Re: [PATCH] Initialise mmu_notifier_range correctly
On Thu, Jan 03, 2019 at 06:43:13AM -0800, Matthew Wilcox wrote:
> On Thu, Jan 03, 2019 at 09:31:16AM -0500, Jerome Glisse wrote:
> > On Wed, Jan 02, 2019 at 04:21:26PM -0800, Matthew Wilcox wrote:
> > >
> > > One of the paths in follow_pte_pmd() initialised the mmu_notifier_range
> > > incorrectly.
> > >
> > > Signed-off-by: Matthew Wilcox
> > > Fixes: ac46d4f3c432 ("mm/mmu_notifier: use structure for
> > > invalidate_range_start/end calls v2")
> > > Tested-by: Dave Chinner
> >
> > Actually now that i have read the code again this is not ok to
> > do so. The caller of follow_pte_pmd() will call range_init and
> > follow pmd will only update the range address. So existing code
> > is ok.
>
> I think you need to re-read your own patch.
>
> `git show ac46d4f3c43241ffa23d5bf36153a0830c0e02cc`
>
> @@ -4058,10 +4059,10 @@ static int __follow_pte_pmd(struct mm_struct *mm,
> unsigned long address,
> if (!pmdpp)
> goto out;
>
> - if (start && end) {
> - *start = address & PMD_MASK;
> - *end = *start + PMD_SIZE;
> - mmu_notifier_invalidate_range_start(mm, *start, *end);
> + if (range) {
> + mmu_notifier_range_init(range, mm, address & PMD_MASK,
> +(address & PMD_MASK) + PMD_SIZE);
> + mmu_notifier_invalidate_range_start(range);
>
> ... so it's fine to call range_init() *here*.
>
> @@ -4069,17 +4070,17 @@ static int __follow_pte_pmd(struct mm_struct *mm,
> unsign
> ed long address,
> [...]
> if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
> goto out;
>
> - if (start && end) {
> - *start = address & PAGE_MASK;
> - *end = *start + PAGE_SIZE;
> - mmu_notifier_invalidate_range_start(mm, *start, *end);
> + if (range) {
> + range->start = address & PAGE_MASK;
> + range->end = range->start + PAGE_SIZE;
> + mmu_notifier_invalidate_range_start(range);
>
> ... but then *not* here later in the same function? You're not making
> any sense.
Ok i see that the patch that add the reason why mmu notifier is
call have been drop. So yes using range_init in follow_pte_pmd
is fine. With that other patch the reasons is set by the caller
of follow_pte_pmd and using range_init would have overwritten
it.
So this patch is fine for current tree. Sorry i was thinking with
the other patch included in mind.
Cheers,
Jérôme
Re: [PATCH] Initialise mmu_notifier_range correctly
On Thu, Jan 03, 2019 at 06:39:08AM -0800, Matthew Wilcox wrote: > On Thu, Jan 03, 2019 at 09:29:59AM -0500, Jerome Glisse wrote: > > On Wed, Jan 02, 2019 at 08:18:33PM -0800, Matthew Wilcox wrote: > > > On Wed, Jan 02, 2019 at 07:32:08PM -0800, John Hubbard wrote: > > > > Having the range struct declared in separate places from the > > > > mmu_notifier_range_init() > > > > calls is not great. But I'm not sure I see a way to make it > > > > significantly cleaner, given > > > > that __follow_pte_pmd uses the range pointer as a way to decide to > > > > issue the mmn calls. > > > > > > Yeah, I don't think there's anything we can do. But I started reviewing > > > the comments, and they don't make sense together: > > > > > > /* > > > * Note because we provide range to follow_pte_pmd it will > > > * call mmu_notifier_invalidate_range_start() on our > > > behalf > > > * before taking any lock. > > > */ > > > if (follow_pte_pmd(vma->vm_mm, address, , > > >, , )) > > > continue; > > > > > > /* > > > * No need to call mmu_notifier_invalidate_range() as we > > > are > > > * downgrading page table protection not changing it to > > > point > > > * to a new page. > > > * > > > * See Documentation/vm/mmu_notifier.rst > > > */ > > > > > > So if we don't call mmu_notifier_invalidate_range, why are we calling > > > mmu_notifier_invalidate_range_start and mmu_notifier_invalidate_range_end? > > > ie, why not this ... > > > > Thus comments looks wrong to me ... we need to call > > mmu_notifier_invalidate_range() those are use by > > IOMMU. I might be to blame for those comments thought. > > Yes, you're to blame for both of them. > > a4d1a88525138 (Jérôme Glisse 2017-08-31 17:17:26 -0400 791) >* Note because we provide start/end to follow_pte_pmd it will > a4d1a88525138 (Jérôme Glisse 2017-08-31 17:17:26 -0400 792) >* call mmu_notifier_invalidate_range_start() on our behalf > a4d1a88525138 (Jérôme Glisse 2017-08-31 17:17:26 -0400 793) >* before taking any lock. > > 0f10851ea475e (Jérôme Glisse 2017-11-15 17:34:07 -0800 794) >* No need to call mmu_notifier_invalidate_range() as we are > 0f10851ea475e (Jérôme Glisse 2017-11-15 17:34:07 -0800 795) >* downgrading page table protection not changing it to point > 0f10851ea475e (Jérôme Glisse 2017-11-15 17:34:07 -0800 796) >* to a new page. > I remember now we do not need to call invalidate range because invalidate_range_end() does call invalidate_range so it is fine. Comments should be better thought. So existing code is fine. Cheers, Jérôme
Re: [PATCH] Initialise mmu_notifier_range correctly
On Thu, Jan 03, 2019 at 09:31:16AM -0500, Jerome Glisse wrote:
> On Wed, Jan 02, 2019 at 04:21:26PM -0800, Matthew Wilcox wrote:
> >
> > One of the paths in follow_pte_pmd() initialised the mmu_notifier_range
> > incorrectly.
> >
> > Signed-off-by: Matthew Wilcox
> > Fixes: ac46d4f3c432 ("mm/mmu_notifier: use structure for
> > invalidate_range_start/end calls v2")
> > Tested-by: Dave Chinner
>
> Actually now that i have read the code again this is not ok to
> do so. The caller of follow_pte_pmd() will call range_init and
> follow pmd will only update the range address. So existing code
> is ok.
I think you need to re-read your own patch.
`git show ac46d4f3c43241ffa23d5bf36153a0830c0e02cc`
@@ -4058,10 +4059,10 @@ static int __follow_pte_pmd(struct mm_struct *mm,
unsigned long address,
if (!pmdpp)
goto out;
- if (start && end) {
- *start = address & PMD_MASK;
- *end = *start + PMD_SIZE;
- mmu_notifier_invalidate_range_start(mm, *start, *end);
+ if (range) {
+ mmu_notifier_range_init(range, mm, address & PMD_MASK,
+(address & PMD_MASK) + PMD_SIZE);
+ mmu_notifier_invalidate_range_start(range);
... so it's fine to call range_init() *here*.
@@ -4069,17 +4070,17 @@ static int __follow_pte_pmd(struct mm_struct *mm, unsign
ed long address,
[...]
if (pmd_none(*pmd) || unlikely(pmd_bad(*pmd)))
goto out;
- if (start && end) {
- *start = address & PAGE_MASK;
- *end = *start + PAGE_SIZE;
- mmu_notifier_invalidate_range_start(mm, *start, *end);
+ if (range) {
+ range->start = address & PAGE_MASK;
+ range->end = range->start + PAGE_SIZE;
+ mmu_notifier_invalidate_range_start(range);
... but then *not* here later in the same function? You're not making
any sense.
