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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 <fdmanana@gmail.com>
Reviewed-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Josef Bacik <jbacik@fusionio.com>
Signed-off-by: Chris Mason <chris.mason@fusionio.com>
This commit is contained in:
Filipe David Borba Manana 2013-07-30 12:03:04 +01:00 committed by Chris Mason
parent 6596a92819
commit 395927a9d8
1 changed files with 11 additions and 19 deletions
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30
fs/btrfs/volumes.c
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@ -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 @@ int btrfs_read_chunk_tree(struct btrfs_root *root)
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 @@ int btrfs_read_chunk_tree(struct btrfs_root *root)
}
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);