From: Mike Snitzer <snitzer@redhat.com>
To: "Pali Rohár" <pali.rohar@gmail.com>
Cc: Alasdair Kergon <agk@redhat.com>, Neil Brown <neilb@suse.de>,
"Rafael J. Wysocki" <rjw@rjwysocki.net>,
Len Brown <len.brown@intel.com>, Pavel Machek <pavel@ucw.cz>,
linux-raid@vger.kernel.org, dm-devel@redhat.com,
linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org
Subject: Re: [PATCH v2 2/3] dm: Export function dm_suspend_md()
Date: Fri, 17 Jul 2015 11:22:53 -0400 [thread overview]
Message-ID: <20150717152253.GA1021@redhat.com> (raw)
In-Reply-To: <20150717142251.GA12011@pali>
On Fri, Jul 17 2015 at 10:22am -0400,
Pali Rohár <pali.rohar@gmail.com> wrote:
> On Friday 17 July 2015 10:04:39 Mike Snitzer wrote:
> > On Sun, Jun 21 2015 at 7:20am -0400,
> > Pali Rohár <pali.rohar@gmail.com> 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 Rohár <pali.rohar@gmail.com>
> > > ---
> > > 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.
next prev parent reply other threads:[~2015-07-17 15:22 UTC|newest]
Thread overview: 50+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-04-05 17:20 [PATCH 0/3] dm-crypt: Adds support for wiping key when doing suspend/hibernation Pali Rohár
2015-04-05 17:20 ` [PATCH 1/3] PM suspend/hibernate: Call notifier after freezing processes Pali Rohár
2015-04-09 0:28 ` Rafael J. Wysocki
2015-04-09 6:36 ` Pali Rohár
2015-04-09 17:13 ` Rafael J. Wysocki
2015-04-09 16:55 ` Pali Rohár
2015-04-05 17:20 ` [PATCH 2/3] dm: Export function dm_suspend_md() Pali Rohár
2015-04-05 17:20 ` [PATCH 3/3] dm-crypt: Adds support for wiping key when doing suspend/hibernation Pali Rohár
2015-04-07 13:55 ` [dm-devel] " Alasdair G Kergon
2015-04-06 13:00 ` [PATCH 0/3] " Mike Snitzer
2015-04-06 13:25 ` Pavel Machek
2015-04-06 20:51 ` Mike Snitzer
2015-04-06 21:13 ` Why wipe crypto keys during suspend (was Re: [PATCH 0/3] dm-crypt: Adds support for wiping key when doing suspend/hibernation) Pavel Machek
2015-04-06 13:29 ` [PATCH 0/3] dm-crypt: Adds support for wiping key when doing suspend/hibernation Pali Rohár
2015-04-06 18:17 ` Pavel Machek
2015-04-06 21:27 ` Pali Rohár
2015-04-09 13:12 ` Mike Snitzer
2015-04-09 13:28 ` Pali Rohár
2015-04-09 14:08 ` Mike Snitzer
2015-04-09 14:16 ` Pali Rohár
2015-04-09 14:26 ` Mike Snitzer
2015-04-09 14:38 ` Pali Rohár
2015-04-14 6:50 ` Pavel Machek
2015-04-23 17:02 ` Pali Rohár
[not found] ` <mgnv2g$if5$2@ger.gmane.org>
2015-04-17 7:52 ` Mike Snitzer
2015-04-17 8:52 ` [dm-devel] " Ondrej Kozina
2015-04-17 15:53 ` Alex Elsayed
2015-04-14 6:41 ` Pavel Machek
2015-06-21 11:20 ` [PATCH v2 " Pali Rohár
2015-06-21 11:20 ` [PATCH v2 1/3] PM suspend/hibernate: Call notifier after freezing processes Pali Rohár
2015-07-16 1:02 ` Rafael J. Wysocki
2015-07-16 7:33 ` Pali Rohár
2015-07-17 23:27 ` Rafael J. Wysocki
2015-07-20 7:32 ` Pali Rohár
2015-07-20 21:46 ` Rafael J. Wysocki
2015-07-21 22:08 ` NeilBrown
2015-07-21 23:00 ` Rafael J. Wysocki
2015-07-21 23:03 ` Rafael J. Wysocki
2016-12-27 14:29 ` Pali Rohár
2015-06-21 11:20 ` [PATCH v2 2/3] dm: Export function dm_suspend_md() Pali Rohár
2015-07-17 14:04 ` Mike Snitzer
2015-07-17 14:22 ` Pali Rohár
2015-07-17 15:22 ` Mike Snitzer [this message]
2015-07-17 15:30 ` Mike Snitzer
2015-07-17 17:13 ` Pali Rohár
2015-07-17 17:31 ` Mike Snitzer
2015-06-21 11:20 ` [PATCH v2 3/3] dm-crypt: Adds support for wiping key when doing suspend/hibernation Pali Rohár
2015-07-28 14:44 ` Pavel Machek
2015-07-28 14:48 ` Pali Rohár
2015-07-07 7:59 ` [PATCH v2 0/3] " Pali Rohár
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