Re: [PATCH] Initialise mmu_notifier_range correctly
On Thu, Jan 03, 2019 at 09:29:59AM -0500, Jerome Glisse wrote: > On Wed, Jan 02, 2019 at 08:18:33PM -0800, Matthew Wilcox wrote: > > On Wed, Jan 02, 2019 at 07:32:08PM -0800, John Hubbard wrote: > > > Having the range struct declared in separate places from the > > > mmu_notifier_range_init() > > > calls is not great. But I'm not sure I see a way to make it significantly > > > cleaner, given > > > that __follow_pte_pmd uses the range pointer as a way to decide to issue > > > the mmn calls. > > > > Yeah, I don't think there's anything we can do. But I started reviewing > > the comments, and they don't make sense together: > > > > /* > > * Note because we provide range to follow_pte_pmd it will > > * call mmu_notifier_invalidate_range_start() on our behalf > > * before taking any lock. > > */ > > if (follow_pte_pmd(vma->vm_mm, address, , > >, , )) > > continue; > > > > /* > > * No need to call mmu_notifier_invalidate_range() as we are > > * downgrading page table protection not changing it to > > point > > * to a new page. > > * > > * See Documentation/vm/mmu_notifier.rst > > */ > > > > So if we don't call mmu_notifier_invalidate_range, why are we calling > > mmu_notifier_invalidate_range_start and mmu_notifier_invalidate_range_end? > > ie, why not this ... > > Thus comments looks wrong to me ... we need to call > mmu_notifier_invalidate_range() those are use by > IOMMU. I might be to blame for those comments thought. Yes, you're to blame for both of them. a4d1a88525138 (Jérôme Glisse 2017-08-31 17:17:26 -0400 791) * Note because we provide start/end to follow_pte_pmd it will a4d1a88525138 (Jérôme Glisse 2017-08-31 17:17:26 -0400 792) * call mmu_notifier_invalidate_range_start() on our behalf a4d1a88525138 (Jérôme Glisse 2017-08-31 17:17:26 -0400 793) * before taking any lock. 0f10851ea475e (Jérôme Glisse 2017-11-15 17:34:07 -0800 794) * No need to call mmu_notifier_invalidate_range() as we are 0f10851ea475e (Jérôme Glisse 2017-11-15 17:34:07 -0800 795) * downgrading page table protection not changing it to point 0f10851ea475e (Jérôme Glisse 2017-11-15 17:34:07 -0800 796) * to a new page.
Re: [PATCH] Initialise mmu_notifier_range correctly
On Thu, Jan 03, 2019 at 09:31:16AM -0500, Jerome Glisse wrote:
> On Wed, Jan 02, 2019 at 04:21:26PM -0800, Matthew Wilcox wrote:
> >
> > One of the paths in follow_pte_pmd() initialised the mmu_notifier_range
> > incorrectly.
> >
> > Signed-off-by: Matthew Wilcox
> > Fixes: ac46d4f3c432 ("mm/mmu_notifier: use structure for
> > invalidate_range_start/end calls v2")
> > Tested-by: Dave Chinner
>
> Actually now that i have read the code again this is not ok to
> do so. The caller of follow_pte_pmd() will call range_init and
> follow pmd will only update the range address. So existing code
> is ok.
The only caller of follow_pte_pmd() does not call range_init() because it
doesn't know the address. That's the point of follow_pte_pmd().
> I know this is kind of ugly but i do not see a way around that
> uglyness.
You wrote the code ...
Re: [PATCH] Initialise mmu_notifier_range correctly
On Wed, Jan 02, 2019 at 04:21:26PM -0800, Matthew Wilcox wrote:
>
> One of the paths in follow_pte_pmd() initialised the mmu_notifier_range
> incorrectly.
>
> Signed-off-by: Matthew Wilcox
> Fixes: ac46d4f3c432 ("mm/mmu_notifier: use structure for
> invalidate_range_start/end calls v2")
> Tested-by: Dave Chinner
Actually now that i have read the code again this is not ok to
do so. The caller of follow_pte_pmd() will call range_init and
follow pmd will only update the range address. So existing code
is ok.
I know this is kind of ugly but i do not see a way around that
uglyness.
>
> diff --git a/mm/memory.c b/mm/memory.c
> index 2dd2f9ab57f4..21a650368be0 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -4078,8 +4078,8 @@ static int __follow_pte_pmd(struct mm_struct *mm,
> unsigned long address,
> goto out;
>
> if (range) {
> - range->start = address & PAGE_MASK;
> - range->end = range->start + PAGE_SIZE;
> + mmu_notifier_range_init(range, mm, address & PAGE_MASK,
> + (address & PAGE_MASK) + PAGE_SIZE);
> mmu_notifier_invalidate_range_start(range);
> }
> ptep = pte_offset_map_lock(mm, pmd, address, ptlp);
Re: [PATCH] Initialise mmu_notifier_range correctly
On Wed, Jan 02, 2019 at 08:18:33PM -0800, Matthew Wilcox wrote:
> On Wed, Jan 02, 2019 at 07:32:08PM -0800, John Hubbard wrote:
> > Having the range struct declared in separate places from the
> > mmu_notifier_range_init()
> > calls is not great. But I'm not sure I see a way to make it significantly
> > cleaner, given
> > that __follow_pte_pmd uses the range pointer as a way to decide to issue
> > the mmn calls.
