Ensure that gang_copies is always at least as large as copies #17484
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13 tasks
amotin
approved these changes
Jun 24, 2025
As discussed in the comments of PR openzfs#17004, you can theoretically run into a case where a gang child has more copies than the gang header, which can lead to some odd accounting behavior (and even trip a VERIFY). While the accounting code could be changed to handle this, it fundamentally doesn't seem to make a lot of sense to allow this to happen. If the data is supposed to have a certain level of reliability, that isn't actually achieved unless the gang_copies property is set to match it. Signed-off-by: Paul Dagnelie <[email protected]> Sponsored-by: Klara, Inc. Sponsored-by: Wasabi Technology, Inc.
ixhamza
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to truenas/zfs
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Jul 14, 2025
As discussed in the comments of PR openzfs#17004, you can theoretically run into a case where a gang child has more copies than the gang header, which can lead to some odd accounting behavior (and even trip a VERIFY). While the accounting code could be changed to handle this, it fundamentally doesn't seem to make a lot of sense to allow this to happen. If the data is supposed to have a certain level of reliability, that isn't actually achieved unless the gang_copies property is set to match it. Sponsored-by: Klara, Inc. Sponsored-by: Wasabi Technology, Inc. Reviewed-by: Alexander Motin <[email protected]> Signed-off-by: Paul Dagnelie <[email protected]> Closes openzfs#17484
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Sponsored-by: Klara, Inc.
Sponsored-by: Wasabi Technology, Inc.
Motivation and Context
As discussed in the comments of PR #17004, you can theoretically run into a case where a gang child has more copies than the gang header, which can lead to some odd accounting behavior (and even trip a VERIFY). While the accounting code could be changed to handle this, it fundamentally doesn't seem to make a lot of sense to allow this to happen. If the data is supposed to have a certain level of reliability, that isn't actually achieved unless the gang_copies property is set to match it.
Description
We simply set the gang_copies property to be at least as high as the copies property at the end of
dmu_write_policy.How Has This Been Tested?
ZFS test suite, manually setting
dmu_ddt_copiesto 3.Types of changes
Checklist:
Signed-off-by.