Changes between Initial Version and Version 1 of FSDesign

Timestamp:

2009-06-01T11:02:47Z (15 years ago)

Author:

Jakub Jermář

Comment:

—

FSDesign

@@ +1 @@
+= Implementation and design of the file system layer =
+
+Unlike in monolitic designs, the file system functionality is spread across
+several layers in HelenOS:
+
+ * [#FSDesignLibc standard library support],
+ * [#FSDesignVFS VFS server],
+ * [#FSDesignFS set of individual file system servers], and
+ * [#FSDesignLibFS libfs library].
+
+== Standard library support == #FSDesignLibc
+
+The standard library translates more or less POSIX file system requests made by 
+the user application to the VFS server frontend protocol and passes them to
+''VFS''. The library emulates some calls such as ''opendir()'', ''readdir()'', 
+''rewinddir()'' and ''closedir()'' using other calls. In this case these will
+be ''open()'', ''read()'', ''lseek()'' and ''close()''.
+
+The VFS server accepts only absolute file paths and so the standard library 
+takes care of providing the ''getcwd()'' and ''chdir()'' interfaces. It also
+translates all relative paths to absolute. Passing absolute paths may not be
+always optimal, but it simplifies the design of the VFS server and the libfs
+algorithms. In addition, thanks to this feature, the ''..'' file path
+components can be processed lexically, which leads to further simplifications.
+
+The standard library forwards all other requests, which it is unable to handle 
+itslef, to the VFS server and does not contribute to the file system
+functionality by any other means. Each file system request forwarded to VFS
+is composed of one or more IPC phone calls.