Question

I’m trying to make a linux kernel module, which supports open, close, read and write operations.
So I want to register these functions via struct file_operations, however I can’t find ‘close’ entry in the struct.
I think I should use ‘release’ instead of ‘close’, but I wonder why the name is ‘release’ and not ‘close’?

Answer 1

Because the file may be opened multiple times, when you close a descriptor, only on the last close call for the last reference to the file invokes release. So there is a difference between close and release.

release: called at the last close(2) of this file, i.e. when
file->f_count reaches 0. Although defined as returning int, the return
value is ignored by VFS (see fs/file_table.c:__fput()). more