bcachefs: bch2_extent_fallocate()

This factors out part of __bchfs_fallocate() in fs-io.c into an new,
lower level io.c helper, which creates a single extent reservation.

This is prep work for nocow support - the new helper will shortly gain
the ability to create unwritten extents.

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

1 files changed, 30 insertions, 0 deletions

diff --git a/fs/bcachefs/io.c b/fs/bcachefs/io.c
index af6b9a7456f5..bde3a4c42189 100644
--- a/fs/bcachefs/io.c
+++ b/fs/bcachefs/io.c
@@ -360,6 +360,36 @@ err:
 	return ret;
 }
 
+/* Overwrites whatever was present with zeroes: */
+int bch2_extent_fallocate(struct btree_trans *trans,
+			  subvol_inum inum,
+			  struct btree_iter *iter,
+			  unsigned sectors,
+			  struct bch_io_opts opts,
+			  s64 *i_sectors_delta,
+			  struct write_point_specifier write_point)
+{
+	int ret;
+	struct bch_fs *c = trans->c;
+	struct disk_reservation disk_res = { 0 };
+	struct bkey_i_reservation *reservation =
+		bch2_trans_kmalloc(trans, sizeof(*reservation));
+
+	ret = PTR_ERR_OR_ZERO(reservation);
+	if (ret)
+		return ret;
+
+	bkey_reservation_init(&reservation->k_i);
+	reservation->k.p = iter->pos;
+	bch2_key_resize(&reservation->k, sectors);
+	reservation->v.nr_replicas = opts.data_replicas;
+
+	ret = bch2_extent_update(trans, inum, iter, &reservation->k_i, &disk_res,
+				 0, i_sectors_delta, true);
+	bch2_disk_reservation_put(c, &disk_res);
+	return ret;
+}
+
 /*
  * Returns -BCH_ERR_transacton_restart if we had to drop locks:
  */