Re: [PATCH] Per-superblock unused dentry LRU lists V3

[Balbir Singh]

David Chinner wrote:
> On Tue, May 30, 2006 at 05:04:38PM +0200, Jan Blunck wrote:
> > > David Chinner <dgc@xxxxxxx> wrote:
> > > -
> > > void shrink_dcache_sb(struct super_block * sb)
> > > {
> ....
> > > +       __shrink_dcache_sb(sb, &sb->s_dentry_lru_nr, 0);
> > > }
> > This doesn't prune all the dentries on the unused list. The parents of the
> > pruned dentries are added to the unused list. Therefore just shrinking
> > sb->s_dentry_lru_nr dentries isn't enough.
>
> Yes, you are right, Jan. I'm surprised I didn't see problems due to this.
> The original patch got this right by shrinking in this case until the list
> was empty. I'll wrap this one in a while loop...
>
> Cheers,
>
> Dave.

Good catch,

I suspect the reason why the problem never showed up is because select_parent()
would take care of ensuring that the parent entries move to LRU list (this is
the case of regular umounts, which do not call shrink_dcache_sb() directly).

Maybe even the dentry_unused list should be per-superblock now.

--
       Regards,
	Balbir Singh,
	Linux Technology Center,
	IBM Software Labs
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