From 486a81f387bb59b2fbbc6aff7b41adbe1621394e Mon Sep 17 00:00:00 2001 From: Paul Eggert Date: Thu, 6 Jun 2019 21:18:11 -0700 Subject: [PATCH] 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. --- admin/merge-gnulib | 2 +- lib/copy-file-range.c | 33 +++++++++++++++++++++++++++++++++ lib/gnulib.mk.in | 12 ++++++++++++ m4/copy-file-range.m4 | 36 ++++++++++++++++++++++++++++++++++++ m4/gnulib-comp.m4 | 8 ++++++++ src/fileio.c | 41 +++++++++++++++++++++++++++++++++-------- 6 files changed, 123 insertions(+), 9 deletions(-) create mode 100644 lib/copy-file-range.c create mode 100644 m4/copy-file-range.m4 diff --git a/admin/merge-gnulib b/admin/merge-gnulib index 4a69310d83c..c2d9291b843 100755 --- a/admin/merge-gnulib +++ b/admin/merge-gnulib @@ -27,7 +27,7 @@ GNULIB_URL=git://git.savannah.gnu.org/gnulib.git GNULIB_MODULES=' alloca-opt binary-io byteswap c-ctype c-strcase - careadlinkat close-stream + careadlinkat close-stream copy-file-range count-leading-zeros count-one-bits count-trailing-zeros crypto/md5-buffer crypto/sha1-buffer crypto/sha256-buffer crypto/sha512-buffer d-type diffseq dosname dtoastr dtotimespec dup2 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 . */ + +#include + +#include + +#include + +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)) diff --git a/m4/copy-file-range.m4 b/m4/copy-file-range.m4 new file mode 100644 index 00000000000..20fd05697fe --- /dev/null +++ b/m4/copy-file-range.m4 @@ -0,0 +1,36 @@ +# copy-file-range.m4 +dnl Copyright 2019 Free Software Foundation, Inc. +dnl This file is free software; the Free Software Foundation +dnl gives unlimited permission to copy and/or distribute it, +dnl with or without modifications, as long as this notice is preserved. + +AC_DEFUN([gl_FUNC_COPY_FILE_RANGE], +[ + AC_REQUIRE([gl_UNISTD_H_DEFAULTS]) + + dnl Persuade glibc to declare copy_file_range. + AC_REQUIRE([AC_USE_SYSTEM_EXTENSIONS]) + + dnl Use AC_LINK_IFELSE, rather than AC_CHECK_FUNCS or a variant, + dnl since we don't want AC_CHECK_FUNCS's checks for glibc stubs. + dnl Programs that use copy_file_range must fall back on read+write + dnl anyway, and there's little point to substituting the Gnulib stub + dnl for a glibc stub. + AC_CACHE_CHECK([for copy_file_range], [gl_cv_func_copy_file_range], + [AC_LINK_IFELSE( + [AC_LANG_PROGRAM( + [[#include + ]], + [[ssize_t (*func) (int, off_t *, int, off_t, size_t, unsigned) + = copy_file_range; + return func (0, 0, 0, 0, 0, 0) & 127; + ]]) + ], + [gl_cv_func_copy_file_range=yes], + [gl_cv_func_copy_file_range=no]) + ]) + + if test "$gl_cv_func_copy_file_range" != yes; then + HAVE_COPY_FILE_RANGE=0 + fi +]) diff --git a/m4/gnulib-comp.m4 b/m4/gnulib-comp.m4 index 0a7a30e5ae2..4627575bf63 100644 --- a/m4/gnulib-comp.m4 +++ b/m4/gnulib-comp.m4 @@ -56,6 +56,7 @@ AC_DEFUN([gl_EARLY], # Code from module clock-time: # Code from module cloexec: # Code from module close-stream: + # Code from module copy-file-range: # Code from module count-leading-zeros: # Code from module count-one-bits: # Code from module count-trailing-zeros: @@ -201,6 +202,11 @@ AC_DEFUN([gl_INIT], AC_CHECK_FUNCS_ONCE([readlinkat]) gl_CLOCK_TIME gl_MODULE_INDICATOR([close-stream]) + gl_FUNC_COPY_FILE_RANGE + if test $HAVE_COPY_FILE_RANGE = 0; then + AC_LIBOBJ([copy-file-range]) + fi + gl_UNISTD_MODULE_INDICATOR([copy-file-range]) gl_COUNT_LEADING_ZEROS gl_COUNT_ONE_BITS gl_COUNT_TRAILING_ZEROS @@ -846,6 +852,7 @@ AC_DEFUN([gl_FILE_LIST], [ lib/cloexec.h lib/close-stream.c lib/close-stream.h + lib/copy-file-range.c lib/count-leading-zeros.c lib/count-leading-zeros.h lib/count-one-bits.c @@ -995,6 +1002,7 @@ AC_DEFUN([gl_FILE_LIST], [ m4/builtin-expect.m4 m4/byteswap.m4 m4/clock_time.m4 + m4/copy-file-range.m4 m4/count-leading-zeros.m4 m4/count-one-bits.m4 m4/count-trailing-zeros.m4 diff --git a/src/fileio.c b/src/fileio.c index 9e9779967dd..f7376ce74fe 100644 --- a/src/fileio.c +++ b/src/fileio.c @@ -2117,14 +2117,39 @@ permissions. */) newsize = st.st_size; else { - char buf[MAX_ALLOCA]; - ptrdiff_t n; - for (newsize = 0; 0 < (n = emacs_read_quit (ifd, buf, sizeof buf)); - newsize += n) - if (emacs_write_quit (ofd, buf, n) != n) - report_file_error ("Write error", newname); - if (n < 0) - report_file_error ("Read error", file); + off_t insize = st.st_size; + ssize_t copied; + + for (newsize = 0; newsize < insize; newsize += copied) + { + /* Copy at most COPY_MAX bytes at a time; this is min + (PTRDIFF_MAX, SIZE_MAX) truncated to a value that is + surely aligned well. */ + ptrdiff_t copy_max = min (PTRDIFF_MAX, SIZE_MAX) >> 30 << 30; + off_t intail = insize - newsize; + ptrdiff_t len = min (intail, copy_max); + copied = copy_file_range (ifd, NULL, ofd, NULL, len, 0); + if (copied <= 0) + break; + maybe_quit (); + } + + /* Fall back on read+write if copy_file_range failed, or if the + input is empty and so could be a /proc file. read+write will + either succeed, or report an error more precisely than + copy_file_range would. */ + if (newsize != insize || insize == 0) + { + char buf[MAX_ALLOCA]; + for (; (copied = emacs_read_quit (ifd, buf, sizeof buf)); + newsize += copied) + { + if (copied < 0) + report_file_error ("Read error", file); + if (emacs_write_quit (ofd, buf, copied) != copied) + report_file_error ("Write error", newname); + } + } } /* Truncate any existing output file after writing the data. This -- 2.39.2