Re: [PATCH v2 02/15] mm/mmu_notifier: add an interval tree notifier
On Thu, Nov 07, 2019 at 09:00:34PM -0500, Jerome Glisse wrote:
> On Fri, Nov 08, 2019 at 12:32:25AM +, Jason Gunthorpe wrote:
> > On Thu, Nov 07, 2019 at 04:04:08PM -0500, Jerome Glisse wrote:
> > > On Thu, Nov 07, 2019 at 08:11:06PM +, Jason Gunthorpe wrote:
> > > > On Wed, Nov 06, 2019 at 09:08:07PM -0500, Jerome Glisse wrote:
> > > >
> > > > > >
> > > > > > Extra credit: IMHO, this clearly deserves to all be in a new
> > > > > > mmu_range_notifier.h
> > > > > > header file, but I know that's extra work. Maybe later as a
> > > > > > follow-up patch,
> > > > > > if anyone has the time.
> > > > >
> > > > > The range notifier should get the event too, it would be a waste, i
> > > > > think it is
> > > > > an oversight here. The release event is fine so NAK to you separate
> > > > > event. Event
> > > > > is really an helper for notifier i had a set of patch for nouveau to
> > > > > leverage
> > > > > this i need to resucite them. So no need to split thing, i would just
> > > > > forward
> > > > > the event ie add event to mmu_range_notifier_ops.invalidate() i
> > > > > failed to catch
> > > > > that in v1 sorry.
> > > >
> > > > I think what you mean is already done?
> > > >
> > > > struct mmu_range_notifier_ops {
> > > > bool (*invalidate)(struct mmu_range_notifier *mrn,
> > > >const struct mmu_notifier_range *range,
> > > >unsigned long cur_seq);
> > >
> > > Yes it is sorry, i got confuse with mmu_range_notifier and
> > > mmu_notifier_range :)
> > > It is almost a palyndrome structure ;)
> >
> > Lets change the name then, this is clearly not working. I'll reflow
> > everything tomorrow
>
> Semantic patch to do that run from your linux kernel directory with your patch
> applied (you can run it one patch after the other and the git commit -a
> --fixup HEAD)
>
> spatch --sp-file name-of-the-file-below --dir . --all-includes --in-place
>
> %< --
> @@
> @@
> struct
> -mmu_range_notifier
> +mmu_interval_notifier
>
> @@
> @@
> struct
> -mmu_range_notifier
> +mmu_interval_notifier
> {...};
>
> // Change mrn name to mmu_in
> @@
> struct mmu_interval_notifier *mrn;
> @@
> -mrn
> +mmu_in
>
> @@
> identifier fn;
> @@
> fn(...,
> -struct mmu_interval_notifier *mrn,
> +struct mmu_interval_notifier *mmu_in,
> ...) {...}
>
> You need coccinelle (which provides spatch). It is untested but it should work
> also i could not come up with a nice name to update mrn as min is way too
> confusing. If you have better name feel free to use it.
I used 'mni' as we already use 'mn' to refer to the notifier, and
'mmu_in' looks like some input parameter or something
It mostly worked, lots of comments to fix manually though:
https://github.com/jgunthorpe/linux/commits/mmu_notifier
Thanks,
Jason
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Re: [PATCH v2 02/15] mm/mmu_notifier: add an interval tree notifier
On Thu, Nov 07, 2019 at 12:53:56PM -0800, John Hubbard wrote:
> > > > +/**
> > > > + * struct mmu_range_notifier_ops
> > > > + * @invalidate: Upon return the caller must stop using any SPTEs
> > > > within this
> > > > + * range, this function can sleep. Return false if
> > > > blocking was
> > > > + * required but range is non-blocking
> > > > + */
> > >
> > > How about this (I'm not sure I fully understand the return value, though):
> > >
> > > /**
> > > * struct mmu_range_notifier_ops
> > > * @invalidate: Upon return the caller must stop using any SPTEs within
> > > this
> > > * range.
> > > *
> > > * This function is permitted to sleep.
> > > *
> > > * @Return: false if blocking was required, but @range is
> > > * non-blocking.
> > > *
> > > */
> >
> > Is this kdoc format for function pointers?
>
> heh, I'm sort of winging it, I'm not sure how function pointers are supposed
> to be documented in kdoc. Actually the only key take-away here is to write
>
> "This function can sleep"
>
> as a separate sentence..
Sure
> > This odd duality has already cause some confusion, but names here are
> > hard. mmu_interval_notifier is the best alternative I've heard.
> >
> > Changing this name is a lot of work - are we happy
> > 'mmu_interval_notifier' is the right choice?
>
> Yes, it's my favorite too. I'd vote for going with that.
Okay, lets give it a go
> Very nice, would you be open to putting that into (any) one of the comment
> headers? That's an unusually clear and concise description:
Yep, done
> > > > +int mmu_range_notifier_insert(struct mmu_range_notifier *mrn,
> > > > + unsigned long start, unsigned long length,
> > > > + struct mm_struct *mm)
> > > > +{
> > > > + struct mmu_notifier_mm *mmn_mm;
> > > > + int ret;
> > >
> > > Hmmm, I think a later patch improperly changes the above to "int ret =
> > > 0;".
> > > I'll check on that. It's correct here, though.
> >
> > Looks OK in my tree?
>
> Nope, that's how I found it. The top of your mmu_notifier branch has this:
>
> int __mmu_notifier_invalidate_range_start(struct mmu_notifier_range *range)
> {
> struct mmu_notifier_mm *mmn_mm = range->mm->mmu_notifier_mm;
> int ret = 0;
>
> if (mmn_mm->has_interval) {
> ret = mn_itree_invalidate(mmn_mm, range);
> if (ret)
> return ret;
> }
> if (!hlist_empty(_mm->list))
> return mn_hlist_invalidate_range_start(mmn_mm, range);
> return 0;
> }
Ah, that is a different function :) Fixed
> Looks good. We're just polishing up minor points now, so you can add:
>
> Reviewed-by: John Hubbard
Great, thanks, I'll post a v3 with the rename
Jason
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Re: [PATCH v2 02/15] mm/mmu_notifier: add an interval tree notifier
On Thu, Nov 07, 2019 at 10:33:02PM -0800, Christoph Hellwig wrote:
> On Thu, Nov 07, 2019 at 08:06:08PM +, Jason Gunthorpe wrote:
> > >
> > > enum mmu_range_notifier_event {
> > > MMU_NOTIFY_RELEASE,
> > > };
> > >
> > > ...assuming that we stay with "mmu_range_notifier" as a core name for
> > > this
> > > whole thing.
