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Commit b1cdbcb5 authored by Nikolay Borisov's avatar Nikolay Borisov Committed by David Sterba
Browse files

btrfs: Factor out ref head locking code in __btrfs_run_delayed_refs 



This is in preparation to refactor the giant loop in
__btrfs_run_delayed_refs. As a first step define a new function
which implements acquiring a reference to a btrfs_delayed_refs_head and
use it. 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 b2fa1154

fs/btrfs/extent-tree.c

+36 −17
Original line number Diff line number Diff line
@@ -2502,6 +2502,39 @@ static int cleanup_ref_head(struct btrfs_trans_handle *trans, 
	return 0;

}



static struct btrfs_delayed_ref_head *btrfs_obtain_ref_head(

					struct btrfs_trans_handle *trans)

{

	struct btrfs_delayed_ref_root *delayed_refs =

		&trans->transaction->delayed_refs;

	struct btrfs_delayed_ref_head *head = NULL;

	int ret;



	spin_lock(&delayed_refs->lock);

	head = btrfs_select_ref_head(trans);

	if (!head) {

		spin_unlock(&delayed_refs->lock);

		return head;

	}



	/*

	 * Grab the lock that says we are going to process all the refs for

	 * this head

	 */

	ret = btrfs_delayed_ref_lock(trans, head);

	spin_unlock(&delayed_refs->lock);



	/*

	 * We may have dropped the spin lock to get the head mutex lock, and

	 * that might have given someone else time to free the head.  If that's

	 * true, it has been removed from our list and we can move on.

	 */

	if (ret == -EAGAIN)

		head = ERR_PTR(-EAGAIN);



	return head;

}



/*

 * Returns 0 on success or if called with an already aborted transaction.

 * Returns -ENOMEM or -EIO on failure and will abort the transaction.
@@ -2526,24 +2559,10 @@ static noinline int __btrfs_run_delayed_refs(struct btrfs_trans_handle *trans, 
			if (count >= nr)

				break;



			spin_lock(&delayed_refs->lock);

			locked_ref = btrfs_select_ref_head(trans);

			if (!locked_ref) {

				spin_unlock(&delayed_refs->lock);

			locked_ref = btrfs_obtain_ref_head(trans);

			if (!locked_ref)

				break;

			}



			/* grab the lock that says we are going to process

			 * all the refs for this head */

			ret = btrfs_delayed_ref_lock(trans, locked_ref);

			spin_unlock(&delayed_refs->lock);

			/*

			 * we may have dropped the spin lock to get the head

			 * mutex lock, and that might have given someone else

			 * time to free the head.  If that's true, it has been

			 * removed from our list and we can move on.

			 */

			if (ret == -EAGAIN) {

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

				locked_ref = NULL;

				count++;

				continue;