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Btrfs: delayed-refs: use rb_first_cached for ref_tree

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rb_first_cached() trades an extra pointer "leftmost" for doing the same
job as rb_first() but in O(1).

Functions manipulating href->ref_tree need to get the first entry, this
converts href->ref_tree to use rb_first_cached().

For more details about the optimization see patch "Btrfs: delayed-refs:
use rb_first_cached for href_root".

Tested-by: Holger Hoffstätte <holger@applied-asynchrony.com>
Signed-off-by: Liu Bo <bo.liu@linux.alibaba.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
This commit is contained in:
Liu Bo
2018-08-23 03:51:50 +08:00
committed by David Sterba
parent 5c9d028b3b
commit e3d0396563
5 changed files with 25 additions and 20 deletions
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4
fs/btrfs/disk-io.c
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@@ -4221,11 +4221,11 @@ static int btrfs_destroy_delayed_refs(struct btrfs_transaction *trans,
continue;
}
spin_lock(&head->lock);
while ((n = rb_first(&head->ref_tree)) != NULL) {
while ((n = rb_first_cached(&head->ref_tree)) != NULL) {
ref = rb_entry(n, struct btrfs_delayed_ref_node,
ref_node);
ref->in_tree = 0;
rb_erase(&ref->ref_node, &head->ref_tree);
rb_erase_cached(&ref->ref_node, &head->ref_tree);
RB_CLEAR_NODE(&ref->ref_node);
if (!list_empty(&ref->add_list))
list_del(&ref->add_list);