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

From: Alexander Viro (
Date: Mon Jan 07 2002 - 14:38:45 EST

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
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.

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