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* [gcc r14-1569] libstdc++: Use copy_file_range for filesystem::copy_file
@ 2023-06-06 11:35 Jonathan Wakely
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From: Jonathan Wakely @ 2023-06-06 11:35 UTC (permalink / raw)
To: gcc-cvs, libstdc++-cvs
https://gcc.gnu.org/g:d87caacf8e2df563afda85f3a5b7b852e08b6b2c
commit r14-1569-gd87caacf8e2df563afda85f3a5b7b852e08b6b2c
Author: Jannik Glückert <jannik.glueckert@gmail.com>
Date: Wed Mar 8 19:37:43 2023 +0100
libstdc++: Use copy_file_range for filesystem::copy_file
copy_file_range is a recent-ish syscall for copying files. It is similar
to sendfile but allows filesystem-specific optimizations. Common are:
Reflinks: BTRFS, XFS, ZFS (does not implement the syscall yet)
Server-side copy: NFS, SMB, Ceph
If copy_file_range is not available for the given files, fall back to
sendfile / userspace copy.
libstdc++-v3/ChangeLog:
* acinclude.m4 (_GLIBCXX_USE_COPY_FILE_RANGE): Define.
* config.h.in: Regenerate.
* configure: Regenerate.
* src/filesystem/ops-common.h (copy_file_copy_file_range):
Define new function.
(do_copy_file): Use it.
Signed-off-by: Jannik Glückert <jannik.glueckert@gmail.com>
Diff:
---
libstdc++-v3/acinclude.m4 | 20 +++++++++++
libstdc++-v3/config.h.in | 3 ++
libstdc++-v3/configure | 62 ++++++++++++++++++++++++++++++++
libstdc++-v3/src/filesystem/ops-common.h | 56 +++++++++++++++++++++++++++++
4 files changed, 141 insertions(+)
diff --git a/libstdc++-v3/acinclude.m4 b/libstdc++-v3/acinclude.m4
index 1920444e5cd..13c3966b317 100644
--- a/libstdc++-v3/acinclude.m4
+++ b/libstdc++-v3/acinclude.m4
@@ -4954,6 +4954,7 @@ dnl _GLIBCXX_USE_UTIMENSAT
dnl _GLIBCXX_USE_ST_MTIM
dnl _GLIBCXX_USE_FCHMOD
dnl _GLIBCXX_USE_FCHMODAT
+dnl _GLIBCXX_USE_COPY_FILE_RANGE
dnl _GLIBCXX_USE_SENDFILE
dnl HAVE_LINK
dnl HAVE_LSEEK
@@ -5152,6 +5153,25 @@ dnl
if test $glibcxx_cv_truncate = yes; then
AC_DEFINE(HAVE_TRUNCATE, 1, [Define if truncate is available in <unistd.h>.])
fi
+dnl
+ AC_CACHE_CHECK([for copy_file_range that can copy files],
+ glibcxx_cv_copy_file_range, [dnl
+ case "${target_os}" in
+ linux*)
+ GCC_TRY_COMPILE_OR_LINK(
+ [#include <unistd.h>],
+ [copy_file_range(1, nullptr, 2, nullptr, 1, 0);],
+ [glibcxx_cv_copy_file_range=yes],
+ [glibcxx_cv_copy_file_range=no])
+ ;;
+ *)
+ glibcxx_cv_copy_file_range=no
+ ;;
+ esac
+ ])
+ if test $glibcxx_cv_copy_file_range = yes; then
+ AC_DEFINE(_GLIBCXX_USE_COPY_FILE_RANGE, 1, [Define if copy_file_range is available in <unistd.h>.])
+ fi
dnl
AC_CACHE_CHECK([for sendfile that can copy files],
glibcxx_cv_sendfile, [dnl
diff --git a/libstdc++-v3/config.h.in b/libstdc++-v3/config.h.in
index 99ce682670e..e156650792e 100644
--- a/libstdc++-v3/config.h.in
+++ b/libstdc++-v3/config.h.in
@@ -971,6 +971,9 @@
/* Defined if clock_gettime has realtime clock support. */
#undef _GLIBCXX_USE_CLOCK_REALTIME
+/* Define if copy_file_range is available in <unistd.h>. */
+#undef _GLIBCXX_USE_COPY_FILE_RANGE
+
/* Define if ISO/IEC TR 24733 decimal floating point types are supported on
this host. */
#undef _GLIBCXX_USE_DECIMAL_FLOAT
diff --git a/libstdc++-v3/configure b/libstdc++-v3/configure
index 50a7c30665b..47db64ff8fb 100755
--- a/libstdc++-v3/configure
+++ b/libstdc++-v3/configure
@@ -71279,6 +71279,68 @@ $as_echo "$glibcxx_cv_truncate" >&6; }
$as_echo "#define HAVE_TRUNCATE 1" >>confdefs.h
+ fi
+ { $as_echo "$as_me:${as_lineno-$LINENO}: checking for copy_file_range that can copy files" >&5
+$as_echo_n "checking for copy_file_range that can copy files... " >&6; }
+if ${glibcxx_cv_copy_file_range+:} false; then :
+ $as_echo_n "(cached) " >&6
+else
+ case "${target_os}" in
+ linux*)
+ if test x$gcc_no_link = xyes; then
+ cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h. */
+#include <unistd.h>
+int
+main ()
+{
+copy_file_range(1, nullptr, 2, nullptr, 1, 0);
