cgroupv2: fix fs2 driver initialization #2299

kolyshkin · 2020-04-07T21:40:39Z

The main goal of this patchset is to fix fs2 driver initialization. With these patches, the tests that I added in #2295 are now passing with fs2 driver (i.e. when RUNC_USE_SYSTEMD is not set), except for one case (#2298).

I also did some major cleanups, mostly for systemd driver. A high-level overview:

remove legacy paths map from v2 driver
untangle systemd v2 initialization;
reorganized systemd code into v1, v2, common, and unsupported.

Please see individual commits for details.

@AkihiroSuda PTAL (this was discussed before in #2281 (comment))

AkihiroSuda

--- FAIL: TestUsernsCheckpoint (0.26s)
    checkpoint_test.go:130: container_linux.go:349: starting container process caused "process_linux.go:306: applying cgroup configuration for process caused \"write /sys/fs/cgroup/cgroup.subtree_control: device or resource busy\""
=== RUN   TestCheckpoint
time="2020-04-07T21:54:51Z" level=warning msg="signal: killed"
--- FAIL: TestCheckpoint (0.03s)
    checkpoint_test.go:130: container_linux.go:349: starting container process caused "process_linux.go:306: applying cgroup configuration for process caused \"write /sys/fs/cgroup/cgroup.subtree_control: device or resource busy\""
=== RUN   TestExecPS
time="2020-04-07T21:54:51Z" level=warning msg="signal: killed"
--- FAIL: TestExecPS (0.03s)
    exec_test.go:52: |: container_linux.go:349: starting container process caused "process_linux.go:306: applying cgroup configuration for process caused \"write /sys/fs/cgroup/cgroup.subtree_control: device or resource busy\""
=== RUN   TestUsernsExecPS
time="2020-04-07T21:54:51Z" level=warning msg="signal: killed"
--- FAIL: TestUsernsExecPS (0.03s)
    exec_test.go:52: |: container_linux.go:349: starting container process caused "process_linux.go:306: applying cgroup configuration for process caused \"write /sys/fs/cgroup/cgroup.subtree_control: device or resource busy\""
=== RUN   TestIPCPrivate
time="2020-04-07T21:54:51Z" level=warning msg="signal: killed"
--- FAIL: TestIPCPrivate (0.03s)
    utils_test.go:55: exec_test.go:82: unexpected error: container_linux.go:349: starting container process caused "process_linux.go:306: applying cgroup configuration for process caused \"write /sys/fs/cgroup/cgroup.subtree_control: device or resource busy\""
        
=== RUN   TestIPCHost
time="2020-04-07T21:54:51Z" level=warning msg="signal: killed"
--- FAIL: TestIPCHost (0.02s)
    utils_test.go:55: exec_test.go:108: unexpected error: container_linux.go:349: starting container process caused "process_linux.go:306: applying cgroup configuration for process caused \"write /sys/fs/cgroup/cgroup.subtree_control: device or resource busy\""
        
=== RUN   TestIPCJoinPath
time="2020-04-07T21:54:51Z" level=warning msg="signal: killed"
--- FAIL: TestIPCJoinPath (0.03s)
    utils_test.go:55: exec_test.go:135: unexpected error: container_linux.go:349: starting container process caused "process_linux.go:306: applying cgroup configuration for process caused \"write /sys/fs/cgroup/cgroup.subtree_control: device or resource busy\""
        
=== RUN   TestIPCBadPath
--- PASS: TestIPCBadPath (0.03s)
=== RUN   TestRlimit
time="2020-04-07T21:54:51Z" level=warning msg="signal: killed"
--- FAIL: TestRlimit (0.03s)
    utils_test.go:55: exec_test.go:200: unexpected error: container_linux.go:349: starting container process caused "process_linux.go:306: applying cgroup configuration for process caused \"write /sys/fs/cgroup/cgroup.subtree_control: device or resource busy\""
        
