From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Snitzer Subject: Re: [PATCH v2 2/3] dm: Export function dm_suspend_md() Date: Fri, 17 Jul 2015 11:30:45 -0400 Message-ID: <20150717153045.GB1021@redhat.com> References: <1428254419-7334-1-git-send-email-pali.rohar@gmail.com> <1434885634-19895-1-git-send-email-pali.rohar@gmail.com> <1434885634-19895-3-git-send-email-pali.rohar@gmail.com> <20150717140438.GA29704@redhat.com> <20150717142251.GA12011@pali> <20150717152253.GA1021@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: Content-Disposition: inline In-Reply-To: <20150717152253.GA1021@redhat.com> Sender: linux-kernel-owner@vger.kernel.org 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 List-Id: linux-pm@vger.kernel.org On Fri, Jul 17 2015 at 11:22am -0400, Mike Snitzer wrote: > On Fri, Jul 17 2015 at 10:22am -0400, > Pali Roh=E1r wrote: >=20 > > On Friday 17 July 2015 10:04:39 Mike Snitzer wrote: > > > On Sun, Jun 21 2015 at 7:20am -0400, > > > Pali Roh=E1r wrote: > > >=20 > > > > This patch exports function dm_suspend_md() which suspend mappe= d device so other > > > > kernel drivers can use it and could suspend mapped device when = needed. > > > >=20 > > > > Signed-off-by: Pali Roh=E1r > > > > --- > > > > drivers/md/dm.c | 6 ++++++ > > > > drivers/md/dm.h | 5 +++++ > > > > 2 files changed, 11 insertions(+) > > > >=20 > > > > 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; > > > > } > > > > =20 > > > > +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= =2E It waits > > > > * until all bios finish and prevents issuing new bios to the = target drivers. > > >=20 > > > 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 > > >=20 > > > The reason to use a dm_internal_suspend variant is this suspend w= as > > > _not_ initiated by an upper level ioctl (from userspace). It was > > > done internally from within the target. > > >=20 > > > You're explicitly using DM_SUSPEND_LOCKFS_FLAG above.. meaning yo= u're > > > interested in flushing all pending IO (in the FS layered on dm-cr= upt, if > > > one exists). > > >=20 > > > But see the comment in __dm_internal_suspend() about TASK_UNINTER= RUPTIBLE. > > > If you're OK with the dm-crypt initiated suspend being > > > TASK_UNINTERRUPTIBLE then you could just introduce: > > >=20 > > > void dm_internal_suspend_uninterruptible_flush(struct mapped_devi= ce *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); > > >=20 > > > Otherwise, there is much more extensive DM core changes needed to > > > __dm_internal_suspend() and .presuspend to properly support > > > TASK_INTERRUPTIBLE. > >=20 > > 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 t= hat > > without entering key again from userspace, resume is not possible. = So my > > question is: It is possible to do internal suspend and then using r= esume > > from userspace via ioctl? >=20 > Good question: no, userspace resume would block waiting for internal > resume. >=20 > 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.