FreeBSD: Return Mach error codes from VOP_(GET|PUT)PAGES

FreeBSD's memory management system uses its own error numbers and gets
confused when these VOPs return EIO.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: Ryan Moeller <ryan@iXsystems.com>
Reported-by: Peter Holm <pho@FreeBSD.org>
Signed-off-by: Mark Johnston <markj@FreeBSD.org>
Closes #13311

module/os/freebsd/zfs/zfs_vnops_os.c

@@ -4062,8 +4062,8 @@ zfs_getpages(struct vnode *vp, vm_page_t *ma, int count, int *rbehind,
 	int pgsin_b, pgsin_a;
 	int error;
 
-	ZFS_ENTER(zfsvfs);
-	ZFS_VERIFY_ZP(zp);
+	ZFS_ENTER_ERROR(zfsvfs, zfs_vm_pagerret_error);
+	ZFS_VERIFY_ZP_ERROR(zp, zfs_vm_pagerret_error);
 
 	start = IDX_TO_OFF(ma[0]->pindex);
 	end = IDX_TO_OFF(ma[count - 1]->pindex + 1);
@@ -4187,19 +4187,18 @@ zfs_putpages(struct vnode *vp, vm_page_t *ma, size_t len, int flags,
 	int		err;
 	int		i;
 
-	ZFS_ENTER(zfsvfs);
-	ZFS_VERIFY_ZP(zp);
-
 	object = vp->v_object;
-	pcount = btoc(len);
-	ncount = pcount;
-
 	KASSERT(ma[0]->object == object, ("mismatching object"));
 	KASSERT(len > 0 && (len & PAGE_MASK) == 0, ("unexpected length"));
 
+	pcount = btoc(len);
+	ncount = pcount;
 	for (i = 0; i < pcount; i++)
 		rtvals[i] = zfs_vm_pagerret_error;
 
+	ZFS_ENTER_ERROR(zfsvfs, zfs_vm_pagerret_error);
+	ZFS_VERIFY_ZP_ERROR(zp, zfs_vm_pagerret_error);
+
 	off = IDX_TO_OFF(ma[0]->pindex);
 	blksz = zp->z_blksz;
 	lo_off = rounddown(off, blksz);