFS_readres_sz - NFS_pagepad_sz);
 	req->rq_rcv_buf.flags |= XDRBUF_READ;
+	if (args->p2pdma)
+		req->rq_rcv_buf.flags |= XDRBUF_P2PDMA;
 }
 
 /*
@@ -668,6 +670,8 @@ static void nfs2_xdr_enc_writeargs(struct rpc_rqst *req,
 
 	encode_writeargs(xdr, args);
 	xdr->buf->flags |= XDRBUF_WRITE;
+	if (args->p2pdma)
+		xdr->buf->flags |= XDRBUF_P2PDMA;
 }
 
 /*
diff --git a/fs/nfs/nfs3xdr.c b/fs/nfs/nfs3xdr.c
index e745e78faab0..e39c58883a2a 100644
--- a/fs/nfs/nfs3xdr.c
+++ b/fs/nfs/nfs3xdr.c
@@ -946,6 +946,8 @@ static void nfs3_xdr_enc_read3args(struct rpc_rqst *req,
 	rpc_prepare_reply_pages(req, args->pages, args->pgbase,
 				args->count, replen);
 	req->rq_rcv_buf.flags |= XDRBUF_READ;
+	if (args->p2pdma)
+		req->rq_rcv_buf.flags |= XDRBUF_P2PDMA;
 }
 
 /*
@@ -988,6 +990,8 @@ static void nfs3_xdr_enc_write3args(struct rpc_rqst *req,
 
 	encode_write3args(xdr, args);
 	xdr->buf->flags |= XDRBUF_WRITE;
+	if (args->p2pdma)
+		xdr->buf->flags |= XDRBUF_P2PDMA;
 }
 
 /*
diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
index beb659744760..443079f5adc9 100644
--- a/fs/nfs/nfs4proc.c
+++ b/fs/nfs/nfs4proc.c
@@ -5721,6 +5721,9 @@ static int nfs4_read_done(struct rpc_task *task, struct nfs_pgio_header *hdr)
 static bool nfs42_read_plus_support(struct nfs_pgio_header *hdr,
 				    struct rpc_message *msg)
 {
+	/* P2PDMA payloads move only by DMA */
+	if (hdr->args.p2pdma)
+		return false;
 	/* Note: We don't use READ_PLUS with pNFS yet */
 	if (nfs_server_capable(hdr->inode, NFS_CAP_READ_PLUS) && !hdr->ds_clp) {
 		msg->rpc_proc = &nfs4_procedures[NFSPROC4_CLNT_READ_PLUS];
diff --git a/fs/nfs/nfs4xdr.c b/fs/nfs/nfs4xdr.c
index 8b3d96b4a0f0..04765b56de28 100644
--- a/fs/nfs/nfs4xdr.c
+++ b/fs/nfs/nfs4xdr.c
@@ -2621,6 +2621,8 @@ static void nfs4_xdr_enc_read(struct rpc_rqst *req, struct xdr_stream *xdr,
 	rpc_prepare_reply_pages(req, args->pages, args->pgbase,
 				args->count, hdr.replen - pagepad_maxsz);
 	req->rq_rcv_buf.flags |= XDRBUF_READ;
+	if (args->p2pdma)
+		req->rq_rcv_buf.flags |= XDRBUF_P2PDMA;
 	encode_nops(&hdr);
 }
 
@@ -2686,6 +2688,8 @@ static void nfs4_xdr_enc_write(struct rpc_rqst *req, struct xdr_stream *xdr,
 	encode_putfh(xdr, args->fh, &hdr);
 	encode_write(xdr, args, &hdr);
 	req->rq_snd_buf.flags |= XDRBUF_WRITE;
+	if (args->p2pdma)
+		req->rq_snd_buf.flags |= XDRBUF_P2PDMA;
 	if (args->bitmask)
 		encode_getfattr(xdr, args->bitmask, &hdr);
 	encode_nops(&hdr);
diff --git a/fs/nfs/pagelist.c b/fs/nfs/pagelist.c
index 71f0ce2bc4ea..3ec4e1e5fe1f 100644
--- a/fs/nfs/pagelist.c
+++ b/fs/nfs/pagelist.c
@@ -970,6 +970,8 @@ int nfs_generic_pgio(struct nfs_pageio_descriptor *desc,
 				if (pageused > pagecount)
 					goto full;
 				*pages++ = last_page = page;
+				if (is_pci_p2pdma_page(page))
+					hdr->args.p2pdma = true;
 			}
 		}
 	}
diff --git a/include/linux/nfs_xdr.h b/include/linux/nfs_xdr.h
index c0e29b4dfa62..85cdee107559 100644
--- a/include/linux/nfs_xdr.h
+++ b/include/linux/nfs_xdr.h
@@ -685,6 +685,7 @@ struct nfs_pgio_args {
 	__u32			count;
 	unsigned int		pgbase;
 	struct page **		pages;
+	bool			p2pdma;		/* pages include P2PDMA memory */
 	union {
 		unsigned int		replen;			/* used by read */
 		struct {
-- 
2.56.0.rc1.315.gc6ed9934b7-goog