From 960ea6ae7a9e2aca3594318ab893f7d5383e46b6 Mon Sep 17 00:00:00 2001

From: Lennart Poettering <lennart@poettering.net>

Date: Fri, 24 Apr 2015 12:29:05 +0200

Subject: [PATCH] device: rework how we enter tentative state

This reworks how we enter tentative state and does so only when a device

was previously not announced via udev. The previous check actually just

checked whether a new state bit was set, which is not correct.

Also, to be able to reliably maintain the tentative state across daemon

reloads, we need to serialize and deserialize it.

Cherry-picked from: f62009410

Resolves: #1283579

---

 src/core/device.c | 79 +++++++++++++++++++++++++++++++++++++++++++++++--------

 src/core/device.h |  2 +-

 2 files changed, 69 insertions(+), 12 deletions(-)

diff --git a/src/core/device.c b/src/core/device.c

index cc4ebd2..8a6855d 100644

--- a/src/core/device.c

+++ b/src/core/device.c

@@ -151,14 +151,47 @@ static int device_coldplug(Unit *u, Hashmap *deferred_work) {

         if (d->found & DEVICE_FOUND_UDEV)

                 /* If udev says the device is around, it's around */

                 device_set_state(d, DEVICE_PLUGGED);

-        else if (d->found != DEVICE_NOT_FOUND)

+        else if (d->found != DEVICE_NOT_FOUND && d->deserialized_state != DEVICE_PLUGGED)

                 /* If a device is found in /proc/self/mountinfo or

-                 * /proc/swaps, it's "tentatively" around. */

+                 * /proc/swaps, and was not yet announced via udev,

+                 * it's "tentatively" around. */

                 device_set_state(d, DEVICE_TENTATIVE);

         return 0;

 }

+static int device_serialize(Unit *u, FILE *f, FDSet *fds) {

+        Device *d = DEVICE(u);

+

+        assert(u);

+        assert(f);

+        assert(fds);

+

+        unit_serialize_item(u, f, "state", device_state_to_string(d->state));

+}

+

+static int device_deserialize_item(Unit *u, const char *key, const char *value, FDSet *fds) {

+        Device *d = DEVICE(u);

+

+        assert(u);

+        assert(key);

+        assert(value);

+        assert(fds);

+

+        if (streq(key, "state")) {

+                DeviceState state;

+

+                state = device_state_from_string(value);

+                if (state < 0)

+                        log_unit_debug(u->id, "Failed to parse state value %s", value);

+                else

+                        d->deserialized_state = state;

+        } else

+                log_unit_debug(u->id, "Unknown serialization key '%s'", key);

+

+        return 0;

+}

+

 static void device_dump(Unit *u, FILE *f, const char *prefix) {

         Device *d = DEVICE(u);

@@ -408,7 +441,7 @@ static int device_process_new(Manager *m, struct udev_device *dev) {

 }

 static void device_update_found_one(Device *d, bool add, DeviceFound found, bool now) {

-        DeviceFound n;

+        DeviceFound n, previous;

         assert(d);

@@ -416,16 +449,27 @@ static void device_update_found_one(Device *d, bool add, DeviceFound found, bool

         if (n == d->found)

                 return;

+        previous = d->found;

         d->found = n;

-        if (now) {

-                if (d->found & DEVICE_FOUND_UDEV)

-                        device_set_state(d, DEVICE_PLUGGED);

-                else if (add && d->found != DEVICE_NOT_FOUND)

-                        device_set_state(d, DEVICE_TENTATIVE);

-                else

-                        device_set_state(d, DEVICE_DEAD);

-        }

+        if (!now)

+                return;

+

+        if (d->found & DEVICE_FOUND_UDEV)

+                /* When the device is known to udev we consider it

+                 * plugged. */

+                device_set_state(d, DEVICE_PLUGGED);

+        else if (d->found != DEVICE_NOT_FOUND && (previous & DEVICE_FOUND_UDEV) == 0)

+                /* If the device has not been seen by udev yet, but is

+                 * now referenced by the kernel, then we assume the

+                 * kernel knows it now, and udev might soon too. */

+                device_set_state(d, DEVICE_TENTATIVE);

+        else

+                /* If nobody sees the device, or if the device was

+                 * previously seen by udev and now is only referenced

+                 * from the kernel, then we consider the device is

+                 * gone, the kernel just hasn't noticed it yet. */

+                device_set_state(d, DEVICE_DEAD);

 }

 static int device_update_found_by_sysfs(Manager *m, const char *sysfs, bool add, DeviceFound found, bool now) {

@@ -735,6 +779,16 @@ int device_found_node(Manager *m, const char *node, bool add, DeviceFound found,

                 if (!path_startswith(node, "/dev"))

                         return 0;

+                /* We make an extra check here, if the device node

+                 * actually exists. If it's missing, then this is an

+                 * indication that device was unplugged but is still

+                 * referenced in /proc/swaps or

+                 * /proc/self/mountinfo. Note that this check doesn't

+                 * really cover all cases where a device might be gone

+                 * away, since drives that can have a medium inserted

+                 * will still have a device node even when the medium

+                 * is not there... */

+

                 if (stat(node, &st) < 0) {

                         if (errno == ENOENT)

                                 return 0;

@@ -788,6 +842,9 @@ const UnitVTable device_vtable = {

         .coldplug = device_coldplug,

+        .serialize = device_serialize,

+        .deserialize_item = device_deserialize_item,

+

         .dump = device_dump,

         .active_state = device_active_state,

diff --git a/src/core/device.h b/src/core/device.h

index 0609b20..6724ab2 100644

--- a/src/core/device.h

+++ b/src/core/device.h

@@ -53,7 +53,7 @@ struct Device {

         devices for the same sysfs path. We chain them up here. */

         LIST_FIELDS(struct Device, same_sysfs);

-        DeviceState state;

+        DeviceState state, deserialized_state;

 };

 extern const UnitVTable device_vtable;