bcachefs: Set preallocated transaction mem to avoid restarts

this will reduce transaction restarts, from observation of tracepoints.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>

fs/bcachefs/btree_iter.c

@@ -2370,8 +2370,12 @@ void bch2_trans_init(struct btree_trans *trans, struct bch_fs *c,
 	 */
 	bch2_trans_alloc_iters(trans, c);
 
-	if (expected_mem_bytes)
-		bch2_trans_preload_mem(trans, expected_mem_bytes);
+	if (expected_mem_bytes) {
+		expected_mem_bytes = roundup_pow_of_two(expected_mem_bytes);
+		trans->mem = kmalloc(expected_mem_bytes, GFP_KERNEL);
+		if (trans->mem)
+			trans->mem_bytes = expected_mem_bytes;
+	}
 
 	trans->srcu_idx = srcu_read_lock(&c->btree_trans_barrier);
 

fs/bcachefs/btree_update_interior.c

@@ -523,6 +523,7 @@ static void btree_update_nodes_written(struct btree_update *as)
 {
 	struct bch_fs *c = as->c;
 	struct btree *b = as->b;
+	struct btree_trans trans;
 	u64 journal_seq = 0;
 	unsigned i;
 	int ret;
@@ -540,7 +541,8 @@ static void btree_update_nodes_written(struct btree_update *as)
 	 * journal reclaim does btree updates when flushing bkey_cached entries,
 	 * which may require allocations as well.
 	 */
-	ret = bch2_trans_do(c, &as->disk_res, &journal_seq,
+	bch2_trans_init(&trans, c, 0, 512);
+	ret = __bch2_trans_do(&trans, &as->disk_res, &journal_seq,
 			      BTREE_INSERT_NOFAIL|
 			      BTREE_INSERT_USE_RESERVE|
 			      BTREE_INSERT_USE_ALLOC_RESERVE|
@@ -548,6 +550,7 @@ static void btree_update_nodes_written(struct btree_update *as)
 			      BTREE_INSERT_JOURNAL_RECLAIM|
 			      BTREE_INSERT_JOURNAL_RESERVED,
 			      btree_update_nodes_written_trans(&trans, as));
+	bch2_trans_exit(&trans);
 	BUG_ON(ret && !bch2_journal_error(&c->journal));
 
 	if (b) {

fs/bcachefs/fs.c

@@ -278,7 +278,8 @@ __bch2_create(struct mnt_idmap *idmap,
 	if (!tmpfile)
 		mutex_lock(&dir->ei_update_lock);
 
-	bch2_trans_init(&trans, c, 8, 1024);
+	bch2_trans_init(&trans, c, 8,
+			2048 + (!tmpfile ? dentry->d_name.len : 0));
 retry:
 	bch2_trans_begin(&trans);