udev: add helper udev_device_new_from_stat_rdev()

This is a simple wrapper around udev_device_new_from_devnum(), and uses
the data from a struct stat's .st_rdev field to derive the udev_device
object.

src/core/device.c

@@ -943,6 +943,7 @@ static bool device_supported(void) {
 
 static int validate_node(Manager *m, const char *node, struct udev_device **ret) {
         struct stat st;
+        int r;
 
         assert(m);
         assert(node);
@@ -966,19 +967,15 @@ static int validate_node(Manager *m, const char *node, struct udev_device **ret)
         } else {
                 _cleanup_(udev_device_unrefp) struct udev_device *dev = NULL;
 
-                if (!S_ISBLK(st.st_mode) && !S_ISCHR(st.st_mode)) {
-                        *ret = NULL;
-                        return 0; /* bad! */
-                }
-
-                dev = udev_device_new_from_devnum(m->udev, S_ISBLK(st.st_mode) ? 'b' : 'c', st.st_rdev);
-                if (!dev) {
-                        if (errno != ENOENT)
-                                return log_error_errno(errno, "Failed to get udev device from devnum %u:%u: %m", major(st.st_rdev), minor(st.st_rdev));
-
+                r = udev_device_new_from_stat_rdev(m->udev, &st, &dev);
+                if (r == -ENOENT) {
                         *ret = NULL;
                         return 1; /* good! (though missing) */
-                }
+                } else if (r == -ENOTTY) {
+                        *ret = NULL;
+                        return 0; /* bad! (not a device node but some other kind of file system node) */
+                } else if (r < 0)
+                        return log_error_errno(r, "Failed to get udev device from devnum %u:%u: %m", major(st.st_rdev), minor(st.st_rdev));
 
                 *ret = TAKE_PTR(dev);
                 return 1; /* good! */

src/core/swap.c

@@ -255,15 +255,19 @@ static int swap_load_devnode(Swap *s) {
         _cleanup_(udev_device_unrefp) struct udev_device *d = NULL;
         struct stat st;
         const char *p;
+        int r;
 
         assert(s);
 
         if (stat(s->what, &st) < 0 || !S_ISBLK(st.st_mode))
                 return 0;
 
-        d = udev_device_new_from_devnum(UNIT(s)->manager->udev, 'b', st.st_rdev);
-        if (!d)
+        r = udev_device_new_from_stat_rdev(UNIT(s)->manager->udev, &st, &d);
+        if (r < 0) {
+                log_unit_full(UNIT(s), r == -ENOENT ? LOG_DEBUG : LOG_WARNING, r,
+                              "Failed to allocate udev device for swap %s: %m", s->what);
                 return 0;
+        }
 
         p = udev_device_get_devnode(d);
         if (!p)
@@ -443,9 +447,12 @@ static int swap_process_new(Manager *m, const char *device, int prio, bool set_f
         if (stat(device, &st) < 0 || !S_ISBLK(st.st_mode))
                 return 0;
 
-        d = udev_device_new_from_devnum(m->udev, 'b', st.st_rdev);
-        if (!d)
+        r = udev_device_new_from_stat_rdev(m->udev, &st, &d);
+        if (r < 0) {
+                log_full_errno(r == -ENOENT ? LOG_DEBUG : LOG_WARNING, r,
+                               "Failed to allocate udev device for swap %s: %m", device);
                 return 0;
+        }
 
         /* Add the main device node */
         dn = udev_device_get_devnode(d);

src/journal/journalctl.c

@@ -182,11 +182,11 @@ typedef struct BootId {
 } BootId;
 
 static int add_matches_for_device(sd_journal *j, const char *devpath) {
-        int r;
         _cleanup_(udev_unrefp) struct udev *udev = NULL;
         _cleanup_(udev_device_unrefp) struct udev_device *device = NULL;
         struct udev_device *d = NULL;
         struct stat st;
+        int r;
 
         assert(j);
         assert(devpath);
@@ -200,13 +200,12 @@ static int add_matches_for_device(sd_journal *j, const char *devpath) {
         if (!udev)
                 return log_oom();
 
-        r = stat(devpath, &st);
-        if (r < 0)
-                log_error_errno(errno, "Couldn't stat file: %m");
+        if (stat(devpath, &st) < 0)
+                return log_error_errno(errno, "Couldn't stat file: %m");
 
-        d = device = udev_device_new_from_devnum(udev, S_ISBLK(st.st_mode) ? 'b' : 'c', st.st_rdev);
-        if (!device)
-                return log_error_errno(errno, "Failed to get udev device from devnum %u:%u: %m", major(st.st_rdev), minor(st.st_rdev));
+        r = udev_device_new_from_stat_rdev(udev, &st, &device);
+        if (r < 0)
+                return log_error_errno(r, "Failed to get udev device from devnum %u:%u: %m", major(st.st_rdev), minor(st.st_rdev));
 
         while (d) {
                 _cleanup_free_ char *match = NULL;

src/shared/udev-util.c

@@ -42,3 +42,26 @@ int udev_parse_config(void) {
 
         return 0;
 }
+
+int udev_device_new_from_stat_rdev(struct udev *udev, const struct stat *st, struct udev_device **ret) {
+        struct udev_device *nd;
+        char type;
+
+        assert(udev);
+        assert(st);
+        assert(ret);
+
+        if (S_ISBLK(st->st_mode))
+                type = 'b';
+        else if (S_ISCHR(st->st_mode))
+                type = 'c';
+        else
+                return -ENOTTY;
+
+        nd = udev_device_new_from_devnum(udev, type, st->st_rdev);
+        if (!nd)
+                return -errno;
+
+        *ret = nd;
+        return 0;
+}

src/shared/udev-util.h

@@ -21,3 +21,5 @@ DEFINE_TRIVIAL_CLEANUP_FUNC(struct udev_ctrl_msg*, udev_ctrl_msg_unref);
 DEFINE_TRIVIAL_CLEANUP_FUNC(struct udev_monitor*, udev_monitor_unref);
 
 int udev_parse_config(void);
+
+int udev_device_new_from_stat_rdev(struct udev *udev, const struct stat *st, struct udev_device **ret);