A couple more small fixes, and new repair code.
We can now automatically recover from arbitrary corrupted interior btree
nodes by scanning, and we can reconstruct metadata as needed to bring a
filesystem back into a working, consistent, read-write state and
preserve access to whatevver wasn't corrupted.
Meaning - you can blow away all metadata except for extents and dirents
leaf nodes, and repair will reconstruct everything else and give you
your data, and under the correct paths. If inodes are missing i_size
will be slightly off and permissions/ownership/timestamps will be gone,
and we do still need the snapshots btree if snapshots were in use - in
the future we'll be able to guess the snapshot tree structure in some
situations.
IOW - aside from shaking out remaining bugs (fuzz testing is still
coming), repair code should be complete and if repair ever doesn't work
that's the highest priority bug that I want to know about immediately.
This patchset was kindly tested by a user from India who accidentally
wiped one drive out of a three drive filesystem with no replication on
the family computer - it took a couple weeks but we got everything
important back.
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Merge tag 'bcachefs-2024-04-03' of https://evilpiepirate.org/git/bcachefs
Pull bcachefs repair code from Kent Overstreet:
"A couple more small fixes, and new repair code.
We can now automatically recover from arbitrary corrupted interior
btree nodes by scanning, and we can reconstruct metadata as needed to
bring a filesystem back into a working, consistent, read-write state
and preserve access to whatevver wasn't corrupted.
Meaning - you can blow away all metadata except for extents and
dirents leaf nodes, and repair will reconstruct everything else and
give you your data, and under the correct paths. If inodes are missing
i_size will be slightly off and permissions/ownership/timestamps will
be gone, and we do still need the snapshots btree if snapshots were in
use - in the future we'll be able to guess the snapshot tree structure
in some situations.
IOW - aside from shaking out remaining bugs (fuzz testing is still
coming), repair code should be complete and if repair ever doesn't
work that's the highest priority bug that I want to know about
immediately.
This patchset was kindly tested by a user from India who accidentally
wiped one drive out of a three drive filesystem with no replication on
the family computer - it took a couple weeks but we got everything
important back"
* tag 'bcachefs-2024-04-03' of https://evilpiepirate.org/git/bcachefs:
bcachefs: reconstruct_inode()
bcachefs: Subvolume reconstruction
bcachefs: Check for extents that point to same space
bcachefs: Reconstruct missing snapshot nodes
bcachefs: Flag btrees with missing data
bcachefs: Topology repair now uses nodes found by scanning to fill holes
bcachefs: Repair pass for scanning for btree nodes
bcachefs: Don't skip fake btree roots in fsck
bcachefs: bch2_btree_root_alloc() -> bch2_btree_root_alloc_fake()
bcachefs: Etyzinger cleanups
bcachefs: bch2_shoot_down_journal_keys()
bcachefs: Clear recovery_passes_required as they complete without errors
bcachefs: ratelimit informational fsck errors
bcachefs: Check for bad needs_discard before doing discard
bcachefs: Improve bch2_btree_update_to_text()
mean_and_variance: Drop always failing tests
bcachefs: fix nocow lock deadlock
bcachefs: BCH_WATERMARK_interior_updates
bcachefs: Fix btree node reserve
ec25bd8d98