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, 29 insertions, 17 deletions

diff --git a/src/core/mount.c b/src/core/mount.c
index 40037e7866..8e4a376944 100644
--- a/src/core/mount.c
+++ b/src/core/mount.c
@@ -1386,7 +1386,7 @@ static int mount_dispatch_timer(sd_event_source *source, usec_t usec, void *user
         return 0;
 }
 
-static int mount_add_one(
+static int mount_setup_unit(
                 Manager *m,
                 const char *what,
                 const char *where,
@@ -1429,7 +1429,7 @@ static int mount_add_one(
 
                 u = unit_new(m, sizeof(Mount));
                 if (!u)
-                        return -ENOMEM;
+                        return log_oom();
 
                 r = unit_add_name(u, e);
                 if (r < 0)
@@ -1542,6 +1542,8 @@ static int mount_add_one(
         return 0;
 
 fail:
+        log_warning_errno(r, "Failed to set up mount unit: %m");
+
         if (delete && u)
                 unit_free(u);
 
@@ -1549,33 +1551,36 @@ fail:
 }
 
 static int mount_load_proc_self_mountinfo(Manager *m, bool set_flags) {
-        _cleanup_(mnt_free_tablep) struct libmnt_table *tb = NULL;
-        _cleanup_(mnt_free_iterp) struct libmnt_iter *itr = NULL;
-        struct libmnt_fs *fs;
+        _cleanup_(mnt_free_tablep) struct libmnt_table *t = NULL;
+        _cleanup_(mnt_free_iterp) struct libmnt_iter *i = NULL;
         int r = 0;
 
         assert(m);
 
-        tb = mnt_new_table();
-        itr = mnt_new_iter(MNT_ITER_FORWARD);
-        if (!tb || !itr)
+        t = mnt_new_table();
+        if (!t)
                 return log_oom();
 
-        r = mnt_table_parse_mtab(tb, NULL);
+        i = mnt_new_iter(MNT_ITER_FORWARD);
+        if (!i)
+                return log_oom();
+
+        r = mnt_table_parse_mtab(t, NULL);
         if (r < 0)
-                return r;
+                return log_error_errno(r, "Failed to parse /proc/self/mountinfo: %m");
 
         r = 0;
         for (;;) {
                 const char *device, *path, *options, *fstype;
                 _cleanup_free_ const char *d = NULL, *p = NULL;
+                struct libmnt_fs *fs;
                 int k;
 
-                k = mnt_table_next_fs(tb, itr, &fs);
+                k = mnt_table_next_fs(t, i, &fs);
                 if (k == 1)
                         break;
-                else if (k < 0)
-                        return log_error_errno(k, "Failed to get next entry from /etc/fstab: %m");
+                if (k < 0)
+                        return log_error_errno(k, "Failed to get next entry from /proc/self/mountinfo: %m");
 
                 device = mnt_fs_get_source(fs);
                 path = mnt_fs_get_target(fs);
@@ -1583,11 +1588,16 @@ static int mount_load_proc_self_mountinfo(Manager *m, bool set_flags) {
                 fstype = mnt_fs_get_fstype(fs);
 
                 d = cunescape(device);
+                if (!d)
+                        return log_oom();
+
                 p = cunescape(path);
-                if (!d || !p)
+                if (!p)
                         return log_oom();
 
-                k = mount_add_one(m, d, p, options, fstype, set_flags);
+                (void) device_found_node(m, d, true, DEVICE_FOUND_MOUNT, set_flags);
+
+                k = mount_setup_unit(m, d, p, options, fstype, set_flags);
                 if (r == 0 && k < 0)
                         r = k;
         }
@@ -1731,8 +1741,6 @@ static int mount_dispatch_io(sd_event_source *source, int fd, uint32_t revents,
 
         r = mount_load_proc_self_mountinfo(m, true);
         if (r < 0) {
-                log_error_errno(r, "Failed to reread /proc/self/mountinfo: %m");
-
                 /* Reset flags, just in case, for later calls */
                 LIST_FOREACH(units_by_type, u, m->units_by_type[UNIT_MOUNT]) {
                         Mount *mount = MOUNT(u);
@@ -1765,6 +1773,10 @@ static int mount_dispatch_io(sd_event_source *source, int fd, uint32_t revents,
                                 break;
                         }
 
+                        if (mount->parameters_proc_self_mountinfo.what)
+                                (void) device_found_node(m, mount->parameters_proc_self_mountinfo.what, false, DEVICE_FOUND_MOUNT, true);
+
+
                 } else if (mount->just_mounted || mount->just_changed) {
 
                         /* New or changed mount entry */