From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nick Piggin Subject: [patch 01/44] mm: revert KERNEL_DS buffered write optimisation Date: Tue, 24 Apr 2007 11:23:47 +1000 Message-ID: <20070424013431.935100000@suse.de> References: <20070424012346.696840000@suse.de> Cc: Linux Filesystems , Mark Fasheh , Linux Memory Management , Neil Brown To: Andrew Morton Return-path: Received: from cantor.suse.de ([195.135.220.2]:60267 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753169AbXDXFUv (ORCPT ); Tue, 24 Apr 2007 01:20:51 -0400 Content-Disposition: inline; filename=mm-revert-nfsd-writev-opt.patch Sender: linux-fsdevel-owner@vger.kernel.org List-Id: linux-fsdevel.vger.kernel.org Revert the patch from Neil Brown to optimise NFSD writev handling. Cc: Linux Memory Management Cc: Linux Filesystems Cc: Neil Brown Signed-off-by: Nick Piggin mm/filemap.c | 32 +++++++++++++------------------- 1 file changed, 13 insertions(+), 19 deletions(-) Index: linux-2.6/mm/filemap.c =================================================================== --- linux-2.6.orig/mm/filemap.c +++ linux-2.6/mm/filemap.c @@ -1980,27 +1980,21 @@ generic_file_buffered_write(struct kiocb /* Limit the size of the copy to the caller's write size */ bytes = min(bytes, count); - /* We only need to worry about prefaulting when writes are from - * user-space. NFSd uses vfs_writev with several non-aligned - * segments in the vector, and limiting to one segment a time is - * a noticeable performance for re-write + /* + * Limit the size of the copy to that of the current segment, + * because fault_in_pages_readable() doesn't know how to walk + * segments. */ - if (!segment_eq(get_fs(), KERNEL_DS)) { - /* - * Limit the size of the copy to that of the current - * segment, because fault_in_pages_readable() doesn't - * know how to walk segments. - */ - bytes = min(bytes, cur_iov->iov_len - iov_base); + bytes = min(bytes, cur_iov->iov_len - iov_base); + + /* + * Bring in the user page that we will copy from _first_. + * Otherwise there's a nasty deadlock on copying from the + * same page as we're writing to, without it being marked + * up-to-date. + */ + fault_in_pages_readable(buf, bytes); - /* - * Bring in the user page that we will copy from - * _first_. Otherwise there's a nasty deadlock on - * copying from the same page as we're writing to, - * without it being marked up-to-date. - */ - fault_in_pages_readable(buf, bytes); - } page = __grab_cache_page(mapping,index,&cached_page,&lru_pvec); if (!page) { status = -ENOMEM; --