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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>
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1 changed files with 36 additions and 17 deletions
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@ -2502,6 +2502,39 @@ static int cleanup_ref_head(struct btrfs_trans_handle *trans,
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return 0;
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return 0;
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}
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}
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static struct btrfs_delayed_ref_head *btrfs_obtain_ref_head(
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struct btrfs_trans_handle *trans)
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{
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struct btrfs_delayed_ref_root *delayed_refs =
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&trans->transaction->delayed_refs;
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struct btrfs_delayed_ref_head *head = NULL;
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int ret;
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spin_lock(&delayed_refs->lock);
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head = btrfs_select_ref_head(trans);
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if (!head) {
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spin_unlock(&delayed_refs->lock);
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return head;
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}
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/*
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* Grab the lock that says we are going to process all the refs for
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* this head
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*/
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ret = btrfs_delayed_ref_lock(trans, head);
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spin_unlock(&delayed_refs->lock);
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/*
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* We may have dropped the spin lock to get the head mutex lock, and
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* that might have given someone else time to free the head. If that's
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* true, it has been removed from our list and we can move on.
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*/
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if (ret == -EAGAIN)
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head = ERR_PTR(-EAGAIN);
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return head;
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}
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/*
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/*
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* Returns 0 on success or if called with an already aborted transaction.
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* Returns 0 on success or if called with an already aborted transaction.
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* Returns -ENOMEM or -EIO on failure and will abort the transaction.
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* Returns -ENOMEM or -EIO on failure and will abort the transaction.
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@ -2526,24 +2559,10 @@ static noinline int __btrfs_run_delayed_refs(struct btrfs_trans_handle *trans,
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if (count >= nr)
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if (count >= nr)
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break;
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break;
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spin_lock(&delayed_refs->lock);
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locked_ref = btrfs_obtain_ref_head(trans);
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locked_ref = btrfs_select_ref_head(trans);
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if (!locked_ref)
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if (!locked_ref) {
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spin_unlock(&delayed_refs->lock);
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break;
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break;
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}
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else if (PTR_ERR(locked_ref) == -EAGAIN) {
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/* grab the lock that says we are going to process
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* all the refs for this head */
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ret = btrfs_delayed_ref_lock(trans, locked_ref);
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spin_unlock(&delayed_refs->lock);
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/*
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* we may have dropped the spin lock to get the head
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* mutex lock, and that might have given someone else
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* time to free the head. If that's true, it has been
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* removed from our list and we can move on.
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*/
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if (ret == -EAGAIN) {
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locked_ref = NULL;
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locked_ref = NULL;
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count++;
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count++;
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continue;
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continue;
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