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-rw-r--r--src/udev/udevadm-lock.c367
1 files changed, 367 insertions, 0 deletions
diff --git a/src/udev/udevadm-lock.c b/src/udev/udevadm-lock.c
new file mode 100644
index 0000000..ca5fa87
--- /dev/null
+++ b/src/udev/udevadm-lock.c
@@ -0,0 +1,367 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#include <getopt.h>
+#include <stdlib.h>
+#include <sys/file.h>
+#include <unistd.h>
+
+#include "blockdev-util.h"
+#include "btrfs-util.h"
+#include "device-util.h"
+#include "fd-util.h"
+#include "fdset.h"
+#include "main-func.h"
+#include "parse-util.h"
+#include "path-util.h"
+#include "pretty-print.h"
+#include "process-util.h"
+#include "signal-util.h"
+#include "sort-util.h"
+#include "strv.h"
+#include "time-util.h"
+#include "udevadm.h"
+
+static usec_t arg_timeout_usec = USEC_INFINITY;
+static char **arg_devices = NULL;
+static char **arg_backing = NULL;
+static char **arg_cmdline = NULL;
+static bool arg_print = false;
+
+STATIC_DESTRUCTOR_REGISTER(arg_devices, strv_freep);
+STATIC_DESTRUCTOR_REGISTER(arg_backing, strv_freep);
+STATIC_DESTRUCTOR_REGISTER(arg_cmdline, strv_freep);
+
+static int help(void) {
+ _cleanup_free_ char *link = NULL;
+ int r;
+
+ r = terminal_urlify_man("udevadm", "8", &link);
+ if (r < 0)
+ return log_oom();
+
+ printf("%s [OPTIONS...] COMMAND\n"
+ "%s [OPTIONS...] --print\n"
+ "\n%sLock a block device and run a command.%s\n\n"
+ " -h --help Print this message\n"
+ " -V --version Print version of the program\n"
+ " -d --device=DEVICE Block device to lock\n"
+ " -b --backing=FILE File whose backing block device to lock\n"
+ " -t --timeout=SECS Block at most the specified time waiting for lock\n"
+ " -p --print Only show which block device the lock would be taken on\n"
+ "\nSee the %s for details.\n",
+ program_invocation_short_name,
+ program_invocation_short_name,
+ ansi_highlight(),
+ ansi_normal(),
+ link);
+
+ return 0;
+}
+
+static int parse_argv(int argc, char *argv[]) {
+
+ static const struct option options[] = {
+ { "help", no_argument, NULL, 'h' },
+ { "version", no_argument, NULL, 'V' },
+ { "device", required_argument, NULL, 'd' },
+ { "backing", required_argument, NULL, 'b' },
+ { "timeout", required_argument, NULL, 't' },
+ { "print", no_argument, NULL, 'p' },
+ {}
+ };
+
+ int c, r;
+
+ assert(argc >= 0);
+ assert(argv);
+
+ /* Resetting to 0 forces the invocation of an internal initialization routine of getopt_long()
+ * that checks for GNU extensions in optstring ('-' or '+' at the beginning). */
+ optind = 0;
+ while ((c = getopt_long(argc, argv, arg_print ? "hVd:b:t:p" : "+hVd:b:t:p", options, NULL)) >= 0)
+
+ switch (c) {
+
+ case 'h':
+ return help();
+
+ case 'V':
+ return print_version();
+
+ case 'd':
+ case 'b': {
+ _cleanup_free_ char *s = NULL;
+ char ***l = c == 'd' ? &arg_devices : &arg_backing;
+
+ r = path_make_absolute_cwd(optarg, &s);
+ if (r < 0)
+ return log_error_errno(r, "Failed to make path '%s' absolute: %m", optarg);
+
+ path_simplify(s);
+
+ if (strv_consume(l, TAKE_PTR(s)) < 0)
+ return log_oom();
+
+ strv_uniq(*l);
+ break;
+ }
+
+ case 't':
+ r = parse_sec(optarg, &arg_timeout_usec);
+ if (r < 0)
+ return log_error_errno(r, "Failed to parse --timeout= parameter: %s", optarg);
+ break;
+
+ case 'p':
+ arg_print = true;
+ break;
+
+ case '?':
