bcachefs: Preallocate transaction mem

This helps avoid transaction restarts.
Signed-off-by: Kent Overstreet <kent.overstreet@gmail.com>

fs/bcachefs/fs-io.c

@@ -2531,7 +2531,7 @@ static long bchfs_fcollapse_finsert(struct bch_inode_info *inode,
 	}
 
 	bch2_bkey_buf_init(&copy);
-	bch2_trans_init(&trans, c, BTREE_ITER_MAX, 256);
+	bch2_trans_init(&trans, c, BTREE_ITER_MAX, 1024);
 	src = bch2_trans_get_iter(&trans, BTREE_ID_extents,
 			POS(inode->v.i_ino, src_start >> 9),
 			BTREE_ITER_INTENT);
@@ -2651,7 +2651,7 @@ static int __bchfs_fallocate(struct bch_inode_info *inode, int mode,
 	unsigned replicas = io_opts(c, &inode->ei_inode).data_replicas;
 	int ret = 0;
 
-	bch2_trans_init(&trans, c, BTREE_ITER_MAX, 0);
+	bch2_trans_init(&trans, c, BTREE_ITER_MAX, 512);
 
 	iter = bch2_trans_get_iter(&trans, BTREE_ID_extents,
 			POS(inode->v.i_ino, start_sector),

fs/bcachefs/fs.c

@@ -146,7 +146,7 @@ int __must_check bch2_write_inode(struct bch_fs *c,
 	struct bch_inode_unpacked inode_u;
 	int ret;
 
-	bch2_trans_init(&trans, c, 0, 256);
+	bch2_trans_init(&trans, c, 0, 512);
 retry:
 	bch2_trans_begin(&trans);
 

fs/bcachefs/inode.c

@@ -579,7 +579,7 @@ int bch2_inode_rm(struct bch_fs *c, u64 inode_nr, bool cached)
 	struct bkey_s_c k;
 	int ret;
 
-	bch2_trans_init(&trans, c, 0, 0);
+	bch2_trans_init(&trans, c, 0, 1024);
 
 	/*
 	 * If this was a directory, there shouldn't be any real dirents left -