From 3eaf03766e0b56263c55750eaee4b7b74f91c99a Mon Sep 17 00:00:00 2001
From: Rick Macklem <rmacklem@FreeBSD.org>
Date: Wed, 8 Jul 2020 02:28:08 +0000
Subject: [PATCH] Add support for ext_pgs mbufs to nfsm_uiombuf().

This patch uses a slightly different algorithm for the non-ext_pgs case,
where a variable called "mcp" is maintained, pointing to the current
location that mbuf data can be filled into. This avoids use of
mtod(mp, char *) + mp->m_len to calculate the location, since this does
not work for ext_pgs mbufs and I think it makes the algorithm more readable.
This change should not result in semantic changes for the non-ext_pgs case.

This is another in the series of commits that add support to the NFS client
and server for building RPC messages in ext_pgs mbufs with anonymous pages.
This is useful so that the entire mbuf list does not need to be
copied before calling sosend() when NFS over TLS is enabled.

Since ND_EXTPG is never set yet, there is no semantic change at this time.
---
 sys/fs/nfsclient/nfs_clcomsubs.c | 75 +++++++++++++++++++++-----------
 1 file changed, 49 insertions(+), 26 deletions(-)

diff --git a/sys/fs/nfsclient/nfs_clcomsubs.c b/sys/fs/nfsclient/nfs_clcomsubs.c
index 6f08e11aaaa8..a96c4c3d6d6e 100644
--- a/sys/fs/nfsclient/nfs_clcomsubs.c
+++ b/sys/fs/nfsclient/nfs_clcomsubs.c
@@ -62,7 +62,7 @@ nfsm_uiombuf(struct nfsrv_descript *nd, struct uio *uiop, int siz)
 	struct mbuf *mp, *mp2;
 	int xfer, left, mlen;
 	int uiosiz, clflg, rem;
-	char *cp, *tcp;
+	char *mcp, *tcp;
 
 	KASSERT(uiop->uio_iovcnt == 1, ("nfsm_uiotombuf: iovcnt != 1"));
 
@@ -72,41 +72,52 @@ nfsm_uiombuf(struct nfsrv_descript *nd, struct uio *uiop, int siz)
 		clflg = 0;
 	rem = NFSM_RNDUP(siz) - siz;
 	mp = mp2 = nd->nd_mb;
+	mcp = nd->nd_bpos;
 	while (siz > 0) {
+		KASSERT((nd->nd_flag & ND_EXTPG) != 0 || mcp ==
+		    mtod(mp, char *) + mp->m_len, ("nfsm_uiombuf: mcp wrong"));
 		left = uiop->uio_iov->iov_len;
 		uiocp = uiop->uio_iov->iov_base;
 		if (left > siz)
 			left = siz;
 		uiosiz = left;
 		while (left > 0) {
-			mlen = M_TRAILINGSPACE(mp);
-			if (mlen == 0) {
-				if (clflg)
-					NFSMCLGET(mp, M_WAITOK);
-				else
-					NFSMGET(mp);
-				mp->m_len = 0;
-				mp2->m_next = mp;
-				mp2 = mp;
+			if ((nd->nd_flag & ND_EXTPG) != 0)
+				mlen = nd->nd_bextpgsiz;
+			else
 				mlen = M_TRAILINGSPACE(mp);
+			if (mlen == 0) {
+				if ((nd->nd_flag & ND_EXTPG) != 0) {
+					mp = nfsm_add_ext_pgs(mp,
+					    nd->nd_maxextsiz, &nd->nd_bextpg);
+					mcp = (char *)(void *)PHYS_TO_DMAP(
+					  mp->m_epg_pa[nd->nd_bextpg]);
+					nd->nd_bextpgsiz = PAGE_SIZE;
+				} else {
+					if (clflg)
+						NFSMCLGET(mp, M_WAITOK);
+					else
+						NFSMGET(mp);
+					mp->m_len = 0;
+					mlen = M_TRAILINGSPACE(mp);
+					mcp = mtod(mp, char *);
+					mp2->m_next = mp;
+					mp2 = mp;
+				}
 			}
 			xfer = (left > mlen) ? mlen : left;
-#ifdef notdef
-			/* Not Yet.. */
-			if (uiop->uio_iov->iov_op != NULL)
-				(*(uiop->uio_iov->iov_op))
-				(uiocp, mtod(mp, caddr_t) + mp->m_len,
-				    xfer);
-			else
-#endif
 			if (uiop->uio_segflg == UIO_SYSSPACE)
-			    NFSBCOPY(uiocp, mtod(mp, caddr_t) + mp->m_len,
-				xfer);
+				NFSBCOPY(uiocp, mcp, xfer);
 			else
-			    copyin(uiocp, mtod(mp, caddr_t) + mp->m_len, xfer);
+				copyin(uiocp, mcp, xfer);
 			mp->m_len += xfer;
 			left -= xfer;
 			uiocp += xfer;
+			mcp += xfer;
+			if ((nd->nd_flag & ND_EXTPG) != 0) {
+				nd->nd_bextpgsiz -= xfer;
+				mp->m_epg_last_len += xfer;
+			}
 			uiop->uio_offset += xfer;
 			uiop->uio_resid -= xfer;
 		}
@@ -117,18 +128,30 @@ nfsm_uiombuf(struct nfsrv_descript *nd, struct uio *uiop, int siz)
 		siz -= uiosiz;
 	}
 	if (rem > 0) {
-		if (rem > M_TRAILINGSPACE(mp)) {
+		if ((nd->nd_flag & ND_EXTPG) == 0 && rem >
+		    M_TRAILINGSPACE(mp)) {
 			NFSMGET(mp);
 			mp->m_len = 0;
 			mp2->m_next = mp;
+			mcp = mtod(mp, char *);
+		} else if ((nd->nd_flag & ND_EXTPG) != 0 && rem >
+		    nd->nd_bextpgsiz) {
+			mp = nfsm_add_ext_pgs(mp, nd->nd_maxextsiz,
+			    &nd->nd_bextpg);
+			mcp = (char *)(void *)
+			    PHYS_TO_DMAP(mp->m_epg_pa[nd->nd_bextpg]);
+			nd->nd_bextpgsiz = PAGE_SIZE;
 		}
-		cp = mtod(mp, caddr_t) + mp->m_len;
 		for (left = 0; left < rem; left++)
-			*cp++ = '\0';
+			*mcp++ = '\0';
 		mp->m_len += rem;
-		nd->nd_bpos = cp;
+		nd->nd_bpos = mcp;
+		if ((nd->nd_flag & ND_EXTPG) != 0) {
+			nd->nd_bextpgsiz -= rem;
+			mp->m_epg_last_len += rem;
+		}
 	} else
-		nd->nd_bpos = mtod(mp, caddr_t) + mp->m_len;
+		nd->nd_bpos = mcp;
 	nd->nd_mb = mp;
 }