> > >
> > > Also, it is best moved down to be next to the new MNR structs, so that
> > > all the
> > > MNR stuff is in one group.
> >
> > I agree with Jerome, this enum is part of the 'struct
> > mmu_notifier_range' (ie the description of the invalidation) and it
> > doesn't really matter that only these new notifiers can be called with
> > this type, it is still part of the mmu_notifier_range.
> >
> > The comment already says it only applies to the mmu_range_notifier
> > scheme..
>
> In fact the enum is entirely unused. We might as well just kill it off
> entirely.
I had patches to use it, i need to re-post them. I posted them long ago
and i droped the ball. I will re-spin after this.
Cheers,
Jérôme
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Re: [PATCH v2 02/15] mm/mmu_notifier: add an interval tree notifier
On Thu, Nov 07, 2019 at 04:04:08PM -0500, Jerome Glisse wrote:
> On Thu, Nov 07, 2019 at 08:11:06PM +, Jason Gunthorpe wrote:
> > On Wed, Nov 06, 2019 at 09:08:07PM -0500, Jerome Glisse wrote:
> >
> > > >
> > > > Extra credit: IMHO, this clearly deserves to all be in a new
> > > > mmu_range_notifier.h
> > > > header file, but I know that's extra work. Maybe later as a follow-up
> > > > patch,
> > > > if anyone has the time.
> > >
> > > The range notifier should get the event too, it would be a waste, i think
> > > it is
> > > an oversight here. The release event is fine so NAK to you separate
> > > event. Event
> > > is really an helper for notifier i had a set of patch for nouveau to
> > > leverage
> > > this i need to resucite them. So no need to split thing, i would just
> > > forward
> > > the event ie add event to mmu_range_notifier_ops.invalidate() i failed to
> > > catch
> > > that in v1 sorry.
> >
> > I think what you mean is already done?
> >
> > struct mmu_range_notifier_ops {
> > bool (*invalidate)(struct mmu_range_notifier *mrn,
> >const struct mmu_notifier_range *range,
> >unsigned long cur_seq);
>
> Yes it is sorry, i got confuse with mmu_range_notifier and mmu_notifier_range
> :)
> It is almost a palyndrome structure ;)
Lets change the name then, this is clearly not working. I'll reflow
everything tomorrow
Jason
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Re: [PATCH v2 02/15] mm/mmu_notifier: add an interval tree notifier
On Thu, Nov 07, 2019 at 08:06:08PM +, Jason Gunthorpe wrote:
> >
> > enum mmu_range_notifier_event {
> > MMU_NOTIFY_RELEASE,
> > };
> >
> > ...assuming that we stay with "mmu_range_notifier" as a core name for this
> > whole thing.
> >
> > Also, it is best moved down to be next to the new MNR structs, so that all
> > the
> > MNR stuff is in one group.
>
> I agree with Jerome, this enum is part of the 'struct
> mmu_notifier_range' (ie the description of the invalidation) and it
> doesn't really matter that only these new notifiers can be called with
> this type, it is still part of the mmu_notifier_range.
>
> The comment already says it only applies to the mmu_range_notifier
> scheme..
In fact the enum is entirely unused. We might as well just kill it off
entirely.
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Re: [PATCH v2 02/15] mm/mmu_notifier: add an interval tree notifier
On Fri, Nov 08, 2019 at 12:32:25AM +, Jason Gunthorpe wrote:
> On Thu, Nov 07, 2019 at 04:04:08PM -0500, Jerome Glisse wrote:
> > On Thu, Nov 07, 2019 at 08:11:06PM +, Jason Gunthorpe wrote:
> > > On Wed, Nov 06, 2019 at 09:08:07PM -0500, Jerome Glisse wrote:
> > >
> > > > >
> > > > > Extra credit: IMHO, this clearly deserves to all be in a new
> > > > > mmu_range_notifier.h
> > > > > header file, but I know that's extra work. Maybe later as a follow-up
> > > > > patch,
> > > > > if anyone has the time.
> > > >
> > > > The range notifier should get the event too, it would be a waste, i
> > > > think it is
> > > > an oversight here. The release event is fine so NAK to you separate
> > > > event. Event
> > > > is really an helper for notifier i had a set of patch for nouveau to
> > > > leverage
> > > > this i need to resucite them. So no need to split thing, i would just
> > > > forward
> > > > the event ie add event to mmu_range_notifier_ops.invalidate() i failed
> > > > to catch
> > > > that in v1 sorry.
> > >
> > > I think what you mean is already done?
> > >
> > > struct mmu_range_notifier_ops {
> > > bool (*invalidate)(struct mmu_range_notifier *mrn,
> > > const struct mmu_notifier_range *range,
> > > unsigned long cur_seq);
> >
> > Yes it is sorry, i got confuse with mmu_range_notifier and
> > mmu_notifier_range :)
> > It is almost a palyndrome structure ;)
>
> Lets change the name then, this is clearly not working. I'll reflow
> everything tomorrow
Semantic patch to do that run from your linux kernel directory with your patch
applied (you can run it one patch after the other and the git commit -a --fixup
HEAD)
spatch --sp-file name-of-the-file-below --dir . --all-includes --in-place
%< --
@@
@@
struct
-mmu_range_notifier
+mmu_interval_notifier
@@
@@
struct
-mmu_range_notifier
+mmu_interval_notifier
{...};
// Change mrn name to mmu_in
@@
struct mmu_interval_notifier *mrn;
@@
-mrn
+mmu_in
@@
identifier fn;
@@
fn(...,
-struct mmu_interval_notifier *mrn,
+struct mmu_interval_notifier *mmu_in,
...) {...}
-- >%
You need coccinelle (which provides spatch). It is untested but it should work
also i could not come up with a nice name to update mrn as min is way too
confusing. If you have better name feel free to use it.
Oh and coccinelle is pretty clever about code formating so it should do a good
jobs at keeping things nicely formated and align.
Cheers,
Jérôme
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Re: [PATCH v2 02/15] mm/mmu_notifier: add an interval tree notifier
On 11/7/19 12:06 PM, Jason Gunthorpe wrote:
...
Also, it is best moved down to be next to the new MNR structs, so that all the
MNR stuff is in one group.
I agree with Jerome, this enum is part of the 'struct
mmu_notifier_range' (ie the description of the invalidation) and it
doesn't really matter that only these new notifiers can be called with
this type, it is still part of the mmu_notifier_range.
OK.
