TLDR; Show Me the Code!
-----------------------
-Code is posted to the kernel.org git trees as follows:
-`kernel changes <https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/log/?h=repair-symlink>`_,
-`userspace changes <https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfsprogs-dev.git/log/?h=scrub-media-scan-service>`_, and
-`QA test changes <https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfstests-dev.git/log/?h=repair-dirs>`_.
+Kernel and userspace code has been fully merged as of October 2025.
+
Each kernel patchset adding an online repair function will use the same branch
name across the kernel, xfsprogs, and fstests git repos.
and they enable XFS developers to find deficiencies in the code base.
Proposed patchsets include
-`general fuzzer improvements
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfstests-dev.git/log/?h=fuzzer-improvements>`_,
`fuzzing baselines
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfstests-dev.git/log/?h=fuzz-baseline>`_,
-and `improvements in fuzz testing comprehensiveness
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfstests-dev.git/log/?h=more-fuzz-testing>`_.
+<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfstests-dev.git/log/?h=fuzz-baseline>`_.
Stress Testing
--------------
any unexpected filesystem shutdowns due to corrupted metadata, kernel hang
check warnings, or any other sort of mischief.
-Proposed patchsets include `general stress testing
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfstests-dev.git/log/?h=race-scrub-and-mount-state-changes>`_
-and the `evolution of existing per-function stress testing
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfstests-dev.git/log/?h=refactor-scrub-stress>`_.
-
4. User Interface
=================
This measure was taken to minimize delays in the rest of the filesystem.
No such hardening has been performed for the cron job.
-Proposed patchset:
-`Enabling the xfs_scrub background service
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfsprogs-dev.git/log/?h=scrub-media-scan-service>`_.
-
Health Reporting
----------------
*Answer*: These questions remain unanswered, but should be a part of the
conversation with early adopters and potential downstream users of XFS.
-Proposed patchsets include
-`wiring up health reports to correction returns
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/log/?h=corruption-health-reports>`_
-and
-`preservation of sickness info during memory reclaim
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/log/?h=indirect-health-reporting>`_.
-
5. Kernel Algorithms and Data Structures
========================================
are there the same number of reverse mapping records for each block as the
reference count record claims?
-Proposed patchsets are the series to find gaps in
-`refcount btree
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/log/?h=scrub-detect-refcount-gaps>`_,
-`inode btree
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/log/?h=scrub-detect-inobt-gaps>`_, and
-`rmap btree
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/log/?h=scrub-detect-rmapbt-gaps>`_ records;
-to find
-`mergeable records
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/log/?h=scrub-detect-mergeable-records>`_;
-and to
-`improve cross referencing with rmap
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/log/?h=scrub-strengthen-rmap-checking>`_
-before starting a repair.
-
Checking Extended Attributes
````````````````````````````
To avoid polling in step 4, the drain provides a waitqueue for scrub threads to
be woken up whenever the intent count drops to zero.
-The proposed patchset is the
-`scrub intent drain series
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/log/?h=scrub-drain-intents>`_.
-
.. _jump_labels:
Static Keys (aka Jump Label Patching)
null record slot in the bag; and the ``xfarray_unset`` function removes a
record from the bag.
-The proposed patchset is the
-`big in-memory array
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/log/?h=big-array>`_.
-
Iterating Array Elements
^^^^^^^^^^^^^^^^^^^^^^^^
to cache a small number of entries before adding them to a temporary ondisk
file, which is why compaction is not required.
-The proposed patchset is at the start of the
-`extended attribute repair
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/log/?h=repair-xattrs>`_ series.
-
.. _xfbtree:
In-Memory B+Trees
Btrees built atop an xfile are collectively known as ``xfbtrees``.
The next few sections describe how they actually work.
-The proposed patchset is the
-`in-memory btree
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/log/?h=in-memory-btrees>`_
-series.
-
Using xfiles as a Buffer Cache Target
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
EFIs have a role to play during the commit and reaping phases; please see the
next section and the section about :ref:`reaping<reaping>` for more details.
-Proposed patchsets are the
-`bitmap rework
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/log/?h=repair-bitmap-rework>`_
-and the
-`preparation for bulk loading btrees
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/log/?h=repair-prep-for-bulk-loading>`_.
