bcachefs: Don't use key cache during fsck

The btree key cache mainly helps with lock contention, at the cost of
additional memory overhead. During some fsck passes the memory overhead
really matters, but fsck is single threaded so lock contention is an
issue - so skipping the key cache during fsck will help with
performance.
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/alloc_foreground.c

@@ -352,7 +352,8 @@ static struct open_bucket *try_alloc_bucket(struct btree_trans *trans, struct bc
 		u64 bp_offset = 0;
 
 		ret = bch2_get_next_backpointer(trans, POS(ca->dev_idx, b), -1,
-						&bp_offset, &bp);
+						&bp_offset, &bp,
+						BTREE_ITER_NOPRESERVE);
 		if (ret) {
 			ob = ERR_PTR(ret);
 			goto err;

fs/bcachefs/backpointers.c

@@ -300,7 +300,8 @@ int bch2_bucket_backpointer_mod_nowritebuffer(struct btree_trans *trans,
 int bch2_get_next_backpointer(struct btree_trans *trans,
 			      struct bpos bucket, int gen,
 			      u64 *bp_offset,
-			      struct bch_backpointer *dst)
+			      struct bch_backpointer *dst,
+			      unsigned iter_flags)
 {
 	struct bch_fs *c = trans->c;
 	struct bpos bp_pos, bp_end_pos;
@@ -921,7 +922,7 @@ static int check_one_backpointer(struct btree_trans *trans,
 	struct printbuf buf = PRINTBUF;
 	int ret;
 
-	ret = bch2_get_next_backpointer(trans, bucket, -1, bp_offset, &bp);
+	ret = bch2_get_next_backpointer(trans, bucket, -1, bp_offset, &bp, 0);
 	if (ret || *bp_offset == U64_MAX)
 		return ret;
 

fs/bcachefs/backpointers.h

@@ -118,7 +118,7 @@ static inline void bch2_extent_ptr_to_bp(struct bch_fs *c,
 }
 
 int bch2_get_next_backpointer(struct btree_trans *, struct bpos, int,
-			      u64 *, struct bch_backpointer *);
+			      u64 *, struct bch_backpointer *, unsigned);
 struct bkey_s_c bch2_backpointer_get_key(struct btree_trans *, struct btree_iter *,
 					 struct bpos, u64, struct bch_backpointer);
 struct btree *bch2_backpointer_get_node(struct btree_trans *, struct btree_iter *,

fs/bcachefs/ec.c

@@ -841,7 +841,8 @@ static int ec_stripe_update_extent(struct btree_trans *trans,
 	struct bkey_i *n;
 	int ret, dev, block;
 
-	ret = bch2_get_next_backpointer(trans, bucket, gen, bp_offset, &bp);
+	ret = bch2_get_next_backpointer(trans, bucket, gen,
+				bp_offset, &bp, BTREE_ITER_CACHED);
 	if (ret)
 		return ret;
 	if (*bp_offset == U64_MAX)

fs/bcachefs/move.c

@@ -608,7 +608,8 @@ static int verify_bucket_evacuated(struct btree_trans *trans, struct bpos bucket
 		bch2_trans_begin(trans);
 
 		ret = bch2_get_next_backpointer(trans, bucket, gen,
-						&bp_offset, &bp);
+						&bp_offset, &bp,
+						BTREE_ITER_CACHED);
 		if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
 			continue;
 		if (ret)
@@ -681,7 +682,8 @@ int __bch2_evacuate_bucket(struct moving_context *ctxt,
 		bch2_trans_begin(&trans);
 
 		ret = bch2_get_next_backpointer(&trans, bucket, gen,
-						&bp_offset, &bp);
+						&bp_offset, &bp,
+						BTREE_ITER_CACHED);
 		if (bch2_err_matches(ret, BCH_ERR_transaction_restart))
 			continue;
 		if (ret)