From 395927a9d8e64af518c2ccdbfbbdf9184b558315 Mon Sep 17 00:00:00 2001 From: Filipe David Borba Manana Date: Tue, 30 Jul 2013 12:03:04 +0100 Subject: [PATCH] Btrfs: optimize function btrfs_read_chunk_tree After reading all device items from the chunk tree, don't exit the loop and then navigate down the tree again to find the chunk items. Instead just read all device items and chunk items with a single tree search. This is possible because all device items are found before any chunk item in the chunks tree. Signed-off-by: Filipe David Borba Manana Reviewed-by: Miao Xie Signed-off-by: Josef Bacik Signed-off-by: Chris Mason --- fs/btrfs/volumes.c | 30 +++++++++++------------------- 1 file changed, 11 insertions(+), 19 deletions(-) diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 557a7438f92..93f39b1e717 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -5646,14 +5646,15 @@ int btrfs_read_chunk_tree(struct btrfs_root *root) mutex_lock(&uuid_mutex); lock_chunks(root); - /* first we search for all of the device items, and then we - * read in all of the chunk items. This way we can create chunk - * mappings that reference all of the devices that are afound + /* + * Read all device items, and then all the chunk items. All + * device items are found before any chunk item (their object id + * is smaller than the lowest possible object id for a chunk + * item - BTRFS_FIRST_CHUNK_TREE_OBJECTID). */ key.objectid = BTRFS_DEV_ITEMS_OBJECTID; key.offset = 0; key.type = 0; -again: ret = btrfs_search_slot(NULL, root, &key, path, 0, 0); if (ret < 0) goto error; @@ -5669,17 +5670,13 @@ again: break; } btrfs_item_key_to_cpu(leaf, &found_key, slot); - if (key.objectid == BTRFS_DEV_ITEMS_OBJECTID) { - if (found_key.objectid != BTRFS_DEV_ITEMS_OBJECTID) - break; - if (found_key.type == BTRFS_DEV_ITEM_KEY) { - struct btrfs_dev_item *dev_item; - dev_item = btrfs_item_ptr(leaf, slot, + if (found_key.type == BTRFS_DEV_ITEM_KEY) { + struct btrfs_dev_item *dev_item; + dev_item = btrfs_item_ptr(leaf, slot, struct btrfs_dev_item); - ret = read_one_dev(root, leaf, dev_item); - if (ret) - goto error; - } + ret = read_one_dev(root, leaf, dev_item); + if (ret) + goto error; } else if (found_key.type == BTRFS_CHUNK_ITEM_KEY) { struct btrfs_chunk *chunk; chunk = btrfs_item_ptr(leaf, slot, struct btrfs_chunk); @@ -5689,11 +5686,6 @@ again: } path->slots[0]++; } - if (key.objectid == BTRFS_DEV_ITEMS_OBJECTID) { - key.objectid = 0; - btrfs_release_path(path); - goto again; - } ret = 0; error: unlock_chunks(root); -- 2.41.0