Re: fatfs locking

[Thomas Bushnell, BSG]

Roland McGrath <roland@frob.com> writes:

> It seems reasonable to me to leave it up to the filesystem-specific code to
> decide what nodes it might need to lock, and just give it enough
> information to avoid deadlock.  I have in my tree a slightly different
> change that adds a struct node * argument to diskfs_cached_lookup instead
> of a flag, indicating the directory node (or none if null) that the caller
> has locked.  I think that by using this the special case for ".." in
> libdiskfs/name-cache.c can be removed.  I have changes that add the
> argument, remove the ".." special case for unlocking in
> diskfs_check_lookup_cache, and instead makes each diskfs_cached_lookup
> implementation check for the lookup matching the already-locked node.

Ok, I've now had a chance to think more about this.

This is basically sure to be wrong, at least, it will suffer from the
consistency problems that I mentioned in the previous message I sent.

I will think about how to make fatfs work, but I don't think this kind
of "solution" is at all right.