=== RUN   TestUsernsRlimit
time="2020-04-07T21:54:51Z" level=warning msg="signal: killed"
--- FAIL: TestUsernsRlimit (0.03s)
    utils_test.go:55: exec_test.go:200: unexpected error: container_linux.go:349: starting container process caused "process_linux.go:306: applying cgroup configuration for process caused \"write /sys/fs/cgroup/cgroup.subtree_control: device or resource busy\""
        
=== RUN   TestEnter
--- SKIP: TestEnter (0.00s)
    exec_test.go:211: cgroup v2 is not supported
=== RUN   TestProcessEnv
time="2020-04-07T21:54:51Z" level=warning msg="signal: killed"
--- FAIL: TestProcessEnv (0.03s)
    utils_test.go:55: exec_test.go:326: unexpected error: container_linux.go:349: starting container process caused "process_linux.go:306: applying cgroup configuration for process caused \"write /sys/fs/cgroup/cgroup.subtree_control: device or resource busy\""
        
=== RUN   TestProcessEmptyCaps
time="2020-04-07T21:54:51Z" level=warning msg="signal: killed"
--- FAIL: TestProcessEmptyCaps (0.03s)
    utils_test.go:55: exec_test.go:370: unexpected error: container_linux.go:349: starting container process caused "process_linux.go:306: applying cgroup configuration for process caused \"write /sys/fs/cgroup/cgroup.subtree_control: device or resource busy\""
        
=== RUN   TestProcessCaps
time="2020-04-07T21:54:51Z" level=warning msg="signal: killed"
--- FAIL: TestProcessCaps (0.03s)
    utils_test.go:55: exec_test.go:423: unexpected error: container_linux.go:349: starting container process caused "process_linux.go:306: applying cgroup configuration for process caused \"write /sys/fs/cgroup/cgroup.subtree_control: device or resource busy\""
        
=== RUN   TestAdditionalGroups
time="2020-04-07T21:54:52Z" level=warning msg="signal: killed"
--- FAIL: TestAdditionalGroups (0.03s)
    utils_test.go:55: exec_test.go:487: unexpected error: container_linux.go:349: starting container process caused "process_linux.go:306: applying cgroup configuration for process caused \"write /sys/fs/cgroup/cgroup.subtree_control: device or resource busy\""

kolyshkin · 2020-04-08T03:53:19Z

write /sys/fs/cgroup/cgroup.subtree_control: device or resource busy

if this is in test with --systemd-cgroup, then I don't understand why is this happening as I haven't changed anything;
if this is in test without --systemd-cgroup but systemd is present, then --systemd-cgroup should be used;
if this is in test without --systemd-cgroup and systemd is not present, then I don't have an idea about what is going on :(

AkihiroSuda · 2020-04-08T04:05:58Z

the errors are happening on Travis
https://travis-ci.org/github/opencontainers/runc/jobs/672264460

kolyshkin · 2020-04-08T09:38:33Z

The problem is we're enabling all the controllers no matter what limits are set. Two ways to fix this are:

enable all controllers on a "best effort" basis (i.e. ignore the errors during init time, return errors during set time)
only enable needed controllers.

I like 2 much better. Let's see if this can be done (and it will fix the above tests since looks like they do not set any limits)

kolyshkin · 2020-04-08T11:19:15Z

Added a commit to enable controllers only when required and on a best-effort basis.

cgroup-v2 is passing now. The tests I add/enable in #2295 are passing, too, on my test box.

kolyshkin · 2020-04-08T14:53:48Z

@crosbymichael @mrunalp PTAL

kolyshkin · 2020-04-08T18:50:23Z

@cyphar PTAL (at least for those two patches that add/remove securejoin usage)

kolyshkin · 2020-04-08T18:57:38Z

Rebased to resolve conflict after #2288 is merged

kolyshkin · 2020-04-08T18:58:57Z

Let me rework the last patch (enable controllers on demand) -- while it works fine, I don't like that neededControllers() has the intimate knowledge of all subsystems in one place.

