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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>
This commit is contained in:
Nikolay Borisov 2018-08-15 10:39:54 +03:00 committed by David Sterba
parent b2fa11547b
commit b1cdbcb53a
1 changed files with 36 additions and 17 deletions
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53
fs/btrfs/extent-tree.c
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@ -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;