Livelist logic should handle dedup blkptrs #12177
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= Problem When the livelist logic was designed it didn't take into account that when dedup is enabled the sublivelists can have consecutive FREE entries for the same block without an ALLOC entry for it in-between them. This caused panics in systems that were deleting/condesing clones where dedup is enabled. = This patch Update the logic to handle the dedup-case of consecutive FREEs in the livelist code. The logic still ensured that all the FREE entries are matched up with a respective ALLOC by keeping a refcount for each FREE blkptr that we encounter and ensuring that this refcount gets to zero by the time we are done processing the livelist. = Testing After I reproduced the issue with a shell script, I added a variant of that shell script to ZTS. After ensuring that this new test panics the system the same way as the original reproducer I tried it against the updated logic in this patch and verified that the system no longer panics. = Side Fixes * zdb -y no longer panics when encountering double frees Signed-off-by: Serapheim Dimitropoulos <[email protected]> Closes openzfs#11480
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ahrens
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Status: Accepted
behlendorf
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Jun 8, 2021
Update the logic to handle the dedup-case of consecutive FREEs in the livelist code. The logic still ensures that all the FREE entries are matched up with a respective ALLOC by keeping a refcount for each FREE blkptr that we encounter and ensuring that this refcount gets to zero by the time we are done processing the livelist. zdb -y no longer panics when encountering double frees Reviewed-by: Matthew Ahrens <[email protected]> Reviewed-by: John Kennedy <[email protected]> Reviewed-by: Don Brady <[email protected]> Signed-off-by: Serapheim Dimitropoulos <[email protected]> Closes openzfs#11480 Closes openzfs#12177
behlendorf
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Jun 8, 2021
Update the logic to handle the dedup-case of consecutive FREEs in the livelist code. The logic still ensures that all the FREE entries are matched up with a respective ALLOC by keeping a refcount for each FREE blkptr that we encounter and ensuring that this refcount gets to zero by the time we are done processing the livelist. zdb -y no longer panics when encountering double frees Reviewed-by: Matthew Ahrens <[email protected]> Reviewed-by: John Kennedy <[email protected]> Reviewed-by: Don Brady <[email protected]> Signed-off-by: Serapheim Dimitropoulos <[email protected]> Closes openzfs#11480 Closes openzfs#12177
behlendorf
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Jun 9, 2021
Update the logic to handle the dedup-case of consecutive FREEs in the livelist code. The logic still ensures that all the FREE entries are matched up with a respective ALLOC by keeping a refcount for each FREE blkptr that we encounter and ensuring that this refcount gets to zero by the time we are done processing the livelist. zdb -y no longer panics when encountering double frees Reviewed-by: Matthew Ahrens <[email protected]> Reviewed-by: John Kennedy <[email protected]> Reviewed-by: Don Brady <[email protected]> Signed-off-by: Serapheim Dimitropoulos <[email protected]> Closes openzfs#11480 Closes openzfs#12177
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Aug 7, 2021
Update the logic to handle the dedup-case of consecutive FREEs in the livelist code. The logic still ensures that all the FREE entries are matched up with a respective ALLOC by keeping a refcount for each FREE blkptr that we encounter and ensuring that this refcount gets to zero by the time we are done processing the livelist. zdb -y no longer panics when encountering double frees Reviewed-by: Matthew Ahrens <[email protected]> Reviewed-by: John Kennedy <[email protected]> Reviewed-by: Don Brady <[email protected]> Signed-off-by: Serapheim Dimitropoulos <[email protected]> Closes openzfs#11480 Closes openzfs#12177
tonyhutter
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Sep 13, 2021
Update the logic to handle the dedup-case of consecutive FREEs in the livelist code. The logic still ensures that all the FREE entries are matched up with a respective ALLOC by keeping a refcount for each FREE blkptr that we encounter and ensuring that this refcount gets to zero by the time we are done processing the livelist. zdb -y no longer panics when encountering double frees Reviewed-by: Matthew Ahrens <[email protected]> Reviewed-by: John Kennedy <[email protected]> Reviewed-by: Don Brady <[email protected]> Signed-off-by: Serapheim Dimitropoulos <[email protected]> Closes openzfs#11480 Closes openzfs#12177
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Sep 21, 2021
Update the logic to handle the dedup-case of consecutive FREEs in the livelist code. The logic still ensures that all the FREE entries are matched up with a respective ALLOC by keeping a refcount for each FREE blkptr that we encounter and ensuring that this refcount gets to zero by the time we are done processing the livelist. zdb -y no longer panics when encountering double frees Reviewed-by: Matthew Ahrens <[email protected]> Reviewed-by: John Kennedy <[email protected]> Reviewed-by: Don Brady <[email protected]> Signed-off-by: Serapheim Dimitropoulos <[email protected]> Closes #11480 Closes #12177
tonyhutter
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Sep 22, 2021
Update the logic to handle the dedup-case of consecutive FREEs in the livelist code. The logic still ensures that all the FREE entries are matched up with a respective ALLOC by keeping a refcount for each FREE blkptr that we encounter and ensuring that this refcount gets to zero by the time we are done processing the livelist. zdb -y no longer panics when encountering double frees Reviewed-by: Matthew Ahrens <[email protected]> Reviewed-by: John Kennedy <[email protected]> Reviewed-by: Don Brady <[email protected]> Signed-off-by: Serapheim Dimitropoulos <[email protected]> Closes #11480 Closes #12177
ghost
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Oct 7, 2021
Update the logic to handle the dedup-case of consecutive FREEs in the livelist code. The logic still ensures that all the FREE entries are matched up with a respective ALLOC by keeping a refcount for each FREE blkptr that we encounter and ensuring that this refcount gets to zero by the time we are done processing the livelist. zdb -y no longer panics when encountering double frees Reviewed-by: Matthew Ahrens <[email protected]> Reviewed-by: John Kennedy <[email protected]> Reviewed-by: Don Brady <[email protected]> Signed-off-by: Serapheim Dimitropoulos <[email protected]> Closes openzfs#11480 Closes openzfs#12177
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= Problem
When the livelist logic was designed it didn't take into
account that when dedup is enabled the sublivelists can
have consecutive FREE entries for the same block without
an ALLOC entry for it in-between them. This caused panics
in systems that were deleting/condesing clones where dedup
is enabled.
= This patch
Update the logic to handle the dedup-case of consecutive
FREEs in the livelist code. The logic still ensured that
all the FREE entries are matched up with a respective
ALLOC by keeping a refcount for each FREE blkptr that we
encounter and ensuring that this refcount gets to zero
by the time we are done processing the livelist.
= Testing
After I reproduced the issue with a shell script, I added
a variant of that shell script to ZTS. After ensuring that
this new test panics the system the same way as the original
reproducer I tried it against the updated logic in this
patch and verified that the system no longer panics.
= Side Fixes
Signed-off-by: Serapheim Dimitropoulos [email protected]
Closes #11480