Update: done

kolyshkin · 2020-04-08T19:19:57Z

@AkihiroSuda please let me know if you want me to split into two PRs, as this one might be too big to review. I tried hard to split it into small logical commits but there are too many.

kolyshkin · 2020-04-08T20:37:13Z

fixed a bug in last commit

AkihiroSuda · 2020-04-08T20:44:37Z

libcontainer/cgroups/fs2/cpu.go

 func setCpu(dirPath string, cgroup *configs.Cgroup) error {
+	if !isCpuSet(cgroup) {


Not sure whether this validation is useful.

The reason I added it is peculiar -- if someone will be modifying setCpu(), adding more fields to set, they will be reminded to also modify isCpuSet(). Having this check here might also help to uncover bugs.

E.g. someone adds cpuFoobar setting to setCpu(), but forgets to modify isCpuSet(). They add a unit test to check if cpuFoobar is applied, and the test fails! Hope it makes sense.

Can be just code comment lines?

Can be just code comment lines?

What do you mean? Add a comment like "if you're modifying this, don't forget to modify isSetCpu"? In my experience, this never works. The added runtime check might actually help to uncover such a bug.

Or do you mean adding a comment stating the reason why this check is added?

Or do you mean adding a comment stating the reason why this check is added?

I have amended the commit telling why is*Set is added to set*:

Amend all setFoo() functions to call isFooSet(). While this might
seem unnecessary, it might actually help to uncover a bug.
Imagine someone:

adds a cgroup.Resources.CpuFoo setting;

modifies setCpu() to apply the new setting;

but forgets to amend isCpuSet() accordingly <-- BUG

In this case, a test case modifying CpuFoo will help
to uncover the BUG. This is the reason why it's added.

I mean the former, but not a blocker

libcontainer/cgroups/fs2/cpuset.go

libcontainer/cgroups/fs2/create.go

AkihiroSuda · 2020-04-08T20:49:41Z

libcontainer/cgroups/systemd/common.go

+// systemd represents slice hierarchy using `-`, so we need to follow suit when
+// generating the path of slice. Essentially, test-a-b.slice becomes
+// /test.slice/test-a.slice/test-a-b.slice.
+func ExpandSlice(slice string) (string, error) {


Not new in this PR, but can we have UT for this?

Will do (maybe in a separate PR?)

Yes, can be a separate PR

libcontainer/factory_linux.go

AkihiroSuda · 2020-04-08T21:19:57Z

Looks good, but I'd like to merge the integration tests (#2295) before this.

Those needs to be run on the (Vagrant Fedora 31) host (since we need real systemd running), and so we have to have all the tools needed to compile runc and run the tests. The good news is Fedora packages a decent and recent release of bats-core (1.1.0), which we can use (Debian does not), and we can also use golang (currently 1.13.9) from Fedora. The bad news are 1. Currently cgroups tests are only working with RUNC_USE_SYSTEMD=yes (addressed by opencontainers#2299, opencontainers#2305) 2. Some tests that are not yet working: - ps.bats with RUNC_USE_SYSTEMD=yes (investigating) - events.bats (need cgroupv2 memory.events support) [v2: add -t to ssh to enforce pty] Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

Those needs to be run on the (Vagrant Fedora 31) host (since we need real systemd running), and so we have to have all the tools needed to compile runc and run the tests. The good news is Fedora packages a decent and recent release of bats-core (1.1.0), which we can use (Debian does not), and we can also use golang (currently 1.13.9) from Fedora. The bad news are 1. Currently cgroups tests are only working with RUNC_USE_SYSTEMD=yes (addressed by opencontainers#2299, opencontainers#2305) 2. Tests in events.bats do not work (need cgroupv2 memory.events support) [v2: add -t to ssh to enforce pty] [v3: disable events tests for cgroupv2] [v4: update container-selinux to fix ps tests] Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

