From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cn.fujitsu.com ([222.73.24.84]:14781 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1754922Ab3GaBLb (ORCPT ); Tue, 30 Jul 2013 21:11:31 -0400 Message-ID: <51F8647F.8010401@cn.fujitsu.com> Date: Wed, 31 Jul 2013 09:12:31 +0800 From: Miao Xie Reply-To: miaox@cn.fujitsu.com MIME-Version: 1.0 To: Filipe David Borba Manana CC: linux-btrfs@vger.kernel.org, jbacik@fusionio.com Subject: Re: [PATCH v3] Btrfs: optimize function btrfs_read_chunk_tree References: <1372853956-10569-1-git-send-email-fdmanana@gmail.com> <1375182184-30490-1-git-send-email-fdmanana@gmail.com> In-Reply-To: <1375182184-30490-1-git-send-email-fdmanana@gmail.com> Content-Type: text/plain; charset=UTF-8 Sender: linux-btrfs-owner@vger.kernel.org List-ID: On tue, 30 Jul 2013 12:03:04 +0100, Filipe David Borba Manana wrote: > 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 > --- > > V2: Simplified logic inside the loop > (suggested by Josef Bacik on irc). > V3: Updated comment to comply with kernel coding style. Reviewed-by: Miao Xie > > 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 090f57c..125a60e 100644 > --- a/fs/btrfs/volumes.c > +++ b/fs/btrfs/volumes.c > @@ -5676,14 +5676,15 @@ 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; > @@ -5699,17 +5700,13 @@ 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); > @@ -5719,11 +5716,6 @@ 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); >