From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932266Ab3IYBDK (ORCPT ); Tue, 24 Sep 2013 21:03:10 -0400 Received: from e28smtp06.in.ibm.com ([122.248.162.6]:41694 "EHLO e28smtp06.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754979Ab3IYBDD (ORCPT ); Tue, 24 Sep 2013 21:03:03 -0400 From: Wanpeng Li To: Andrew Morton Cc: Joonsoo Kim , David Rientjes , KOSAKI Motohiro , Zhang Yanfei , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Wanpeng Li Subject: [PATCH v7 2/4] mm/vmalloc: fix show vmap_area information race with vmap_area tear down Date: Wed, 25 Sep 2013 09:02:42 +0800 Message-Id: <1380070964-12975-2-git-send-email-liwanp@linux.vnet.ibm.com> X-Mailer: git-send-email 1.7.5.4 In-Reply-To: <1380070964-12975-1-git-send-email-liwanp@linux.vnet.ibm.com> References: <1380070964-12975-1-git-send-email-liwanp@linux.vnet.ibm.com> X-TM-AS-MML: No X-Content-Scanned: Fidelis XPS MAILER x-cbid: 13092501-9574-0000-0000-000009C9028F Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Changelog: *v4 -> v5: return directly for !VM_VM_AREA case and remove (VM_LAZY_FREE | VM_LAZY_FREEING) check *v5 -> v6: add KOSAKI's ack There is a race window between vmap_area tear down and show vmap_area information. A B remove_vm_area spin_lock(&vmap_area_lock); va->vm = NULL; va->flags &= ~VM_VM_AREA; spin_unlock(&vmap_area_lock); spin_lock(&vmap_area_lock); if (va->flags & (VM_LAZY_FREE | VM_LAZY_FREEZING)) return 0; if (!(va->flags & VM_VM_AREA)) { seq_printf(m, "0x%pK-0x%pK %7ld vm_map_ram\n", (void *)va->va_start, (void *)va->va_end, va->va_end - va->va_start); return 0; } free_unmap_vmap_area(va); flush_cache_vunmap free_unmap_vmap_area_noflush unmap_vmap_area free_vmap_area_noflush va->flags |= VM_LAZY_FREE The assumption !VM_VM_AREA represents vm_map_ram allocation is introduced by commit: d4033afd(mm, vmalloc: iterate vmap_area_list, instead of vmlist, in vmallocinfo()). However, !VM_VM_AREA also represents vmap_area is being tear down in race window mentioned above. This patch fix it by don't dump any information for !VM_VM_AREA case and also remove (VM_LAZY_FREE | VM_LAZY_FREEING) check since they are not possible for !VM_VM_AREA case. Suggested-by: Joonsoo Kim Acked-by: KOSAKI Motohiro Signed-off-by: Wanpeng Li --- mm/vmalloc.c | 13 +++++-------- 1 files changed, 5 insertions(+), 8 deletions(-) diff --git a/mm/vmalloc.c b/mm/vmalloc.c index f75c2aa..7647e69 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -2578,15 +2578,12 @@ static int s_show(struct seq_file *m, void *p) struct vmap_area *va = p; struct vm_struct *v; - if (va->flags & (VM_LAZY_FREE | VM_LAZY_FREEING)) - return 0; - - if (!(va->flags & VM_VM_AREA)) { - seq_printf(m, "0x%pK-0x%pK %7ld vm_map_ram\n", - (void *)va->va_start, (void *)va->va_end, - va->va_end - va->va_start); + /* + * s_show can encounter race with remove_vm_area, !VM_VM_AREA on + * behalf of vmap area is being tear down or vm_map_ram allocation. + */ + if (!(va->flags & VM_VM_AREA)) return 0; - } v = va->vm; -- 1.7.5.4