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Commit 0110a4c4 authored by Nikolay Borisov's avatar Nikolay Borisov Committed by David Sterba
Browse files

btrfs: refactor __btrfs_run_delayed_refs loop 



Refactor the delayed refs loop by using the newly introduced
btrfs_run_delayed_refs_for_head function. This greatly simplifies
__btrfs_run_delayed_refs and makes it more obvious what is happening.

We now have 1 loop which iterates the existing delayed_heads and then
each selected ref head is processed by the new helper. All existing
semantics of the code are preserved so no functional changes.

Signed-off-by: default avatarNikolay Borisov <nborisov@suse.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent e7261386

fs/btrfs/extent-tree.c

+28 −80
Original line number Diff line number Diff line
@@ -2548,6 +2548,9 @@ static int btrfs_run_delayed_refs_for_head(struct btrfs_trans_handle *trans, 


	delayed_refs = &trans->transaction->delayed_refs;



	lockdep_assert_held(&locked_ref->mutex);

	lockdep_assert_held(&locked_ref->lock);



	while ((ref = select_delayed_ref(locked_ref))) {

		if (ref->seq &&

		    btrfs_check_delayed_seq(fs_info, ref->seq)) {
@@ -2621,31 +2624,25 @@ static noinline int __btrfs_run_delayed_refs(struct btrfs_trans_handle *trans, 
{

	struct btrfs_fs_info *fs_info = trans->fs_info;

	struct btrfs_delayed_ref_root *delayed_refs;

	struct btrfs_delayed_ref_node *ref;

	struct btrfs_delayed_ref_head *locked_ref = NULL;

	struct btrfs_delayed_extent_op *extent_op;

	ktime_t start = ktime_get();

	int ret;

	unsigned long count = 0;

	unsigned long actual_count = 0;

	int must_insert_reserved = 0;



	delayed_refs = &trans->transaction->delayed_refs;

	while (1) {

	do {

		if (!locked_ref) {

			if (count >= nr)

				break;



			locked_ref = btrfs_obtain_ref_head(trans);

			if (!locked_ref)

				break;

			else if (PTR_ERR(locked_ref) == -EAGAIN) {

				locked_ref = NULL;

				count++;

			if (IS_ERR_OR_NULL(locked_ref)) {

				if (PTR_ERR(locked_ref) == -EAGAIN) {

					continue;

				} else {

					break;

				}

			}



			count++;

		}

		/*

		 * We need to try and merge add/drops of the same ref since we

		 * can run into issues with relocate dropping the implicit ref
@@ -2661,23 +2658,19 @@ static noinline int __btrfs_run_delayed_refs(struct btrfs_trans_handle *trans, 
		spin_lock(&locked_ref->lock);

		btrfs_merge_delayed_refs(trans, delayed_refs, locked_ref);



		ref = select_delayed_ref(locked_ref);



		if (ref && ref->seq &&

		    btrfs_check_delayed_seq(fs_info, ref->seq)) {

			spin_unlock(&locked_ref->lock);

			unselect_delayed_ref_head(delayed_refs, locked_ref);

			locked_ref = NULL;

			cond_resched();

			count++;

			continue;

		}



		ret = btrfs_run_delayed_refs_for_head(trans, locked_ref,

						      &actual_count);

		if (ret < 0 && ret != -EAGAIN) {

			/*

		 * We're done processing refs in this ref_head, clean everything

		 * up and move on to the next ref_head.

			 * Error, btrfs_run_delayed_refs_for_head already

			 * unlocked everything so just bail out

			 */

			return ret;

		} else if (!ret) {

			/*

			 * Success, perform the usual cleanup of a processed

			 * head

			 */

		if (!ref) {

			ret = cleanup_ref_head(trans, locked_ref);

			if (ret > 0 ) {

				/* We dropped our lock, we need to loop. */
@@ -2686,61 +2679,16 @@ static noinline int __btrfs_run_delayed_refs(struct btrfs_trans_handle *trans, 
			} else if (ret) {

				return ret;

			}

			locked_ref = NULL;

			count++;

			continue;

		}



		actual_count++;

		ref->in_tree = 0;

		rb_erase_cached(&ref->ref_node, &locked_ref->ref_tree);

		RB_CLEAR_NODE(&ref->ref_node);

		if (!list_empty(&ref->add_list))

			list_del(&ref->add_list);

		/*

		 * When we play the delayed ref, also correct the ref_mod on

		 * head

		 * Either success case or btrfs_run_delayed_refs_for_head

		 * returned -EAGAIN, meaning we need to select another head

		 */

		switch (ref->action) {

		case BTRFS_ADD_DELAYED_REF:

		case BTRFS_ADD_DELAYED_EXTENT:

			locked_ref->ref_mod -= ref->ref_mod;

			break;

		case BTRFS_DROP_DELAYED_REF:

			locked_ref->ref_mod += ref->ref_mod;

			break;

		default:

			WARN_ON(1);

		}

		atomic_dec(&delayed_refs->num_entries);



		/*

		 * Record the must-insert_reserved flag before we drop the spin

		 * lock.

		 */

		must_insert_reserved = locked_ref->must_insert_reserved;

		locked_ref->must_insert_reserved = 0;



		extent_op = locked_ref->extent_op;

		locked_ref->extent_op = NULL;

		spin_unlock(&locked_ref->lock);



		ret = run_one_delayed_ref(trans, ref, extent_op,

					  must_insert_reserved);



		btrfs_free_delayed_extent_op(extent_op);

		if (ret) {

			unselect_delayed_ref_head(delayed_refs, locked_ref);

			btrfs_put_delayed_ref(ref);

			btrfs_debug(fs_info, "run_one_delayed_ref returned %d",

				    ret);

			return ret;

		}



		btrfs_put_delayed_ref(ref);

		count++;

		locked_ref = NULL;

		cond_resched();

	}

	} while ((nr != -1 && count < nr) || locked_ref);



	/*

	 * We don't want to include ref heads since we can have empty ref heads