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Changes between Version 17 and Version 18 of FSDesign


Ignore:
Timestamp:
2009-11-17T11:16:58Z (10 years ago)
Author:
Jakub Jermář
Comment:

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  • FSDesign

    v17 v18  
    129129In the above code snippet, the ''vfs_rdwr()'' function first translates the file handle using the ''vfs_file_get()'' interface to a ''vfs_file_t'' structure and then locks the result. The VFS node is directly accessed in the two RW-lock lock operations at the end of the example.
    130130
    131 
    132 ==== VFS backend ====
     131=== VFS backend ===
    133132
    134133As soon as the VFS server knows the VFS node associated with the request, it either asks one of the endpoint file system servers to carry out the operation for it or, when it has enough information, it completes the operation itself. For example, VFS handles the VFS_IN_SEEK request, which corresponds to the POSIX call ''lseek()'', entirely on its own, because it just manipulates the current position pointer within the respective ''vfs_file_t'' structure. In the worst case, when seeking to the end of the file, VFS needs to know the size of the file, but this is not a problem, because the server maintains the current file size in each VFS node.
    135134
     135We refer to the part which communicates with the endpoint file system servers as to VFS backend. VFS backend knows the handle of the endpoint file system (and also of the underlying device) from the VFS node, so it can use it to obtain an IPC phone and communicate with it.