>
> Yeah, I don't think there's anything we can do. But I started reviewing
> the comments, and they don't make sense together:
>
> /*
> * Note because we provide range to follow_pte_pmd it will
> * call mmu_notifier_invalidate_range_start() on our behalf
> * before taking any lock.
> */
> if (follow_pte_pmd(vma->vm_mm, address, ,
>, , ))
> continue;
>
> /*
> * No need to call mmu_notifier_invalidate_range() as we are
> * downgrading page table protection not changing it to point
> * to a new page.
> *
> * See Documentation/vm/mmu_notifier.rst
> */
>
> So if we don't call mmu_notifier_invalidate_range, why are we calling
> mmu_notifier_invalidate_range_start and mmu_notifier_invalidate_range_end?
> ie, why not this ...
Thus comments looks wrong to me ... we need to call
mmu_notifier_invalidate_range() those are use by
IOMMU. I might be to blame for those comments thought.
>
> diff --git a/fs/dax.c b/fs/dax.c
> index 6959837cc465..905340149924 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -777,7 +777,6 @@ static void dax_entry_mkclean(struct address_space
> *mapping, pgoff_t index,
>
> i_mmap_lock_read(mapping);
> vma_interval_tree_foreach(vma, >i_mmap, index, index) {
> - struct mmu_notifier_range range;
> unsigned long address;
>
> cond_resched();
> @@ -787,12 +786,7 @@ static void dax_entry_mkclean(struct address_space
> *mapping, pgoff_t index,
>
> address = pgoff_address(index, vma);
>
> - /*
> - * Note because we provide start/end to follow_pte_pmd it will
> - * call mmu_notifier_invalidate_range_start() on our behalf
> - * before taking any lock.
> - */
> - if (follow_pte_pmd(vma->vm_mm, address, ,
> + if (follow_pte_pmd(vma->vm_mm, address, NULL,
> , , ))
> continue;
>
> @@ -834,8 +828,6 @@ static void dax_entry_mkclean(struct address_space
> *mapping, pgoff_t index,
> unlock_pte:
> pte_unmap_unlock(ptep, ptl);
> }
> -
> - mmu_notifier_invalidate_range_end();
> }
> i_mmap_unlock_read(mapping);
> }
Re: [PATCH] Initialise mmu_notifier_range correctly
On Wed, Jan 02, 2019 at 07:32:08PM -0800, John Hubbard wrote:
> Having the range struct declared in separate places from the
> mmu_notifier_range_init()
> calls is not great. But I'm not sure I see a way to make it significantly
> cleaner, given
> that __follow_pte_pmd uses the range pointer as a way to decide to issue the
> mmn calls.
Yeah, I don't think there's anything we can do. But I started reviewing
the comments, and they don't make sense together:
/*
* Note because we provide range to follow_pte_pmd it will
* call mmu_notifier_invalidate_range_start() on our behalf
* before taking any lock.
*/
if (follow_pte_pmd(vma->vm_mm, address, ,
, , ))
continue;
/*
* No need to call mmu_notifier_invalidate_range() as we are
* downgrading page table protection not changing it to point
* to a new page.
*
* See Documentation/vm/mmu_notifier.rst
*/
So if we don't call mmu_notifier_invalidate_range, why are we calling
mmu_notifier_invalidate_range_start and mmu_notifier_invalidate_range_end?
ie, why not this ...
diff --git a/fs/dax.c b/fs/dax.c
index 6959837cc465..905340149924 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -777,7 +777,6 @@ static void dax_entry_mkclean(struct address_space
*mapping, pgoff_t index,
i_mmap_lock_read(mapping);
vma_interval_tree_foreach(vma, >i_mmap, index, index) {
- struct mmu_notifier_range range;
unsigned long address;
cond_resched();
@@ -787,12 +786,7 @@ static void dax_entry_mkclean(struct address_space
*mapping, pgoff_t index,
address = pgoff_address(index, vma);
- /*
-* Note because we provide start/end to follow_pte_pmd it will
-* call mmu_notifier_invalidate_range_start() on our behalf
-* before taking any lock.
