zfs promote should delete livelist of origin #10652
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When a clone is promoted, its livelist is no longer accurate, so it is discarded. If the clone's origin is also a clone (i.e. we are promoting a clone of a clone), then the origin's livelist is also no longer accurate, so it should be discarded, but the code doesn't actually do that. Consider a pool with: * Filesystem A * Clone B, a clone of A * Clone C, a clone of B If we promote C, it discards C's livelist. It should discard B's livelist, but that is not happening. The impact is that when B is destroyed, we use the livelist to find the blocks to free, but the livelist is no longer correct so we end up freeing blocks that are still in use by C. The incorrectly-freed blocks can be reallocated causing checksum errors. And when C is destroyed it can double-free the incorrectly-freed blocks. The problem is that we remove the livelist of `origin_ds->ds_dir`, but the origin snapshot has already been moved to the promoted dsl_dir. So this is actually trying to remove the livelist of the promoted dsl_dir, which was already removed. As explained in a comment in the beginning of `dsl_dataset_promote_sync()`, we need to use the saved `odd` for the origin's dsl_dir. Signed-off-by: Matthew Ahrens <[email protected]>
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## master #10652 +/- ##
==========================================
- Coverage 79.52% 79.49% -0.04%
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Files 394 394
Lines 124631 124631
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- Hits 99118 99076 -42
- Misses 25513 25555 +42
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grwilson
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Jul 31, 2020
shartse
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Jul 31, 2020
behlendorf
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Jul 31, 2020
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Status: Accepted
pzakha
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Jul 31, 2020
jsai20
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When a clone is promoted, its livelist is no longer accurate, so it is discarded. If the clone's origin is also a clone (i.e. we are promoting a clone of a clone), then the origin's livelist is also no longer accurate, so it should be discarded, but the code doesn't actually do that. Consider a pool with: * Filesystem A * Clone B, a clone of A * Clone C, a clone of B If we promote C, it discards C's livelist. It should discard B's livelist, but that is not happening. The impact is that when B is destroyed, we use the livelist to find the blocks to free, but the livelist is no longer correct so we end up freeing blocks that are still in use by C. The incorrectly-freed blocks can be reallocated causing checksum errors. And when C is destroyed it can double-free the incorrectly-freed blocks. The problem is that we remove the livelist of `origin_ds->ds_dir`, but the origin snapshot has already been moved to the promoted dsl_dir. So this is actually trying to remove the livelist of the promoted dsl_dir, which was already removed. As explained in a comment in the beginning of `dsl_dataset_promote_sync()`, we need to use the saved `odd` for the origin's dsl_dir. Reviewed-by: Pavel Zakharov <[email protected]> Reviewed-by: Brian Behlendorf <[email protected]> Reviewed-by: George Wilson <[email protected]> Reviewed by: Sara Hartse <[email protected]> Signed-off-by: Matthew Ahrens <[email protected]> Closes openzfs#10652
sempervictus
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May 31, 2021
When a clone is promoted, its livelist is no longer accurate, so it is discarded. If the clone's origin is also a clone (i.e. we are promoting a clone of a clone), then the origin's livelist is also no longer accurate, so it should be discarded, but the code doesn't actually do that. Consider a pool with: * Filesystem A * Clone B, a clone of A * Clone C, a clone of B If we promote C, it discards C's livelist. It should discard B's livelist, but that is not happening. The impact is that when B is destroyed, we use the livelist to find the blocks to free, but the livelist is no longer correct so we end up freeing blocks that are still in use by C. The incorrectly-freed blocks can be reallocated causing checksum errors. And when C is destroyed it can double-free the incorrectly-freed blocks. The problem is that we remove the livelist of `origin_ds->ds_dir`, but the origin snapshot has already been moved to the promoted dsl_dir. So this is actually trying to remove the livelist of the promoted dsl_dir, which was already removed. As explained in a comment in the beginning of `dsl_dataset_promote_sync()`, we need to use the saved `odd` for the origin's dsl_dir. Reviewed-by: Pavel Zakharov <[email protected]> Reviewed-by: Brian Behlendorf <[email protected]> Reviewed-by: George Wilson <[email protected]> Reviewed by: Sara Hartse <[email protected]> Signed-off-by: Matthew Ahrens <[email protected]> Closes openzfs#10652
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Motivation and Context
When a clone is promoted, its livelist is no longer accurate, so it is
discarded. If the clone's origin is also a clone (i.e. we are promoting
a clone of a clone), then the origin's livelist is also no longer
accurate, so it should be discarded, but the code doesn't actually do
that.
Consider a pool with:
If we promote C, it discards C's livelist. It should discard B's
livelist, but that is not happening. The impact is that when B is
destroyed, we use the livelist to find the blocks to free, but the
livelist is no longer correct so we end up freeing blocks that are still
in use by C. The incorrectly-freed blocks can be reallocated causing
checksum errors. And when C is destroyed it can double-free the
incorrectly-freed blocks.
Description
The problem is that we remove the livelist of
origin_ds->ds_dir, butthe origin snapshot has already been moved to the promoted dsl_dir. So
this is actually trying to remove the livelist of the promoted dsl_dir,
which was already removed. As explained in a comment in the beginning
of
dsl_dataset_promote_sync(), we need to use the savedoddfor theorigin's dsl_dir.
Note: this problem is not present in any release (including 0.8.x), because the livelist feature is only present in the main branch.
How Has This Been Tested?
new test case
Types of changes
Checklist:
Signed-off-by.