Re: SLUB defrag pull request?

From: Miklos Szeredi
Date: Mon Oct 20 2008 - 14:02:37 EST

On Mon, 20 Oct 2008, Christoph Lameter wrote:
> >> kick_inodes() only works on inodes that first have undergone
> >> get_inodes() where we establish a refcount under inode_lock(). The final
> >> cleanup in kick_inodes() is done under iprune_mutex. You are looking at
> >> the loop that does writeback and invalidates attached dentries. This can
> >> fail for various reasons.
> >
> > Yes, but I'm not at all sure that calling remove_inode_buffers() or
> > invalidate_mapping_pages() is OK on a live inode. They should be done
> > after checking the refcount, just like prune_icache() does.
> Dont we do the same on a truncate?

Yes, with i_mutex and i_alloc_sem held.

> > Also, while d_invalidate() is not actually wrong here, because you
> > check S_ISDIR(), but it's still the wrong function to use. You really
> > just want to shrink the children. Invalidation means: the filesystem
> > found out that the cached inode is invalid, so we want to throw it
> > away. In the future it might actually be able to do it for
> > directories as well, but currently it cannot because of possible
> > mounts on the dentry.
> Thats the same issue as with the dentries. The new function could deal with
> both situations?


The big issue is dealing with umount. You could do something like
grab_super() on sb before getting a ref on the inode/dentry. But I'm
not sure this is a good idea. There must be a simpler way to achieve

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