From mboxrd@z Thu Jan 1 00:00:00 1970 From: Hoeun Ryu Subject: Re: [PATCH v2] mm: add VM_STATIC flag to vmalloc and prevent from removing the areas Date: Wed, 19 Apr 2017 14:32:14 +0900 Message-ID: References: <1492494570-21068-1-git-send-email-hoeun.ryu@gmail.com> <20170418065946.GB22360@dhcp22.suse.cz> Mime-Version: 1.0 (1.0) Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <20170418065946.GB22360@dhcp22.suse.cz> Sender: owner-linux-mm@kvack.org To: Michal Hocko Cc: hch@infradead.org, khandual@linux.vnet.ibm.com, Andrew Morton , Roman Pen , Andreas Dilger , Andrey Ryabinin , Chris Wilson , Ingo Molnar , zijun_hu , Matthew Wilcox , Thomas Garnier , "Kirill A. Shutemov" , linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org List-Id: linux-arch.vger.kernel.org > On Apr 18, 2017, at 3:59 PM, Michal Hocko wrote: >=20 >> On Tue 18-04-17 14:48:39, Hoeun Ryu wrote: >> vm_area_add_early/vm_area_register_early() are used to reserve vmalloc ar= ea >> 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 t= he >> rbtree by accident. >=20 > Has this been a problem in the past or currently so that it is worth > handling? >=20 >> This flags can be also used by other vmalloc APIs to >> specify that the area will never go away. >=20 > Do we have a user for that? >=20 >> This makes remove_vm_area() more robust against other kind of errors (eg.= >> programming errors). >=20 > Well, yes it will help to prevent from vfree(early_mem) but we have 4 > users of vm_area_register_early so I am really wondering whether this is > worth additional code. It would really help to understand your > motivation for the patch if we were explicit about the problem you are > trying to solve. I just think that it would be good to make it robust against various kind of= errors. You might think that's not an enough reason to do so though. >=20 > Thanks >=20 > --=20 > Michal Hocko > SUSE Labs -- 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 From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pg0-f66.google.com ([74.125.83.66]:34884 "EHLO mail-pg0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759596AbdDSFcX (ORCPT ); Wed, 19 Apr 2017 01:32:23 -0400 Content-Type: text/plain; charset=us-ascii Mime-Version: 1.0 (1.0) Subject: Re: [PATCH v2] mm: add VM_STATIC flag to vmalloc and prevent from removing the areas From: Hoeun Ryu In-Reply-To: <20170418065946.GB22360@dhcp22.suse.cz> Date: Wed, 19 Apr 2017 14:32:14 +0900 Content-Transfer-Encoding: quoted-printable Message-ID: References: <1492494570-21068-1-git-send-email-hoeun.ryu@gmail.com> <20170418065946.GB22360@dhcp22.suse.cz> Sender: linux-arch-owner@vger.kernel.org List-ID: To: Michal Hocko Cc: hch@infradead.org, khandual@linux.vnet.ibm.com, Andrew Morton , Roman Pen , Andreas Dilger , Andrey Ryabinin , Chris Wilson , Ingo Molnar , zijun_hu , Matthew Wilcox , Thomas Garnier , "Kirill A. Shutemov" , linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Message-ID: <20170419053214.69VaxcHWiLxaXOmVkZWjQjdtbf-JKVCJsCmxF9NvSOc@z> > On Apr 18, 2017, at 3:59 PM, Michal Hocko wrote: >=20 >> On Tue 18-04-17 14:48:39, Hoeun Ryu wrote: >> vm_area_add_early/vm_area_register_early() are used to reserve vmalloc ar= ea >> 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 t= he >> rbtree by accident. >=20 > Has this been a problem in the past or currently so that it is worth > handling? >=20 >> This flags can be also used by other vmalloc APIs to >> specify that the area will never go away. >=20 > Do we have a user for that? >=20 >> This makes remove_vm_area() more robust against other kind of errors (eg.= >> programming errors). >=20 > Well, yes it will help to prevent from vfree(early_mem) but we have 4 > users of vm_area_register_early so I am really wondering whether this is > worth additional code. It would really help to understand your > motivation for the patch if we were explicit about the problem you are > trying to solve. I just think that it would be good to make it robust against various kind of= errors. You might think that's not an enough reason to do so though. >=20 > Thanks >=20 > --=20 > Michal Hocko > SUSE Labs