From mboxrd@z Thu Jan 1 00:00:00 1970 From: npiggin@suse.de Subject: [patch 7/9] mm: write_cache_pages terminate quickly Date: Wed, 29 Oct 2008 01:47:22 +1100 Message-ID: <20081028145734.493118000@nick.local0.net> References: <20081028144715.683011000@suse.de> Cc: linux-fsdevel@vger.kernel.org, Dave Chinner , Chris Mason To: akpm@linux-foundation.org Return-path: Received: from mail.suse.de ([195.135.220.2]:47930 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752924AbYJ1PBM (ORCPT ); Tue, 28 Oct 2008 11:01:12 -0400 Content-Disposition: inline; filename=mm-wcp-terminate-quickly.patch Sender: linux-fsdevel-owner@vger.kernel.org List-ID: Terminate the write_cache_pages loop upon encountering the first page past end, without locking the page. Pages cannot have their index change when we have a reference on them (truncate, eg truncate_inode_pages_range performs the same check without the page lock). Signed-off-by: Nick Piggin --- Index: linux-2.6/mm/page-writeback.c =================================================================== --- linux-2.6.orig/mm/page-writeback.c +++ linux-2.6/mm/page-writeback.c @@ -911,15 +911,24 @@ retry: for (i = 0; i < nr_pages; i++) { struct page *page = pvec.pages[i]; - done_index = page->index + 1; - /* - * At this point we hold neither mapping->tree_lock nor - * lock on the page itself: the page may be truncated or - * invalidated (changing page->mapping to NULL), or even - * swizzled back from swapper_space to tmpfs file - * mapping + * At this point, the page may be truncated or + * invalidated (changing page->mapping to NULL), or + * even swizzled back from swapper_space to tmpfs file + * mapping. However, page->index will not change + * because we have a reference on the page. */ + if (page->index > end) { + /* + * can't be range_cyclic (1st pass) because + * end == -1 in that case. + */ + done = 1; + break; + } + + done_index = page->index + 1; + lock_page(page); /* @@ -936,15 +945,6 @@ continue_unlock: continue; } - if (page->index > end) { - /* - * can't be range_cyclic (1st pass) because - * end == -1 in that case. - */ - done = 1; - goto continue_unlock; - } - if (!PageDirty(page)) { /* someone wrote it for us */ goto continue_unlock; --