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core: do BindMount/MountImage operations in async control process

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These operations might require slow I/O, and thus might block PID1's main
loop for an undeterminated amount of time. Instead of performing them
inline, fork a worker process and stash away the D-Bus message, and reply
once we get a SIGCHILD indicating they have completed. That way we don't
break compatibility and callers can continue to rely on the fact that when
they get the method reply the operation either succeeded or failed.

To keep backward compatibility, unlike reload control processes, these
are ran inside init.scope and not the target cgroup. Unlike ExecReload,
this is under our control and is not defined by the unit. This is necessary
because previously the operation also wasn't ran from the target cgroup,
so suddenly forking a copy-on-write copy of pid1 into the target cgroup
will make memory usage spike, and if there is a MemoryMax= or MemoryHigh=
set and the cgroup is already close to the limit, it will cause an OOM
kill, where previously it would have worked fine.
This commit is contained in:
Luca Boccassi
2024-08-29 12:48:55 +01:00
committed by Luca Boccassi
parent 5121f7c45b
commit 5162829ec8
25 changed files with 480 additions and 146 deletions
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test/units/TEST-23-UNIT-FILE.runtime-bind-paths.sh
+4
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@@ -34,10 +34,14 @@ systemctl bind --mkdir TEST-23-UNIT-FILE-namespaced.service /run/TEST-23-UNIT-FI
timeout 10 bash -xec 'while [[ "$(systemctl show -P SubState TEST-23-UNIT-FILE-namespaced.service)" == running ]]; do sleep .5; done'
systemctl is-active TEST-23-UNIT-FILE-namespaced.service
test "$(busctl --json=short get-property org.freedesktop.systemd1 /org/freedesktop/systemd1/unit/TEST_2d23_2dUNIT_2dFILE_2dnamespaced_2eservice org.freedesktop.systemd1.Unit CanLiveMount)" = "{\"type\":\"b\",\"data\":true}"
# Now test that systemctl bind fails when attempted on a non-namespaced unit
systemctl start TEST-23-UNIT-FILE-non-namespaced.service
(! systemctl bind --mkdir TEST-23-UNIT-FILE-non-namespaced.service /run/TEST-23-UNIT-FILE-marker-runtime /tmp/testfile-marker-runtime)
test "$(busctl --json=short get-property org.freedesktop.systemd1 /org/freedesktop/systemd1/unit/TEST_2d23_2dUNIT_2dFILE_2dnon_2dnamespaced_2eservice org.freedesktop.systemd1.Unit CanLiveMount)" = "{\"type\":\"b\",\"data\":false}"
timeout 10 bash -xec 'while [[ "$(systemctl show -P SubState TEST-23-UNIT-FILE-non-namespaced.service)" == running ]]; do sleep .5; done'
(! systemctl is-active TEST-23-UNIT-FILE-non-namespaced.service)