Those needs to be run on the (Vagrant Fedora 31) host (since we need real systemd running), and so we have to have all the tools needed to compile runc and run the tests. The good news is Fedora packages a decent and recent release of bats-core (1.1.0), which we can use (Debian does not), and we can also use golang (currently 1.13.9) from Fedora. The bad news are 1. Currently cgroups tests are only working with RUNC_USE_SYSTEMD=yes (addressed by opencontainers#2299, opencontainers#2305) 2. Tests in events.bats do not work (need cgroupv2 memory.events support) 3. Fedora 31 image is 6 months old (and has broken container-selinux policy) so we need `dnf update`. [v2: add -t to ssh to enforce pty] [v3: disable events tests for cgroupv2] Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

kolyshkin · 2020-04-19T01:44:50Z

Disabled checkpoint tests (runc currently does not support cgroup v2 c/r). All others should pass

kolyshkin · 2020-04-19T02:22:29Z

Something ugly with CI -- logs for failed jobs are empty. Restarting

kolyshkin · 2020-04-19T15:36:15Z

This one is ready for merge.

@crosbymichael @mrunalp @filbranden PTAL

AkihiroSuda · 2020-04-19T16:05:12Z

LGTM

Having map of per-subsystem paths in systemd unified cgroups driver does not make sense and makes the code less readable. To get rid of it, move the systemd v1-or-v2 init code to libcontainer/factory_linux.go which already has a function to deduce unified path out of paths map. End result is much cleaner code. Besides, we no longer write pid to the same cgroup file 7 times in Apply() like we did before. While at it - add `rootless` flag which is passed on to fs2 manager - merge getv2Path() into GetUnifiedPath(), don't overwrite path if it is set during initialization (on Load). Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

It seems that some paths are coming from user and are therefore untrusted. Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

... and its Cgroup field. There is no sense to keep it public. This was generated by gorename. Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

The fs2 cgroup driver has a sanity check for path. Since systemd driver is relying on the same path, it makes sense to move this check to the common code. Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

fs2 cgroup driver was not working because it did not enable controllers while creating cgroup directory; instead it was merely doing MkdirAll() and gathered the list of available controllers in NewManager(). Also, cgroup should be created in Apply(), not while creating a new manager instance. To fix: 1. Move the createCgroupsv2Path function from systemd driver to fs2 driver, renaming it to CreateCgroupPath. Use in Apply() from both fs2 and systemd drivers. 2. Delay available controllers map initialization to until it is needed. With this patch: - NewManager() only performs minimal initialization (initializin m.dirPath, if not provided); - Apply() properly creates cgroup path, enabling the controllers; - m.controllers is initialized lazily on demand. Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

This check was removed in commit 5406833. Now, when this function is called from a few places, it is no longer obvious that the path always starts with /sys/fs/cgroup/, so reinstate the check just to be on the safe side. This check also ensures that elements[3:] can be used safely. Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

This slightly improves code readability. Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

1. Rename the files - v1.go: cgroupv1 aka legacy; - v2.go: cgroupv2 aka unified hierarchy; - unsupported.go: when systemd is not available. 2. Move the code that is common between v1 and v2 to common.go Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

1. Instead of enabling all available controllers, figure out which ones are required, and only enable those. 2. Amend all setFoo() functions to call isFooSet(). While this might seem unnecessary, it might actually help to uncover a bug. Imagine someone: - adds a cgroup.Resources.CpuFoo setting; - modifies setCpu() to apply the new setting; - but forgets to amend isCpuSet() accordingly <-- BUG In this case, a test case modifying CpuFoo will help to uncover the BUG. This is the reason why it's added. This patch *could be* amended by enabling controllers on a best-effort basis, i.e. : - do not return an error early if we can't enable some controllers; - if we fail to enable all controllers at once (usually because one of them can't be enabled), try enabling them one by one. Currently this is not implemented, and it's not clear whether this would be a good way to go or not. [v2: add/use is${Controller}Set() functions] [v3: document neededControllers()] [v4: drop "best-effort" part] Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

Run in the same environment as systemd tests. Disable CRIU tests because: - they all fail with cgroup v2; - CRIU v3.14 is required and it's not yet released, and rebuilding it from sources with patches applied (like it is currently done in Dockerfile) is too much work. Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

