Fix trailing / when a file is bind-mounted

[eagleonhill]

Fix an issue where a trailing / is added when a file bind mount is used in check-pointing.
E.g. I have a /etc/hosts in workspace mounted from the host, and get the following message.

(00.141008)      1: mnt-v2: Create plain mountpoint /tmp/.criu.mntns.K1biY1/mnt-0000000938 for 938
(00.141546)      1: mnt-v2:     Mounting unsupported @938 (0)
(00.141887)      1: mnt-v2:     Bind /tmp/agent/1-d8c746c6fda3a8b2/workspace/etc/hosts/ to /tmp/.criu.mntns.K1biY1/mnt-0000000938
(00.142179)      1: Error (criu/mount-v2.c:319): mnt-v2: Failed to open_tree /tmp/agent/1-d8c746c6fda3a8b2/workspace/etc/hosts/: Not a directory
(00.143774) Error (criu/cr-restore.c:2320): Restoring FAILED.

[Snorch]

Code looks correct. But maybe it's better to instead remove trailing slashes in plain_mountpoint in or just after detect_is_dir() where we know if it's file or directory bindmount.

There is no signed-off-by in the commit message, @eagleonhill can you please update the commit to have:

Signed-off-by: Chuan Qiu <[email protected]>

see https://github.com/checkpoint-restore/criu/blob/criu-dev/CONTRIBUTING.md#developers-certificate-of-origin-11

Also while on it, please add "mount: " prefix to your commit subject and put PR description into commit message to explain things.
see https://github.com/checkpoint-restore/criu/blob/criu-dev/CONTRIBUTING.md#describe-your-changes

I believe fix is simple enough to merge without test (if it's confirmed that it helps in this situation). But we need a regression test in zdtm so that we know that we don't break this case in future.

[Snorch]

I've rewrote the test

• we should not use shared mounts when we don't need them
• in your case auto mount detection code will probably not be hit
• test should be in separate commit

[avagin]

LGTM. Thanks a lot.

[Snorch]

Still one test fails:

https://github.com/checkpoint-restore/criu/actions/runs/15791341032/job/44517392026?pr=2682
https://productionresultssa12.blob.core.windows.net/actions-results/f7c2ad75-0ecb-419d-94d8-737e32f582a3/workflow-job-run-a4cfd10f-f68f-50f4-9e49-82e92fd1600e/logs/job/job-logs.txt?rsct=text%2Fplain&se=2025-06-21T04%3A03%3A40Z&sig=agduxqQ1D4f%2B4gPCd63PAj9bW7Q7WRJ%2B%2FVjmDWQoiKc%3D&ske=2025-06-21T13%3A03%3A03Z&skoid=ca7593d4-ee42-46cd-af88-8b886a2f84eb&sks=b&skt=2025-06-21T01%3A03%3A03Z&sktid=398a6654-997b-47e9-b12b-9515b896b4de&skv=2025-05-05&sp=r&spr=https&sr=b&st=2025-06-21T03%3A53%3A35Z&sv=2025-05-05

2025-06-21T03:18:18.4387595Z + ./test/zdtm.py run -t zdtm/static/env00 --freezecg zdtm:t --fault 137
2025-06-21T03:18:18.5195779Z userns is supported
...
2025-06-21T03:18:19.2358397Z ========================= Run zdtm/static/env00 in uns =========================
2025-06-21T03:18:19.3086196Z Start test
2025-06-21T03:18:19.3572268Z ./env00 --pidfile=env00.pid --outfile=env00.out --envname=ENV_00_TEST
...
2025-06-21T03:18:19.6194172Z =[log]=> dump/zdtm/static/env00/197/1/restore.log
2025-06-21T03:18:19.6194515Z ------------------------ grep Error ------------------------
2025-06-21T03:18:19.6195032Z b'profiling:/home/runner/work/criu/criu/images/core-mips.gcda:Cannot open'
2025-06-21T03:18:19.6195562Z b'profiling:/home/runner/work/criu/criu/images/core-x86.gcda:Cannot open'
2025-06-21T03:18:19.6196073Z b'profiling:/home/runner/work/criu/criu/images/core.gcda:Cannot open'
2025-06-21T03:18:19.6196562Z b'profiling:/home/runner/work/criu/criu/images/stats.gcda:Cannot open'
2025-06-21T03:18:19.6196954Z b'Error: ipv4: Address already assigned.'
2025-06-21T03:18:19.6197433Z b'Error: ipv6: address already assigned.'
2025-06-21T03:18:19.6197753Z b'(00.067006)      1: mnt-v2: Mount 690 is detected as dir-mount'
2025-06-21T03:18:19.6198227Z b'(00.067008)      1: mnt-v2: Create plain mountpoint /tmp/.criu.mntns.CH1Sn5/mnt-0000000690 for 690'
2025-06-21T03:18:19.6198701Z b'(00.067013)      1: mnt-v2: \tMounting unsupported @690 (0)'
2025-06-21T03:18:19.6199189Z b'(00.067015)      1: mnt-v2: \tBind /home/runner/work/criu/criu to /tmp/.criu.mntns.CH1Sn5/mnt-0000000690'
2025-06-21T03:18:19.6199928Z b'(00.067025)      1: Error (criu/mount-v2.c:319): mnt-v2: Failed to open_tree /home/runner/work/criu/criu: Invalid argument'
2025-06-21T03:18:19.6200427Z b'(00.067742) uns: calling exit_usernsd (-1, 1)'
2025-06-21T03:18:19.6200751Z b'(00.067769) uns: daemon calls 0x557ef0d92410 (222, -1, 1)'
2025-06-21T03:18:19.6201057Z b'(00.067773) uns: `- daemon exits w/ 0'
2025-06-21T03:18:19.6201325Z b'(00.071092) uns: daemon stopped'
2025-06-21T03:18:19.6201630Z b'(00.071101) Error (criu/cr-restore.c:2324): Restoring FAILED.'
2025-06-21T03:18:19.6202094Z b'(00.074514) Error (criu/cgroup.c:1998): cg: cgroupd: recv req error: No such file or directory'
2025-06-21T03:18:19.6202543Z ------------------------ ERROR OVER ------------------------
2025-06-21T03:18:19.6202916Z ################# Test zdtm/static/env00 FAIL at CRIU restore ##################

I will look next week, but this does not reproduce on my node (also I'm not sure how fix in resolve_external_mounts can affect env00 test without automatic external mount resolving...).

[eagleonhill]

I've rewrote the test

• we should not use shared mounts when we don't need them
• in your case auto mount detection code will probably not be hit
• test should be in separate commit

Thanks for updating the test. Just to confirm this updated test will repro the original issue before the fix.