+ return -EINVAL;
+
+ default:
+ assert_not_reached();
+ }
+
+ if (arg_print) {
+ if (optind != argc)
+ return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "No arguments expected");
+ } else {
+ if (optind + 1 > argc)
+ return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Too few arguments, command to execute.");
+
+ arg_cmdline = strv_copy(argv + optind);
+ if (!arg_cmdline)
+ return log_oom();
+ }
+
+ if (strv_isempty(arg_devices) && strv_isempty(arg_backing))
+ return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "No devices to lock specified, refusing.");
+
+ return 1;
+}
+
+static int find_devno(
+ dev_t **devnos,
+ size_t *n_devnos,
+ const char *device,
+ bool backing) {
+
+ dev_t devt;
+ int r;
+
+ assert(devnos);
+ assert(n_devnos);
+ assert(*devnos || *n_devnos == 0);
+ assert(device);
+
+ r = path_get_whole_disk(device, backing, &devt);
+ if (r < 0)
+ return log_error_errno(r, "Failed to find whole block device for '%s': %m", device);
+
+ if (typesafe_bsearch(&devt, *devnos, *n_devnos, devt_compare_func)) {
+ log_debug("Device %u:%u already listed for locking, ignoring.", major(devt), minor(devt));
+ return 0;
+ }
+
+ if (!GREEDY_REALLOC(*devnos, *n_devnos + 1))
+ return log_oom();
+
+ (*devnos)[(*n_devnos)++] = devt;
+
+ /* Immediately sort again, to ensure the binary search above will work for the next device we add */
+ typesafe_qsort(*devnos, *n_devnos, devt_compare_func);
+ return 1;
+}
+
+static int lock_device(
+ const char *path,
+ dev_t devno,
+ usec_t deadline) {
+
+ _cleanup_close_ int fd = -1;
+ struct stat st;
+ int r;
+
+ fd = open(path, O_RDONLY|O_CLOEXEC|O_NONBLOCK|O_NOCTTY);
+ if (fd < 0)
+ return log_error_errno(errno, "Failed to open '%s': %m", path);
+
+ if (fstat(fd, &st) < 0)
+ return log_error_errno(errno, "Failed to stat '%s': %m", path);
+
+ /* Extra safety: check that the device still refers to what we think it refers to */
+ if (!S_ISBLK(st.st_mode) || st.st_rdev != devno)
+ return log_error_errno(SYNTHETIC_ERRNO(ENXIO), "Path '%s' no longer refers to specified block device %u:%u: %m", path, major(devno), minor(devno));
+
+ if (flock(fd, LOCK_EX|LOCK_NB) < 0) {
+
+ if (errno != EAGAIN)
+ return log_error_errno(errno, "Failed to lock device '%s': %m", path);
+
+ if (deadline == 0)
+ return log_error_errno(SYNTHETIC_ERRNO(EBUSY), "Device '%s' is currently locked.", path);
+
+ if (deadline == USEC_INFINITY) {
+
+ log_info("Device '%s' is currently locked, waiting%s", path, special_glyph(SPECIAL_GLYPH_ELLIPSIS));
+
+ if (flock(fd, LOCK_EX) < 0)
+ return log_error_errno(errno, "Failed to lock device '%s': %m", path);
+
+ } else {
+ _cleanup_(sigkill_waitp) pid_t flock_pid = 0;
+
+ /* flock() doesn't support a time-out. Let's fake one then. The traditional way to do
+ * this is via alarm()/setitimer()/timer_create(), but that's racy, given that the
+ * SIGALRM might already fire between the alarm() and the flock() in which case the
+ * flock() is never cancelled and we lock up (this is a short time window, but with
+ * short timeouts on a loaded machine we might run into it, who knows?). Let's
+ * instead do the lock out-of-process: fork off a child that does the locking, and
+ * that we'll wait on and kill if it takes too long. */
+
+ log_info("Device '%s' is currently locked, waiting %s%s",
