Hi,
On Wed 30-11-16 09:08:41, Jan Kara wrote:
> > > +static int __dax_invalidate_mapping_entry(struct address_space *mapping,
> > > + pgoff_t index, bool trunc)
> > > +{
> > > + int ret = 0;
> > > + void *entry;
> > > + struct radix_tree_root *page_tree = &mapping->page_tree;
> > > +
> > > + spin_lock_irq(&mapping->tree_lock);
> > > + entry = get_unlocked_mapping_entry(mapping, index, NULL);
> > > + if (!entry || !radix_tree_exceptional_entry(entry))
> > > + goto out;
> > > + if (!trunc &&
> > > + (radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_DIRTY) ||
> > > + radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_TOWRITE)))
> > > + goto out;
> > > + radix_tree_delete(page_tree, index);
> >
> > You could use the new __radix_tree_replace() here and save a second
> > tree lookup.
>
> Hum, I'd need to return 'node' from get_unlocked_mapping_entry(). So
> probably I'll do it in a patch separate from this fix. But thanks for
> suggestion.
So I did this and quickly spotted a problem that when you use
__radix_tree_replace() to clear an entry, it will leave tags for that entry
set and that results in surprises. So I think I'll leave the code with
radix_tree_delete() for now.
It would probably make sense to make __radix_tree_replace() to clear tags
when we replace entry with NULL or at least WARN if some tags are set...
What do you think?
Honza
--
Jan Kara <jack@xxxxxxxx>
SUSE Labs, CR
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