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: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 26fb9cbf..ee027a7 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -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;