From 75b183700853e616362cf2f22831e1e9dc8a5515 Mon Sep 17 00:00:00 2001

From: Harald Hoyer <harald@redhat.com>

Date: Tue, 24 Nov 2015 09:41:26 +0100

Subject: [PATCH] core: Do not bind a mount unit to a device, if it was from

 mountinfo

If a mount unit is bound to a device, systemd tries to umount the

mount point, if it thinks the device has gone away.

Due to the uevent queue and inotify of /proc/self/mountinfo being two

different sources, systemd can never get the ordering reliably correct.

It can happen, that in the uevent queue ADD,REMOVE,ADD is queued

and an inotify of mountinfo (or libmount event) happend with the

device in question.

systemd cannot know, at which point of time the mount happend in the

ADD,REMOVE,ADD sequence.

The real ordering might have been ADD,REMOVE,ADD,mount

and systemd might think ADD,mount,REMOVE,ADD and would umount the

mountpoint.

A test script which triggered this behaviour is:

rm -f test-efi-disk.img

dd if=/dev/null of=test-efi-disk.img bs=1M seek=512 count=1

parted --script test-efi-disk.img \

  "mklabel gpt" \

  "mkpart ESP fat32 1MiB 511MiB" \

  "set 1 boot on"

LOOP=$(losetup --show -f -P test-efi-disk.img)

udevadm settle

mkfs.vfat -F32 ${LOOP}p1

mkdir -p mnt

mount ${LOOP}p1 mnt

... <dostuffwith mnt>

Without the "udevadm settle" systemd unmounted mnt while the script was

operating on mnt.

Of course the question is, why there was a REMOVE in the first place,

but this is not part of this patch.

Cherry-picked from: 9d06297e262966de71095debd1537fc223f940a3

Resolves: #1283579

---

 src/core/mount.c  | 2 +-

 src/core/socket.c | 2 +-

 src/core/swap.c   | 2 +-

 src/core/unit.c   | 4 ++--

 src/core/unit.h   | 2 +-

 5 files changed, 6 insertions(+), 6 deletions(-)

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

index 1f1a41a..23f63ce 100644

--- a/src/core/mount.c

+++ b/src/core/mount.c

@@ -321,7 +321,7 @@ static int mount_add_device_links(Mount *m) {

         if (mount_is_auto(p) && UNIT(m)->manager->running_as == SYSTEMD_SYSTEM)

                 device_wants_mount = true;

-        r = unit_add_node_link(UNIT(m), p->what, device_wants_mount);

+        r = unit_add_node_link(UNIT(m), p->what, device_wants_mount, m->from_fragment ? UNIT_BINDS_TO : UNIT_REQUIRES);

         if (r < 0)

                 return r;

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

index 7022e77..bc677a2 100644

--- a/src/core/socket.c

+++ b/src/core/socket.c

@@ -267,7 +267,7 @@ static int socket_add_device_link(Socket *s) {

                 return 0;

         t = strjoina("/sys/subsystem/net/devices/", s->bind_to_device);

-        return unit_add_node_link(UNIT(s), t, false);

+        return unit_add_node_link(UNIT(s), t, false, UNIT_BINDS_TO);

 }

 static int socket_add_default_dependencies(Socket *s) {

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

index 369abf0..34a2c40 100644

--- a/src/core/swap.c

+++ b/src/core/swap.c

@@ -201,7 +201,7 @@ static int swap_add_device_links(Swap *s) {

                 return 0;

         if (is_device_path(s->what))

-                return unit_add_node_link(UNIT(s), s->what, UNIT(s)->manager->running_as == SYSTEMD_SYSTEM);

+                return unit_add_node_link(UNIT(s), s->what, UNIT(s)->manager->running_as == SYSTEMD_SYSTEM, UNIT_BINDS_TO);

         else

                 /* File based swap devices need to be ordered after

                  * systemd-remount-fs.service, since they might need a

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

index fa17567..ae47a28 100644

--- a/src/core/unit.c

+++ b/src/core/unit.c

@@ -2823,7 +2823,7 @@ int unit_deserialize(Unit *u, FILE *f, FDSet *fds) {

         }

 }

-int unit_add_node_link(Unit *u, const char *what, bool wants) {

+int unit_add_node_link(Unit *u, const char *what, bool wants, UnitDependency dep) {

         Unit *device;

         _cleanup_free_ char *e = NULL;

         int r;

@@ -2850,7 +2850,7 @@ int unit_add_node_link(Unit *u, const char *what, bool wants) {

         if (r < 0)

                 return r;

-        r = unit_add_two_dependencies(u, UNIT_AFTER, u->manager->running_as == SYSTEMD_SYSTEM ? UNIT_BINDS_TO : UNIT_WANTS, device, true);

+        r = unit_add_two_dependencies(u, UNIT_AFTER, u->manager->running_as == SYSTEMD_SYSTEM ? dep : UNIT_WANTS, device, true);

         if (r < 0)

                 return r;

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

index 7ebc489..0eebc0b 100644

--- a/src/core/unit.h

+++ b/src/core/unit.h

@@ -548,7 +548,7 @@ void unit_serialize_item_format(Unit *u, FILE *f, const char *key, const char *v

 void unit_serialize_item(Unit *u, FILE *f, const char *key, const char *value);

 int unit_deserialize(Unit *u, FILE *f, FDSet *fds);

-int unit_add_node_link(Unit *u, const char *what, bool wants);

+int unit_add_node_link(Unit *u, const char *what, bool wants, UnitDependency d);

 int unit_coldplug(Unit *u, Hashmap *deferred_work);