64 lines
1.5 KiB
HTML
64 lines
1.5 KiB
HTML
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<html>
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<head>
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<title>Homework: Files and Disk I/O</title>
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</head>
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<body>
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<h1>Homework: Files and Disk I/O</h1>
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<p>
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<b>Read</b>: bio.c, fd.c, fs.c, and ide.c
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<p>
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This homework should be turned in at the beginning of lecture.
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<p>
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<b>File and Disk I/O</b>
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<p>Insert a print statement in bwrite so that you get a
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print every time a block is written to disk:
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<pre>
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cprintf("bwrite sector %d\n", sector);
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</pre>
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<p>Build and boot a new kernel and run these three commands at the shell:
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<pre>
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echo >a
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echo >a
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rm a
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mkdir d
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</pre>
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(You can try <tt>rm d</tt> if you are curious, but it should look
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almost identical to <tt>rm a</tt>.)
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<p>You should see a sequence of bwrite prints after running each command.
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Record the list and annotate it with the calling function and
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what block is being written.
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For example, this is the <i>second</i> <tt>echo >a</tt>:
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<pre>
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$ echo >a
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bwrite sector 121 # writei (data block)
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bwrite sector 3 # iupdate (inode block)
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$
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</pre>
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<p>Hint: the easiest way to get the name of the
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calling function is to add a string argument to bwrite,
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edit all the calls to bwrite to pass the name of the
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calling function, and just print it.
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You should be able to reason about what kind of
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block is being written just from the calling function.
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<p>You need not write the following up, but try to
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understand why each write is happening. This will
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help your understanding of the file system layout
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and the code.
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<p>
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<b>This completes the homework.</b>
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</body>
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