1. There is no need to try removing it recursively. 2. Do not treat ENOENT as an error (similar to fs and systemd v1 drivers). Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

AkihiroSuda · 2020-04-20T09:31:59Z

LGTM (still)

mrunalp · 2020-04-21T04:27:36Z

LGTM

AkihiroSuda · 2020-04-21T15:14:31Z

This commit caused regression #2339

kolyshkin mentioned this pull request Apr 7, 2020

Initial integration tests for cgroupv2 #2295

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AkihiroSuda requested changes Apr 8, 2020

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kolyshkin force-pushed the fs2-init-ctrl branch from ef0813a to 4ca9810 Compare April 8, 2020 18:56

kolyshkin force-pushed the fs2-init-ctrl branch from 4ca9810 to 3c277fb Compare April 8, 2020 19:17

kolyshkin requested a review from AkihiroSuda April 8, 2020 20:26

kolyshkin force-pushed the fs2-init-ctrl branch from 3c277fb to 8bbe881 Compare April 8, 2020 20:37

AkihiroSuda reviewed Apr 8, 2020

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kolyshkin force-pushed the fs2-init-ctrl branch 2 times, most recently from 4edf797 to 95e0b4e Compare April 8, 2020 21:17

kolyshkin mentioned this pull request Apr 9, 2020

cgroupv2 fs driver does not work with default cgroups path #2298

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kolyshkin force-pushed the fs2-init-ctrl branch from 95e0b4e to dcdc45b Compare April 13, 2020 23:46

kolyshkin force-pushed the fs2-init-ctrl branch 3 times, most recently from a040eda to 4fe6a28 Compare April 19, 2020 14:58

kolyshkin marked this pull request as ready for review April 19, 2020 15:35

kolyshkin added 11 commits April 19, 2020 16:19

cgroupv2: use SecureJoin in systemd driver

88c13c0

It seems that some paths are coming from user and are therefore untrusted. Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

cgroupv2/systemd: privatize UnifiedManager

dbeff89

... and its Cgroup field. There is no sense to keep it public. This was generated by gorename. Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

cgroupv2: move sanity path check to common code

60eaed2

The fs2 cgroup driver has a sanity check for path. Since systemd driver is relying on the same path, it makes sense to move this check to the common code. Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

cgroups/fs2/CreateCgroupPath: nit

de11341

This slightly improves code readability. Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

cgroup/systemd: reorganize

bb47e35

1. Rename the files - v1.go: cgroupv1 aka legacy; - v2.go: cgroupv2 aka unified hierarchy; - unsupported.go: when systemd is not available. 2. Move the code that is common between v1 and v2 to common.go Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

cgroups/fs2/Destroy: use Remove, ignore ENOENT

ab276b1

1. There is no need to try removing it recursively. 2. Do not treat ENOENT as an error (similar to fs and systemd v1 drivers). Signed-off-by: Kir Kolyshkin <kolyshkin@gmail.com>

kolyshkin force-pushed the fs2-init-ctrl branch from 4fe6a28 to ab276b1 Compare April 19, 2020 23:28

lifubang mentioned this pull request Apr 20, 2020

check that StartTransientUnit/StopUnit succeeds #2331

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kolyshkin added kind/bug area/cgroupv2 labels Apr 21, 2020

mrunalp merged commit 46be7b6 into opencontainers:master Apr 21, 2020

lifubang mentioned this pull request Apr 21, 2020

cgroupv2: fix Poststop hooks could not run when using systemd driver #2329

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AkihiroSuda mentioned this pull request Apr 21, 2020

cgroup2: \"open /sys/fs/cgroup/cgroup.subtree_control: permission denied\"": unknown. #2339

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kolyshkin mentioned this pull request Apr 21, 2020

fs2: fix cgroup.subtree_control EPERM on rootless + add CI #2340

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		func setCpu(dirPath string, cgroup *configs.Cgroup) error {
		if !isCpuSet(cgroup) {

cgroupv2: fix fs2 driver initialization #2299

cgroupv2: fix fs2 driver initialization #2299

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