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From: Michael Biebl <biebl@debian.org>
Date: Sat, 25 Sep 2021 21:08:36 +0200
Subject: Revert "udev: make algorithm that selects highest priority devlink
less susceptible to race conditions"
This reverts commit 30f6dce62cb3a738b20253f2192270607c31b55b.
---
src/udev/udev-event.c | 7 -----
src/udev/udev-node.c | 75 +++++++++++----------------------------------------
2 files changed, 15 insertions(+), 67 deletions(-)
diff --git a/src/udev/udev-event.c b/src/udev/udev-event.c
index 5159d19..9cf5190 100644
--- a/src/udev/udev-event.c
+++ b/src/udev/udev-event.c
@@ -1041,13 +1041,6 @@ int udev_event_execute_rules(UdevEvent *event,
if (r < 0)
return log_device_debug_errno(dev, r, "Failed to update database under /run/udev/data/: %m");
- /* Yes, we run update_devnode() twice, because in the first invocation, that is before update of udev database,
- * it could happen that two contenders are replacing each other's symlink. Hence we run it again to make sure
- * symlinks point to devices that claim them with the highest priority. */
- r = update_devnode(event);
- if (r < 0)
- return r;
-
device_set_is_initialized(dev);
return 0;
diff --git a/src/udev/udev-node.c b/src/udev/udev-node.c
index bde18f7..9d4b7d9 100644
--- a/src/udev/udev-node.c
+++ b/src/udev/udev-node.c
@@ -20,15 +20,12 @@
#include "path-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 "udev-node.h"
#include "user-util.h"
-#define LINK_UPDATE_MAX_RETRIES 128
-
static int node_symlink(sd_device *dev, const char *node, const char *slink) {
_cleanup_free_ char *slink_dirname = NULL, *target = NULL;
const char *id_filename, *slink_tmp;
@@ -102,9 +99,7 @@ static int node_symlink(sd_device *dev, const char *node, const char *slink) {
if (rename(slink_tmp, slink) < 0) {
r = log_device_error_errno(dev, errno, "Failed to rename '%s' to '%s': %m", slink_tmp, slink);
(void) unlink(slink_tmp);
- } else
- /* Tell caller that we replaced already existing symlink. */
- r = 1;
+ }
return r;
}
@@ -197,7 +192,7 @@ static int link_update(sd_device *dev, const char *slink, bool add) {
_cleanup_free_ char *target = NULL, *filename = NULL, *dirname = NULL;
char name_enc[PATH_MAX];
const char *id_filename;
- int i, r, retries;
+ int r;
assert(dev);
assert(slink);
@@ -217,6 +212,14 @@ static int link_update(sd_device *dev, const char *slink, bool add) {
if (!add && unlink(filename) == 0)
(void) rmdir(dirname);
+ r = link_find_prioritized(dev, add, dirname, &target);
+ if (r < 0) {
+ log_device_debug(dev, "No reference left, removing '%s'", slink);
+ if (unlink(slink) == 0)
+ (void) rmdir_parents(slink, "/");
+ } else
+ (void) node_symlink(dev, target, slink);
+
if (add)
do {
_cleanup_close_ int fd = -1;
@@ -229,49 +232,7 @@ static int link_update(sd_device *dev, const char *slink, bool add) {
r = -errno;
} while (r == -ENOENT);
- /* If the database entry is not written yet we will just do one iteration and possibly wrong symlink
- * will be fixed in the second invocation. */
- retries = sd_device_get_is_initialized(dev) > 0 ? LINK_UPDATE_MAX_RETRIES : 1;
-
- for (i = 0; i < retries; i++) {
- struct stat st1 = {}, st2 = {};
-
- r = stat(dirname, &st1);
- if (r < 0 && errno != ENOENT)
- return -errno;
-
- r = link_find_prioritized(dev, add, dirname, &target);
- if (r == -ENOENT) {
- log_device_debug(dev, "No reference left, removing '%s'", slink);
- if (unlink(slink) == 0)
- (void) rmdir_parents(slink, "/");
-
- break;
- } else if (r < 0)
- return log_device_error_errno(dev, r, "Failed to determine highest priority symlink: %m");
-
- r = node_symlink(dev, target, slink);
- if (r < 0) {
- (void) unlink(filename);
- break;
- } else if (r == 1)
- /* We have replaced already existing symlink, possibly there is some other device trying
- * to claim the same symlink. Let's do one more iteration to give us a chance to fix
- * the error if other device actually claims the symlink with higher priority. */
- continue;
-
- /* Skip the second stat() if the first failed, stat_inode_unmodified() would return false regardless. */
- if ((st1.st_mode & S_IFMT) != 0) {
- r = stat(dirname, &st2);
- if (r < 0 && errno != ENOENT)
- return -errno;
-
- if (stat_inode_unmodified(&st1, &st2))
- break;
- }
- }
-
- return i < LINK_UPDATE_MAX_RETRIES ? 0 : -ELOOP;
+ return r;
}
int udev_node_update_old_links(sd_device *dev, sd_device *dev_old) {
@@ -490,11 +451,8 @@ int udev_node_add(sd_device *dev, bool apply,
(void) node_symlink(dev, devnode, filename);
/* create/update symlinks, add symlinks to name index */
- FOREACH_DEVICE_DEVLINK(dev, devlink) {
- r = link_update(dev, devlink, true);
- if (r < 0)
- log_device_info_errno(dev, r, "Failed to update device symlinks: %m");
- }
+ FOREACH_DEVICE_DEVLINK(dev, devlink)
+ (void) link_update(dev, devlink, true);
return 0;
}
@@ -507,11 +465,8 @@ int udev_node_remove(sd_device *dev) {
assert(dev);
/* remove/update symlinks, remove symlinks from name index */
- FOREACH_DEVICE_DEVLINK(dev, devlink) {
- r = link_update(dev, devlink, false);
- if (r < 0)
- log_device_info_errno(dev, r, "Failed to update device symlinks: %m");
- }
+ FOREACH_DEVICE_DEVLINK(dev, devlink)
+ (void) link_update(dev, devlink, false);
r = xsprintf_dev_num_path_from_sd_device(dev, &filename);
if (r < 0)
|
