Extend zdb to print inconsistencies in livelists and metaslabs #10515
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ahrens
added
Status: Code Review Needed
Codecov Report
@@ Coverage Diff @@
## master #10515 +/- ##
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- Coverage 79.71% 79.68% -0.03%
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Files 392 392
Lines 124609 124807 +198
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+ Hits 99327 99458 +131
- Misses 25282 25349 +67
Continue to review full report at Codecov.
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Thanks for opening this Matt. We'll need to update the tests |
Livelists and spacemaps are data structures that are logs of allocations and frees. Livelists entries are block pointers (blkptr_t). Spacemaps entries are ranges of numbers, most often used as to track allocated/freed regions of metaslabs/vdevs. These data structures can become self-inconsistent, for example if a block or range can be "double allocated" (two allocation records without an intervening free) or "double freed" (two free records without an intervening allocation). ZDB (as well as zfs running in the kernel) can detect these inconsistencies when loading livelists and metaslab. However, it generally halts processing when the error is detected. When analyzing an on-disk problem, we often want to know the entire set of inconsistencies, which is not possible with the current behavior. This commit adds a new flag, `zdb -y`, which analyzes the livelist and metaslab data structures and displays all of their inconsistencies. Note that this is different from the leak detection performed by `zdb -b`, which checks for inconsistencies between the spacemaps and the tree of block pointers, but assumes the spacemaps are self-consistent. The specific checks added are: Verify livelists by iterating through each sublivelists and: - report leftover FREEs - report double ALLOCs and double FREEs - record leftover ALLOCs together with their TXG [see Cross Check] Verify spacemaps by iterating over each metaslab and: - iterate over spacemap and then the metaslab's entries in the spacemap log, then report any double FREEs and double ALLOCs Verify that livelists are consistenet with spacemaps. The space referenced by livelists (after using the FREE's to cancel out corresponding ALLOCs) should be allocated, according to the spacemaps. External-issue: DLPX-66031 Signed-off-by: Matthew Ahrens <[email protected]>
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@shartse Thanks for the pointer, I've updated those tests. |
sdimitro
approved these changes
Jul 13, 2020
behlendorf
approved these changes
Jul 13, 2020
|
@shartse is there anything else you'd like to add this to PR. You mentioned doing another round of testing above. |
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Yeah, I'll do those tests today and report back |
shartse
approved these changes
Jul 15, 2020
behlendorf
added
Status: Accepted
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Great. Thanks for re-testing, then this is ready to integrate. |
jsai20
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to jsai20/zfs
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Mar 30, 2021
Livelists and spacemaps are data structures that are logs of allocations and frees. Livelists entries are block pointers (blkptr_t). Spacemaps entries are ranges of numbers, most often used as to track allocated/freed regions of metaslabs/vdevs. These data structures can become self-inconsistent, for example if a block or range can be "double allocated" (two allocation records without an intervening free) or "double freed" (two free records without an intervening allocation). ZDB (as well as zfs running in the kernel) can detect these inconsistencies when loading livelists and metaslab. However, it generally halts processing when the error is detected. When analyzing an on-disk problem, we often want to know the entire set of inconsistencies, which is not possible with the current behavior. This commit adds a new flag, `zdb -y`, which analyzes the livelist and metaslab data structures and displays all of their inconsistencies. Note that this is different from the leak detection performed by `zdb -b`, which checks for inconsistencies between the spacemaps and the tree of block pointers, but assumes the spacemaps are self-consistent. The specific checks added are: Verify livelists by iterating through each sublivelists and: - report leftover FREEs - report double ALLOCs and double FREEs - record leftover ALLOCs together with their TXG [see Cross Check] Verify spacemaps by iterating over each metaslab and: - iterate over spacemap and then the metaslab's entries in the spacemap log, then report any double FREEs and double ALLOCs Verify that livelists are consistenet with spacemaps. The space referenced by livelists (after using the FREE's to cancel out corresponding ALLOCs) should be allocated, according to the spacemaps. Reviewed-by: Serapheim Dimitropoulos <[email protected]> Reviewed-by: Brian Behlendorf <[email protected]> Co-authored-by: Sara Hartse <[email protected]> Signed-off-by: Matthew Ahrens <[email protected]> External-issue: DLPX-66031 Closes openzfs#10515
sempervictus
pushed a commit
to sempervictus/zfs
that referenced
this pull request
May 31, 2021
Livelists and spacemaps are data structures that are logs of allocations and frees. Livelists entries are block pointers (blkptr_t). Spacemaps entries are ranges of numbers, most often used as to track allocated/freed regions of metaslabs/vdevs. These data structures can become self-inconsistent, for example if a block or range can be "double allocated" (two allocation records without an intervening free) or "double freed" (two free records without an intervening allocation). ZDB (as well as zfs running in the kernel) can detect these inconsistencies when loading livelists and metaslab. However, it generally halts processing when the error is detected. When analyzing an on-disk problem, we often want to know the entire set of inconsistencies, which is not possible with the current behavior. This commit adds a new flag, `zdb -y`, which analyzes the livelist and metaslab data structures and displays all of their inconsistencies. Note that this is different from the leak detection performed by `zdb -b`, which checks for inconsistencies between the spacemaps and the tree of block pointers, but assumes the spacemaps are self-consistent. The specific checks added are: Verify livelists by iterating through each sublivelists and: - report leftover FREEs - report double ALLOCs and double FREEs - record leftover ALLOCs together with their TXG [see Cross Check] Verify spacemaps by iterating over each metaslab and: - iterate over spacemap and then the metaslab's entries in the spacemap log, then report any double FREEs and double ALLOCs Verify that livelists are consistenet with spacemaps. The space referenced by livelists (after using the FREE's to cancel out corresponding ALLOCs) should be allocated, according to the spacemaps. Reviewed-by: Serapheim Dimitropoulos <[email protected]> Reviewed-by: Brian Behlendorf <[email protected]> Co-authored-by: Sara Hartse <[email protected]> Signed-off-by: Matthew Ahrens <[email protected]> External-issue: DLPX-66031 Closes openzfs#10515
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Motivation and Context
Livelists and spacemaps are data structures that are logs of allocations
and frees. Livelists entries are block pointers (blkptr_t). Spacemaps
entries are ranges of numbers, most often used as to track
allocated/freed regions of metaslabs/vdevs.
These data structures can become self-inconsistent, for example if a
block or range can be "double allocated" (two allocation records without
an intervening free) or "double freed" (two free records without an
intervening allocation).
ZDB (as well as zfs running in the kernel) can detect these
inconsistencies when loading livelists and metaslab. However, it
generally halts processing when the error is detected.
Description
When analyzing an on-disk problem, we often want to know the entire set
of inconsistencies, which is not possible with the current behavior.
This commit adds a new flag,
zdb -y, which analyzes the livelist andmetaslab data structures and displays all of their inconsistencies.
Note that this is different from the leak detection performed by
zdb -b, which checks for inconsistencies between the spacemaps and thetree of block pointers, but assumes the spacemaps are self-consistent.
The specific checks added are:
Verify livelists by iterating through each sublivelists and:
Verify spacemaps by iterating over each metaslab and:
spacemap log, then report any double FREEs and double ALLOCs
Verify that livelists are consistenet with spacemaps. The space
referenced by livelists (after using the FREE's to cancel out
corresponding ALLOCs) should be allocated, according to the spacemaps.
Implemented by @shartse and @sdimitro.
How Has This Been Tested?
ztestrunszdbwith the new-yflag.Tested on a broken pool.
Types of changes
Checklist:
Signed-off-by.