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6774931dfa
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 <serapheim@delphix.com> Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov> Co-authored-by: Sara Hartse <sara.hartse@delphix.com> Signed-off-by: Matthew Ahrens <mahrens@delphix.com> External-issue: DLPX-66031 Closes #10515 |
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