From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f49.google.com (mail-pa0-f49.google.com [209.85.220.49]) by kanga.kvack.org (Postfix) with ESMTP id A29646B0032 for ; Tue, 17 Sep 2013 20:30:15 -0400 (EDT) Received: by mail-pa0-f49.google.com with SMTP id ld10so7505289pab.36 for ; Tue, 17 Sep 2013 17:30:15 -0700 (PDT) Received: from /spool/local by e28smtp07.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Wed, 18 Sep 2013 06:00:08 +0530 Received: from d28relay02.in.ibm.com (d28relay02.in.ibm.com [9.184.220.59]) by d28dlp02.in.ibm.com (Postfix) with ESMTP id 674973940058 for ; Wed, 18 Sep 2013 05:59:51 +0530 (IST) Received: from d28av04.in.ibm.com (d28av04.in.ibm.com [9.184.220.66]) by d28relay02.in.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id r8I0WEnm6357096 for ; Wed, 18 Sep 2013 06:02:15 +0530 Received: from d28av04.in.ibm.com (localhost [127.0.0.1]) by d28av04.in.ibm.com (8.14.4/8.14.4/NCO v10.0 AVout) with ESMTP id r8I0U3KV025760 for ; Wed, 18 Sep 2013 06:00:04 +0530 From: Wanpeng Li Subject: [PATCH v6 1/2] mm/vmalloc: fix show vmap_area information race with vmap_area tear down Date: Wed, 18 Sep 2013 08:30:01 +0800 Message-Id: <1379464202-21104-1-git-send-email-liwanp@linux.vnet.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton Cc: Joonsoo Kim , David Rientjes , KOSAKI Motohiro , Zhang Yanfei , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Wanpeng Li 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 | 15 ++++++--------- 1 file changed, 6 insertions(+), 9 deletions(-) diff --git a/mm/vmalloc.c b/mm/vmalloc.c index 5368b17..9b75028 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -2582,16 +2582,13 @@ 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; -- 1.8.1.2 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org