Re: [PATCH 03/35] btrfs: use cleanup_extent_op in check_ref_cleanup

Omar Sandoval
2018-09-01T03:10:10Z

On Thu, Aug 30, 2018 at 01:41:53PM -0400, Josef Bacik wrote:
> From: Josef Bacik <jbacik@fb.com>
>
> Unify the extent_op handling as well, just add a flag so we don't
> actually run the extent op from check_ref_cleanup and instead return a
> value so that we can skip cleaning up the ref head.
>
> Signed-off-by: Josef Bacik <jbacik@fb.com>
> ---
> fs/btrfs/extent-tree.c | 17 +++++++++--------
> 1 file changed, 9 insertions(+), 8 deletions(-)
>
> diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
> index 4c9fd35bca07..87c42a2c45b1 100644
> --- a/fs/btrfs/extent-tree.c
> +++ b/fs/btrfs/extent-tree.c
> @@ -2443,18 +2443,23 @@ static void unselect_delayed_ref_head(struct btrfs_delayed_ref_root *delayed_ref
> }
>
> static int cleanup_extent_op(struct btrfs_trans_handle *trans,
> - struct btrfs_delayed_ref_head *head)
> + struct btrfs_delayed_ref_head *head,
> + bool run_extent_op)
> {
> struct btrfs_delayed_extent_op *extent_op = head->extent_op;
> int ret;
>
> if (!extent_op)
> return 0;
> +
> head->extent_op = NULL;
> if (head->must_insert_reserved) {
> btrfs_free_delayed_extent_op(extent_op);
> return 0;
> + } else if (!run_extent_op) {
> + return 1;
> }
> +
> spin_unlock(&head->lock);
> ret = run_delayed_extent_op(trans, head, extent_op);
> btrfs_free_delayed_extent_op(extent_op);

So if cleanup_extent_op() returns 1, then the head was unlocked, unless
run_extent_op was true. That's pretty confusing. Can we make it always
unlock in the !must_insert_reserved case?

> @@ -2506,7 +2511,7 @@ static int cleanup_ref_head(struct btrfs_trans_handle *trans,
>
> delayed_refs = &trans->transaction->delayed_refs;
>
> - ret = cleanup_extent_op(trans, head);
> + ret = cleanup_extent_op(trans, head, true);
> if (ret < 0) {
> unselect_delayed_ref_head(delayed_refs, head);
> btrfs_debug(fs_info, "run_delayed_extent_op returned %d", ret);
> @@ -6977,12 +6982,8 @@ static noinline int check_ref_cleanup(struct btrfs_trans_handle *trans,
> if (!RB_EMPTY_ROOT(&head->ref_tree))
> goto out;
>
> - if (head->extent_op) {
> - if (!head->must_insert_reserved)
> - goto out;
> - btrfs_free_delayed_extent_op(head->extent_op);
> - head->extent_op = NULL;
> - }
> + if (cleanup_extent_op(trans, head, false))
> + goto out;
>
> /*
> * waiting for the lock here would deadlock. If someone else has it
> --
> 2.14.3
>