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From ff6c50a1451e0e8fdca72039a0a00ebb0a20ba6c Mon Sep 17 00:00:00 2001
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From: Lennart Poettering <lennart@poettering.net>
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Date: Fri, 24 Apr 2015 12:29:05 +0200
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Subject: [PATCH] device: rework how we enter tentative state
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This reworks how we enter tentative state and does so only when a device
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was previously not announced via udev. The previous check actually just
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checked whether a new state bit was set, which is not correct.
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Also, to be able to reliably maintain the tentative state across daemon
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reloads, we need to serialize and deserialize it.
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Cherry-picked from: f62009410
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Resolves: #1283579
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---
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 src/core/device.c | 79 ++++++++++++++++++++++++++++++++++++++++-------
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 src/core/device.h |  2 +-
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 2 files changed, 69 insertions(+), 12 deletions(-)
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diff --git a/src/core/device.c b/src/core/device.c
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index cc4ebd2c87..8a6855dfc3 100644
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--- a/src/core/device.c
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+++ b/src/core/device.c
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@@ -151,14 +151,47 @@ static int device_coldplug(Unit *u, Hashmap *deferred_work) {
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         if (d->found & DEVICE_FOUND_UDEV)
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                 /* If udev says the device is around, it's around */
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                 device_set_state(d, DEVICE_PLUGGED);
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-        else if (d->found != DEVICE_NOT_FOUND)
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+        else if (d->found != DEVICE_NOT_FOUND && d->deserialized_state != DEVICE_PLUGGED)
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                 /* If a device is found in /proc/self/mountinfo or
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-                 * /proc/swaps, it's "tentatively" around. */
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+                 * /proc/swaps, and was not yet announced via udev,
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+                 * it's "tentatively" around. */
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                 device_set_state(d, DEVICE_TENTATIVE);
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         return 0;
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 }
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+static int device_serialize(Unit *u, FILE *f, FDSet *fds) {
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+        Device *d = DEVICE(u);
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+
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+        assert(u);
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+        assert(f);
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+        assert(fds);
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+
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+        unit_serialize_item(u, f, "state", device_state_to_string(d->state));
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+}
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+
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+static int device_deserialize_item(Unit *u, const char *key, const char *value, FDSet *fds) {
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+        Device *d = DEVICE(u);
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+
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+        assert(u);
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+        assert(key);
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+        assert(value);
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+        assert(fds);
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+
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+        if (streq(key, "state")) {
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+                DeviceState state;
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+
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+                state = device_state_from_string(value);
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+                if (state < 0)
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+                        log_unit_debug(u->id, "Failed to parse state value %s", value);
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+                else
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+                        d->deserialized_state = state;
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+        } else
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+                log_unit_debug(u->id, "Unknown serialization key '%s'", key);
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+
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+        return 0;
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+}
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+
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 static void device_dump(Unit *u, FILE *f, const char *prefix) {
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         Device *d = DEVICE(u);
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@@ -408,7 +441,7 @@ static int device_process_new(Manager *m, struct udev_device *dev) {
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 }
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 static void device_update_found_one(Device *d, bool add, DeviceFound found, bool now) {
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-        DeviceFound n;
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+        DeviceFound n, previous;
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         assert(d);
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@@ -416,16 +449,27 @@ static void device_update_found_one(Device *d, bool add, DeviceFound found, bool
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         if (n == d->found)
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                 return;
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+        previous = d->found;
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         d->found = n;
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-        if (now) {
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-                if (d->found & DEVICE_FOUND_UDEV)
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-                        device_set_state(d, DEVICE_PLUGGED);
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-                else if (add && d->found != DEVICE_NOT_FOUND)
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-                        device_set_state(d, DEVICE_TENTATIVE);
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-                else
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-                        device_set_state(d, DEVICE_DEAD);
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-        }
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+        if (!now)
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+                return;
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+
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+        if (d->found & DEVICE_FOUND_UDEV)
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+                /* When the device is known to udev we consider it
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+                 * plugged. */
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+                device_set_state(d, DEVICE_PLUGGED);
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+        else if (d->found != DEVICE_NOT_FOUND && (previous & DEVICE_FOUND_UDEV) == 0)
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+                /* If the device has not been seen by udev yet, but is
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+                 * now referenced by the kernel, then we assume the
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+                 * kernel knows it now, and udev might soon too. */
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+                device_set_state(d, DEVICE_TENTATIVE);
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+        else
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+                /* If nobody sees the device, or if the device was
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+                 * previously seen by udev and now is only referenced
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+                 * from the kernel, then we consider the device is
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+                 * gone, the kernel just hasn't noticed it yet. */
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+                device_set_state(d, DEVICE_DEAD);
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 }
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 static int device_update_found_by_sysfs(Manager *m, const char *sysfs, bool add, DeviceFound found, bool now) {
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@@ -735,6 +779,16 @@ int device_found_node(Manager *m, const char *node, bool add, DeviceFound found,
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                 if (!path_startswith(node, "/dev"))
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                         return 0;
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+                /* We make an extra check here, if the device node
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+                 * actually exists. If it's missing, then this is an
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+                 * indication that device was unplugged but is still
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+                 * referenced in /proc/swaps or
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+                 * /proc/self/mountinfo. Note that this check doesn't
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+                 * really cover all cases where a device might be gone
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+                 * away, since drives that can have a medium inserted
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+                 * will still have a device node even when the medium
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+                 * is not there... */
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+
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                 if (stat(node, &st) < 0) {
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                         if (errno == ENOENT)
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                                 return 0;
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@@ -788,6 +842,9 @@ const UnitVTable device_vtable = {
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         .coldplug = device_coldplug,
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+        .serialize = device_serialize,
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+        .deserialize_item = device_deserialize_item,
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+
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         .dump = device_dump,
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         .active_state = device_active_state,
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diff --git a/src/core/device.h b/src/core/device.h
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index 0609b20fdb..6724ab21ea 100644
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--- a/src/core/device.h
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+++ b/src/core/device.h
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@@ -53,7 +53,7 @@ struct Device {
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         devices for the same sysfs path. We chain them up here. */
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         LIST_FIELDS(struct Device, same_sysfs);
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-        DeviceState state;
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+        DeviceState state, deserialized_state;
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 };
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 extern const UnitVTable device_vtable;