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为什么条目数量多的目录删除条目后大小没有缩小？

tag-icon • tag-icon directory disk-usage ext4 inode
为什么条目数量多的目录删除条目后大小没有缩小？

问题是为什么删除目录项后目录到底会收缩吗？是否由于ext4文件系统配置为保留目录元数据的方式所致？显然，删除目录并重新创建它不是一种解决方案，因为它会删除原始索引节点并创建一个新索引节点。可以采取什么措施来手动减少数量？

答案1

引用一位开发者的话（在linux内核线程中删除大量文件后 ext3/ext4 目录不会缩小）：

On Thu, May 14, 2009 at 08:45:38PM -0400, Timo Sirainen wrote:
>
> I was rather thinking something that I could run while the system was  
> fully operational. Otherwise just moving the files to a temp directory +
> rmdir() + rename() would have been fine too.
>
> I just tested that xfs, jfs and reiserfs all shrink the directories  
> immediately. Is it more difficult to implement for ext* or has no one  
> else found this to be a problem?

It's probably fairest to say no one has thought it worth the effort.
It would require some fancy games to swap out block locations in the
extent trees (life would be easier with non-extent-using inodes), and
in the case of htree, we would have to keep track of the index block
so we could remove it from the htree index.  So it's all doable, if a
bit tricky in terms of the technical details; it's just that the
people who could do it have been busy enough with other things.

It's hasn't been considered high priority because most of the time
directories don't go from holding thousands of files down to a small
handful.  

                                                - Ted

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