From: Nick Piggin Date: Tue, 16 Oct 2007 08:24:41 +0000 (-0700) Subject: mm: improve find_lock_page X-Git-Tag: v2.6.24-rc1~1224 X-Git-Url: https://err.no/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=45726cb43d11b288c58243a26010f397054222f0;p=linux-2.6 mm: improve find_lock_page find_lock_page does not need to recheck ->index because if the page is in the right mapping then the index must be the same. Also, tree_lock does not need to be retaken after the page is locked in order to test that ->mapping has not changed, because holding the page lock pins its mapping. Signed-off-by: Nick Piggin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- diff --git a/mm/filemap.c b/mm/filemap.c index b436cbb3a8..7989c44cb2 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -621,26 +621,27 @@ struct page *find_lock_page(struct address_space *mapping, { struct page *page; - read_lock_irq(&mapping->tree_lock); repeat: + read_lock_irq(&mapping->tree_lock); page = radix_tree_lookup(&mapping->page_tree, offset); if (page) { page_cache_get(page); if (TestSetPageLocked(page)) { read_unlock_irq(&mapping->tree_lock); __lock_page(page); - read_lock_irq(&mapping->tree_lock); /* Has the page been truncated while we slept? */ - if (unlikely(page->mapping != mapping || - page->index != offset)) { + if (unlikely(page->mapping != mapping)) { unlock_page(page); page_cache_release(page); goto repeat; } + VM_BUG_ON(page->index != offset); + goto out; } } read_unlock_irq(&mapping->tree_lock); +out: return page; } EXPORT_SYMBOL(find_lock_page);