-*/
- if (follow_pte_pmd(vma->vm_mm, address, ,
+ if (follow_pte_pmd(vma->vm_mm, address, NULL,
, , ))
continue;
@@ -834,8 +828,6 @@ static void dax_entry_mkclean(struct address_space
*mapping, pgoff_t index,
unlock_pte:
pte_unmap_unlock(ptep, ptl);
}
-
- mmu_notifier_invalidate_range_end();
}
i_mmap_unlock_read(mapping);
}
Re: [PATCH] Initialise mmu_notifier_range correctly
On 1/2/19 5:56 PM, Jerome Glisse wrote:
> On Wed, Jan 02, 2019 at 04:21:26PM -0800, Matthew Wilcox wrote:
>>
>> One of the paths in follow_pte_pmd() initialised the mmu_notifier_range
>> incorrectly.
>>
>> Signed-off-by: Matthew Wilcox
>> Fixes: ac46d4f3c432 ("mm/mmu_notifier: use structure for
>> invalidate_range_start/end calls v2")
>> Tested-by: Dave Chinner
>
> Reviewed-by: Jérôme Glisse
>
>>
>> diff --git a/mm/memory.c b/mm/memory.c
>> index 2dd2f9ab57f4..21a650368be0 100644
>> --- a/mm/memory.c
>> +++ b/mm/memory.c
>> @@ -4078,8 +4078,8 @@ static int __follow_pte_pmd(struct mm_struct *mm,
>> unsigned long address,
>> goto out;
>>
>> if (range) {
>> -range->start = address & PAGE_MASK;
>> -range->end = range->start + PAGE_SIZE;
>> +mmu_notifier_range_init(range, mm, address & PAGE_MASK,
>> + (address & PAGE_MASK) + PAGE_SIZE);
>> mmu_notifier_invalidate_range_start(range);
>> }
>> ptep = pte_offset_map_lock(mm, pmd, address, ptlp);
>
Looks correct to me, as well.
Having the range struct declared in separate places from the
mmu_notifier_range_init()
calls is not great. But I'm not sure I see a way to make it significantly
cleaner, given
that __follow_pte_pmd uses the range pointer as a way to decide to issue the
mmn calls.
thanks,
--
John Hubbard
NVIDIA
Re: [PATCH] Initialise mmu_notifier_range correctly
On Wed, Jan 02, 2019 at 04:21:26PM -0800, Matthew Wilcox wrote:
>
> One of the paths in follow_pte_pmd() initialised the mmu_notifier_range
> incorrectly.
>
> Signed-off-by: Matthew Wilcox
> Fixes: ac46d4f3c432 ("mm/mmu_notifier: use structure for
> invalidate_range_start/end calls v2")
> Tested-by: Dave Chinner
Reviewed-by: Jérôme Glisse
>
> diff --git a/mm/memory.c b/mm/memory.c
> index 2dd2f9ab57f4..21a650368be0 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -4078,8 +4078,8 @@ static int __follow_pte_pmd(struct mm_struct *mm,
> unsigned long address,
> goto out;
>
> if (range) {
> - range->start = address & PAGE_MASK;
> - range->end = range->start + PAGE_SIZE;
> + mmu_notifier_range_init(range, mm, address & PAGE_MASK,
> + (address & PAGE_MASK) + PAGE_SIZE);
> mmu_notifier_invalidate_range_start(range);
> }
> ptep = pte_offset_map_lock(mm, pmd, address, ptlp);
[PATCH] Initialise mmu_notifier_range correctly
One of the paths in follow_pte_pmd() initialised the mmu_notifier_range
incorrectly.
Signed-off-by: Matthew Wilcox
Fixes: ac46d4f3c432 ("mm/mmu_notifier: use structure for
invalidate_range_start/end calls v2")
Tested-by: Dave Chinner
diff --git a/mm/memory.c b/mm/memory.c
index 2dd2f9ab57f4..21a650368be0 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -4078,8 +4078,8 @@ static int __follow_pte_pmd(struct mm_struct *mm,
unsigned long address,
goto out;
if (range) {
- range->start = address & PAGE_MASK;
- range->end = range->start + PAGE_SIZE;
+ mmu_notifier_range_init(range, mm, address & PAGE_MASK,
+(address & PAGE_MASK) + PAGE_SIZE);
mmu_notifier_invalidate_range_start(range);
}
ptep = pte_offset_map_lock(mm, pmd, address, ptlp);
