libnetfs: new user callback: netfs_get_filemap()

Provide the user with a new callback so they can implement file
mapping over file system nodes.

* libnetfs/netfs.h: Add prototype for netfs_get_filemap
* libnetfs/file-map.c: netfs_get_filemap definition
* libnetfs/Makefile: add file-map.c to sources
Message-Id: <20211224172132.15058-2-jlledom@mailfence.com>

3 files changed, 37 insertions, 1 deletions

diff --git a/libnetfs/Makefile b/libnetfs/Makefile
index 0d4205d5..24606ff9 100644
--- a/libnetfs/Makefile
+++ b/libnetfs/Makefile
@@ -31,7 +31,7 @@ FSSRCS= dir-link.c dir-lookup.c dir-mkdir.c dir-mkfile.c \
 	file-check-access.c file-chflags.c file-chmod.c file-chown.c \
 	file-exec.c file-get-fs-options.c file-get-storage-info.c \
 	file-get-translator.c file-getcontrol.c file-getlinknode.c \
-	file-lock-stat.c file-lock.c file-set-size.c \
+	file-lock-stat.c file-lock.c file-map.c file-set-size.c \
 	file-set-translator.c file-statfs.c file-sync.c file-syncfs.c \
 	file-utimes.c file-record-lock.c file-reparent.c fsstubs.c \
 	file-get-transcntl.c
diff --git a/libnetfs/file-map.c b/libnetfs/file-map.c
new file mode 100644
index 00000000..85fe93f2
--- /dev/null
+++ b/libnetfs/file-map.c
@@ -0,0 +1,31 @@
+/* Default version of netfs_get_filemap
+
+   Copyright (C) 2021 Free Software Foundation, Inc.
+
+   This file is part of the GNU Hurd.
+
+   The GNU Hurd is free software; you can redistribute it and/or
+   modify it under the terms of the GNU General Public License as
+   published by the Free Software Foundation; either version 2, or (at
+   your option) any later version.
+
+   The GNU Hurd is distributed in the hope that it will be useful, but
+   WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program; if not, write to the Free Software
+   Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111, USA. */
+
+#include "netfs.h"
+
+/* The user may define this function. Return a memory object proxy port (send
+   right) for the file contents of NP. PROT is the maximum allowable
+   access. On errors, return MACH_PORT_NULL and set errno.  */
+mach_port_t __attribute__ ((weak))
+netfs_get_filemap (struct node *np, vm_prot_t prot)
+{
+  errno = EOPNOTSUPP;
+  return MACH_PORT_NULL;
+}
diff --git a/libnetfs/netfs.h b/libnetfs/netfs.h
index 38182ab7..ca506747 100644
--- a/libnetfs/netfs.h
+++ b/libnetfs/netfs.h
@@ -303,6 +303,11 @@ error_t netfs_get_dirents (struct iouser *cred, struct node *dir,
 			   mach_msg_type_number_t *datacnt,
 			   vm_size_t bufsize, int *amt);
 
+/* The user may define this function. Return a memory object proxy port (send
+   right) for the file contents of NP. PROT is the maximum allowable
+   access. On errors, return MACH_PORT_NULL and set errno.  */
+mach_port_t netfs_get_filemap (struct node *np, vm_prot_t prot);
+
 /* The user may define this function.  For a full description,
    see hurd/hurd_types.h.  The default response indicates a network
    store.  If the supplied buffers are not large enough, they should