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 11:22:53 -0400 Message-ID: <20150717152253.GA1021@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> 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: <20150717142251.GA12011@pali> Sender: linux-pm-owner@vger.kernel.org To: Pali =?iso-8859-1?Q?Roh=E1r?= Cc: Alasdair Kergon , Neil Brown , "Rafael J. Wysocki" , Len Brown , Pavel Machek , linux-raid@vger.kernel.org, dm-devel@redhat.com, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org List-Id: linux-raid.ids On Fri, Jul 17 2015 at 10:22am -0400, Pali Roh=E1r wrote: > 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 mapped = device so other > > > kernel drivers can use it and could suspend mapped device when ne= eded. > > >=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. = It waits > > > * until all bios finish and prevents issuing new bios to the ta= rget 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 was > > _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 you'= re > > interested in flushing all pending IO (in the FS layered on dm-crup= t, if > > one exists). > >=20 > > But see the comment in __dm_internal_suspend() about TASK_UNINTERRU= PTIBLE. > > 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_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); > >=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 i= s > from dm-crypt to do both operations: suspend + key wipe. It means tha= t > without entering key again from userspace, resume is not possible. So= my > question is: It is possible to do internal suspend and then using res= ume > 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 i= s needing to initiate the suspend internally but then userspace is initiating the resume... this imbalance is concerning.