Merge pull request #17622 from yuwata/udev-database-set-udev-version

sd-device: make sd_device_has_current_tag() compatible with udev database generated by older udevd

src/libsystemd/sd-device/device-internal.h

@@ -8,9 +8,19 @@
 #include "set.h"
 #include "time-util.h"
 
+#define LATEST_UDEV_DATABASE_VERSION 1
+
 struct sd_device {
         unsigned n_ref;
 
+        /* The database version indicates the supported features by the udev database.
+         * This is saved and parsed in V field.
+         *
+         * 0: None of the following features are supported (systemd version <= 246).
+         * 1: The current tags (Q) and the database version (V) features are implemented (>= 247).
+         */
+        unsigned database_version;
+
         int watch_handle;
 
         sd_device *parent;
@@ -88,7 +98,9 @@ struct sd_device {
 
 int device_new_aux(sd_device **ret);
 int device_add_property_aux(sd_device *device, const char *key, const char *value, bool db);
-int device_add_property_internal(sd_device *device, const char *key, const char *value);
+static inline int device_add_property_internal(sd_device *device, const char *key, const char *value) {
+        return device_add_property_aux(device, key, value, false);
+}
 int device_read_uevent_file(sd_device *device);
 
 int device_set_syspath(sd_device *device, const char *_syspath, bool verify);

src/libsystemd/sd-device/device-private.c

@@ -948,6 +948,10 @@ int device_update_db(sd_device *device) {
 
                 SET_FOREACH(tag, device->current_tags)
                         fprintf(f, "Q:%s\n", tag); /* Current tag */
+
+                /* Always write the latest database version here, instead of the value stored in
+                 * device->database_version, as which may be 0. */
+                fputs("V:" STRINGIFY(LATEST_UDEV_DATABASE_VERSION) "\n", f);
         }
 
         r = fflush_and_check(f);

src/libsystemd/sd-device/sd-device.c

@@ -128,10 +128,6 @@ int device_add_property_aux(sd_device *device, const char *_key, const char *_va
         return 0;
 }
 
-int device_add_property_internal(sd_device *device, const char *key, const char *value) {
-        return device_add_property_aux(device, key, value, false);
-}
-
 int device_set_syspath(sd_device *device, const char *_syspath, bool verify) {
         _cleanup_free_ char *syspath = NULL;
         const char *devpath;
@@ -1208,6 +1204,12 @@ static int handle_db_line(sd_device *device, char key, const char *value) {
                 if (r < 0)
                         return r;
 
+                break;
+        case 'V':
+                r = safe_atou(value, &device->database_version);
+                if (r < 0)
+                        return r;
+
                 break;
         default:
                 log_device_debug(device, "sd-device: Unknown key '%c' in device db, ignoring", key);
@@ -1442,11 +1444,26 @@ _public_ const char *sd_device_get_tag_next(sd_device *device) {
         return v;
 }
 
+static bool device_database_supports_current_tags(sd_device *device) {
+        assert(device);
+
+        (void) device_read_db(device);
+
+        /* The current tags (saved in Q field) feature is implemented in database version 1.
+         * If the database version is 0, then the tags (NOT current tags, saved in G field) are not
+         * sticky. Thus, we can safely bypass the operations for the current tags (Q) to tags (G). */
+
+        return device->database_version >= 1;
+}
+
 _public_ const char *sd_device_get_current_tag_first(sd_device *device) {
         void *v;
 
         assert_return(device, NULL);
 
+        if (!device_database_supports_current_tags(device))
+                return sd_device_get_tag_first(device);
+
         (void) device_read_db(device);
 
         device->current_tags_iterator_generation = device->tags_generation;
@@ -1461,6 +1478,9 @@ _public_ const char *sd_device_get_current_tag_next(sd_device *device) {
 
         assert_return(device, NULL);
 
+        if (!device_database_supports_current_tags(device))
+                return sd_device_get_tag_next(device);
+
         (void) device_read_db(device);
 
         if (device->current_tags_iterator_generation != device->tags_generation)
@@ -1763,6 +1783,9 @@ _public_ int sd_device_has_current_tag(sd_device *device, const char *tag) {
         assert_return(device, -EINVAL);
         assert_return(tag, -EINVAL);
 
+        if (!device_database_supports_current_tags(device))
+                return sd_device_has_tag(device, tag);
+
         (void) device_read_db(device);
 
         return set_contains(device->current_tags, tag);