The comment already says it only applies to the mmu_range_notifier
scheme..
#define MMU_NOTIFIER_RANGE_BLOCKABLE (1 << 0)
@@ -222,6 +228,26 @@ struct mmu_notifier {
unsigned int users;
};
That should also be moved down, next to the new structs.
Which this?
I was referring to MMU_NOTIFIER_RANGE_BLOCKABLE, above. Trying
to put all the new range notifier stuff in one place. But maybe not,
if these are really not as separate as I thought.
+/**
+ * struct mmu_range_notifier_ops
+ * @invalidate: Upon return the caller must stop using any SPTEs within this
+ * range, this function can sleep. Return false if blocking was
+ * required but range is non-blocking
+ */
How about this (I'm not sure I fully understand the return value, though):
/**
* struct mmu_range_notifier_ops
* @invalidate: Upon return the caller must stop using any SPTEs within this
* range.
*
* This function is permitted to sleep.
*
* @Return: false if blocking was required, but @range is
* non-blocking.
*
*/
Is this kdoc format for function pointers?
heh, I'm sort of winging it, I'm not sure how function pointers are supposed
to be documented in kdoc. Actually the only key take-away here is to write
"This function can sleep"
as a separate sentence..
...
c) Rename new one. Ideas:
struct mmu_interval_notifier
struct mmu_range_intersection
...other ideas?
This odd duality has already cause some confusion, but names here are
hard. mmu_interval_notifier is the best alternative I've heard.
Changing this name is a lot of work - are we happy
'mmu_interval_notifier' is the right choice?
Yes, it's my favorite too. I'd vote for going with that.
...
OK, this either needs more documentation and assertions, or a different
approach. Because I see addition, subtraction, AND, OR and booleans
all being applied to this field, and it's darn near hopeless to figure
out whether or not it really is even or odd at the right times.
This is a standard design for a seqlock scheme and follows the
existing design of the linux seq lock.
The lower bit indicates the lock'd state and the upper bits indicate
the generation of the lock
The operations on the lock itself are then:
seq |= 1 # Take the lock
seq++ # Release an acquired lock
seq & 1 # True if locked
Which is how this is written
Very nice, would you be open to putting that into (any) one of the comment
headers? That's an unusually clear and concise description:
/*
* This is a standard design for a seqlock scheme and follows the
* existing design of the linux seq lock.
*
* The lower bit indicates the lock'd state and the upper bits indicate
* the generation of the lock
*
* The operations on the lock itself are then:
*seq |= 1 # Take the lock
*seq++ # Release an acquired lock
*seq & 1 # True if locked
*/
Different approach: why not just add a mmn_mm->is_invalidating
member variable? It's not like you're short of space in that struct.
Splitting it makes alot of stuff more complex and unnatural.
OK, agreed.
The ops above could be put in inline wrappers, but they only occur
only in functions already called mn_itree_inv_start_range() and
mn_itree_inv_end() and mn_itree_is_invalidating().
There is the one 'take the lock' outlier in
__mmu_range_notifier_insert() though
+static void mn_itree_inv_end(struct mmu_notifier_mm *mmn_mm)
+{
+ struct mmu_range_notifier *mrn;
+ struct hlist_node *next;
+ bool need_wake = false;
+
+ spin_lock(_mm->lock);
+ if (--mmn_mm->active_invalidate_ranges ||
+ !mn_itree_is_invalidating(mmn_mm)) {
+ spin_unlock(_mm->lock);
+ return;
+ }
+
+ mmn_mm->invalidate_seq++;
Is this the right place for an assertion that this is now an even value?
Yes, but I'm reluctant to add such a runtime check on this fastish path..
How about a comment?
Sure.
+ need_wake = true;
+
+ /*
+* The inv_end incorporates a deferred mechanism like
+* rtnl_lock(). Adds and removes are queued until the final inv_end
Let me point out that rtnl_lock() itself is a one-liner that calls mutex_lock().
But I suppose if one studies that file closely there is more. :)
Lets change that to rtnl_unlock() then
Thanks :)
...
+* mrn->invalidate_seq is always set to an odd value. This ensures
This claim just looks wrong the first N times one reads the code, given that
Re: [PATCH v2 02/15] mm/mmu_notifier: add an interval tree notifier
On Thu, Nov 07, 2019 at 08:11:06PM +, Jason Gunthorpe wrote:
> On Wed, Nov 06, 2019 at 09:08:07PM -0500, Jerome Glisse wrote:
>
> > >
> > > Extra credit: IMHO, this clearly deserves to all be in a new
> > > mmu_range_notifier.h
> > > header file, but I know that's extra work. Maybe later as a follow-up
> > > patch,
> > > if anyone has the time.
> >
> > The range notifier should get the event too, it would be a waste, i think
> > it is
> > an oversight here. The release event is fine so NAK to you separate event.
> > Event
> > is really an helper for notifier i had a set of patch for nouveau to
> > leverage
> > this i need to resucite them. So no need to split thing, i would just
> > forward
> > the event ie add event to mmu_range_notifier_ops.invalidate() i failed to
> > catch
> > that in v1 sorry.
>
> I think what you mean is already done?
>
> struct mmu_range_notifier_ops {
> bool (*invalidate)(struct mmu_range_notifier *mrn,
> const struct mmu_notifier_range *range,
> unsigned long cur_seq);
Yes it is sorry, i got confuse with mmu_range_notifier and mmu_notifier_range :)
It is almost a palyndrome structure ;)
>
> > No it is always odd, you must call mmu_range_set_seq() only from the
> > op->invalidate_range() callback at which point the seq is odd. As well
> > when mrn is added and its seq first set it is set to an odd value
> > always. Maybe the comment, should read:
> >
> > * mrn->invalidate_seq is always, yes always, set to an odd value. This
> > ensures
> >
> > To stress that it is not an error.
>
> I went with this:
>
> /*
>* mrn->invalidate_seq must always be set to an odd value via
>* mmu_range_set_seq() using the provided cur_seq from
>* mn_itree_inv_start_range(). This ensures that if seq does wrap we
>* will always clear the below sleep in some reasonable time as
>* mmn_mm->invalidate_seq is even in the idle state.
>*/
Yes fine with me.
[...]
> > > > + might_lock(>mmap_sem);
> > > > +
> > > > + mmn_mm = smp_load_acquire(>mmu_notifier_mm);
> > >
> > > What does the above pair with? Should have a comment that specifies that.
