/* SPDX-License-Identifier: GPL-2.0-or-later */
-#include <errno.h>
-#include <fcntl.h>
-#include <stdbool.h>
-#include <stddef.h>
-#include <sys/stat.h>
-#include <unistd.h>
+#include <sys/file.h>
#include "sd-id128.h"
#include "mkdir-label.h"
#include "parse-util.h"
#include "path-util.h"
-#include "random-util.h"
#include "selinux-util.h"
#include "smack-util.h"
#include "stat-util.h"
-#include "stdio-util.h"
#include "string-util.h"
-#include "strxcpyx.h"
-#include "time-util.h"
#include "udev-node.h"
#include "user-util.h"
-#define CREATE_LINK_MAX_RETRIES 128
-#define LINK_UPDATE_MAX_RETRIES 128
-#define UPDATE_TIMESTAMP_MAX_RETRIES 128
-#define MAX_RANDOM_DELAY (250 * USEC_PER_MSEC)
-#define MIN_RANDOM_DELAY ( 50 * USEC_PER_MSEC)
#define UDEV_NODE_HASH_KEY SD_ID128_MAKE(b9,6a,f1,ce,40,31,44,1a,9e,19,ec,8b,ae,f3,e3,2f)
-static int create_symlink(const char *target, const char *slink) {
- int r;
-
- assert(target);
- assert(slink);
-
- for (unsigned i = 0; i < CREATE_LINK_MAX_RETRIES; i++) {
- r = mkdir_parents_label(slink, 0755);
- if (r == -ENOENT)
- continue;
- if (r < 0)
- return r;
-
- mac_selinux_create_file_prepare(slink, S_IFLNK);
- r = RET_NERRNO(symlink(target, slink));
- mac_selinux_create_file_clear();
- if (r != -ENOENT)
- return r;
- }
-
- return r;
-}
-
static int node_symlink(sd_device *dev, const char *devnode, const char *slink) {
_cleanup_free_ char *target = NULL;
const char *id, *slink_tmp;
slink_tmp = strjoina(slink, ".tmp-", id);
(void) unlink(slink_tmp);
- r = create_symlink(target, slink_tmp);
+ r = mkdir_parents_label(slink_tmp, 0755);
+ if (r < 0)
+ return log_device_debug_errno(dev, r, "Failed to create parent directory of '%s': %m", slink_tmp);
+
+ mac_selinux_create_file_prepare(slink_tmp, S_IFLNK);
+ r = RET_NERRNO(symlink(target, slink_tmp));
+ mac_selinux_create_file_clear();
if (r < 0)
return log_device_debug_errno(dev, r, "Failed to create symlink '%s' to '%s': %m", slink_tmp, target);
return !!*ret;
}
-static int update_timestamp(sd_device *dev, int fd, struct stat *prev) {
- assert(fd >= 0);
- assert(prev);
-
- /* Even if a symlink in the stack directory is created/removed, the mtime of the directory may
- * not be changed. Why? Let's consider the following situation. For simplicity, let's assume
- * there exist two udev workers (A and B) and all of them calls link_update() for the same
- * devlink simultaneously.
- *
- * 1. A creates/removes a symlink in the stack directory.
- * 2. A calls the first stat() in the loop of link_update().
- * 3. A calls link_find_prioritized().
- * 4. B creates/removes another symlink in the stack directory, so the result of the step 3 is outdated.
- * 5. B finishes link_update().
- * 6. A creates/removes devlink according to the outdated result in the step 3.
- * 7. A calls the second stat() in the loop of link_update().
- *
- * If these 7 steps are processed in this order within a short time period that kernel's timer
- * does not increase, then even if the contents in the stack directory is changed, the results
- * of two stat() called by A shows the same timestamp, and A cannot detect the change.
