From bf71fe61af655c34ade3f8ef731498109b1951bd Mon Sep 17 00:00:00 2001
From: Andriy Gapon <avg@FreeBSD.org>
Date: Tue, 21 Nov 2017 18:01:43 +0000
Subject: [PATCH] make illumos uiocopy use vn_io_fault_uiomove

uiocopy() is currently unused, its purpose is copy data from a uio
without modifying the uio.  It was in use before the vn_io_fault support
was added to ZFS, at which point our code diverged from the illumos code
a little bit.  Because ZFS is the only (potential) user of the function
we are free to modify it to better suit ZFS needs.

The intention behind this change is to remove the differences introduced
earlier in zfs_write().

While here, re-implement uioskip() using uiomove() with
uio_segflg == UIO_NOCOPY.
The story of uioskip is the same as with uiocopy.

Reviewed by:	mav
MFC after:	1 week
---
 .../compat/opensolaris/kern/opensolaris_uio.c | 78 +++++++------------
 1 file changed, 29 insertions(+), 49 deletions(-)

diff --git a/sys/cddl/compat/opensolaris/kern/opensolaris_uio.c b/sys/cddl/compat/opensolaris/kern/opensolaris_uio.c
index c319f6280da5..e6b760e69812 100644
--- a/sys/cddl/compat/opensolaris/kern/opensolaris_uio.c
+++ b/sys/cddl/compat/opensolaris/kern/opensolaris_uio.c
@@ -42,6 +42,7 @@
 
 #include <sys/types.h>
 #include <sys/uio.h>
+#include <sys/vnode.h>
 
 /*
  * same as uiomove() but doesn't modify uio structure.
@@ -50,63 +51,42 @@
 int
 uiocopy(void *p, size_t n, enum uio_rw rw, struct uio *uio, size_t *cbytes)
 {
-	struct iovec *iov;
-	ulong_t cnt;
-	int error, iovcnt;
+	struct iovec small_iovec[1];
+	struct uio small_uio_clone;
+	struct uio *uio_clone;
+	int error;
 
-	iovcnt = uio->uio_iovcnt;
-	*cbytes = 0;
-
-	for (iov = uio->uio_iov; n > 0 && iovcnt > 0; iov++, iovcnt--) {
-		cnt = MIN(iov->iov_len, n);
-		if (cnt == 0)
-			continue;
-
-		switch (uio->uio_segflg) {
-		case UIO_USERSPACE:
-			if (rw == UIO_READ)
-				error = copyout(p, iov->iov_base, cnt);
-			else
-				error = copyin(iov->iov_base, p, cnt);
-			if (error)
-				return (error);
-			break;
-		case UIO_SYSSPACE:
-			if (uio->uio_rw == UIO_READ)
-				bcopy(p, iov->iov_base, cnt);
-			else
-				bcopy(iov->iov_base, p, cnt);
-			break;
-		}
-
-		p = (caddr_t)p + cnt;
-		n -= cnt;
-		*cbytes += cnt;
+	ASSERT3U(uio->uio_rw, ==, rw);
+	if (uio->uio_iovcnt == 1) {
+		small_uio_clone = *uio;
+		small_iovec[0] = *uio->uio_iov;
+		small_uio_clone.uio_iov = small_iovec;
+		uio_clone = &small_uio_clone;
+	} else {
+		uio_clone = cloneuio(uio);
 	}
-	return (0);
+
+	error = vn_io_fault_uiomove(p, n, uio_clone);
+	*cbytes = uio->uio_resid - uio_clone->uio_resid;
+	if (uio_clone != &small_uio_clone)
+		free(uio_clone, M_IOV);
+	return (error);
 }
 
 /*
  * Drop the next n chars out of *uiop.
  */
 void
-uioskip(uio_t *uiop, size_t n)
+uioskip(uio_t *uio, size_t n)
 {
-	if (n > uiop->uio_resid)
-		return;
-	while (n != 0) {
-		register iovec_t	*iovp = uiop->uio_iov;
-		register size_t		niovb = MIN(iovp->iov_len, n);
+	enum uio_seg segflg;
 
-		if (niovb == 0) {
-			uiop->uio_iov++;
-			uiop->uio_iovcnt--;
-			continue;
-		}
-		iovp->iov_base += niovb;
-		uiop->uio_loffset += niovb;
-		iovp->iov_len -= niovb;
-		uiop->uio_resid -= niovb;
-		n -= niovb;
-	}
+	/* For the full compatibility with illumos. */
+	if (n > uio->uio_resid)
+		return;
+
+	segflg = uio->uio_segflg;
+	uio->uio_segflg = UIO_NOCOPY;
+	uiomove(NULL, n, uio->uio_rw, uio);
+	uio->uio_segflg = segflg;
 }