Revert "osd/OSDMap: allow bidirectional swap of pg-upmap-items" #17760
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This reverts commit 09af9b8. We need to prevent duplicates in the final result. For example, we can currently take [1,2,3] and apply [(1,2)] and get [2,2,3] or [1,2,3] and apply [(3,2)] and get [1,2,2] The rest of the system is not prepared to handle duplicates in the result set like this. The reverted commit was intended to allow [1,2,3] and [(1,2),(2,1)] to get [2,1,3] to reorder primaries. First, this bidirectional swap is hard to implement in a way that also prevents dups. For example, [1,2,3] and [(1,4),(2,3),(3,4)] would give [4,3,4] but would we just drop the last step we'd have [4,3,3] which is also invalid, etc. Simpler to just not handle bidirectional swaps. In practice, they are not needed: if you just want to choose a different primary then use primary_affinity, or pg_upmap (not pg_upmap_items). Fixes: http://tracker.ceph.com/issues/21410 Signed-off-by: Sage Weil <sage@redhat.com>
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Sigh... whatever fix we use will need to go upstream in the kernel too, @idryomov! |
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@liewegas ack |
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This reverts commit 09af9b8.
We need to prevent duplicates in the final result. For example, we
can currently take
[1,2,3] and apply [(1,2)] and get [2,2,3]
or
[1,2,3] and apply [(3,2)] and get [1,2,2]
The rest of the system is not prepared to handle duplicates in the
result set like this.
The reverted commit was intended to allow
[1,2,3] and [(1,2),(2,1)] to get [2,1,3]
to reorder primaries. First, this bidirectional swap is hard to implement
in a way that also prevents dups. For example,
[1,2,3] and [(1,4),(2,3),(3,4)] would give [4,3,4]
but would we just drop the last step we'd have [4,3,3] which
is also invalid, etc. Simpler to just not handle bidirectional
swaps. In practice, they are not needed: if you just want to choose
a different primary then use primary_affinity, or pg_upmap
(not pg_upmap_items).
Fixes: http://tracker.ceph.com/issues/21410
Signed-off-by: Sage Weil sage@redhat.com