From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from cn.fujitsu.com ([222.73.24.84]:53748 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1753257Ab2GRMDL (ORCPT ); Wed, 18 Jul 2012 08:03:11 -0400 Message-ID: <5006A5E8.4050907@cn.fujitsu.com> Date: Wed, 18 Jul 2012 20:02:48 +0800 From: Liu Bo MIME-Version: 1.0 To: Alex Lyakas CC: linux-btrfs@vger.kernel.org Subject: Re: [PATCH 1/2] Btrfs: fix btrfs_is_free_space_inode to recognize btree inode References: <1341919719-13825-1-git-send-email-liubo2009@cn.fujitsu.com> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 07/18/2012 06:02 PM, Alex Lyakas wrote: > Hi Liu, > can you pls explain this a bit more to me. > I see in my fs that there are (FREE_SPACE,0, offset) items in the root > tree. It seems that offset here is the objectid of the appropriate > BLOCK_GROUP_ITEM. Also, I see that each FREE_SPACE points at some > INODE_ITEM within the root tree, and this INODE_ITEM also has extents. > I presume that these extents contain the free space cache in some > format, is that correct? > More or less. As its name shows, a free space inode's data (you name it extents) consists of free space info, meanwhile, a free space inode is issued to a block group, so the free space info actually stands for free space in the block group: |<- a block group len ->| |----vvv----vvv-------vvv-----| 'v' : occupied. '-' : available. (free space) these free space info are indexed in a rbtree in memory, and each entry has [start, len]. > However, I don't see any FREE_INO entries, what are they? Are they > perhaps used only when "inode_cache" mount option is used, so inode > numbers are not always incremented in btrfs_find_free_ino(), but > smaller unused numbers are reused? > Yes, that's what it is used for. > Also, I don't see anywhere BTRFS_BTREE_INODE_OBJECTID in the tree root > tree. So what is this "btree inode" that you mention? > The code refers to disk_io.c, in the function 'open_ctree()' you can see the definition. Basically btree inode's data stands for btrfs's metadata, I think you can find something in btrfs's wiki page? And thanks for your energy on btrfs! :) thanks, liubo > Thanks, > Alex. > > > On Tue, Jul 10, 2012 at 2:28 PM, Liu Bo wrote: >> For btree inode, its root is also 'tree root', so btree inode can be >> misunderstood as a free space inode. >> >> We should add one more check for btree inode. >> >> Signed-off-by: Liu Bo >> --- >> fs/btrfs/btrfs_inode.h | 6 ++++-- >> 1 files changed, 4 insertions(+), 2 deletions(-) >> >> diff --git a/fs/btrfs/btrfs_inode.h b/fs/btrfs/btrfs_inode.h >> index 12394a9..b168238 100644 >> --- a/fs/btrfs/btrfs_inode.h >> +++ b/fs/btrfs/btrfs_inode.h >> @@ -194,8 +194,10 @@ static inline void btrfs_i_size_write(struct inode *inode, u64 size) >> static inline bool btrfs_is_free_space_inode(struct btrfs_root *root, >> struct inode *inode) >> { >> - if (root == root->fs_info->tree_root || >> - BTRFS_I(inode)->location.objectid == BTRFS_FREE_INO_OBJECTID) >> + if (root == root->fs_info->tree_root && >> + btrfs_ino(inode) != BTRFS_BTREE_INODE_OBJECTID) >> + return true; >> + if (BTRFS_I(inode)->location.objectid == BTRFS_FREE_INO_OBJECTID) >> return true; >> return false; >> } >> -- >> 1.6.5.2 >> >> -- >> To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html > -- > To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >