Re: [RFC][PATCH 3/8 v2] ext4: initialize extent status tree

On Wed, Sep 19, 2012 at 03:05:41PM -0400, Theodore Ts'o wrote:

On Wed, Aug 22, 2012 at 02:05:40PM +0800, Zheng Liu wrote:

quoted

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 3e0851e..353b1fd 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c

@@ -944,6 +944,7 @@ static struct inode *ext4_alloc_inode(struct super_block *sb)
 	memset(&ei->i_cached_extent, 0, sizeof(struct ext4_ext_cache));
 	INIT_LIST_HEAD(&ei->i_prealloc_list);
 	spin_lock_init(&ei->i_prealloc_lock);
+	ext4_es_init_tree(&ei->i_es_tree);
 	ei->i_reserved_data_blocks = 0;
 	ei->i_reserved_meta_blocks = 0;
 	ei->i_allocated_meta_blocks = 0;

This patch hunk immediately me ask, "so when does the extent_status
tree get freed?"  And I believe the answer is that currently, since it
only tracks delayed extents (and we're not using it for locking
purposes), by the time we have evicted the inode and are ready to call
ext4_clear_inode(), we should have released all of the nodes in the
ext4_es_tree.   Is that correct?

If so, we might want to think about adding a sanity check to make sure
that by the time we are done with the inode in ext4_evict_inode()
(after we have forced writeback), the ext4_es_tree is empty.  Agreed?

Hi Ted,

Today I revise this patch again, and I find extent_status_tree is freed
in ext4_clear_inode().  So maybe I don't think that we need to check
this tree to be freed in ext4_evict_inode().  This change is in this
patch '[RFC][PATCH 4/8 v2] ext4: let ext4 maintain extent status tree'.
What's your opinion?

Regards,
Zheng