From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756450Ab2FFOwe (ORCPT ); Wed, 6 Jun 2012 10:52:34 -0400 Received: from mx1.redhat.com ([209.132.183.28]:61543 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756040Ab2FFOwd (ORCPT ); Wed, 6 Jun 2012 10:52:33 -0400 Date: Wed, 6 Jun 2012 16:50:09 +0200 From: Oleg Nesterov To: Ingo Molnar , Peter Zijlstra , Srikar Dronamraju Cc: Ananth N Mavinakayanahalli , Anton Arapov , Linus Torvalds , Masami Hiramatsu , linux-kernel@vger.kernel.org Subject: [PATCH v2 2/3] uprobes: change build_map_info() to try kmalloc(GFP_NOWAIT) first Message-ID: <20120606145009.GC24078@redhat.com> References: <20120604145238.GA6408@redhat.com> <20120606144933.GA24078@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20120606144933.GA24078@redhat.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org build_map_info() doesn't allocate the memory under i_mmap_mutex to avoid the deadlock with page reclaim. But it can try GFP_NOWAIT first, it should work in the likely case and thus we almost never need the pre-alloc-and-retry path. Signed-off-by: Oleg Nesterov --- kernel/events/uprobes.c | 10 ++++++++++ 1 files changed, 10 insertions(+), 0 deletions(-) diff --git a/kernel/events/uprobes.c b/kernel/events/uprobes.c index a1bbcab..88e903d 100644 --- a/kernel/events/uprobes.c +++ b/kernel/events/uprobes.c @@ -771,6 +771,16 @@ build_map_info(struct address_space *mapping, loff_t offset, bool is_register) if (!valid_vma(vma, is_register)) continue; + if (!prev && !more) { + /* + * Needs GFP_NOWAIT to avoid i_mmap_mutex recursion through + * reclaim. This is optimistic, no harm done if it fails. + */ + prev = kmalloc(sizeof(struct map_info), + GFP_NOWAIT | __GFP_NOMEMALLOC | __GFP_NOWARN); + if (prev) + prev->next = NULL; + } if (!prev) { more++; continue; -- 1.5.5.1