> >
> > It was discussed in v1 but maybe a comment of what was said back then would
> > be helpful. Something like:
> >
> > /*
> > * We need to insure that all writes to mm->mmu_notifier_mm are visible
> > before
> > * any checks we do on mmn_mm below as otherwise CPU might re-order write
> > done
> > * by another CPU core to mm->mmu_notifier_mm structure fields after the
> > read
> > * belows.
> > */
>
> This comment made it, just at the store side:
>
> /*
>* Serialize the update against mmu_notifier_unregister. A
>* side note: mmu_notifier_release can't run concurrently with
>* us because we hold the mm_users pin (either implicitly as
>* current->mm or explicitly with get_task_mm() or similar).
>* We can't race against any other mmu notifier method either
>* thanks to mm_take_all_locks().
>*
>* release semantics on the initialization of the mmu_notifier_mm's
> * contents are provided for unlocked readers. acquire can only be
> * used while holding the mmgrab or mmget, and is safe because once
> * created the mmu_notififer_mm is not freed until the mm is
> * destroyed. As above, users holding the mmap_sem or one of the
> * mm_take_all_locks() do not need to use acquire semantics.
>*/
> if (mmu_notifier_mm)
> smp_store_release(>mmu_notifier_mm, mmu_notifier_mm);
>
> Which I think is really overly belaboring the typical smp
> store/release pattern, but people do seem unfamiliar with them...
Perfect with me. I think also sometimes you forgot what memory model is
and thus store/release pattern do, i know i do and i need to refresh my
mind.
Cheers,
Jérôme
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Re: [PATCH v2 02/15] mm/mmu_notifier: add an interval tree notifier
On Wed, Nov 06, 2019 at 09:08:07PM -0500, Jerome Glisse wrote:
> >
> > Extra credit: IMHO, this clearly deserves to all be in a new
> > mmu_range_notifier.h
> > header file, but I know that's extra work. Maybe later as a follow-up patch,
> > if anyone has the time.
>
> The range notifier should get the event too, it would be a waste, i think it
> is
> an oversight here. The release event is fine so NAK to you separate event.
> Event
> is really an helper for notifier i had a set of patch for nouveau to leverage
> this i need to resucite them. So no need to split thing, i would just forward
> the event ie add event to mmu_range_notifier_ops.invalidate() i failed to
> catch
> that in v1 sorry.
I think what you mean is already done?
struct mmu_range_notifier_ops {
bool (*invalidate)(struct mmu_range_notifier *mrn,
const struct mmu_notifier_range *range,
unsigned long cur_seq);
> No it is always odd, you must call mmu_range_set_seq() only from the
> op->invalidate_range() callback at which point the seq is odd. As well
> when mrn is added and its seq first set it is set to an odd value
> always. Maybe the comment, should read:
>
> * mrn->invalidate_seq is always, yes always, set to an odd value. This
> ensures
>
> To stress that it is not an error.
I went with this:
/*
* mrn->invalidate_seq must always be set to an odd value via
* mmu_range_set_seq() using the provided cur_seq from
* mn_itree_inv_start_range(). This ensures that if seq does wrap we
* will always clear the below sleep in some reasonable time as
* mmn_mm->invalidate_seq is even in the idle state.
*/
> > > + spin_lock(_mm->lock);
> > > + if (mmn_mm->active_invalidate_ranges) {
> > > + if (mn_itree_is_invalidating(mmn_mm))
> > > + hlist_add_head(>deferred_item,
> > > +_mm->deferred_list);
> > > + else {
> > > + mmn_mm->invalidate_seq |= 1;
> > > + interval_tree_insert(>interval_tree,
> > > + _mm->itree);
> > > + }
> > > + mrn->invalidate_seq = mmn_mm->invalidate_seq;
> > > + } else {
> > > + WARN_ON(mn_itree_is_invalidating(mmn_mm));
> > > + mrn->invalidate_seq = mmn_mm->invalidate_seq - 1;
> >
> > Ohhh, checkmate. I lose. Why is *subtracting* the right thing to do
> > for seq numbers here? I'm acutely unhappy trying to figure this out.
> > I suspect it's another unfortunate side effect of trying to use the
> > lower bit of the seq number (even/odd) for something else.
>
> If there is no mmn_mm->active_invalidate_ranges then it means that
> mmn_mm->invalidate_seq is even and thus mmn_mm->invalidate_seq - 1
> is an odd number which means that mrn->invalidate_seq is initialized
> to odd value and if you follow the rule for calling mmu_range_set_seq()
> then it will _always_ be an odd number and this close the loop with
> the above comments :)
The key thing is that it is an odd value that will take a long time
before mmn_mm->invalidate seq reaches it
> > > + might_lock(>mmap_sem);
> > > +
> > > + mmn_mm = smp_load_acquire(>mmu_notifier_mm);
> >
> > What does the above pair with? Should have a comment that specifies that.
>
> It was discussed in v1 but maybe a comment of what was said back then would
> be helpful. Something like:
>
> /*
> * We need to insure that all writes to mm->mmu_notifier_mm are visible before
> * any checks we do on mmn_mm below as otherwise CPU might re-order write done
> * by another CPU core to mm->mmu_notifier_mm structure fields after the read
> * belows.
> */
This comment made it, just at the store side:
/*
* Serialize the update against mmu_notifier_unregister. A
* side note: mmu_notifier_release can't run concurrently with
* us because we hold the mm_users pin (either implicitly as
* current->mm or explicitly with get_task_mm() or similar).
* We can't race against any other mmu notifier method either
* thanks to mm_take_all_locks().
*
* release semantics on the initialization of the mmu_notifier_mm's
* contents are provided for unlocked readers. acquire can only be
* used while holding the mmgrab or mmget, and is safe because once
* created the mmu_notififer_mm is not freed until the mm is
* destroyed. As above, users holding the mmap_sem or one of the
* mm_take_all_locks() do not need to use acquire semantics.
*/
if (mmu_notifier_mm)
smp_store_release(>mmu_notifier_mm, mmu_notifier_mm);
Which I think is really overly belaboring the typical smp
store/release pattern, but people do seem unfamiliar with them...
Thanks,
Jason
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Re: [PATCH v2 02/15] mm/mmu_notifier: add an interval tree notifier
On Wed, Nov 06, 2019 at 04:23:21PM -0800, John Hubbard wrote:
> Nice design, I love the seq foundation! So far, I'm not able to spot anything
> actually wrong with the implementation, sorry about that.
Alas :( I feel there must be a bug in here still, but onwards!