-
-
Writing the New Tree
````````````````````
but the record count for the free inode btree has to be computed as inode chunk
records are stored in the xfarray.
-The proposed patchset is the
-`AG btree repair
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/log/?h=repair-ag-btrees>`_
-series.
-
Case Study: Rebuilding the Space Reference Counts
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
removed via ``xfarray_unset``.
Bag members are examined through ``xfarray_iter`` loops.
-The proposed patchset is the
-`AG btree repair
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/log/?h=repair-ag-btrees>`_
-series.
-
Case Study: Rebuilding File Fork Mapping Indices
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Third, the incore extent map must be reloaded carefully to avoid disturbing
any delayed allocation extents.
-The proposed patchset is the
-`file mapping repair
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/log/?h=repair-file-mappings>`_
-series.
-
.. _reaping:
Reaping Old Metadata Blocks
As stated earlier, online repair functions use very large transactions to
minimize the chances of this occurring.
-The proposed patchset is the
-`preparation for bulk loading btrees
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/log/?h=repair-prep-for-bulk-loading>`_
-series.
-
Case Study: Reaping After a Regular Btree Repair
````````````````````````````````````````````````
btrees.
These blocks can then be reaped using the methods outlined above.
-The proposed patchset is the
-`AG btree repair
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/log/?h=repair-ag-btrees>`_
-series.
-
.. _rmap_reap:
Case Study: Reaping After Repairing Reverse Mapping Btrees
The rest of the process of rebuildng the reverse mapping btree is discussed
in a separate :ref:`case study<rmap_repair>`.
-The proposed patchset is the
-`AG btree repair
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/log/?h=repair-ag-btrees>`_
-series.
-
Case Study: Rebuilding the AGFL
```````````````````````````````
forks, or if that fails, leaving the fields invalid and waiting for the fork
fsck functions to run.
-The proposed patchset is the
-`inode
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/log/?h=repair-inodes>`_
-repair series.
-
Quota Record Repairs
--------------------
Quota usage counters are checked, repaired, and discussed separately in the
section about :ref:`live quotacheck <quotacheck>`.
-The proposed patchset is the
-`quota
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/log/?h=repair-quota>`_
-repair series.
-
.. _fscounters:
Freezing to Fix Summary Counters
| This bug was fixed in Linux 5.17. |
+--------------------------------------------------------------------------+
-The proposed patchset is the
-`summary counter cleanup
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/log/?h=repair-fscounters>`_
-series.
-
Full Filesystem Scans
---------------------
coordinator must release the AGI and push the main filesystem to get the inode
back into a loadable state.
-The proposed patches are the
-`inode scanner
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/log/?h=scrub-iscan>`_
-series.
-The first user of the new functionality is the
-`online quotacheck
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/log/?h=repair-quotacheck>`_
-series.
-
Inode Management
````````````````
function to set or clear the ``DONTCACHE`` flag to get the required release
behavior.
-Proposed patchsets include fixing
-`scrub iget usage
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/log/?h=scrub-iget-fixes>`_ and
-`dir iget usage
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/log/?h=scrub-dir-iget-fixes>`_.
-
.. _ilocking:
Locking Inodes
rename operation must have changed the child's parentage, and the scan can
exit early.
-The proposed patchset is the
-`directory repair
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/log/?h=repair-dirs>`_
-series.
-
.. _fshooks:
Filesystem Hooks
- ``xchk_iscan_teardown`` to finish the scan
-This functionality is also a part of the
-`inode scanner
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/log/?h=scrub-iscan>`_
-series.
-
.. _quotacheck:
Case Study: Quota Counter Checking
If repairs are desired, the real and shadow dquots are locked and their
resource counts are set to the values in the shadow dquot.
-The proposed patchset is the
-`online quotacheck
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/log/?h=repair-quotacheck>`_
-series.
-
.. _nlinks:
Case Study: File Link Count Checking
If no parents are found, the file must be :ref:`reparented <orphanage>` to the
orphanage to prevent the file from being lost forever.
-The proposed patchset is the
-`file link count repair
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/log/?h=scrub-nlinks>`_
-series.
-
.. _rmap_repair:
Case Study: Rebuilding Reverse Mapping Records
12. Free the xfbtree now that it not needed.
-The proposed patchset is the
-`rmap repair
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/log/?h=repair-rmap-btree>`_
-series.
