From c83ec7f213bd2e435043a435906e46aa9c0a2b6a Mon Sep 17 00:00:00 2001 From: Colin Walters Date: Wed, 1 Mar 2017 22:13:14 -0500 Subject: [PATCH] fdio: Expose wrappers for renameat2() EXCHANGE and NOREPLACE I want the `RENAME_EXCHANGE` version for rpm-ostree, to atomically swap `/usr/share/rpm` (a directory) with a new verison. While we're here we might as well expose `RENAME_NOREPLACE` in case something else wants it. These both have fallbacks to the non-atomic version. Closes: https://github.com/GNOME/libglnx/pull/36 --- Makefile-libglnx.am | 9 ++- glnx-fdio.c | 91 ++++++++++++++++------ glnx-fdio.h | 6 ++ glnx-missing.h | 3 + tests/test-libglnx-fdio.c | 155 ++++++++++++++++++++++++++++++++++++++ 5 files changed, 239 insertions(+), 25 deletions(-) create mode 100644 tests/test-libglnx-fdio.c diff --git a/Makefile-libglnx.am b/Makefile-libglnx.am index d3a46e55..dfe65263 100644 --- a/Makefile-libglnx.am +++ b/Makefile-libglnx.am @@ -52,9 +52,14 @@ libglnx_la_CFLAGS = $(AM_CFLAGS) $(libglnx_cflags) libglnx_la_LDFLAGS = -avoid-version -Bsymbolic-functions -export-symbols-regex "^glnx_" -no-undefined -export-dynamic libglnx_la_LIBADD = $(libglnx_libs) -TESTS += test-libglnx-xattrs +libglnx_tests = test-libglnx-xattrs test-libglnx-fdio +TESTS += $(libglnx_tests) -check_PROGRAMS += test-libglnx-xattrs +check_PROGRAMS += $(libglnx_tests) test_libglnx_xattrs_SOURCES = $(libglnx_srcpath)/tests/test-libglnx-xattrs.c test_libglnx_xattrs_CFLAGS = $(AM_CFLAGS) $(libglnx_cflags) test_libglnx_xattrs_LDADD = $(libglnx_libs) libglnx.la + +test_libglnx_fdio_SOURCES = $(libglnx_srcpath)/tests/test-libglnx-fdio.c +test_libglnx_fdio_CFLAGS = $(AM_CFLAGS) $(libglnx_cflags) +test_libglnx_fdio_LDADD = $(libglnx_libs) libglnx.la diff --git a/glnx-fdio.c b/glnx-fdio.c index 7ee57cd6..68704cb1 100644 --- a/glnx-fdio.c +++ b/glnx-fdio.c @@ -54,11 +54,13 @@ sizeof(type) <= 4 ? 10 : \ sizeof(type) <= 8 ? 20 : sizeof(int[-2*(sizeof(type) > 8)]))) -static gboolean -rename_file_noreplace_at (int olddirfd, const char *oldpath, - int newdirfd, const char *newpath, - gboolean ignore_eexist, - GError **error) + +/* An implementation of renameat2(..., RENAME_NOREPLACE) + * with fallback to a non-atomic version. + */ +int +glnx_renameat2_noreplace (int olddirfd, const char *oldpath, + int newdirfd, const char *newpath) { #ifndef ENABLE_WRPSEUDO_COMPAT if (renameat2 (olddirfd, oldpath, newdirfd, newpath, RENAME_NOREPLACE) < 0) @@ -66,9 +68,35 @@ rename_file_noreplace_at (int olddirfd, const char *oldpath, if (errno == EINVAL || errno == ENOSYS) { /* Fall through */ - ; } - else if (errno == EEXIST && ignore_eexist) + else + { + return -1; + } + } + else + return TRUE; +#endif + + if (linkat (olddirfd, oldpath, newdirfd, newpath, 0) < 0) + return -1; + + if (unlinkat (olddirfd, oldpath, 0) < 0) + return -1; + + return 0; +} + +static gboolean +rename_file_noreplace_at (int olddirfd, const char *oldpath, + int newdirfd, const char *newpath, + gboolean ignore_eexist, + GError **error) +{ + if (glnx_renameat2_noreplace (olddirfd, oldpath, + newdirfd, newpath) < 