How does kernel know file is closed

What exactly is the mechanism by which the linux knows that a file has been closed ? I know commands such as INOTIFY would trigger IN_CLOSE_WRITE event when a file is closed. But how does it work ? What trig开发者_开发技巧gers close of a file ?

Similarly how does OS know that a file has been opened and where does it register that fact?

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The OS (i.e. kernel) is the one that actually opens and closes files. A program will have to tell the OS to open/close files on its behalf every time it wants to do so via system calls. The OS can simply keep track of these calls that go through itself.

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There is an open file table that lists all the streams that are open and where they point to in memory.

This may help: http://www.cs.kent.edu/~walker/classes/os.f07/lectures/Walker-11.pdf