1 files changed, 163 insertions, 0 deletions
diff --git a/src/basic/sync-util.c b/src/basic/sync-util.c
new file mode 100644
index 0000000..e2d4a3d
--- /dev/null
+++ b/src/basic/sync-util.c
@@ -0,0 +1,163 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <fcntl.h>
+#include <sys/stat.h>
+
+#include "fd-util.h"
+#include "fs-util.h"
+#include "path-util.h"
+#include "sync-util.h"
+
+int fsync_directory_of_file(int fd) {
+        _cleanup_close_ int dfd = -1;
+        struct stat st;
+        int r;
+
+        assert(fd >= 0);
+
+        /* We only reasonably can do this for regular files and directories, or for O_PATH fds, hence check
+         * for the inode type first */
+        if (fstat(fd, &st) < 0)
+                return -errno;
+
+        if (S_ISDIR(st.st_mode)) {
+                dfd = openat(fd, "..", O_RDONLY|O_DIRECTORY|O_CLOEXEC, 0);
+                if (dfd < 0)
+                        return -errno;
+
+        } else if (!S_ISREG(st.st_mode)) { /* Regular files are OK regardless if O_PATH or not, for all other
+                                            * types check O_PATH flag */
+                int flags;
+
+                flags = fcntl(fd, F_GETFL);
+                if (flags < 0)
+                        return -errno;
+
+                if (!FLAGS_SET(flags, O_PATH)) /* If O_PATH this refers to the inode in the fs, in which case
+                                                * we can sensibly do what is requested. Otherwise this refers
+                                                * to a socket, fifo or device node, where the concept of a
+                                                * containing directory doesn't make too much sense. */
+                        return -ENOTTY;
+        }
+
+        if (dfd < 0) {
+                _cleanup_free_ char *path = NULL;
+
+                r = fd_get_path(fd, &path);
+                if (r < 0) {
+                        log_debug_errno(r, "Failed to query /proc/self/fd/%d%s: %m",
+                                        fd,
+                                        r == -ENOSYS ? ", ignoring" : "");
+
+                        if (r == -ENOSYS)
+                                /* If /proc is not available, we're most likely running in some
+                                 * chroot environment, and syncing the directory is not very
+                                 * important in that case. Let's just silently do nothing. */
+                                return 0;
+
+                        return r;
+                }
+
+                if (!path_is_absolute(path))
+                        return -EINVAL;
+
+                dfd = open_parent(path, O_CLOEXEC|O_NOFOLLOW, 0);
+                if (dfd < 0)
+                        return dfd;
+        }
+
+        return RET_NERRNO(fsync(dfd));
+}
+
+int fsync_full(int fd) {
+        int r, q;
+
+        /* Sync both the file and the directory */
+
+        r = RET_NERRNO(fsync(fd));
+
+        q = fsync_directory_of_file(fd);
+        if (r < 0) /* Return earlier error */
+                return r;
+        if (q == -ENOTTY) /* Ignore if the 'fd' refers to a block device or so which doesn't really have a
+                           * parent dir */
+                return 0;
+        return q;
+}
+
+int fsync_path_at(int at_fd, const char *path) {
+        _cleanup_close_ int opened_fd = -1;
+        int fd;
+
+        if (isempty(path)) {
+                if (at_fd == AT_FDCWD) {
+                        opened_fd = open(".", O_RDONLY|O_DIRECTORY|O_CLOEXEC);
+                        if (opened_fd < 0)
+                                return -errno;
+
+                        fd = opened_fd;
+                } else
+                        fd = at_fd;
+        } else {
+                opened_fd = openat(at_fd, path, O_RDONLY|O_CLOEXEC|O_NONBLOCK);
+                if (opened_fd < 0)
+                        return -errno;
+
+                fd = opened_fd;
+        }
+
+        return RET_NERRNO(fsync(fd));
+}
+
+int fsync_parent_at(int at_fd, const char *path) {
+        _cleanup_close_ int opened_fd = -1;
+
+        if (isempty(path)) {
+                if (at_fd != AT_FDCWD)
+                        return fsync_directory_of_file(at_fd);
+
+                opened_fd = open("..", O_RDONLY|O_DIRECTORY|O_CLOEXEC);
+                if (opened_fd < 0)
+                        return -errno;
+
+                return RET_NERRNO(fsync(opened_fd));
+        }
+
+        opened_fd = openat(at_fd, path, O_PATH|O_CLOEXEC|O_NOFOLLOW);
+        if (opened_fd < 0)
+                return -errno;
+
+        return fsync_directory_of_file(opened_fd);
+}
+
+int fsync_path_and_parent_at(int at_fd, const char *path) {
+        _cleanup_close_ int opened_fd = -1;
+
+        if (isempty(path)) {
+                if (at_fd != AT_FDCWD)
+                        return fsync_full(at_fd);
+
+                opened_fd = open(".", O_RDONLY|O_DIRECTORY|O_CLOEXEC);
+        } else
+                opened_fd = openat(at_fd, path, O_RDONLY|O_NOFOLLOW|O_NONBLOCK|O_CLOEXEC);
+        if (opened_fd < 0)
+                return -errno;
+
+        return fsync_full(opened_fd);
+}
+
+int syncfs_path(int at_fd, const char *path) {
+        _cleanup_close_ int fd = -1;
+
+        if (isempty(path)) {
+                if (at_fd != AT_FDCWD)
+                        return RET_NERRNO(syncfs(at_fd));
+
+                fd = open(".", O_RDONLY|O_DIRECTORY|O_CLOEXEC);
+        } else
+                fd = openat(at_fd, path, O_RDONLY|O_CLOEXEC|O_NONBLOCK);
+        if (fd < 0)
+                return -errno;
+
+        return RET_NERRNO(syncfs(fd));
+}