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- (window.webpackJsonp=window.webpackJsonp||[]).push([[34],{315:function(s,t,a){"use strict";a.r(t);var n=a(14),e=Object(n.a)({},(function(){var s=this,t=s._self._c;return t("ContentSlotsDistributor",{attrs:{"slot-key":s.$parent.slotKey}},[t("h1",{attrs:{id:"文件系统"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#文件系统"}},[s._v("#")]),s._v(" 文件系统")]),s._v(" "),t("h2",{attrs:{id:"本章导读"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#本章导读"}},[s._v("#")]),s._v(" 本章导读")]),s._v(" "),t("p",[s._v("本章意在介绍文件系统相关知识，包括虚拟文件系统、ramfs以及如何在用户程序对自己写的文件系统进行测试")]),s._v(" "),t("h2",{attrs:{id:"dragonos文件系统的架构设计"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#dragonos文件系统的架构设计"}},[s._v("#")]),s._v(" DragonOS文件系统的架构设计")]),s._v(" "),t("p",[s._v("首先，我们来总览一下DragonOS文件系统的架构设计。相关的机制主要包括以下几个部分：")]),s._v(" "),t("blockquote",[t("ul",[t("li",[t("p",[s._v("系统调用接口")])]),s._v(" "),t("li",[t("p",[s._v("虚拟文件系统")])])]),s._v(" "),t("blockquote",[t("p",[s._v("文件抽象（File）")]),s._v(" "),t("p",[s._v("挂载文件系统（MountFS）")])]),s._v(" "),t("ul",[t("li",[s._v("具体的文件系统")])])]),s._v(" "),t("p",[s._v("如图所示：")]),s._v(" "),t("p",[t("img",{attrs:{src:"/OS_lab_tutorial/docs/.vuepress/public/DragonOS/DragonOS.png",alt:"图片1",title:"文件系统架构设计"}})]),s._v(" "),t("p",[s._v("其中我们可以看到，中间部分作为接口对多个并行的物理文件系统实例（每一个都叫做文件系统的实现）提供支持。这就是虚拟文件系统。")]),s._v(" "),t("h2",{attrs:{id:"虚拟文件系统"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#虚拟文件系统"}},[s._v("#")]),s._v(" 虚拟文件系统")]),s._v(" "),t("p",[t("code",[s._v("虚拟文件系统")]),s._v("（Virtual File System，缩写为"),t("code",[s._v("VFS")]),s._v("）是计算机操作系统中的一个抽象层，它提供了文件系统的标准化接口，使得应用程序可以通过统一的方式访问各种不同类型的文件系统。")]),s._v(" "),t("p",[s._v("其设计目的是将文件系统的实现细节与应用程序分离，使得应用程序可以独立于底层文件系统的具体实现方式。它定义了一组通用的文件操作接口，如打开文件、关闭文件、读取文件、写入文件等，应用程序可以通过这些接口来访问和操作文件，而无需关心文件系统的底层细节。例如，一个应用程序可以通过虚拟文件系统接口打开一个文件，而不需要关心这个文件是存储在本地磁盘上的普通文件，还是位于远程服务器上的网络文件。虚拟文件系统会将这些不同类型的文件系统映射到一个统一的文件层次结构中，使得应用程序可以以相同的方式访问这些文件。")]),s._v(" "),t("p",[s._v("在"),t("em",[s._v("DragonOS")]),s._v("中，VFS作为适配器，遮住了具体文件系统之间的差异，对外提供统一的文件操作接口抽象。")]),s._v(" "),t("p",[s._v("VFS是DragonOS文件系统的核心，它提供了一套统一的文件系统接口，使得DragonOS可以支持多种不同的文件系统。VFS的主要功能包括：")]),s._v(" "),t("blockquote",[t("p",[s._v("提供统一的文件系统接口")]),s._v(" "),t("p",[s._v("提供文件系统的挂载和卸载机制（MountFS）")]),s._v(" "),t("p",[s._v("提供文件抽象（File）")]),s._v(" "),t("p",[s._v("提供文件系统的抽象（FileSystem）")]),s._v(" "),t("p",[s._v("提供IndexNode抽象")])]),s._v(" "),t("h2",{attrs:{id:"vfs的架构设计"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#vfs的架构设计"}},[s._v("#")]),s._v(" VFS的架构设计")]),s._v(" "),t("p",[t("img",{attrs:{src:"/OS_lab_tutorial/docs/.vuepress/public/DragonOS/vfs_archi_design.png",alt:"图片2",title:"vfs架构设计"}})]),s._v(" "),t("h3",{attrs:{id:"file"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#file"}},[s._v("#")]),s._v(" File")]),s._v(" "),t("p",[t("code",[s._v("File")]),s._v("结构体是VFS中最基本的抽象，它代表了一个打开的文件。