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Commit 00128188 authored by Nick Piggin's avatar Nick Piggin Committed by Linus Torvalds
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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: default avatarNick Piggin <npiggin@suse.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 557ed1fa

mm/page-writeback.c

+3 −5
Original line number Diff line number Diff line
@@ -1022,17 +1022,15 @@ int test_set_page_writeback(struct page *page) 
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);

mm/readahead.c

+2 −4
Original line number Diff line number Diff line
@@ -149,20 +149,19 @@ __do_page_cache_readahead(struct address_space *mapping, struct file *filp, 
	/*

	 * 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 @@ __do_page_cache_readahead(struct address_space *mapping, struct file *filp, 
			SetPageReadahead(page);

		ret++;

	}

	read_unlock_irq(&mapping->tree_lock);



	/*

	 * Now start the IO.  We ignore I/O errors - if the page is not