core: rework device state logic

This change introduces a new state "tentative" for device units. Device
units are considered "plugged" when udev announced them, "dead" when
they are not available in the kernel, and "tentative" when they are
referenced in /proc/self/mountinfo or /proc/swaps but not (yet)
announced via udev.

This should fix a race when device nodes (like loop devices) are created
and immediately mounted. Previously, systemd might end up seeing the
mount unit before the device, and would thus pull down the mount because
its BindTo dependency on the device would not be fulfilled.

1 files changed, 19 insertions, 13 deletions

diff --git a/src/core/swap.c b/src/core/swap.c
index f73a8e6deb..de3a5d8b10 100644
--- a/src/core/swap.c
+++ b/src/core/swap.c
@@ -331,7 +331,7 @@ static int swap_load(Unit *u) {
         return swap_verify(s);
 }
 
-static int swap_add_one(
+static int swap_setup_unit(
                 Manager *m,
                 const char *what,
                 const char *what_proc_swaps,
@@ -356,8 +356,10 @@ static int swap_add_one(
 
         if (u &&
             SWAP(u)->from_proc_swaps &&
-            !path_equal(SWAP(u)->parameters_proc_swaps.what, what_proc_swaps))
+            !path_equal(SWAP(u)->parameters_proc_swaps.what, what_proc_swaps)) {
+                log_error("Swap %s appeared twice with different device paths %s and %s", e, SWAP(u)->parameters_proc_swaps.what, what_proc_swaps);
                 return -EEXIST;
+        }
 
         if (!u) {
                 delete = true;
@@ -372,7 +374,7 @@ static int swap_add_one(
 
                 SWAP(u)->what = strdup(what);
                 if (!SWAP(u)->what) {
-                        r = log_oom();
+                        r = -ENOMEM;
                         goto fail;
                 }
 
@@ -400,7 +402,6 @@ static int swap_add_one(
         p->priority = priority;
 
         unit_add_to_dbus_queue(u);
-
         return 0;
 
 fail:
@@ -412,7 +413,7 @@ fail:
         return r;
 }
 
-static int swap_process_new_swap(Manager *m, const char *device, int prio, bool set_flags) {
+static int swap_process_new(Manager *m, const char *device, int prio, bool set_flags) {
         _cleanup_udev_device_unref_ struct udev_device *d = NULL;
         struct udev_list_entry *item = NULL, *first = NULL;
         const char *dn;
@@ -421,7 +422,7 @@ static int swap_process_new_swap(Manager *m, const char *device, int prio, bool
 
         assert(m);
 
-        r = swap_add_one(m, device, device, prio, set_flags);
+        r = swap_setup_unit(m, device, device, prio, set_flags);
         if (r < 0)
                 return r;
 
@@ -437,7 +438,7 @@ static int swap_process_new_swap(Manager *m, const char *device, int prio, bool
         /* Add the main device node */
         dn = udev_device_get_devnode(d);
         if (dn && !streq(dn, device))
-                swap_add_one(m, dn, device, prio, set_flags);
+                swap_setup_unit(m, dn, device, prio, set_flags);
 
         /* Add additional units for all symlinks */
         first = udev_device_get_devlinks_list_entry(d);
@@ -458,7 +459,7 @@ static int swap_process_new_swap(Manager *m, const char *device, int prio, bool
                             st.st_rdev != udev_device_get_devnum(d))
                                 continue;
 
-                swap_add_one(m, p, device, prio, set_flags);
+                swap_setup_unit(m, p, device, prio, set_flags);
         }
 
         return r;
@@ -1084,15 +1085,17 @@ static int swap_load_proc_swaps(Manager *m, bool set_flags) {
                         if (k == EOF)
                                 break;
 
-                        log_warning("Failed to parse /proc/swaps:%u", i);
+                        log_warning("Failed to parse /proc/swaps:%u.", i);
                         continue;
                 }
 
                 d = cunescape(dev);
                 if (!d)
-                        return -ENOMEM;
+                        return log_oom();
+
+                device_found_node(m, d, true, DEVICE_FOUND_SWAP, set_flags);
 
-                k = swap_process_new_swap(m, d, prio, set_flags);
+                k = swap_process_new(m, d, prio, set_flags);
                 if (k < 0)
                         r = k;
         }
@@ -1144,6 +1147,9 @@ static int swap_dispatch_io(sd_event_source *source, int fd, uint32_t revents, v
                                 break;
                         }
 
+                        if (swap->what)
+                                device_found_node(m, swap->what, false, DEVICE_FOUND_SWAP, true);
+
                 } else if (swap->just_activated) {
 
                         /* New swap entry */
@@ -1291,7 +1297,7 @@ fail:
         return r;
 }
 
-int swap_process_new_device(Manager *m, struct udev_device *dev) {
+int swap_process_device_new(Manager *m, struct udev_device *dev) {
         struct udev_list_entry *item = NULL, *first = NULL;
         _cleanup_free_ char *e = NULL;
         const char *dn;
@@ -1334,7 +1340,7 @@ int swap_process_new_device(Manager *m, struct udev_device *dev) {
         return r;
 }
 
-int swap_process_removed_device(Manager *m, struct udev_device *dev) {
+int swap_process_device_remove(Manager *m, struct udev_device *dev) {
         const char *dn;
         int r = 0;
         Swap *s;