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-rw-r--r--udev.c194
1 files changed, 194 insertions, 0 deletions
diff --git a/udev.c b/udev.c
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+/*
+ * mdadm - manage Linux "md" devices aka RAID arrays.
+ *
+ * Copyright (C) 2022 Mateusz Grzonka <mateusz.grzonka@intel.com>
+ *
+ * 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 2 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, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+#include "mdadm.h"
+#include "udev.h"
+#include "md_p.h"
+#include "md_u.h"
+#include <sys/wait.h>
+#include <signal.h>
+#include <limits.h>
+#include <syslog.h>
+#include <libudev.h>
+
+static char *unblock_path;
+
+/*
+ * udev_is_available() - Checks for udev in the system.
+ *
+ * Function looks whether udev directories are available and MDADM_NO_UDEV env defined.
+ *
+ * Return:
+ * true if udev is available,
+ * false if not
+ */
+bool udev_is_available(void)
+{
+ struct stat stb;
+
+ if (stat("/dev/.udev", &stb) != 0 &&
+ stat("/run/udev", &stb) != 0)
+ return false;
+ if (check_env("MDADM_NO_UDEV") == 1)
+ return false;
+ return true;
+}
+
+#ifndef NO_LIBUDEV
+
+static struct udev *udev;
+static struct udev_monitor *udev_monitor;
+
+/*
+ * udev_release() - Drops references of udev and udev_monitor.
+ */
+static void udev_release(void)
+{
+ udev_monitor_unref(udev_monitor);
+ udev_unref(udev);
+}
+
+/*
+ * udev_initialize() - Initializes udev and udev_monitor structures.
+ *
+ * Function initializes udev, udev_monitor, and sets udev_monitor filter for block devices.
+ *
+ * Return:
+ * UDEV_STATUS_SUCCESS on success
+ * UDEV_STATUS_ERROR on error
+ * UDEV_STATUS_ERROR_NO_UDEV when udev not available
+ */
+static enum udev_status udev_initialize(void)
+{
+ if (!udev_is_available()) {
+ pr_err("No udev.\n");
+ return UDEV_STATUS_ERROR_NO_UDEV;
+ }
+
+ udev = udev_new();
+ if (!udev) {
+ pr_err("Cannot initialize udev.\n");
+ return UDEV_STATUS_ERROR;
+ }
+
+ udev_monitor = udev_monitor_new_from_netlink(udev, "udev");
+ if (!udev_monitor) {
+ pr_err("Cannot initialize udev monitor.\n");
+ udev = udev_unref(udev);
+ return UDEV_STATUS_ERROR;
+ }
+
+ if (udev_monitor_filter_add_match_subsystem_devtype(udev_monitor, "block", 0) < 0) {
+ pr_err("Cannot add udev monitor event filter for md devices.\n");
+ udev_release();
+ return UDEV_STATUS_ERROR;
+ }
+ if (udev_monitor_enable_receiving(udev_monitor) < 0) {
+ pr_err("Cannot enable receiving udev events through udev monitor.\n");
+ udev_release();
+ return UDEV_STATUS_ERROR;
+ }
+ atexit(udev_release);
+ return UDEV_STATUS_SUCCESS;
+}
+
+/*
+ * udev_wait_for_events() - Waits for events from udev.
+ * @seconds: Timeout in seconds.
+ *
+ * Function waits udev events, wakes up on event or timeout.
+ *
+ * Return:
+ * UDEV_STATUS_SUCCESS on detected event
+ * UDEV_STATUS_TIMEOUT on timeout
+ * UDEV_STATUS_ERROR on error
+ */
+enum udev_status udev_wait_for_events(int seconds)
+{
+ int fd;
+ fd_set readfds;
+ struct timeval tv;
+ int ret;
+
+ if (!udev || !udev_monitor) {
+ ret = udev_initialize();
+ if (ret != UDEV_STATUS_SUCCESS)
+ return ret;
+ }
+
+ fd = udev_monitor_get_fd(udev_monitor);
+ if (fd < 0) {
+ pr_err("Cannot access file descriptor associated with udev monitor.\n");
+ return UDEV_STATUS_ERROR;
+ }
+
+ FD_ZERO(&readfds);
+ FD_SET(fd, &readfds);
+ tv.tv_sec = seconds;
+ tv.tv_usec = 0;
+
+ if (select(fd + 1, &readfds, NULL, NULL, &tv) > 0 && FD_ISSET(fd, &readfds))
+ if (udev_monitor_receive_device(udev_monitor))
+ return UDEV_STATUS_SUCCESS; /* event detected */
+ return UDEV_STATUS_TIMEOUT;
+}
+#endif
+
+/*
+ * udev_block() - Block udev from examining newly created arrays.
+ *
+ * When array is created, we don't want udev to examine it immediately.
+ * Function creates /run/mdadm/creating-mdXXX and expects that udev rule
+ * will notice it and act accordingly.
+ *
+ * Return:
+ * UDEV_STATUS_SUCCESS when successfully blocked udev
+ * UDEV_STATUS_ERROR on error
+ */
+enum udev_status udev_block(char *devnm)
+{
+ int fd;
+ char *path = xcalloc(1, BUFSIZ);
+
+ snprintf(path, BUFSIZ, "/run/mdadm/creating-%s", devnm);
+
+ fd = open(path, O_CREAT | O_RDWR, 0600);
+ if (!is_fd_valid(fd)) {
+ pr_err("Cannot block udev, error creating blocking file.\n");
+ pr_err("%s: %s\n", strerror(errno), path);
+ free(path);
+ return UDEV_STATUS_ERROR;
+ }
+
+ close(fd);
+ unblock_path = path;
+ return UDEV_STATUS_SUCCESS;
+}
+
+/*
+ * udev_unblock() - Unblock udev.
+ */
+void udev_unblock(void)
+{
+ if (unblock_path)
+ unlink(unblock_path);
+ free(unblock_path);
+ unblock_path = NULL;
+}