Hi,

On Wed 30-11-16 09:08:41, Jan Kara wrote:

quoted

quoted

+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 [off-list ref]
SUSE Labs, CR

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