Merge tag 'bcachefs-2024-04-10' of https://evilpiepirate.org/git/bcachefs

Pull more bcachefs fixes from Kent Overstreet:
 "Notable user impacting bugs

   - On multi device filesystems, recovery was looping in
     btree_trans_too_many_iters(). This checks if a transaction has
     touched too many btree paths (because of iteration over many keys),
     and isuses a restart to drop unneeded paths.

     But it's now possible for some paths to exceed the previous limit
     without iteration in the interior btree update path, since the
     transaction commit will do alloc updates for every old and new
     btree node, and during journal replay we don't use the btree write
     buffer for locking reasons and thus those updates use btree paths
     when they wouldn't normally.

   - Fix a corner case in rebalance when moving extents on a
     durability=0 device. This wouldn't be hit when a device was
     formatted with durability=0 since in that case we'll only use it as
     a write through cache (only cached extents will live on it), but
     durability can now be changed on an existing device.

   - bch2_get_acl() could rarely forget to handle a transaction restart;
     this manifested as the occasional missing acl that came back after
     dropping caches.

   - Fix a major performance regression on high iops multithreaded write
     workloads (only since 6.9-rc1); a previous fix for a deadlock in
     the interior btree update path to check the journal watermark
     introduced a dependency on the state of btree write buffer flushing
     that we didn't want.

   - Assorted other repair paths and recovery fixes"

* tag 'bcachefs-2024-04-10' of https://evilpiepirate.org/git/bcachefs: (25 commits)
  bcachefs: Fix __bch2_btree_and_journal_iter_init_node_iter()
  bcachefs: Kill read lock dropping in bch2_btree_node_lock_write_nofail()
  bcachefs: Fix a race in btree_update_nodes_written()
  bcachefs: btree_node_scan: Respect member.data_allowed
  bcachefs: Don't scan for btree nodes when we can reconstruct
  bcachefs: Fix check_topology() when using node scan
  bcachefs: fix eytzinger0_find_gt()
  bcachefs: fix bch2_get_acl() transaction restart handling
  bcachefs: fix the count of nr_freed_pcpu after changing bc->freed_nonpcpu list
  bcachefs: Fix gap buffer bug in bch2_journal_key_insert_take()
  bcachefs: Rename struct field swap to prevent macro naming collision
  MAINTAINERS: Add entry for bcachefs documentation
  Documentation: filesystems: Add bcachefs toctree
  bcachefs: JOURNAL_SPACE_LOW
  bcachefs: Disable errors=panic for BCH_IOCTL_FSCK_OFFLINE
  bcachefs: Fix BCH_IOCTL_FSCK_OFFLINE for encrypted filesystems
  bcachefs: fix rand_delete unit test
  bcachefs: fix ! vs ~ typo in __clear_bit_le64()
  bcachefs: Fix rebalance from durability=0 device
  bcachefs: Print shutdown journal sequence number
  ...