Re: PATCH 2.5.2.9: ext2 unbork fs.h (part 1/7)

[Alexander Viro]

On Mon, 7 Jan 2002, Daniel Phillips wrote:

> On January 7, 2002 04:19 pm, Daniel Phillips wrote:
> >   - You are dreferencing a pointer, and have two allocations for every
> >     inode instead of one.
> 
> Oh no, you only have one allocator, and you have the filesystem do it, with 
> per-sb methods.  Why is this better than having the VFS do it?  Does this 
> imply you might have different sized inodes with different mounts of the same 
> filesystem?

Because exposing sizes of private objects is Wrong.

Now, the problems I see with Jeff's variant:

a) if you make struct inode a part of ext2_inode - WTF bother with pointer?
b) ->destroy_inode() / ->clear_inode().  Merge them - that way it's one
method.
c) get_empty_inode() must die.  Make it new_inode() and be done with that.
And have socket.c explicitly set ->i_dev to NODEV afterwards.
d) ext2/balloc.c cleanup probably should be merged before.

I can live with "maintain refcounts in common part and leave allocation/freeing
to filesystem".  It's definitely better than allocating/freeing opaque objects
in VFS using numeric fields in fs_type.

We will need to set very strict rules on passing around/storing pointers to
ext2_inode and its ilk, though.  There will be bugs when somebody just decides
that keeping such pointers might be a good idea and forgets to be nice with
->i_count.  Or decrement it manually instead of calling iput(), etc.

It _MUST_ be explicitly documented - preferably beaten into skulls.