虚拟文件的文件大小 [英] File size of virtual file

问题描述

我使用FUSE来创建一个覆盖文件系统，其中目录增加虚拟实体。我设置了这些实体的文件大小为0，因为我没有办法知道 - 阅读他们提前，这是在我的情况下，特别是昂贵的 - 他们应该是什么

I'm using FUSE to create an overlay filesystem, where directories are augmented with virtual entities. I am setting the file size of these entities to 0, because I have no way of knowing -- ahead of reading them, which is particularly expensive in my case -- what they should be.

不过，似乎有一个明显的优化发生，只要长度为零的文件不承担任何读通话（仅开放和发布）。

However, there seems to be an obvious optimisation taking place, insofar as zero-length files don't incur any read call (only open and release).

因此​​，我的问题很简单，我应该怎么设置文件的大小？我知道，符号链接的大小的文件名长度的;将这项工作，因为它不是一个符号链接？否则，我所能做的最好是大小提供一个下界......如果读只有一个文件描述符，块大小和偏移，presumably它读取'直到EOF，而不是任何统计可以告诉它。

My question therefore is simply, what should I set the file size to? I know symlinks have a size of their filename length; would this work, given it's not a symlink? Otherwise, the best I can do is provide a lower bound for the size... If read only has a file descriptor, chunk size and offset, presumably it reads 'til EOF rather than whatever stat can tell it.

推荐答案

文件大小必须正确。很多code取决于这些信息，你不能简单地忽略它。

The file size must be correct. A lot of code depends on this information, you can't simply omit it.

这意味着你需要找出一个有效的方法来缓存/ precalculate此信息。

That means you need to figure out an efficient way to cache/precalculate this information.

看一看的来源 cmdfs 运行在文件系统中的所有文件的命令。 Linux杂志有一个概述文章。

Have a look at the sources of cmdfs which runs a command on all files in the filesystem. Linux Magazine has an overview article.

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