One of the main sad points was it didn't make sense to use the
existing seqlock/seqcount primitives as they have both the wrong write
concurrancy model and extra barriers that are not needed when it is
always manipulated under a spinlock
> 1. There is a rather severe naming overlap (not technically a naming conflict,
> but still) with existing mmn work, which already has, for example:
>
> struct mmu_notifier_range
>
> ...and you're adding:
>
> struct mmu_range_notifier
>
> ...so I'll try to help sort that out.
Yes, I've been sad about this too.
> So this should read:
>
> enum mmu_range_notifier_event {
> MMU_NOTIFY_RELEASE,
> };
>
> ...assuming that we stay with "mmu_range_notifier" as a core name for this
> whole thing.
>
> Also, it is best moved down to be next to the new MNR structs, so that all the
> MNR stuff is in one group.
I agree with Jerome, this enum is part of the 'struct
mmu_notifier_range' (ie the description of the invalidation) and it
doesn't really matter that only these new notifiers can be called with
this type, it is still part of the mmu_notifier_range.
The comment already says it only applies to the mmu_range_notifier
scheme..
> > #define MMU_NOTIFIER_RANGE_BLOCKABLE (1 << 0)
> > @@ -222,6 +228,26 @@ struct mmu_notifier {
> > unsigned int users;
> > };
> >
>
> That should also be moved down, next to the new structs.
Which this?
> > +/**
> > + * struct mmu_range_notifier_ops
> > + * @invalidate: Upon return the caller must stop using any SPTEs within
> > this
> > + * range, this function can sleep. Return false if blocking
> > was
> > + * required but range is non-blocking
> > + */
>
> How about this (I'm not sure I fully understand the return value, though):
>
> /**
> * struct mmu_range_notifier_ops
> * @invalidate: Upon return the caller must stop using any SPTEs within this
> *range.
> *
> *This function is permitted to sleep.
> *
> *@Return: false if blocking was required, but @range is
> *non-blocking.
> *
> */
Is this kdoc format for function pointers?
>
> > +struct mmu_range_notifier_ops {
> > + bool (*invalidate)(struct mmu_range_notifier *mrn,
> > + const struct mmu_notifier_range *range,
> > + unsigned long cur_seq);
> > +};
> > +
> > +struct mmu_range_notifier {
> > + struct interval_tree_node interval_tree;
> > + const struct mmu_range_notifier_ops *ops;
> > + struct hlist_node deferred_item;
> > + unsigned long invalidate_seq;
> > + struct mm_struct *mm;
> > +};
> > +
>
> Again, now we have the new struct mmu_range_notifier, and the old
> struct mmu_notifier_range, and it's not good.
>
> Ideas:
>
> a) Live with it.
>
> b) (Discarded, too many callers): rename old one. Nope.
>
> c) Rename new one. Ideas:
>
> struct mmu_interval_notifier
> struct mmu_range_intersection
> ...other ideas?
This odd duality has already cause some confusion, but names here are
hard. mmu_interval_notifier is the best alternative I've heard.
Changing this name is a lot of work - are we happy
'mmu_interval_notifier' is the right choice?
> > +/**
> > + * mmu_range_set_seq - Save the invalidation sequence
>
> How about:
>
> * mmu_range_set_seq - Set the .invalidate_seq to a new value.
It is not a 'new value', it is a value that is provided to the
invalidate callback
>
> > + * @mrn - The mrn passed to invalidate
> > + * @cur_seq - The cur_seq passed to invalidate
> > + *
> > + * This must be called unconditionally from the invalidate callback of a
> > + * struct mmu_range_notifier_ops under the same lock that is used to call
> > + * mmu_range_read_retry(). It updates the sequence number for later use by
> > + * mmu_range_read_retry().
> > + *
> > + * If the user does not call mmu_range_read_begin() or
> > mmu_range_read_retry()
>
> nit: "caller" is better than "user", when referring to...well, callers.
> "user"
> most often refers to user space, whereas a call stack and function calling is
> clearly what you're referring to here (and in other places, especially "user
> lock").
Done
> > +/**
> > + * mmu_range_check_retry - Test if a collision has occurred
> > + * mrn: The range under lock
> > + * seq: The return of the matching mmu_range_read_begin()
> > + *
> > + * This can be used in the critical section between mmu_range_read_begin()
> > and
> > + * mmu_range_read_retry(). A return of true indicates an invalidation has
> > + * collided with this lock and a future mmu_range_read_retry() will return
> > + * true.
> > + *
> > + * False is not reliable and only suggests a collision has not happened. It
>
>
Re: [PATCH v2 02/15] mm/mmu_notifier: add an interval tree notifier
On Wed, Nov 06, 2019 at 04:23:21PM -0800, John Hubbard wrote:
> On 10/28/19 1:10 PM, Jason Gunthorpe wrote:
[...]
> > /**
> > * enum mmu_notifier_event - reason for the mmu notifier callback
> > @@ -32,6 +34,9 @@ struct mmu_notifier_range;
> > * access flags). User should soft dirty the page in the end callback to
> > make
> > * sure that anyone relying on soft dirtyness catch pages that might be
> > written
> > * through non CPU mappings.
> > + *
> > + * @MMU_NOTIFY_RELEASE: used during mmu_range_notifier invalidate to
> > signal that
> > + * the mm refcount is zero and the range is no longer accessible.
> > */
> > enum mmu_notifier_event {
> > MMU_NOTIFY_UNMAP = 0,
> > @@ -39,6 +44,7 @@ enum mmu_notifier_event {
> > MMU_NOTIFY_PROTECTION_VMA,
> > MMU_NOTIFY_PROTECTION_PAGE,
> > MMU_NOTIFY_SOFT_DIRTY,
> > + MMU_NOTIFY_RELEASE,
> > };
>
>
> OK, let the naming debates begin! ha. Anyway, after careful study of the
> overall
> patch, and some browsing of the larger patchset, it's clear that:
>
> * The new "MMU range notifier" that you've created is, approximately, a new
> object. It uses classic mmu notifiers inside, as an implementation detail, and
> it does *similar* things (notifications) as mmn's. But it's certainly not the
> same
> as mmn's, as shown later when you say the need to an entirely new ops struct,
> and
> data struct too.
>
> Therefore, you need a separate events enum as well. This is important. MMN's
> won't be issuing MMN_NOTIFY_RELEASE events, nor will MNR's be issuing the
> first
> four prexisting MMU_NOTIFY_* items. So it would be a design mistake to glom
> them
> together, unless you ultimately decided to merge these MMN and MNR objects
> (which
> I don't really see any intention of, and that's fine).
