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/* SPDX-License-Identifier: GPL-2.0-or-later */
/*
* Copyright © 2009 Canonical Ltd.
* Copyright © 2009 Scott James Remnant <scott@netsplit.com>
*/
#include <sys/inotify.h>
#include "alloc-util.h"
#include "device-private.h"
#include "device-util.h"
#include "dirent-util.h"
#include "fs-util.h"
#include "parse-util.h"
#include "random-util.h"
#include "udev-watch.h"
#define SAVE_WATCH_HANDLE_MAX_RETRIES 128
#define MAX_RANDOM_DELAY (100 * USEC_PER_MSEC)
#define MIN_RANDOM_DELAY ( 10 * USEC_PER_MSEC)
int udev_watch_restore(int inotify_fd) {
struct dirent *ent;
DIR *dir;
int r;
/* Move any old watches directory out of the way, and then restore the watches. */
assert(inotify_fd >= 0);
if (rename("/run/udev/watch", "/run/udev/watch.old") < 0) {
if (errno != ENOENT)
return log_warning_errno(errno, "Failed to move watches directory /run/udev/watch. "
"Old watches will not be restored: %m");
return 0;
}
dir = opendir("/run/udev/watch.old");
if (!dir)
return log_warning_errno(errno, "Failed to open old watches directory /run/udev/watch.old. "
"Old watches will not be restored: %m");
FOREACH_DIRENT_ALL(ent, dir, break) {
_cleanup_(sd_device_unrefp) sd_device *dev = NULL;
int wd;
if (ent->d_name[0] == '.')
continue;
/* For backward compatibility, read symlink from watch handle to device id, and ignore
* the opposite direction symlink. */
if (safe_atoi(ent->d_name, &wd) < 0)
goto unlink;
r = device_new_from_watch_handle_at(&dev, dirfd(dir), wd);
if (r < 0) {
log_full_errno(r == -ENODEV ? LOG_DEBUG : LOG_WARNING, r,
"Failed to create sd_device object from saved watch handle '%s', ignoring: %m",
ent->d_name);
goto unlink;
}
log_device_debug(dev, "Restoring old watch");
(void) udev_watch_begin(inotify_fd, dev);
unlink:
(void) unlinkat(dirfd(dir), ent->d_name, 0);
}
(void) closedir(dir);
(void) rmdir("/run/udev/watch.old");
return 0;
}
int udev_watch_begin(int inotify_fd, sd_device *dev) {
const char *devnode;
int wd, r;
assert(inotify_fd >= 0);
assert(dev);
r = sd_device_get_devname(dev, &devnode);
if (r < 0)
return log_device_debug_errno(dev, r, "Failed to get device name: %m");
log_device_debug(dev, "Adding watch on '%s'", devnode);
wd = inotify_add_watch(inotify_fd, devnode, IN_CLOSE_WRITE);
if (wd < 0) {
bool ignore = errno == ENOENT;
r = log_device_full_errno(dev, ignore ? LOG_DEBUG : LOG_WARNING, errno,
"Failed to add device '%s' to watch%s: %m",
devnode, ignore ? ", ignoring" : "");
(void) device_set_watch_handle(dev, -1);
return ignore ? 0 : r;
}
for (unsigned i = 0; i < SAVE_WATCH_HANDLE_MAX_RETRIES; i++) {
if (i > 0) {
usec_t delay = MIN_RANDOM_DELAY + random_u64_range(MAX_RANDOM_DELAY - MIN_RANDOM_DELAY);
/* When the same handle is reused for different device node, we may fail to
* save the watch handle with -EEXIST. Let's consider the case of two workers A
* and B do the following:
*
* 1. A calls inotify_rm_watch()
* 2. B calls inotify_add_watch()
* 3. B calls device_set_watch_handle()
* 4. A calls device_set_watch_handle(-1)
*
* At step 3, the old symlinks to save the watch handle still exist. So,
* device_set_watch_handle() fails with -EEXIST. */
log_device_debug_errno(dev, r,
"Failed to save watch handle '%i' for %s in "
"/run/udev/watch, retrying in after %s: %m",
wd, devnode, FORMAT_TIMESPAN(delay, USEC_PER_MSEC));
(void) usleep(delay);
}
r = device_set_watch_handle(dev, wd);
if (r >= 0)
return 0;
if (r != -EEXIST)
break;
}
log_device_warning_errno(dev, r,
"Failed to save watch handle '%i' for %s in /run/udev/watch: %m",
wd, devnode);
(void) inotify_rm_watch(inotify_fd, wd);
return r;
}
int udev_watch_end(int inotify_fd, sd_device *dev) {
int wd;
assert(dev);
/* This may be called by 'udevadm test'. In that case, inotify_fd is not initialized. */
if (inotify_fd < 0)
return 0;
if (sd_device_get_devname(dev, NULL) < 0)
return 0;
wd = device_get_watch_handle(dev);
if (wd < 0)
log_device_debug_errno(dev, wd, "Failed to get watch handle, ignoring: %m");
else {
log_device_debug(dev, "Removing watch");
(void) inotify_rm_watch(inotify_fd, wd);
}
(void) device_set_watch_handle(dev, -1);
return 0;
}
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