+ path, FORMAT_TIMESPAN(usec_sub_unsigned(deadline, now(CLOCK_MONOTONIC)), 0),
+ special_glyph(SPECIAL_GLYPH_ELLIPSIS));
+
+ BLOCK_SIGNALS(SIGCHLD);
+
+ r = safe_fork("(timed-flock)", FORK_DEATHSIG|FORK_LOG, &flock_pid);
+ if (r < 0)
+ return r;
+ if (r == 0) {
+ /* Child */
+
+ if (flock(fd, LOCK_EX) < 0) {
+ log_error_errno(errno, "Failed to lock device '%s': %m", path);
+ _exit(EXIT_FAILURE);
+ }
+
+ _exit(EXIT_SUCCESS);
+ }
+
+ for (;;) {
+ siginfo_t si;
+ sigset_t ss;
+ usec_t n;
+
+ assert(sigemptyset(&ss) >= 0);
+ assert(sigaddset(&ss, SIGCHLD) >= 0);
+
+ n = now(CLOCK_MONOTONIC);
+ if (n >= deadline)
+ return log_error_errno(SYNTHETIC_ERRNO(ETIMEDOUT), "Timeout reached.");
+
+ r = sigtimedwait(&ss, NULL, TIMESPEC_STORE(deadline - n));
+ if (r < 0) {
+ if (errno != EAGAIN)
+ return log_error_errno(errno, "Failed to wait for SIGCHLD: %m");
+
+ return log_error_errno(SYNTHETIC_ERRNO(ETIMEDOUT), "Timeout reached.");
+ }
+
+ assert(r == SIGCHLD);
+
+ zero(si);
+
+ if (waitid(P_PID, flock_pid, &si, WEXITED|WNOHANG|WNOWAIT) < 0)
+ return log_error_errno(errno, "Failed to wait for child: %m");
+
+ if (si.si_pid != 0) {
+ assert(si.si_pid == flock_pid);
+
+ if (si.si_code != CLD_EXITED || si.si_status != EXIT_SUCCESS)
+ return log_error_errno(SYNTHETIC_ERRNO(EPROTO), "Unexpected exit status of file lock child.");
+
+ break;
+ }
+
+ log_debug("Got SIGCHLD for other child, continuing.");
+ }
+ }
+ }
+
+ log_debug("Successfully locked %s (%u:%u)%s", path, major(devno), minor(devno), special_glyph(SPECIAL_GLYPH_ELLIPSIS));
+
+ return TAKE_FD(fd);
+}
+
+int lock_main(int argc, char *argv[], void *userdata) {
+ _cleanup_(fdset_freep) FDSet *fds = NULL;
+ _cleanup_free_ dev_t *devnos = NULL;
+ size_t n_devnos = 0;
+ usec_t deadline;
+ pid_t pid;
+ int r;
+
+ r = parse_argv(argc, argv);
+ if (r <= 0)
+ return r;
+
+ STRV_FOREACH(i, arg_devices) {
+ r = find_devno(&devnos, &n_devnos, *i, /* backing= */ false);
+ if (r < 0)
+ return r;
+ }
+
+ STRV_FOREACH(i, arg_backing) {
+ r = find_devno(&devnos, &n_devnos, *i, /* backing= */ true);
+ if (r < 0)
+ return r;
+ }
+
+ assert(n_devnos > 0);
+
+ fds = fdset_new();
+ if (!fds)
+ return log_oom();
+
+ if (!timestamp_is_set(arg_timeout_usec))
+ deadline = arg_timeout_usec;
+ else
+ deadline = usec_add(now(CLOCK_MONOTONIC), arg_timeout_usec);
+
+ for (size_t i = 0; i < n_devnos; i++) {
+ _cleanup_free_ char *node = NULL;
+
+ r = devname_from_devnum(S_IFBLK, devnos[i], &node);
+ if (r < 0)
+ return log_error_errno(r, "Failed to format block device path: %m");
+
+ if (arg_print)
+ printf("%s\n", node);
+ else {
+ _cleanup_close_ int fd = -1;
+
+ fd = lock_device(node, devnos[i], deadline);
+ if (fd < 0)
+ return fd;
+
+ r = fdset_put(fds, fd);
+ if (r < 0)
+ return log_oom();
+
+ TAKE_FD(fd);
+ }
+ }
+
+ if (arg_print)
+ return EXIT_SUCCESS;
+
+ /* Ignore SIGINT and allow the forked process to receive it */
+ (void) ignore_signals(SIGINT);
+
+ r = safe_fork("(lock)", FORK_RESET_SIGNALS|FORK_DEATHSIG|FORK_CLOSE_ALL_FDS|FORK_RLIMIT_NOFILE_SAFE|FORK_LOG, &pid);
+ if (r < 0)
+ return r;
+ if (r == 0) {
+ /* Child */
+
+ execvp(arg_cmdline[0], arg_cmdline);
+ log_open();
+ log_error_errno(errno, "Failed to execute %s: %m", arg_cmdline[0]);
+ _exit(EXIT_FAILURE);
+ }
+
+ return wait_for_terminate_and_check(arg_cmdline[0], pid, 0);
+}
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