Re: [PATCH 2/5] vfs: d_genocide() doesnt add dentries to unused list

[Balbir Singh <balbir@in.ibm.com>]

jblunck@suse.de wrote:
> Calling d_genocide() is only lowering the reference count of the dentries but
> doesn't add them to the unused list.
> 
> Signed-off-by: Jan Blunck <jblunck@suse.de>
> ---
>  fs/dcache.c |   18 ++++++++++++++++--
>  1 file changed, 16 insertions(+), 2 deletions(-)
> 
> Index: work-2.6/fs/dcache.c
> ===================================================================
> --- work-2.6.orig/fs/dcache.c
> +++ work-2.6/fs/dcache.c
> @@ -1612,11 +1612,25 @@ resume:
>  			this_parent = dentry;
>  			goto repeat;
>  		}
> -		atomic_dec(&dentry->d_count);
> +		if (!list_empty(&dentry->d_lru)) {
> +			dentry_stat.nr_unused--;
> +			list_del_init(&dentry->d_lru);
> +		}
> +		if (atomic_dec_and_test(&dentry->d_count)) {
> +			list_add(&dentry->d_lru, dentry_unused.prev);
> +			dentry_stat.nr_unused++;
> +		}

We could have dentries on the LRU list with non-zero d_count. If
we have a dentry on the LRU list with a count of 1, then the code
will remove it from LRU list and then add it back subsequently.

I think the condition below should be an else if

>  	}
>  	if (this_parent != root) {
>  		next = this_parent->d_u.d_child.next;
> -		atomic_dec(&this_parent->d_count);
> +		if (!list_empty(&this_parent->d_lru)) {
> +			dentry_stat.nr_unused--;
> +			list_del_init(&this_parent->d_lru);
> +		}
> +		if (atomic_dec_and_test(&this_parent->d_count)) {
> +			list_add(&this_parent->d_lru, dentry_unused.prev);
> +			dentry_stat.nr_unused++;
> +		}

Ditto

>  		this_parent = this_parent->d_parent;
>  		goto resume;
>  	}
> 

d_genocide() now almost looks like select_parent(). I think we can share a lot
of code between the two.

-- 

	Balbir Singh,
	Linux Technology Center,
	IBM Software Labs