From mboxrd@z Thu Jan 1 00:00:00 1970 From: Anshuman Khandual Subject: Re: [PATCH] mm: add VM_STATIC flag to vmalloc and prevent from removing the areas Date: Thu, 13 Apr 2017 09:47:03 +0530 Message-ID: References: <1491973350-26816-1-git-send-email-hoeun.ryu@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Return-path: Received: from mx0b-001b2d01.pphosted.com ([148.163.158.5]:40260 "EHLO mx0a-001b2d01.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1750746AbdDMERQ (ORCPT ); Thu, 13 Apr 2017 00:17:16 -0400 Received: from pps.filterd (m0098416.ppops.net [127.0.0.1]) by mx0b-001b2d01.pphosted.com (8.16.0.20/8.16.0.20) with SMTP id v3D48ebt069191 for ; Thu, 13 Apr 2017 00:17:15 -0400 Received: from e28smtp01.in.ibm.com (e28smtp01.in.ibm.com [125.16.236.1]) by mx0b-001b2d01.pphosted.com with ESMTP id 29t1rj0vb4-1 (version=TLSv1.2 cipher=AES256-SHA bits=256 verify=NOT) for ; Thu, 13 Apr 2017 00:17:15 -0400 Received: from localhost by e28smtp01.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 13 Apr 2017 09:47:12 +0530 In-Reply-To: <1491973350-26816-1-git-send-email-hoeun.ryu@gmail.com> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Hoeun Ryu , Andrew Morton , Andrey Ryabinin , Andreas Dilger , Vlastimil Babka , Michal Hocko , Chris Wilson , Ingo Molnar , zijun_hu , Matthew Wilcox , Thomas Garnier , "Kirill A. Shutemov" Cc: linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org On 04/12/2017 10:31 AM, Hoeun Ryu wrote: > vm_area_add_early/vm_area_register_early() are used to reserve vmalloc area > during boot process and those virtually mapped areas are never unmapped. > So `OR` VM_STATIC flag to the areas in vmalloc_init() when importing > existing vmlist entries and prevent those areas from being removed from the > rbtree by accident. I am wondering whether protection against accidental deletion of any vmap area should be done in remove_vm_area() function or the callers should take care of it. But I guess either way it works. > > Signed-off-by: Hoeun Ryu > --- > include/linux/vmalloc.h | 1 + > mm/vmalloc.c | 9 ++++++--- > 2 files changed, 7 insertions(+), 3 deletions(-) > > diff --git a/include/linux/vmalloc.h b/include/linux/vmalloc.h > index 46991ad..3df53fc 100644 > --- a/include/linux/vmalloc.h > +++ b/include/linux/vmalloc.h > @@ -19,6 +19,7 @@ struct notifier_block; /* in notifier.h */ > #define VM_UNINITIALIZED 0x00000020 /* vm_struct is not fully initialized */ > #define VM_NO_GUARD 0x00000040 /* don't add guard page */ > #define VM_KASAN 0x00000080 /* has allocated kasan shadow memory */ > +#define VM_STATIC 0x00000200 You might want to add some description in the comment saying its a sticky VM area which will never go away or something. > /* bits [20..32] reserved for arch specific ioremap internals */ > > /* > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index 8ef8ea1..fb5049a 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -1262,7 +1262,7 @@ void __init vmalloc_init(void) > /* Import existing vmlist entries. */ > for (tmp = vmlist; tmp; tmp = tmp->next) { > va = kzalloc(sizeof(struct vmap_area), GFP_NOWAIT); > - va->flags = VM_VM_AREA; > + va->flags = VM_VM_AREA | VM_STATIC; > va->va_start = (unsigned long)tmp->addr; > va->va_end = va->va_start + tmp->size; > va->vm = tmp; > @@ -1480,7 +1480,7 @@ struct vm_struct *remove_vm_area(const void *addr) > might_sleep(); > > va = find_vmap_area((unsigned long)addr); > - if (va && va->flags & VM_VM_AREA) { > + if (va && va->flags & VM_VM_AREA && likely(!(va->flags & VM_STATIC))) { You might want to move the VM_STATIC check before the VM_VM_AREA check so in cases where the former is set we can save one more conditional check.