Merge tag 'bcachefs-2024-06-28' of https://evilpiepirate.org/git/bcachefs

Pull bcachefs fixes from Kent Overstreet:
 "Simple stuff:

   - NULL ptr/err ptr deref fixes

   - fix for getting wedged on shutdown after journal error

   - fix missing recalc_capacity() call, capacity now changes correctly
     after a device goes read only

     however: our capacity calculation still doesn't take into account
     when we have mixed ro/rw devices and the ro devices have data on
     them, that's going to be a more involved fix to separate accounting
     for "capacity used on ro devices" and "capacity used on rw devices"

   - boring syzbot stuff

  Slightly more involved:

   - discard, invalidate workers are now per device

     this has the effect of simplifying how we take device refs in these
     paths, and the device ref cleanup fixes a longstanding race between
     the device removal path and the discard path

   - fixes for how the debugfs code takes refs on btree_trans objects we
     have debugfs code that prints in use btree_trans objects.

     It uses closure_get() on trans->ref, which is mainly for the cycle
     detector, but the debugfs code was using it on a closure that may
     have hit 0, which is not allowed; for performance reasons we cannot
     avoid having not-in-use transactions on the global list.

     Introduce some new primitives to fix this and make the
     synchronization here a whole lot saner"

* tag 'bcachefs-2024-06-28' of https://evilpiepirate.org/git/bcachefs:
  bcachefs: Fix kmalloc bug in __snapshot_t_mut
  bcachefs: Discard, invalidate workers are now per device
  bcachefs: Fix shift-out-of-bounds in bch2_blacklist_entries_gc
  bcachefs: slab-use-after-free Read in bch2_sb_errors_from_cpu
  bcachefs: Add missing bch2_journal_do_writes() call
  bcachefs: Fix null ptr deref in journal_pins_to_text()
  bcachefs: Add missing recalc_capacity() call
  bcachefs: Fix btree_trans list ordering
  bcachefs: Fix race between trans_put() and btree_transactions_read()
  closures: closure_get_not_zero(), closure_return_sync()
  bcachefs: Make btree_deadlock_to_text() clearer
  bcachefs: fix seqmutex_relock()
  bcachefs: Fix freeing of error pointers