six locks: Simplify six_relock()

The next patch is going to move lock->seq out of lock->state. This
replaces six_relock() with a much simpler implementation based on
trylock.

Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

diff --git a/fs/bcachefs/six.c b/fs/bcachefs/six.c
index fcc74e626db0dc73741cbfb5c5e8671e6edfe88f..3fb5959fe40ffa8b1ca3aa7c84687936f6131d68 100644 (file)
--- a/fs/bcachefs/six.c
+++ b/fs/bcachefs/six.c
@@ -409,51 +409,14 @@ EXPORT_SYMBOL_GPL(six_trylock_ip);
 bool six_relock_ip(struct six_lock *lock, enum six_lock_type type,
                   unsigned seq, unsigned long ip)
 {
-       const struct six_lock_vals l[] = LOCK_VALS;
-       u64 old, v;
-
-       EBUG_ON(type == SIX_LOCK_write);
-
-       if (type == SIX_LOCK_read &&
-           lock->readers) {
-               bool ret;
-
-               preempt_disable();
-               this_cpu_inc(*lock->readers);
-
-               smp_mb();
-
-               old = atomic64_read(&lock->state);
-               ret = !(old & l[type].lock_fail) && six_state_seq(old) == seq;
-
-               this_cpu_sub(*lock->readers, !ret);
-               preempt_enable();
-
-               /*
-                * Similar to the lock path, we may have caused a spurious write
-                * lock fail and need to issue a wakeup:
-                */
-               if (ret)
-                       six_acquire(&lock->dep_map, 1, type == SIX_LOCK_read, ip);
-               else if (old & SIX_STATE_WAITING_WRITE)
-                       six_lock_wakeup(lock, old, SIX_LOCK_write);
+       if (six_lock_seq(lock) != seq || !six_trylock_ip(lock, type, ip))
+               return false;
 
-               return ret;
+       if (six_lock_seq(lock) != seq) {
+               six_unlock_ip(lock, type, ip);
+               return false;
        }
 
-       v = atomic64_read(&lock->state);
-       do {
-               old = v;
-
-               if ((old & l[type].lock_fail) || six_state_seq(old) != seq)
-                       return false;
-       } while ((v = atomic64_cmpxchg_acquire(&lock->state,
-                                              old,
-                                              old + l[type].lock_val)) != old);
-
-       six_set_owner(lock, type, old, current);
-       if (type != SIX_LOCK_write)
-               six_acquire(&lock->dep_map, 1, type == SIX_LOCK_read, ip);
        return true;
 }
 EXPORT_SYMBOL_GPL(six_relock_ip);