+ ;
+ return 0;
+}
+_ACEOF
+if ac_fn_cxx_try_compile "$LINENO"; then :
+ glibcxx_cv_copy_file_range=yes
+else
+ glibcxx_cv_copy_file_range=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+else
+ if test x$gcc_no_link = xyes; then
+ as_fn_error $? "Link tests are not allowed after GCC_NO_EXECUTABLES." "$LINENO" 5
+fi
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h. */
+#include <unistd.h>
+int
+main ()
+{
+copy_file_range(1, nullptr, 2, nullptr, 1, 0);
+ ;
+ return 0;
+}
+_ACEOF
+if ac_fn_cxx_try_link "$LINENO"; then :
+ glibcxx_cv_copy_file_range=yes
+else
+ glibcxx_cv_copy_file_range=no
+fi
+rm -f core conftest.err conftest.$ac_objext \
+ conftest$ac_exeext conftest.$ac_ext
+fi
+ ;;
+ *)
+ glibcxx_cv_copy_file_range=no
+ ;;
+ esac
+
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $glibcxx_cv_copy_file_range" >&5
+$as_echo "$glibcxx_cv_copy_file_range" >&6; }
+ if test $glibcxx_cv_copy_file_range = yes; then
+
+$as_echo "#define _GLIBCXX_USE_COPY_FILE_RANGE 1" >>confdefs.h
+
fi
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for sendfile that can copy files" >&5
$as_echo_n "checking for sendfile that can copy files... " >&6; }
diff --git a/libstdc++-v3/src/filesystem/ops-common.h b/libstdc++-v3/src/filesystem/ops-common.h
index 36444388208..7c8d3a694e2 100644
--- a/libstdc++-v3/src/filesystem/ops-common.h
+++ b/libstdc++-v3/src/filesystem/ops-common.h
@@ -49,6 +49,9 @@
#ifdef NEED_DO_COPY_FILE
# include <filesystem>
# include <ext/stdio_filebuf.h>
+# ifdef _GLIBCXX_USE_COPY_FILE_RANGE
+# include <unistd.h> // copy_file_range
+# endif
# ifdef _GLIBCXX_USE_SENDFILE
# include <sys/sendfile.h> // sendfile
# include <unistd.h> // lseek
@@ -359,6 +362,32 @@ _GLIBCXX_BEGIN_NAMESPACE_FILESYSTEM
}
#ifdef NEED_DO_COPY_FILE
+#ifdef _GLIBCXX_USE_COPY_FILE_RANGE
+ bool
+ copy_file_copy_file_range(int fd_in, int fd_out, size_t length) noexcept
+ {
+ // a zero-length file is either empty, or not copyable by this syscall
+ // return early to avoid the syscall cost
+ if (length == 0)
+ {
+ errno = EINVAL;
+ return false;
+ }
+ size_t bytes_left = length;
+ off64_t off_in = 0, off_out = 0;
+ ssize_t bytes_copied;
+ do
+ {
+ bytes_copied = ::copy_file_range(fd_in, &off_in, fd_out, &off_out,
+ bytes_left, 0);
+ bytes_left -= bytes_copied;
+ }
+ while (bytes_left > 0 && bytes_copied > 0);
+ if (bytes_copied < 0)
+ return false;
+ return true;
+ }
+#endif
#if defined _GLIBCXX_USE_SENDFILE && ! defined _GLIBCXX_FILESYSTEM_IS_WINDOWS
bool
copy_file_sendfile(int fd_in, int fd_out, size_t length) noexcept
@@ -529,6 +558,33 @@ _GLIBCXX_BEGIN_NAMESPACE_FILESYSTEM
bool has_copied = false;
+#ifdef _GLIBCXX_USE_COPY_FILE_RANGE
+ if (!has_copied)
+ has_copied = copy_file_copy_file_range(in.fd, out.fd, from_st->st_size);
+ if (!has_copied)
+ {
+ // EINVAL: src and dst are the same file (this is not cheaply
+ // detectable from userspace)
+ // EINVAL: copy_file_range is unsupported for this file type by the
+ // underlying filesystem
+ // ENOTSUP: undocumented, can arise with old kernels and NFS
+ // EOPNOTSUPP: filesystem does not implement copy_file_range
+ // ETXTBSY: src or dst is an active swapfile (nonsensical, but allowed
+ // with normal copying)
+ // EXDEV: src and dst are on different filesystems that do not support
+ // cross-fs copy_file_range
+ // ENOENT: undocumented, can arise with CIFS
+ // ENOSYS: unsupported by kernel or blocked by seccomp
+ if (errno != EINVAL && errno != ENOTSUP && errno != EOPNOTSUPP
+ && errno != ETXTBSY && errno != EXDEV && errno != ENOENT
+ && errno != ENOSYS)
+ {
+ ec.assign(errno, std::generic_category());
+ return false;
+ }
+ }
+#endif
+
#if defined _GLIBCXX_USE_SENDFILE && ! defined _GLIBCXX_FILESYSTEM_IS_WINDOWS
if (!has_copied)
has_copied = copy_file_sendfile(in.fd, out.fd, from_st->st_size);
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