-
Staging Repairs with Temporary Files on Disk
--------------------------------------------
must be conveyed to the file being repaired, which is the topic of the next
section.
-The proposed patches are in the
-`repair temporary files
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/log/?h=repair-tempfiles>`_
-series.
-
Logged File Content Exchanges
-----------------------------
in the superblock protects these new log item records from being replayed on
old kernels.
-The proposed patchset is the
-`file contents exchange
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/log/?h=atomic-file-updates>`_
-series.
-
+--------------------------------------------------------------------------+
| **Sidebar: Using Log-Incompatible Feature Flags** |
+--------------------------------------------------------------------------+
and use atomic mapping exchange to commit the new contents.
The temporary file is then reaped.
-The proposed patchset is the
-`realtime summary repair
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/log/?h=repair-rtsummary>`_
-series.
-
Case Study: Salvaging Extended Attributes
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
4. Reap the temporary file.
-The proposed patchset is the
-`extended attribute repair
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/log/?h=repair-xattrs>`_
-series.
-
Fixing Directories
------------------
every child dentry of a specific directory, which makes this a hard problem.
There is no known solution.
-The proposed patchset is the
-`directory repair
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/log/?h=repair-dirs>`_
-series.
-
Parent Pointers
```````````````
7. Reap the temporary directory.
-The proposed patchset is the
-`parent pointers directory repair
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/log/?h=pptrs-fsck>`_
-series.
-
Case Study: Repairing Parent Pointers
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
8. Reap the temporary file.
-The proposed patchset is the
-`parent pointers repair
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/log/?h=pptrs-fsck>`_
-series.
-
Digression: Offline Checking of Parent Pointers
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
4. Move on to examining link counts, as we do today.
-The proposed patchset is the
-`offline parent pointers repair
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfsprogs-dev.git/log/?h=pptrs-fsck>`_
-series.
-
Rebuilding directories from parent pointers in offline repair would be very
challenging because xfs_repair currently uses two single-pass scans of the
filesystem during phases 3 and 4 to decide which files are corrupt enough to be
6. If the subdirectory has zero paths, attach it to the lost and found.
-The proposed patches are in the
-`directory tree repair
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/log/?h=scrub-directory-tree>`_
-series.
-
-
.. _orphanage:
The Orphanage
7. If a runtime error happens, call ``xrep_adoption_cancel`` to release all
resources.
-The proposed patches are in the
-`orphanage adoption
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/log/?h=repair-orphanage>`_
-series.
-
6. Userspace Algorithms and Data Structures
===========================================
This doesn't completely solve the balancing problem, but reduces it enough to
move on to more pressing issues.
-The proposed patchsets are the scrub
-`performance tweaks
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfsprogs-dev.git/log/?h=scrub-performance-tweaks>`_
-and the
-`inode scan rebalance
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfsprogs-dev.git/log/?h=scrub-iscan-rebalance>`_
-series.
-
.. _scrubrepair:
Scheduling Repairs
Corrupt file data blocks reported by phase 6 cannot be recovered by the
filesystem.
-The proposed patchsets are the
-`repair warning improvements
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfsprogs-dev.git/log/?h=scrub-better-repair-warnings>`_,
-refactoring of the
-`repair data dependency
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfsprogs-dev.git/log/?h=scrub-repair-data-deps>`_
-and
-`object tracking
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfsprogs-dev.git/log/?h=scrub-object-tracking>`_,
-and the
-`repair scheduling
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfsprogs-dev.git/log/?h=scrub-repair-scheduling>`_
-improvement series.
-
Checking Names for Confusable Unicode Sequences
-----------------------------------------------
This emulates an atomic device write in software, and can support arbitrary
scattered writes.
+(This functionality was merged into mainline as of 2025)
+
Vectorized Scrub
----------------
online fsck can use that instead of adding a separate vectored scrub system
call to XFS.
-The relevant patchsets are the
-`kernel vectorized scrub
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfs-linux.git/log/?h=vectorized-scrub>`_
-and
-`userspace vectorized scrub
-<https://git.kernel.org/pub/scm/linux/kernel/git/djwong/xfsprogs-dev.git/log/?h=vectorized-scrub>`_
-series.
+(This functionality was merged into mainline as of 2025)
Quality of Service Targets for Scrub
------------------------------------