Merge tag 'bcachefs-2025-03-24' of git://evilpiepirate.org/bcachefs

Merge tag 'bcachefs-2025-03-24' of git://evilpiepirate.org/bcachefs

Pull bcachefs updates from Kent Overstreet:
 "On disk format is now soft frozen: no more required/automatic are
  anticipated before taking off the experimental label.

  Major changes/features since 6.14:

   - Scrub

   - Blocksize greater than page size support

   - A number of "rebalance spinning and doing no work" issues have been
     fixed; we now check if the write allocation will succeed in
     bch2_data_update_init(), before kicking off the read.

     There's still more work to do in this area. Later we may want to
     add another bitset btree, like rebalance_work, to track "extents
     that rebalance was requested to move but couldn't", e.g. due to
     destination target having insufficient online devices.

   - We can now support scaling well into the petabyte range: latest
     bcachefs-tools will pick an appropriate bucket size at format time
     to ensure fsck can run in available memory (e.g. a server with
     256GB of ram and 100PB of storage would want 16MB buckets).

  On disk format changes:

   - 1.21: cached backpointers (scalability improvement)

     Cached replicas now get backpointers, which means we no longer rely
     on incrementing bucket generation numbers to invalidate cached
     data: this lets us get rid of the bucket generation number garbage
     collection, which had to periodically rescan all extents to
     recompute bucket oldest_gen.

     Bucket generation numbers are now only used as a consistency check,
     but they're quite useful for that.

   - 1.22: stripe backpointers

     Stripes now have backpointers: erasure coded stripes have their own
     checksums, separate from the checksums for the extents they contain
     (and stripe checksums also cover the parity blocks). This is
     required for implementing scrub for stripes.

   - 1.23: stripe lru (scalability improvement)

     Persistent lru for stripes, ordered by "number of empty blocks".
     This is used by the stripe creation path, which depending on free
     space may create a new stripe out of a partially empty existing
     stripe instead of starting a brand new stripe.

     This replaces an in-memory heap, and means we no longer have to
     read in the stripes btree at startup.

   - 1.24: casefolding

     Case insensitive directory support, courtesy of Valve.

     This is an incompatible feature, to enable mount with
       -o version_upgrade=incompatible

   - 1.25: extent_flags

     Another incompatible feature requiring explicit opt-in to enable.

     This adds a flags entry to extents, and a flag bit that marks
     extents as poisoned.

     A poisoned extent is an extent that was unreadable due to checksum
     errors. We can't move such extents without giving them a new
     checksum, and we may have to move them (for e.g. copygc or device
     evacuate). We also don't want to delete them: in the future we'll
     have an API that lets userspace ignore checksum errors and attempt
     to deal with simple bitrot itself. Marking them as poisoned lets us
     continue to return the correct error to userspace on normal read
     calls.

  Other changes/features:

   - BCH_IOCTL_QUERY_COUNTERS: this is used by the new 'bcachefs fs top'
     command, which shows a live view of all internal filesystem
     counters.

   - Improved journal pipelining: we can now have 16 journal writes in
     flight concurrently, up from 4. We're logging significantly more to
     the journal than we used to with all the recent disk accounting
     changes and additions, so some users should see a performance
     increase on some workloads.

   - BCH_MEMBER_STATE_failed: previously, we would do no IO at all to
     devices marked as failed. Now we will attempt to read from them,
     but only if we have no better options.

   - New option, write_error_timeout: devices will be kicked out of the
     filesystem if all writes have been failing for x number of seconds.

     We now also kick devices out when notified by blk_holder_ops that
     they've gone offline.

   - Device option handling improvements: the discard option should now
     be working as expected (additionally, in -tools, all device options
     that can be set at format time can now be set at device add time,
     i.e. data_allowed, state).

   - We now try harder to read data after a checksum error: we'll do
     additional retries if necessary to a device after after it gave us
     data with a checksum error.

   - More self healing work: the full inode <-> dirent consistency
     checks that are currently run by fsck are now also run every time
     we do a lookup, meaning we'll be able to correct errors at runtime.
     Runtime self healing will be flipped on after the new changes have
     seen more testing, currently they're just checking for consistency.

   - KMSAN fixes: our KMSAN builds should be nearly clean now, which
     will put a massive dent in the syzbot dashboard"

* tag 'bcachefs-2025-03-24' of git://evilpiepirate.org/bcachefs: (180 commits)
  bcachefs: Kill unnecessary bch2_dev_usage_read()
  bcachefs: btree node write errors now print btree node
  bcachefs: Fix race in print_chain()
  bcachefs: btree_trans_restart_foreign_task()
  bcachefs: bch2_disk_accounting_mod2()
  bcachefs: zero init journal bios
  bcachefs: Eliminate padding in move_bucket_key
  bcachefs: Fix a KMSAN splat in btree_update_nodes_written()
  bcachefs: kmsan asserts
  bcachefs: Fix kmsan warnings in bch2_extent_crc_pack()
  bcachefs: Disable asm memcpys when kmsan enabled
  bcachefs: Handle backpointers with unknown data types
  bcachefs: Count BCH_DATA_parity backpointers correctly
  bcachefs: Run bch2_check_dirent_target() at lookup time
  bcachefs: Refactor bch2_check_dirent_target()
  bcachefs: Move bch2_check_dirent_target() to namei.c
  bcachefs: fs-common.c -> namei.c
  bcachefs: EIO cleanup
  bcachefs: bch2_write_prep_encoded_data() now returns errcode
  bcachefs: Simplify bch2_write_op_error()
  ...