Re: iget4/read_inode2 race in get_new_inode

[Christoph Hellwig <hch@infradead.org>]

On Mon, Apr 29, 2002 at 08:34:00PM +0100, Anton Altaparmakov wrote:
> 
> - Replace iget4() with iget5() with an additional argument: a callback to 
> initialize a locked inode in order to kill the race condition Jan found.
> 
> struct inode *iget5(sb, ino, find_actor, init_locked_actor, void *opaque);
> 
> - Let get_new_inode() call init_locked_actor before dropping the 
> inode_lock. It then calls ->read_inode as usual.

Don't do this - rather use the XFS-style icreate() plus per-filesystem
exclusion.  The VFS shouldn't have to worry about this kind of problems,
especially with such an ugly API.

> struct inode *fs_iget(sb, ino, find_actor, init_locked_actor, opaque, 
> fs_read_inode)
> {
>          inode = iget5(sb, ino, find_actor, init_locked_actor, opaque);
>          if (inode has I_NEW set) {
>                  fs_read_inode(inode);
>                  unlock_new_inode(inode);
>          }
>          return inode;
> }

I already though about this alot (as generic_iget()), but I wonder whether
it is really worth the effort or whether filesystems should just duplicate
that 5 lines.