mm: use lockless radix-tree probe
Probing pages and radix_tree_tagged are lockless operations with the lockless
radix-tree. Convert these users to RCU locking rather than using tree_lock.
Signed-off-by: Nick Piggin <npiggin@suse.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 4472036..2adb899 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -1022,17 +1022,15 @@
EXPORT_SYMBOL(test_set_page_writeback);
/*
- * Return true if any of the pages in the mapping are marged with the
+ * Return true if any of the pages in the mapping are marked with the
* passed tag.
*/
int mapping_tagged(struct address_space *mapping, int tag)
{
- unsigned long flags;
int ret;
-
- read_lock_irqsave(&mapping->tree_lock, flags);
+ rcu_read_lock();
ret = radix_tree_tagged(&mapping->page_tree, tag);
- read_unlock_irqrestore(&mapping->tree_lock, flags);
+ rcu_read_unlock();
return ret;
}
EXPORT_SYMBOL(mapping_tagged);
diff --git a/mm/readahead.c b/mm/readahead.c
index fc52f9f..c5c8981 100644
--- a/mm/readahead.c
+++ b/mm/readahead.c
@@ -149,20 +149,19 @@
/*
* Preallocate as many pages as we will need.
*/
- read_lock_irq(&mapping->tree_lock);
for (page_idx = 0; page_idx < nr_to_read; page_idx++) {
pgoff_t page_offset = offset + page_idx;
if (page_offset > end_index)
break;
+ rcu_read_lock();
page = radix_tree_lookup(&mapping->page_tree, page_offset);
+ rcu_read_unlock();
if (page)
continue;
- read_unlock_irq(&mapping->tree_lock);
page = page_cache_alloc_cold(mapping);
- read_lock_irq(&mapping->tree_lock);
if (!page)
break;
page->index = page_offset;
@@ -171,7 +170,6 @@
SetPageReadahead(page);
ret++;
}
- read_unlock_irq(&mapping->tree_lock);
/*
* Now start the IO. We ignore I/O errors - if the page is not