btrfs: preallocate radix tree node for readahead

We can preallocate the node so insertion does not have to do that under
the lock. The GFP flags for the per-device radix tree are initialized to
 GFP_NOFS & ~__GFP_DIRECT_RECLAIM
but we can use GFP_KERNEL, same as an allocation above anyway, but also
because readahead is optional and not on any critical writeout path.

Reviewed-by: Liu Bo <bo.li.liu@oracle.com>
Signed-off-by: David Sterba <dsterba@suse.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/fs/btrfs/reada.c b/fs/btrfs/reada.c
index e88bca87f5d2..fdae8ca79401 100644
--- a/fs/btrfs/reada.c
+++ b/fs/btrfs/reada.c
@@ -270,6 +270,12 @@ static struct reada_zone *reada_find_zone(struct btrfs_fs_info *fs_info,
 	if (!zone)
 		return NULL;
 
+	ret = radix_tree_preload(GFP_KERNEL);
+	if (ret) {
+		kfree(zone);
+		return NULL;
+	}
+
 	zone->start = start;
 	zone->end = end;
 	INIT_LIST_HEAD(&zone->list);
@@ -299,6 +305,7 @@ static struct reada_zone *reada_find_zone(struct btrfs_fs_info *fs_info,
 			zone = NULL;
 	}
 	spin_unlock(&fs_info->reada_lock);
+	radix_tree_preload_end();
 
 	return zone;
 }