Re: REMOVING THE DIRECTORY IN WHICH YOU ARE(REDHAT LINUX 9)

[Bob Proulx]

Eric Blake wrote:
> rohit sharma wrote:
> > but how is it possible to remove the directory in which you are
> 
> On other implementations, such as Linux, removing the directory does
> not free up any disk resources as long as a process still has a
> reference to the inode occupied by that directory, but the rmdir
> still succeeds by updating the parent directory to state that the
> directory is no longer reachable via the filesystem.  Then, when all
> processes that use the unlinked directory have exited, the
> filesystem can finally reclaim the disk space that the removed
> directory occupied.

I like to think of it as a garbage collection system implemented using
reference counting.  Every file (and special files such as
directories) have a reference count.  Files can be hard linked and so
have a large count of referencing directories pointing to them.
Additionally the system keeps track of open file descriptors which
also add to the reference count.

Removing a file from a directory decrements the reference count
because when they are removed from their parent directory then the
parent directory is no longer pointing to them.  Closing file
descriptors also decrements the reference count.  The system keeps
disk blocks around as long as the reference count is non-zero.  The
system automatically reclaims any disk blocks that have a reference
count of zero.

None of that is exactly true but it is a useful mental model of
filesystem operation just the same.

Bob