- *
- * By calling this function after creating/removing symlinks in the stack directory, the
- * timestamp of the stack directory is always increased at least in the above step 5, so A can
- * detect the update. */
-
- for (unsigned i = 0; i < UPDATE_TIMESTAMP_MAX_RETRIES; i++) {
- struct stat st;
-
- if (fstat(fd, &st) < 0)
- return -errno;
-
- if (!stat_inode_unmodified(prev, &st))
- return 0;
-
- log_device_debug(dev,
- "Stack directory is modified, but its timestamp is not changed, "
- "updating timestamp after 10ms.");
-
- (void) usleep(10 * USEC_PER_MSEC);
- if (futimens(fd, NULL) < 0)
- return -errno;
- }
-
- return -ELOOP;
-}
-
static int stack_directory_update(sd_device *dev, int fd, bool add) {
- struct stat st;
const char *id;
int r;
if (r < 0)
return r;
- if (fstat(fd, &st) < 0)
- return -errno;
-
if (add) {
_cleanup_free_ char *data = NULL, *buf = NULL;
const char *devname;
}
}
- r = update_timestamp(dev, fd, &st);
- if (r < 0)
- return r;
-
- return 0;
+ return 1; /* Updated. */
}
static int stack_directory_open(const char *dirname) {
return TAKE_FD(fd);
}
+static int stack_directory_lock(int dirfd) {
+ _cleanup_close_ int fd = -1;
+
+ assert(dirfd >= 0);
+
+ fd = openat(dirfd, ".lock", O_CLOEXEC | O_NOFOLLOW | O_RDONLY | O_CREAT, 0600);
+ if (fd < 0)
+ return -errno;
+
+ if (flock(fd, LOCK_EX) < 0)
+ return -errno;
+
+ return TAKE_FD(fd);
+}
+
size_t udev_node_escape_path(const char *src, char *dest, size_t size) {
size_t i, j;
uint64_t h;
}
static int link_update(sd_device *dev, const char *slink, bool add) {
- _cleanup_free_ char *dirname = NULL;
- _cleanup_close_ int dirfd = -1;
+ _cleanup_free_ char *dirname = NULL, *devnode = NULL;
+ _cleanup_close_ int dirfd = -1, lockfd = -1;
int r;
assert(dev);
if (dirfd < 0)
return log_device_debug_errno(dev, dirfd, "Failed to open stack directory '%s': %m", dirname);
+ lockfd = stack_directory_lock(dirfd);
+ if (lockfd < 0)
+ return log_device_debug_errno(dev, lockfd, "Failed to lock stack directory '%s': %m", dirname);
+
r = stack_directory_update(dev, dirfd, add);
if (r < 0)
return log_device_debug_errno(dev, r, "Failed to update stack directory '%s': %m", dirname);
- for (unsigned i = 0; i < LINK_UPDATE_MAX_RETRIES; i++) {
- _cleanup_free_ char *target = NULL;
- struct stat st1 = {}, st2 = {};
-
- if (i > 0) {
- usec_t delay = MIN_RANDOM_DELAY + random_u64_range(MAX_RANDOM_DELAY - MIN_RANDOM_DELAY);
-
- log_device_debug(dev, "Directory %s was updated, retrying to update devlink %s after %s.",
- dirname, slink, FORMAT_TIMESPAN(delay, USEC_PER_MSEC));
- (void) usleep(delay);
- }
-
- if (stat(dirname, &st1) < 0 && errno != ENOENT)
- return log_device_debug_errno(dev, errno, "Failed to stat %s: %m", dirname);
-
- r = stack_directory_find_prioritized_devnode(dev, dirname, add, &target);
- if (r < 0)
- return log_device_debug_errno(dev, r, "Failed to determine device node with the highest priority for '%s': %m", slink);
- if (r == 0) {
- log_device_debug(dev, "No reference left for '%s', removing", slink);
-
- if (unlink(slink) < 0 && errno != ENOENT)
- log_device_debug_errno(dev, errno, "Failed to remove '%s', ignoring: %m", slink);
+ r = stack_directory_find_prioritized_devnode(dev, dirname, add, &devnode);
+ if (r < 0)
+ return log_device_debug_errno(dev, r, "Failed to determine device node with the highest priority for '%s': %m", slink);
+ if (r > 0)
+ return node_symlink(dev, devnode, slink);
- (void) rmdir_parents(slink, "/dev");
- return 0;
- }
+ log_device_debug(dev, "No reference left for '%s', removing", slink);
- r = node_symlink(dev, target, slink);
- if (r < 0)
- return r;
+ if (unlink(slink) < 0 && errno != ENOENT)
+ log_device_debug_errno(dev, errno, "Failed to remove '%s', ignoring: %m", slink);
- if (stat(dirname, &st2) < 0 && errno != ENOENT)
- return log_device_debug_errno(dev, errno, "Failed to stat %s: %m", dirname);
+ (void) rmdir_parents(slink, "/dev");
- if (((st1.st_mode & S_IFMT) == 0 && (st2.st_mode & S_IFMT) == 0) ||
- stat_inode_unmodified(&st1, &st2))
- return 0;
- }
-
- return -ELOOP;
+ return 0;
}
static int device_get_devpath_by_devnum(sd_device *dev, char **ret) {
projects / thirdparty / systemd.git / commitdiff
