bcachefs: drop_locks_do()

Add a new helper for the common pattern of:
 - trans_unlock()
 - do something
 - trans_relock()
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/btree_iter.c

@@ -41,13 +41,10 @@ static struct btree_path *btree_path_alloc(struct btree_trans *, struct btree_pa
  */
 static inline int bch2_trans_cond_resched(struct btree_trans *trans)
 {
-	if (need_resched() || race_fault()) {
-		bch2_trans_unlock(trans);
-		schedule();
-		return bch2_trans_relock(trans);
-	} else {
+	if (need_resched() || race_fault())
+		return drop_locks_do(trans, (schedule(), 0));
+	else
 		return 0;
-	}
 }
 
 static inline int __btree_path_cmp(const struct btree_path *l,

fs/bcachefs/btree_iter.h

@@ -854,6 +854,11 @@ __bch2_btree_iter_peek_upto_and_restart(struct btree_trans *trans,
 	     !((_ret) = bkey_err(_k)) && (_k).k;				\
 	     bch2_btree_iter_advance(&(_iter)))
 
+#define drop_locks_do(_trans, _do)					\
+({									\
+	bch2_trans_unlock(_trans);					\
+	_do ?: bch2_trans_relock(_trans);				\
+})
 /* new multiple iterator interface: */
 
 void bch2_trans_updates_to_text(struct printbuf *, struct btree_trans *);

fs/bcachefs/btree_locking.c

@@ -736,11 +736,8 @@ bool bch2_trans_locked(struct btree_trans *trans)
 int __bch2_trans_mutex_lock(struct btree_trans *trans,
 			    struct mutex *lock)
 {
-	int ret;
+	int ret = drop_locks_do(trans, (mutex_lock(lock), 0));
 
-	bch2_trans_unlock(trans);
-	mutex_lock(lock);
-	ret = bch2_trans_relock(trans);
 	if (ret)
 		mutex_unlock(lock);
 	return ret;

fs/bcachefs/btree_update_interior.c

@@ -1083,9 +1083,7 @@ bch2_btree_update_start(struct btree_trans *trans, struct btree_path *path,
 	if (flags & BTREE_INSERT_GC_LOCK_HELD)
 		lockdep_assert_held(&c->gc_lock);
 	else if (!down_read_trylock(&c->gc_lock)) {
-		bch2_trans_unlock(trans);
-		down_read(&c->gc_lock);
-		ret = bch2_trans_relock(trans);
+		ret = drop_locks_do(trans, (down_read(&c->gc_lock), 0));
 		if (ret) {
 			up_read(&c->gc_lock);
 			return ERR_PTR(ret);
@@ -2256,9 +2254,7 @@ int bch2_btree_node_update_key(struct btree_trans *trans, struct btree_iter *ite
 	if (btree_ptr_hash_val(new_key) != b->hash_val) {
 		ret = bch2_btree_cache_cannibalize_lock(c, &cl);
 		if (ret) {
-			bch2_trans_unlock(trans);
-			closure_sync(&cl);
-			ret = bch2_trans_relock(trans);
+			ret = drop_locks_do(trans, (closure_sync(&cl), 0));
 			if (ret)
 				return ret;
 		}

fs/bcachefs/btree_update_leaf.c

@@ -316,25 +316,11 @@ static noinline int
 bch2_trans_journal_preres_get_cold(struct btree_trans *trans, unsigned flags,
 				   unsigned long trace_ip)
 {
-	struct bch_fs *c = trans->c;
-	int ret;
-
-	bch2_trans_unlock(trans);
-
-	ret = bch2_journal_preres_get(&c->journal,
+	return drop_locks_do(trans,
+		bch2_journal_preres_get(&trans->c->journal,
 			&trans->journal_preres,
 			trans->journal_preres_u64s,
-			(flags & JOURNAL_WATERMARK_MASK));
-	if (ret)
-		return ret;
-
-	ret = bch2_trans_relock(trans);
-	if (ret) {
-		trace_and_count(c, trans_restart_journal_preres_get, trans, trace_ip, 0);
-		return ret;
-	}
-
-	return 0;
+			(flags & JOURNAL_WATERMARK_MASK)));
 }
 
 static __always_inline int bch2_trans_journal_res_get(struct btree_trans *trans,
@@ -1053,10 +1039,7 @@ bch2_trans_commit_get_rw_cold(struct btree_trans *trans, unsigned flags)
 	    test_bit(BCH_FS_STARTED, &c->flags))
 		return -BCH_ERR_erofs_trans_commit;
 
-	bch2_trans_unlock(trans);
-
-	ret =   bch2_fs_read_write_early(c) ?:
-		bch2_trans_relock(trans);
+	ret = drop_locks_do(trans, bch2_fs_read_write_early(c));
 	if (ret)
 		return ret;