From: Nick Piggin 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 Signed-off-by: Andrew Morton --- mm/page-writeback.c | 8 +++----- mm/readahead.c | 6 ++---- 2 files changed, 5 insertions(+), 9 deletions(-) diff -puN mm/page-writeback.c~mm-use-lockless-radix-tree-probe mm/page-writeback.c --- a/mm/page-writeback.c~mm-use-lockless-radix-tree-probe +++ a/mm/page-writeback.c @@ -1022,17 +1022,15 @@ int test_set_page_writeback(struct 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); diff -puN mm/readahead.c~mm-use-lockless-radix-tree-probe mm/readahead.c --- a/mm/readahead.c~mm-use-lockless-radix-tree-probe +++ a/mm/readahead.c @@ -149,20 +149,19 @@ __do_page_cache_readahead(struct address /* * 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 SetPageReadahead(page); ret++; } - read_unlock_irq(&mapping->tree_lock); /* * Now start the IO. We ignore I/O errors - if the page is not _