>
> So this should read:
>
> enum mmu_range_notifier_event {
> MMU_NOTIFY_RELEASE,
> };
>
> ...assuming that we stay with "mmu_range_notifier" as a core name for this
> whole thing.
>
> Also, it is best moved down to be next to the new MNR structs, so that all the
> MNR stuff is in one group.
>
> Extra credit: IMHO, this clearly deserves to all be in a new
> mmu_range_notifier.h
> header file, but I know that's extra work. Maybe later as a follow-up patch,
> if anyone has the time.
The range notifier should get the event too, it would be a waste, i think it is
an oversight here. The release event is fine so NAK to you separate event. Event
is really an helper for notifier i had a set of patch for nouveau to leverage
this i need to resucite them. So no need to split thing, i would just forward
the event ie add event to mmu_range_notifier_ops.invalidate() i failed to catch
that in v1 sorry.
[...]
> > +struct mmu_range_notifier_ops {
> > + bool (*invalidate)(struct mmu_range_notifier *mrn,
> > + const struct mmu_notifier_range *range,
> > + unsigned long cur_seq);
> > +};
> > +
> > +struct mmu_range_notifier {
> > + struct interval_tree_node interval_tree;
> > + const struct mmu_range_notifier_ops *ops;
> > + struct hlist_node deferred_item;
> > + unsigned long invalidate_seq;
> > + struct mm_struct *mm;
> > +};
> > +
>
> Again, now we have the new struct mmu_range_notifier, and the old
> struct mmu_notifier_range, and it's not good.
>
> Ideas:
>
> a) Live with it.
>
> b) (Discarded, too many callers): rename old one. Nope.
>
> c) Rename new one. Ideas:
>
> struct mmu_interval_notifier
> struct mmu_range_intersection
> ...other ideas?
I vote for interval_notifier we do want notifier in name but i am also
fine with current name.
[...]
> > + *
> > + * Note that the core mm creates nested invalidate_range_start()/end()
> > regions
> > + * within the same thread, and runs invalidate_range_start()/end() in
> > parallel
> > + * on multiple CPUs. This is designed to not reduce concurrency or block
> > + * progress on the mm side.
> > + *
> > + * As a secondary function, holding the full write side also serves to
> > prevent
> > + * writers for the itree, this is an optimization to avoid extra locking
> > + * during invalidate_range_start/end notifiers.
> > + *
> > + * The write side has two states, fully excluded:
> > + * - mm->active_invalidate_ranges != 0
> > + * - mnn->invalidate_seq & 1 == True
> > + * - some range on the mm_struct is being invalidated
> > + * - the itree is not allowed to change
> > + *
> > + * And partially excluded:
> > + * - mm->active_invalidate_ranges != 0
>
> I assume this implies mnn->invalidate_seq & 1 == False in this case? If so,
> let's say so. I'm probably getting that wrong, too.
Yes (mnn->invalidate_seq & 1) == 0
>
> > + * - some range on the mm_struct is being invalidated
> > + * - the itree is allowed to change
> > + *
> > + * The later state avoids some expensive work on inv_end in the common
> > case of
> > + * no mrn monitoring the VA.
> > + */
> > +static bool mn_itree_is_invalidating(struct
Re: [PATCH v2 02/15] mm/mmu_notifier: add an interval tree notifier
On 10/28/19 1:10 PM, Jason Gunthorpe wrote:
...
> include/linux/mmu_notifier.h | 98 +++
> mm/Kconfig | 1 +
> mm/mmu_notifier.c| 533 +--
> 3 files changed, 607 insertions(+), 25 deletions(-)
>
> diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h
> index 12bd603d318ce7..51b92ba013ddce 100644
> --- a/include/linux/mmu_notifier.h
> +++ b/include/linux/mmu_notifier.h
> @@ -6,10 +6,12 @@
> #include
> #include
> #include
> +#include
>
> struct mmu_notifier_mm;
> struct mmu_notifier;
> struct mmu_notifier_range;
> +struct mmu_range_notifier;
Hi Jason,
Nice design, I love the seq foundation! So far, I'm not able to spot anything
actually wrong with the implementation, sorry about that.
Generally my reaction is: given that the design is complex, try to mitigate
that with documentation and naming. So the comments are in these areas:
1. There is a rather severe naming overlap (not technically a naming conflict,
but still) with existing mmn work, which already has, for example:
struct mmu_notifier_range
...and you're adding:
struct mmu_range_notifier
...so I'll try to help sort that out.
2. I'm also seeing a couple of things that are really hard for the reader
verify are correct (abuse and battery of the low bit in .invalidate_seq,
for example, haha), so I have some recommendations there.
3. Documentation improvements, which easy to apply, with perhaps one exception.
(Here, because this a complicated area, documentation does make a difference,
so it's worth a little extra fuss.)
4. Other nits that don't matter too much, but just help polish things up
as usual.
>
> /**
> * enum mmu_notifier_event - reason for the mmu notifier callback
> @@ -32,6 +34,9 @@ struct mmu_notifier_range;
> * access flags). User should soft dirty the page in the end callback to make
> * sure that anyone relying on soft dirtyness catch pages that might be
> written
> * through non CPU mappings.
> + *
> + * @MMU_NOTIFY_RELEASE: used during mmu_range_notifier invalidate to signal
> that
> + * the mm refcount is zero and the range is no longer accessible.
> */
> enum mmu_notifier_event {
> MMU_NOTIFY_UNMAP = 0,
> @@ -39,6 +44,7 @@ enum mmu_notifier_event {
> MMU_NOTIFY_PROTECTION_VMA,
> MMU_NOTIFY_PROTECTION_PAGE,
> MMU_NOTIFY_SOFT_DIRTY,
> + MMU_NOTIFY_RELEASE,
> };
OK, let the naming debates begin! ha. Anyway, after careful study of the overall
patch, and some browsing of the larger patchset, it's clear that:
* The new "MMU range notifier" that you've created is, approximately, a new
object. It uses classic mmu notifiers inside, as an implementation detail, and
it does *similar* things (notifications) as mmn's. But it's certainly not the
same
as mmn's, as shown later when you say the need to an entirely new ops struct,
and
data struct too.
Therefore, you need a separate events enum as well. This is important. MMN's
won't be issuing MMN_NOTIFY_RELEASE events, nor will MNR's be issuing the first
four prexisting MMU_NOTIFY_* items. So it would be a design mistake to glom them
together, unless you ultimately decided to merge these MMN and MNR objects
(which
I don't really see any intention of, and that's fine).
