mds: fix rank 0 marked damaged if stopping fails after Elid flush.#65483
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mds: fix rank 0 marked damaged if stopping fails after Elid flush.#65483
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batrick
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Sep 11, 2025
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Great bug report/reproducer, thanks!
src/mds/MDSRank.cc
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| // funny case: is our cache empty? no subtrees? | ||
| if (!mdcache->is_subtrees()) { | ||
| if (whoami == 0) { | ||
| if (whoami == 0 && !mdlog->is_elid_only_journal()) { |
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Suggested change
| if (whoami == 0 && !mdlog->is_elid_only_journal()) { | |
| if (whoami == 0 && mdlog->get_num_events() > 1) { |
is sufficient I think.
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It works and is more concise. I apply the suggested changes and add comments. thanks!
… log trimmed steps to reproduce ../src/vstart.sh --debug --new -x --localhost --bluestore ./bin/ceph tell mds.<rank 0> config set mds_kill_shutdown_at 10 ./bin/ceph fs set <fs name> down true wait for a few seconds and will see the following log from take-over mds and rank 0 is marked damaged 2025-09-11T16:47:24.591+0800 785dabeaa6c0 -1 log_channel(cluster) log [ERR] : No subtrees found for root MDS rank! 2025-09-11T16:47:24.591+0800 785dabeaa6c0 5 mds.beacon.b set_want_state: up:rejoin -> down:damaged During shutdown_pass after submitting Elid and trimming mdlog, mds log will now have only ELid event which does nothing at replay. After replay, no subtree is found. Fix this by checking whther MDLog contains only one event. If so, skip the subtree check for rank 0, and allow it to request STATE_STOPPED just like the other ranks. Fixes: https://tracker.ceph.com/issues/72983 Signed-off-by: ethanwu <ethanwu@synology.com>
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batrick
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Sep 12, 2025
vshankar
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Sep 16, 2025
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This PR is under test in https://tracker.ceph.com/issues/73082. |
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* refs/pull/65483/head: Reviewed-by: Venky Shankar <vshankar@redhat.com> Reviewed-by: Patrick Donnelly <pdonnell@ibm.com>
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This is good to merge 👍 |
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This was referenced Oct 4, 2025
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way to reproduce
../src/vstart.sh --debug --new -x --localhost --bluestore
./bin/ceph tell mds.<rank 0> config set mds_kill_shutdown_at 10
./bin/ceph fs set down true
wait for a few seconds and will see the following log from take-over mds and rank 0 is mark damaged
2025-09-11T16:47:24.591+0800 785dabeaa6c0 -1 log_channel(cluster) log [ERR] : No subtrees found for root MDS rank! 2025-09-11T16:47:24.591+0800 785dabeaa6c0 5 mds.beacon.b set_want_state: up:rejoin -> down:damaged
During shutdown_pass after submitting Elid and trimming mdlog, mds log will now have only ELid event which doesn't do anything at replay. so after replay, no subtree is found.
Fix this by checking MDLog if there's only ELid event. If so, don't check subtree for rank 0, and let it request STATE_STOPPED just as other rank does.
Fixes: https://tracker.ceph.com/issues/72983
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