From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nick Piggin Message-Id: <20070412103242.5564.51057.sendpatchset@linux.site> In-Reply-To: <20070412103151.5564.16127.sendpatchset@linux.site> References: <20070412103151.5564.16127.sendpatchset@linux.site> Subject: [patch 5/9] mm: lockless probe Date: Thu, 12 Apr 2007 14:45:33 +0200 (CEST) Sender: owner-linux-mm@kvack.org Return-Path: To: Linux Memory Management Cc: Nick Piggin , Andrew Morton List-ID: 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 Index: linux-2.6/drivers/mtd/devices/block2mtd.c =================================================================== --- linux-2.6.orig/drivers/mtd/devices/block2mtd.c +++ linux-2.6/drivers/mtd/devices/block2mtd.c @@ -59,28 +59,27 @@ static void cache_readahead(struct addre end_index = ((isize - 1) >> PAGE_CACHE_SHIFT); - read_lock_irq(&mapping->tree_lock); for (i = 0; i < PAGE_READAHEAD; i++) { pagei = index + i; if (pagei > end_index) { INFO("Overrun end of disk in cache readahead\n"); break; } + /* Don't need mapping->tree_lock - lookup can be racy */ + rcu_read_lock(); page = radix_tree_lookup(&mapping->page_tree, pagei); + rcu_read_unlock(); if (page && (!i)) break; 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 = pagei; list_add(&page->lru, &page_pool); ret++; } - read_unlock_irq(&mapping->tree_lock); if (ret) read_cache_pages(mapping, &page_pool, filler, NULL); } Index: linux-2.6/mm/page-writeback.c =================================================================== --- linux-2.6.orig/mm/page-writeback.c +++ linux-2.6/mm/page-writeback.c @@ -965,17 +965,15 @@ 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); Index: linux-2.6/mm/readahead.c =================================================================== --- linux-2.6.orig/mm/readahead.c +++ linux-2.6/mm/readahead.c @@ -281,27 +281,25 @@ __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; list_add(&page->lru, &page_pool); ret++; } - read_unlock_irq(&mapping->tree_lock); /* * Now start the IO. We ignore I/O errors - if the page is not -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org