So this should read:
enum mmu_range_notifier_event {
MMU_NOTIFY_RELEASE,
};
...assuming that we stay with "mmu_range_notifier" as a core name for this
whole thing.
Also, it is best moved down to be next to the new MNR structs, so that all the
MNR stuff is in one group.
Extra credit: IMHO, this clearly deserves to all be in a new
mmu_range_notifier.h
header file, but I know that's extra work. Maybe later as a follow-up patch,
if anyone has the time.
>
> #define MMU_NOTIFIER_RANGE_BLOCKABLE (1 << 0)
> @@ -222,6 +228,26 @@ struct mmu_notifier {
> unsigned int users;
> };
>
That should also be moved down, next to the new structs.
A little bit above these next items, just above "struct mmu_notifier" (not
shown here,
it's outside the diff area), there is some documentation about classic MMNs. It
would
be nice if it were clearer that that documentation is not relevant to MNRs.
Actually,
this is another reason that a separate header file would be nice.
> +/**
> + * struct mmu_range_notifier_ops
> + * @invalidate: Upon return the caller must stop using any SPTEs within this
> + * range, this function can sleep. Return false if blocking was
> + * required but range is non-blocking
> + */
How about this (I'm not sure I fully understand the return value, though):
/**
* struct mmu_range_notifier_ops
* @invalidate: Upon return the caller must stop using any SPTEs within this
* range.
*
* This function is permitted to sleep.
*
* @Return: false if blocking was required, but @range is
* non-blocking.
*
*/
> +struct mmu_range_notifier_ops {
>
Re: [PATCH v2 02/15] mm/mmu_notifier: add an interval tree notifier
On Tue, Oct 29, 2019 at 10:04:45PM +, Kuehling, Felix wrote:
> >* because mm->mm_users > 0 during mmu_notifier_register and exit_mmap
> > @@ -52,17 +286,24 @@ struct mmu_notifier_mm {
> >* can't go away from under us as exit_mmap holds an mm_count pin
> >* itself.
> >*/
> > -void __mmu_notifier_release(struct mm_struct *mm)
> > +static void mn_hlist_release(struct mmu_notifier_mm *mmn_mm,
> > +struct mm_struct *mm)
> > {
> > struct mmu_notifier *mn;
> > int id;
> >
> > + if (mmn_mm->has_interval)
> > + mn_itree_release(mmn_mm, mm);
> > +
> > + if (hlist_empty(_mm->list))
> > + return;
>
> This seems to duplicate the conditions in __mmu_notifier_release. See my
> comments below, I think one of them is wrong. I suspect this one,
> because __mmu_notifier_release follows the same pattern as the other
> notifiers.
Yep, this is a rebasing error from a earlier version, the above two
lines should be deleted.
I think it is harmless so it should not impact any testing.
Thanks,
Jason
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Re: [PATCH v2 02/15] mm/mmu_notifier: add an interval tree notifier
I haven't had enough time to fully understand the deferred logic in this
change. I spotted one problem, see comments inline.
On 2019-10-28 4:10 p.m., Jason Gunthorpe wrote:
> From: Jason Gunthorpe
>
> Of the 13 users of mmu_notifiers, 8 of them use only
> invalidate_range_start/end() and immediately intersect the
> mmu_notifier_range with some kind of internal list of VAs. 4 use an
> interval tree (i915_gem, radeon_mn, umem_odp, hfi1). 4 use a linked list
> of some kind (scif_dma, vhost, gntdev, hmm)
>
> And the remaining 5 either don't use invalidate_range_start() or do some
> special thing with it.
>
> It turns out that building a correct scheme with an interval tree is
> pretty complicated, particularly if the use case is synchronizing against
> another thread doing get_user_pages(). Many of these implementations have
> various subtle and difficult to fix races.
>
> This approach puts the interval tree as common code at the top of the mmu
> notifier call tree and implements a shareable locking scheme.
>
> It includes:
> - An interval tree tracking VA ranges, with per-range callbacks
> - A read/write locking scheme for the interval tree that avoids
> sleeping in the notifier path (for OOM killer)
> - A sequence counter based collision-retry locking scheme to tell
> device page fault that a VA range is being concurrently invalidated.
>
> This is based on various ideas:
> - hmm accumulates invalidated VA ranges and releases them when all
>invalidates are done, via active_invalidate_ranges count.
>This approach avoids having to intersect the interval tree twice (as
>umem_odp does) at the potential cost of a longer device page fault.
>
> - kvm/umem_odp use a sequence counter to drive the collision retry,
>via invalidate_seq
>
> - a deferred work todo list on unlock scheme like RTNL, via deferred_list.
>This makes adding/removing interval tree members more deterministic
>
> - seqlock, except this version makes the seqlock idea multi-holder on the
>write side by protecting it with active_invalidate_ranges and a spinlock
>
> To minimize MM overhead when only the interval tree is being used, the
> entire SRCU and hlist overheads are dropped using some simple
> branches. Similarly the interval tree overhead is dropped when in hlist
> mode.
>
> The overhead from the mandatory spinlock is broadly the same as most of
> existing users which already had a lock (or two) of some sort on the
> invalidation path.
>
> Cc: Andrea Arcangeli
> Cc: Michal Hocko
> Acked-by: Christian König
> Signed-off-by: Jason Gunthorpe
> ---
> include/linux/mmu_notifier.h | 98 +++
> mm/Kconfig | 1 +
> mm/mmu_notifier.c| 533 +--
> 3 files changed, 607 insertions(+), 25 deletions(-)
>
[snip]
> diff --git a/mm/mmu_notifier.c b/mm/mmu_notifier.c
> index 367670cfd02b7b..d02d3c8c223eb7 100644
> --- a/mm/mmu_notifier.c
> +++ b/mm/mmu_notifier.c
[snip]
>* because mm->mm_users > 0 during mmu_notifier_register and exit_mmap
> @@ -52,17 +286,24 @@ struct mmu_notifier_mm {
>* can't go away from under us as exit_mmap holds an mm_count pin
>* itself.
>*/
> -void __mmu_notifier_release(struct mm_struct *mm)
> +static void mn_hlist_release(struct mmu_notifier_mm *mmn_mm,
> + struct mm_struct *mm)
> {
> struct mmu_notifier *mn;
> int id;
>
> + if (mmn_mm->has_interval)
> + mn_itree_release(mmn_mm, mm);
> +
> + if (hlist_empty(_mm->list))
> + return;
This seems to duplicate the conditions in __mmu_notifier_release. See my
comments below, I think one of them is wrong. I suspect this one,
because __mmu_notifier_release follows the same pattern as the other
notifiers.
