Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755929AbbGQRbu (ORCPT ); Fri, 17 Jul 2015 13:31:50 -0400 Received: from mx1.redhat.com ([209.132.183.28]:42908 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754337AbbGQRbt (ORCPT ); Fri, 17 Jul 2015 13:31:49 -0400 Date: Fri, 17 Jul 2015 13:31:47 -0400 From: Mike Snitzer To: Pali =?iso-8859-1?Q?Roh=E1r?= Cc: Len Brown , linux-pm@vger.kernel.org, "Rafael J. Wysocki" , linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org, dm-devel@redhat.com, Pavel Machek , Alasdair Kergon Subject: Re: [PATCH v2 2/3] dm: Export function dm_suspend_md() Message-ID: <20150717173147.GA5060@redhat.com> References: <1428254419-7334-1-git-send-email-pali.rohar@gmail.com> <20150717152253.GA1021@redhat.com> <20150717153045.GB1021@redhat.com> <201507171913.57104@pali> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <201507171913.57104@pali> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4595 Lines: 113 On Fri, Jul 17 2015 at 1:13pm -0400, Pali Roh?r wrote: > On Friday 17 July 2015 17:30:45 Mike Snitzer wrote: > > On Fri, Jul 17 2015 at 11:22am -0400, > > > > Mike Snitzer wrote: > > > On Fri, Jul 17 2015 at 10:22am -0400, > > > > > > Pali Roh?r wrote: > > > > On Friday 17 July 2015 10:04:39 Mike Snitzer wrote: > > > > > On Sun, Jun 21 2015 at 7:20am -0400, > > > > > > > > > > Pali Roh?r wrote: > > > > > > This patch exports function dm_suspend_md() which suspend > > > > > > mapped device so other kernel drivers can use it and could > > > > > > suspend mapped device when needed. > > > > > > > > > > > > Signed-off-by: Pali Roh?r > > > > > > --- > > > > > > > > > > > > drivers/md/dm.c | 6 ++++++ > > > > > > drivers/md/dm.h | 5 +++++ > > > > > > 2 files changed, 11 insertions(+) > > > > > > > > > > > > diff --git a/drivers/md/dm.c b/drivers/md/dm.c > > > > > > index 2caf492..03298ff 100644 > > > > > > --- a/drivers/md/dm.c > > > > > > +++ b/drivers/md/dm.c > > > > > > > > > > > > @@ -3343,6 +3343,12 @@ out: > > > > > > return r; > > > > > > > > > > > > } > > > > > > > > > > > > +int dm_suspend_md(struct mapped_device *md) > > > > > > +{ > > > > > > + return dm_suspend(md, DM_SUSPEND_LOCKFS_FLAG); > > > > > > +} > > > > > > +EXPORT_SYMBOL_GPL(dm_suspend_md); > > > > > > + > > > > > > > > > > > > /* > > > > > > > > > > > > * Internal suspend/resume works like userspace-driven > > > > > > suspend. It waits * until all bios finish and prevents > > > > > > issuing new bios to the target drivers. > > > > > > > > > > To do this properly you should be introducing a variant of > > > > > dm_internal_suspend. We currently have two variants: > > > > > dm_internal_suspend_fast > > > > > dm_internal_suspend_noflush > > > > > > > > > > The reason to use a dm_internal_suspend variant is this suspend > > > > > was _not_ initiated by an upper level ioctl (from userspace). > > > > > It was done internally from within the target. > > > > > > > > > > You're explicitly using DM_SUSPEND_LOCKFS_FLAG above.. meaning > > > > > you're interested in flushing all pending IO (in the FS > > > > > layered on dm-crupt, if one exists). > > > > > > > > > > But see the comment in __dm_internal_suspend() about > > > > > TASK_UNINTERRUPTIBLE. If you're OK with the dm-crypt initiated > > > > > suspend being TASK_UNINTERRUPTIBLE then you could just > > > > > introduce: > > > > > > > > > > void dm_internal_suspend_uninterruptible_flush(struct > > > > > mapped_device *md) { > > > > > > > > > > mutex_lock(&md->suspend_lock); > > > > > __dm_internal_suspend(md, DM_SUSPEND_LOCKFS_FLAG); > > > > > mutex_unlock(&md->suspend_lock); > > > > > > > > > > } > > > > > EXPORT_SYMBOL_GPL(dm_internal_suspend_uninterruptible_flush); > > > > > > > > > > Otherwise, there is much more extensive DM core changes needed > > > > > to __dm_internal_suspend() and .presuspend to properly support > > > > > TASK_INTERRUPTIBLE. > > > > > > > > Hi! I will look at dm_internal_suspend. Anyway use case for > > > > suspend is from dm-crypt to do both operations: suspend + key > > > > wipe. It means that without entering key again from userspace, > > > > resume is not possible. So my question is: It is possible to do > > > > internal suspend and then using resume from userspace via ioctl? > > > > > > Good question: no, userspace resume would block waiting for > > > internal resume. > > > > > > Soooo... I'll have to look at your patch 3 to understand why > > > dm-crypt is needing to initiate the suspend internally but then > > > userspace is initiating the resume... this imbalance is > > > concerning. > > > > Why not introduce a new message that allows you to wipe the key after > > suspend? Both initiated from userspace. > > There is already message for wiping key and it will success only if dm > is suspended. > > But this patch series is fixing another problem: wipe key before > suspend/hibernation action happend and to have it race free it must be > done after userspace is freezed! Yes, I remember now. So it isn't even userspace initiating the suspend_and_wipe, it is the PM chain notifier code you're adding. I'll think more about your use of dm_suspend() -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/