0) + { + if (errno == EEXIST && ignore_eexist) { (void) unlinkat (olddirfd, oldpath, 0); return TRUE; @@ -79,29 +107,46 @@ rename_file_noreplace_at (int olddirfd, const char *oldpath, return FALSE; } } - else - return TRUE; -#endif + return TRUE; +} - if (linkat (olddirfd, oldpath, newdirfd, newpath, 0) < 0) +/* An implementation of renameat2(..., RENAME_EXCHANGE) + * with fallback to a non-atomic version. + */ +int +glnx_renameat2_exchange (int olddirfd, const char *oldpath, + int newdirfd, const char *newpath) +{ +#ifndef ENABLE_WRPSEUDO_COMPAT + if (renameat2 (olddirfd, oldpath, newdirfd, newpath, RENAME_EXCHANGE) == 0) + return 0; + else { - if (errno == EEXIST && ignore_eexist) - /* Fall through */ - ; + if (errno == ENOSYS || errno == EINVAL) + { + /* Fall through */ + } else { - glnx_set_error_from_errno (error); - return FALSE; + return -1; } } - - if (unlinkat (olddirfd, oldpath, 0) < 0) - { - glnx_set_error_from_errno (error); - return FALSE; - } +#endif - return TRUE; + /* Fallback */ + { const char *old_tmp_name = glnx_strjoina (oldpath, ".XXXXXX"); + + /* Move old out of the way */ + if (renameat (olddirfd, oldpath, olddirfd, old_tmp_name) < 0) + return -1; + /* Now move new into its place */ + if (renameat (newdirfd, newpath, olddirfd, oldpath) < 0) + return -1; + /* And finally old(tmp) into new */ + if (renameat (olddirfd, old_tmp_name, newdirfd, newpath) < 0) + return -1; + } + return 0; } gboolean diff --git a/glnx-fdio.h b/glnx-fdio.h index 111df9d5..c3e7573c 100644 --- a/glnx-fdio.h +++ b/glnx-fdio.h @@ -150,4 +150,10 @@ glnx_stream_fstat (GFileDescriptorBased *stream, struct stat *stbuf, GError **error); +int glnx_renameat2_noreplace (int olddirfd, const char *oldpath, + int newdirfd, const char *newpath); +int glnx_renameat2_exchange (int olddirfd, const char *oldpath, + int newdirfd, const char *newpath); + + G_END_DECLS diff --git a/glnx-missing.h b/glnx-missing.h index fa80d3e8..a60705a1 100644 --- a/glnx-missing.h +++ b/glnx-missing.h @@ -48,5 +48,8 @@ #ifndef RENAME_NOREPLACE #define RENAME_NOREPLACE (1 << 0) #endif +#ifndef RENAME_EXCHANGE +#define RENAME_EXCHANGE (1 << 1) +#endif #include "glnx-missing-syscall.h" diff --git a/tests/test-libglnx-fdio.c b/tests/test-libglnx-fdio.c new file mode 100644 index 00000000..9830c107 --- /dev/null +++ b/tests/test-libglnx-fdio.c @@ -0,0 +1,155 @@ +/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*- + * + * Copyright (C) 2017 Red Hat, Inc. + * + * This library is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2 of the License, or (at your option) any later version. + * + * This library 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 + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with this library; if not, write to the + * Free Software Foundation, Inc., 59 Temple Place - Suite 330, + * Boston, MA 02111-1307, USA. + */ + +#include "config.h" +#include "libglnx.h" +#include +#include +#include +#include +#include + +static gboolean +renameat_test_setup (int *out_srcfd, int *out_destfd, + GError **error) +{ + glnx_fd_close int srcfd = -1; + glnx_fd_close int destfd = -1; + + (void) glnx_shutil_rm_rf_at (AT_FDCWD, "srcdir", NULL, NULL); + if (mkdir ("srcdir", 0755) < 0) + err (1, "mkdir"); + if (!glnx_opendirat (AT_FDCWD, "srcdir", TRUE, &srcfd, error)) + return FALSE; + (void) glnx_shutil_rm_rf_at (AT_FDCWD, "destdir", NULL, NULL); + if (mkdir ("destdir", 0755) < 0) + err (1, "mkdir"); + if (!glnx_opendirat (AT_FDCWD, "destdir", TRUE, &destfd, error)) + return FALSE; + + if (!glnx_file_replace_contents_at (srcfd, "foo", (guint8*)"foo contents", strlen ("foo contents"), + GLNX_FILE_REPLACE_NODATASYNC, NULL, error)) + return FALSE; + if (!glnx_file_replace_contents_at (destfd, "bar", (guint8*)"bar contents", strlen ("bar contents"), + GLNX_FILE_REPLACE_NODATASYNC, NULL, error)) + return FALSE; + + *out_srcfd = srcfd; srcfd = -1; + *out_destfd = destfd; destfd = -1; + return TRUE; +} + +static void +test_renameat2_noreplace (void) +{ + g_autoptr(GError) local_error = NULL; + GError **error = &local_error; + glnx_fd_close int srcfd = -1; + glnx_fd_close int destfd = -1; + struct stat stbuf; + + if (!renameat_test_setup (&srcfd, &destfd, error)) + goto out; + + if (glnx_renameat2_noreplace (srcfd, "foo", destfd, "bar") == 0) + g_assert_not_reached (); + else + { + g_assert_cmpint (errno, ==, EEXIST); + } + + if (glnx_renameat2_noreplace (srcfd, "foo", destfd, "baz") < 0) + { + glnx_set_error_from_errno (error); + goto out; + } + if (fstatat (destfd, "bar", &stbuf, AT_SYMLINK_NOFOLLOW) < 0) + { + glnx_set_error_from_errno (error); + goto out; + } + + if (fstatat (srcfd, "foo", &stbuf, AT_SYMLINK_NOFOLLOW) == 0) + g_assert_not_reached (); + else + g_assert_cmpint (errno, ==, ENOENT); + + out: + g_assert_no_error (local_error); +} + +static void +test_renameat2_exchange (void) +{ + g_autoptr(GError) local_error = NULL; + GError **error = &local_error; + glnx_fd_close int srcfd = -1; + glnx_fd_close int destfd = -1; + struct stat stbuf; + + if (!renameat_test_setup (&srcfd, &destfd, error)) + goto out; + + if (glnx_renameat2_exchange (AT_FDCWD, "srcdir", AT_FDCWD, "destdir") < 0) + { + glnx_set_error_from_errno (error); + goto out; + } + + /* Ensure the dir fds are the same */ + if (fstatat (srcfd, "foo", &stbuf, AT_SYMLINK_NOFOLLOW) < 0) + { + glnx_set_error_from_errno (error); + goto out; + } + if (fstatat (destfd, "bar", &stbuf, AT_SYMLINK_NOFOLLOW) < 0) + { + glnx_set_error_from_errno (error); + goto out; + } + /* But the dirs should be swapped */ + if (fstatat (AT_FDCWD, "destdir/foo", &stbuf, AT_SYMLINK_NOFOLLOW) < 0) + { + glnx_set_error_from_errno (error); + goto out; + } + if (fstatat (AT_FDCWD, "srcdir/bar", &stbuf, AT_SYMLINK_NOFOLLOW) < 0) + { + glnx_set_error_from_errno (error); + goto out; + } + + out: + g_assert_no_error (local_error); +} + +int main (int argc, char **argv) +{ + int ret; + + g_test_init (&argc, &argv, NULL); + + g_test_add_func ("/renameat2-noreplace", test_renameat2_noreplace); + g_test_add_func ("/renameat2-exchange", test_renameat2_exchange); + + ret = g_test_run(); + + return ret; +}