每当进程打开了一个文件，就会创建一个File结构体，用于维护该文件的状态信息。")]),s._v(" "),t("div",{staticClass:"language-rust 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@brief MountFS的Index Node ")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("/// 注意，这个IndexNode只是一个中间层。它的目的是将具体文件系统的Inode与挂载机制连接在一起。")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("pub")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("struct")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token type-definition class-name"}},[s._v("MountFSInode")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("{")]),s._v("\n "),t("span",{pre:!0,attrs:{class:"token comment"}},[s._v("/// 当前挂载点对应到具体的文件系统的Inode")]),s._v("\n inner_inode"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(":")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token class-name"}},[s._v("Arc")]),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v("<")]),t("span",{pre:!0,attrs:{class:"token keyword"}},[s._v("dyn")]),s._v(" "),t("span",{pre:!0,attrs:{class:"token class-name"}},[s._v("IndexNode")]),t("span",{pre:!0,attrs:{class:"token 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class-name"}},[s._v("MountFSInode")]),t("span",{pre:!0,attrs:{class:"token operator"}},[s._v(">")]),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v(",")]),s._v("\n"),t("span",{pre:!0,attrs:{class:"token punctuation"}},[s._v("}")]),s._v("\n")])])]),t("p",[s._v("虽然其实现了FileSystem和IndexNode这两个trait，但它并不是一个“文件系统”，而是一种机制，用于将不同的文件系统挂载到同一个文件系统树上。所有的文件系统要挂载到文件系统树上，都需要通过"),t("code",[s._v("MountFS")]),s._v("来完成。也就是说，挂载树上的每个文件系统结构体的外面，都套了一层MountFS结构体。")]),s._v(" "),t("p",[s._v("对于大部分的操作，MountFS都是直接转发给具体的文件系统，而不做任何处理。同时，为了支持跨文件系统的操作，比如在目录树上查找，每次"),t("code",[s._v("lookup")]),s._v("操作或者是"),t("code",[s._v("find")]),s._v("操作，都会通过"),t("code",[s._v("MountFSInode")]),s._v("的对应方法，判断当前inode是否为挂载点，并对挂载点进行特殊处理。如果发现操作跨越了具体文件系统的边界，MountFS就会将操作转发给下一个文件系统，并执行Inode替换。这个功能的实现，也是通过在普通的Inode结构体外面，套一层MountFSInode结构体来实现的。")]),s._v(" "),t("h2",{attrs:{id:"ramfs"}},[t("a",{staticClass:"header-anchor",attrs:{href:"#ramfs"}},[s._v("#")]),s._v(" RamFS")]),s._v(" "),t("p",[s._v("ramfs是vfs下具体实现的一种基于RAM做存储的文件系统，主要实现了以下功能：")]),s._v(" "),t("ul",[t("li",[t("strong",[s._v("read_at")]),s._v(":读")]),s._v(" "),t("li",[t("strong",[s._v("write_at")]),s._v(":写")]),s._v(" "),t("li",[t("strong",[s._v("poll")]),s._v(":获取文件状态")]),s._v(" "),t("li",[t("strong",[s._v("resize")]),s._v(":重置用于存放数据的data的大小")]),s._v(" "),t("li",[t("strong",[s._v("create_with_data")]),s._v(":创建自带数据的文件")]),s._v(" "),t("li",[t("strong",[s._v("link")]),s._v(":链接")]),s._v(" "),t("li",[t("strong",[s._v("unlink")]),s._v(":解链接")]),s._v(" "),t("li",[s._v("**rmdir:**删除文件夹")]),s._v(" "),t("li",[t("strong",[s._v("move_")]),s._v(":移动文件")]),s._v(" "),t("li",[t("strong",[s._v("find")]),s._v(":查找文件")]),s._v(" "),t("li",[t("strong",[s._v("list")]),s._v(":显示当前文件夹下的内容")])])])}),[],!1,null,null,null);t.default=e.exports}}]);
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