Use copy_file_range to copy files

The copy_file_range syscall (introduced in Linux kernel
version 4.5) can copy files more efficiently via server-side
copy etc.
* admin/merge-gnulib (GNULIB_MODULES): Add copy-file-range.
* lib/copy-file-range.c, m4/copy-file-range.m4:
New files, copied from Gnulib.
* lib/gnulib.mk.in, m4/gnulib-comp.m4: Regenerate.
* src/fileio.c (Fcopy_file): Try copy_file_range first,
falling back on read+write only if copy_file_range failed or
if the input is empty and so could be a /proc file.

2 files changed, 45 insertions, 0 deletions

diff --git a/lib/copy-file-range.c b/lib/copy-file-range.c
new file mode 100644
index 00000000000..39b5efbc1cc
--- /dev/null
+++ b/lib/copy-file-range.c
@@ -0,0 +1,33 @@
+/* Stub for copy_file_range
+   Copyright 2019 Free Software Foundation, Inc.
+
+   This program 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 3 of the License, or
+   (at your option) any later version.
+
+   This program 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, see <https://www.gnu.org/licenses/>.  */
+
+#include <config.h>
+
+#include <unistd.h>
+
+#include <errno.h>
+
+ssize_t
+copy_file_range (int infd, off_t *pinoff,
+                 int outfd, off_t *poutoff,
+                 size_t length, unsigned int flags)
+{
+  /* There is little need to emulate copy_file_range with read+write,
+     since programs that use copy_file_range must fall back on
+     read+write anyway.  */
+  errno = ENOSYS;
+  return -1;
+}
diff --git a/lib/gnulib.mk.in b/lib/gnulib.mk.in
index 403d83829cd..6e817fa6897 100644
--- a/lib/gnulib.mk.in
+++ b/lib/gnulib.mk.in
@@ -74,6 +74,7 @@
 #  c-strcase \
 #  careadlinkat \
 #  close-stream \
+#  copy-file-range \
 #  count-leading-zeros \
 #  count-one-bits \
 #  count-trailing-zeros \
@@ -1274,6 +1275,17 @@ EXTRA_DIST += close-stream.h
 endif
 ## end   gnulib module close-stream
 
+## begin gnulib module copy-file-range
+ifeq (,$(OMIT_GNULIB_MODULE_copy-file-range))
+
+
+EXTRA_DIST += copy-file-range.c
+
+EXTRA_libgnu_a_SOURCES += copy-file-range.c
+
+endif
+## end   gnulib module copy-file-range
+
 ## begin gnulib module count-leading-zeros
 ifeq (,$(OMIT_GNULIB_MODULE_count-leading-zeros))