> +
> /*
>* SRCU here will block mmu_notifier_unregister until
>* ->release returns.
>*/
> id = srcu_read_lock();
> - hlist_for_each_entry_rcu(mn, >mmu_notifier_mm->list, hlist)
> + hlist_for_each_entry_rcu(mn, _mm->list, hlist)
> /*
>* If ->release runs before mmu_notifier_unregister it must be
>* handled, as it's the only way for the driver to flush all
> @@ -72,9 +313,9 @@ void __mmu_notifier_release(struct mm_struct *mm)
> if (mn->ops->release)
> mn->ops->release(mn, mm);
>
> - spin_lock(>mmu_notifier_mm->lock);
> - while (unlikely(!hlist_empty(>mmu_notifier_mm->list))) {
> - mn = hlist_entry(mm->mmu_notifier_mm->list.first,
> + spin_lock(_mm->lock);
> + while (unlikely(!hlist_empty(_mm->list))) {
> + mn = hlist_entry(mmn_mm->list.first,
>struct mmu_notifier,
>hlist);
> /*
> @@ -85,7 +326,7 @@ void __mmu_notifier_release(struct mm_struct *mm)
>*/
> hlist_del_init_rcu(>hlist);
> }
> -
[PATCH v2 02/15] mm/mmu_notifier: add an interval tree notifier
From: Jason Gunthorpe
Of the 13 users of mmu_notifiers, 8 of them use only
invalidate_range_start/end() and immediately intersect the
mmu_notifier_range with some kind of internal list of VAs. 4 use an
interval tree (i915_gem, radeon_mn, umem_odp, hfi1). 4 use a linked list
of some kind (scif_dma, vhost, gntdev, hmm)
And the remaining 5 either don't use invalidate_range_start() or do some
special thing with it.
It turns out that building a correct scheme with an interval tree is
pretty complicated, particularly if the use case is synchronizing against
another thread doing get_user_pages(). Many of these implementations have
various subtle and difficult to fix races.
This approach puts the interval tree as common code at the top of the mmu
notifier call tree and implements a shareable locking scheme.
It includes:
- An interval tree tracking VA ranges, with per-range callbacks
- A read/write locking scheme for the interval tree that avoids
sleeping in the notifier path (for OOM killer)
- A sequence counter based collision-retry locking scheme to tell
device page fault that a VA range is being concurrently invalidated.
This is based on various ideas:
- hmm accumulates invalidated VA ranges and releases them when all
invalidates are done, via active_invalidate_ranges count.
This approach avoids having to intersect the interval tree twice (as
umem_odp does) at the potential cost of a longer device page fault.
- kvm/umem_odp use a sequence counter to drive the collision retry,
via invalidate_seq
- a deferred work todo list on unlock scheme like RTNL, via deferred_list.
This makes adding/removing interval tree members more deterministic
- seqlock, except this version makes the seqlock idea multi-holder on the
write side by protecting it with active_invalidate_ranges and a spinlock
To minimize MM overhead when only the interval tree is being used, the
entire SRCU and hlist overheads are dropped using some simple
branches. Similarly the interval tree overhead is dropped when in hlist
mode.
The overhead from the mandatory spinlock is broadly the same as most of
existing users which already had a lock (or two) of some sort on the
invalidation path.
Cc: Andrea Arcangeli
Cc: Michal Hocko
Acked-by: Christian König
Signed-off-by: Jason Gunthorpe
---
include/linux/mmu_notifier.h | 98 +++
mm/Kconfig | 1 +
mm/mmu_notifier.c| 533 +--
3 files changed, 607 insertions(+), 25 deletions(-)
diff --git a/include/linux/mmu_notifier.h b/include/linux/mmu_notifier.h
index 12bd603d318ce7..51b92ba013ddce 100644
--- a/include/linux/mmu_notifier.h
+++ b/include/linux/mmu_notifier.h
@@ -6,10 +6,12 @@
#include
#include
#include
+#include
struct mmu_notifier_mm;
struct mmu_notifier;
struct mmu_notifier_range;
+struct mmu_range_notifier;
/**
* enum mmu_notifier_event - reason for the mmu notifier callback
@@ -32,6 +34,9 @@ struct mmu_notifier_range;
* access flags). User should soft dirty the page in the end callback to make
* sure that anyone relying on soft dirtyness catch pages that might be written
* through non CPU mappings.
+ *
+ * @MMU_NOTIFY_RELEASE: used during mmu_range_notifier invalidate to signal
that
+ * the mm refcount is zero and the range is no longer accessible.
*/
enum mmu_notifier_event {
MMU_NOTIFY_UNMAP = 0,
@@ -39,6 +44,7 @@ enum mmu_notifier_event {
MMU_NOTIFY_PROTECTION_VMA,
MMU_NOTIFY_PROTECTION_PAGE,
MMU_NOTIFY_SOFT_DIRTY,
+ MMU_NOTIFY_RELEASE,
};
#define MMU_NOTIFIER_RANGE_BLOCKABLE (1 << 0)
@@ -222,6 +228,26 @@ struct mmu_notifier {
unsigned int users;
};
+/**
+ * struct mmu_range_notifier_ops
+ * @invalidate: Upon return the caller must stop using any SPTEs within this
+ * range, this function can sleep. Return false if blocking was
+ * required but range is non-blocking
+ */
+struct mmu_range_notifier_ops {
+ bool (*invalidate)(struct mmu_range_notifier *mrn,
+ const struct mmu_notifier_range *range,
+ unsigned long cur_seq);
+};
+
+struct mmu_range_notifier {
+ struct interval_tree_node interval_tree;
+ const struct mmu_range_notifier_ops *ops;
+ struct hlist_node deferred_item;
+ unsigned long invalidate_seq;
+ struct mm_struct *mm;
+};
+
#ifdef CONFIG_MMU_NOTIFIER
#ifdef CONFIG_LOCKDEP
@@ -263,6 +289,78 @@ extern int __mmu_notifier_register(struct mmu_notifier *mn,
struct mm_struct *mm);
extern void mmu_notifier_unregister(struct mmu_notifier *mn,
struct mm_struct *mm);
+
+unsigned long mmu_range_read_begin(struct mmu_range_notifier *mrn);
+int mmu_range_notifier_insert(struct mmu_range_notifier *mrn,
+ unsigned long start, unsigned long length,
+ struct mm_struct *mm);
+int
