Use the helper for the checks. Rename "check_mapping" into "zap_mapping"
because "check_mapping" looks like a bool but in fact it stores the mapping
itself. When it's set, we check the mapping (it must be non-NULL). When it's
cleared we skip the check, which works like the old way.
Move the duplicated comments to the helper too.
Signed-off-by: Peter Xu <[email protected]>
---
include/linux/mm.h | 15 ++++++++++++++-
mm/memory.c | 29 ++++++-----------------------
2 files changed, 20 insertions(+), 24 deletions(-)
diff --git a/include/linux/mm.h b/include/linux/mm.h
index 69259229f090..81e402a5fbc9 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1720,10 +1720,23 @@ extern void user_shm_unlock(size_t, struct ucounts *);
* Parameter block passed down to zap_pte_range in exceptional cases.
*/
struct zap_details {
- struct address_space *check_mapping; /* Check page->mapping if set */
+ struct address_space *zap_mapping; /* Check page->mapping if set */
struct page *single_page; /* Locked page to be unmapped */
};
+/*
+ * We set details->zap_mappings when we want to unmap shared but keep private
+ * pages. Return true if skip zapping this page, false otherwise.
+ */
+static inline bool
+zap_skip_check_mapping(struct zap_details *details, struct page *page)
+{
+ if (!details || !page)
+ return false;
+
+ return details->zap_mapping != page_rmapping(page);
+}
+
struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
pte_t pte);
struct page *vm_normal_page_pmd(struct vm_area_struct *vma, unsigned long addr,
diff --git a/mm/memory.c b/mm/memory.c
index 6bba3b9fef7c..e5ee8399d270 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -1333,16 +1333,8 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
struct page *page;
page = vm_normal_page(vma, addr, ptent);
- if (unlikely(details) && page) {
- /*
- * unmap_shared_mapping_pages() wants to
- * invalidate cache without truncating:
- * unmap shared but keep private pages.
- */
- if (details->check_mapping &&
- details->check_mapping != page_rmapping(page))
- continue;
- }
+ if (unlikely(zap_skip_check_mapping(details, page)))
+ continue;
ptent = ptep_get_and_clear_full(mm, addr, pte,
tlb->fullmm);
tlb_remove_tlb_entry(tlb, pte, addr);
@@ -1375,17 +1367,8 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
is_device_exclusive_entry(entry)) {
struct page *page = pfn_swap_entry_to_page(entry);
- if (unlikely(details && details->check_mapping)) {
- /*
- * unmap_shared_mapping_pages() wants to
- * invalidate cache without truncating:
- * unmap shared but keep private pages.
- */
- if (details->check_mapping !=
- page_rmapping(page))
- continue;
- }
-
+ if (unlikely(zap_skip_check_mapping(details, page)))
+ continue;
pte_clear_not_present_full(mm, addr, pte, tlb->fullmm);
rss[mm_counter(page)]--;
@@ -3368,7 +3351,7 @@ void unmap_mapping_page(struct page *page)
first_index = page->index;
last_index = page->index + thp_nr_pages(page) - 1;
- details.check_mapping = mapping;
+ details.zap_mapping = mapping;
details.single_page = page;
i_mmap_lock_write(mapping);
@@ -3396,7 +3379,7 @@ void unmap_mapping_pages(struct address_space *mapping, pgoff_t start,
pgoff_t first_index = start, last_index = start + nr - 1;
struct zap_details details = { };
- details.check_mapping = even_cows ? NULL : mapping;
+ details.zap_mapping = even_cows ? NULL : mapping;
if (last_index < first_index)
last_index = ULONG_MAX;
--
2.31.1
On Friday, 3 September 2021 6:18:19 AM AEST Peter Xu wrote:
> Use the helper for the checks. Rename "check_mapping" into "zap_mapping"
> because "check_mapping" looks like a bool but in fact it stores the mapping
> itself. When it's set, we check the mapping (it must be non-NULL). When it's
> cleared we skip the check, which works like the old way.
>
> Move the duplicated comments to the helper too.
>
> Signed-off-by: Peter Xu <[email protected]>
> ---
> include/linux/mm.h | 15 ++++++++++++++-
> mm/memory.c | 29 ++++++-----------------------
> 2 files changed, 20 insertions(+), 24 deletions(-)
>
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> index 69259229f090..81e402a5fbc9 100644
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -1720,10 +1720,23 @@ extern void user_shm_unlock(size_t, struct ucounts *);
> * Parameter block passed down to zap_pte_range in exceptional cases.
> */
> struct zap_details {
> - struct address_space *check_mapping; /* Check page->mapping if set */
> + struct address_space *zap_mapping; /* Check page->mapping if set */
> struct page *single_page; /* Locked page to be unmapped */
> };
>
> +/*
> + * We set details->zap_mappings when we want to unmap shared but keep private
> + * pages. Return true if skip zapping this page, false otherwise.
> + */
> +static inline bool
> +zap_skip_check_mapping(struct zap_details *details, struct page *page)
> +{
> + if (!details || !page)
> + return false;
> +
> + return details->zap_mapping != page_rmapping(page);
Shouldn't this check still be
details->zap_mapping && details->zap_mapping != page_rmapping(page)?
Previously we wouldn't skip zapping pages if even_cows == true (ie.
details->check_mapping == NULL). With this change the check when
even_cows == true becomes NULL != page_rmapping(page). Doesn't this mean we
will now skip zapping any pages with a mapping when even_cows == true?
> +}
> +
> struct page *vm_normal_page(struct vm_area_struct *vma, unsigned long addr,
> pte_t pte);
> struct page *vm_normal_page_pmd(struct vm_area_struct *vma, unsigned long addr,
> diff --git a/mm/memory.c b/mm/memory.c
> index 6bba3b9fef7c..e5ee8399d270 100644
> --- a/mm/memory.c
> +++ b/mm/memory.c
> @@ -1333,16 +1333,8 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
> struct page *page;
>
> page = vm_normal_page(vma, addr, ptent);
> - if (unlikely(details) && page) {
> - /*
> - * unmap_shared_mapping_pages() wants to
> - * invalidate cache without truncating:
> - * unmap shared but keep private pages.
> - */
> - if (details->check_mapping &&
> - details->check_mapping != page_rmapping(page))
> - continue;
> - }
> + if (unlikely(zap_skip_check_mapping(details, page)))
> + continue;
>
> ptent = ptep_get_and_clear_full(mm, addr, pte,
> tlb->fullmm);
> tlb_remove_tlb_entry(tlb, pte, addr);
> @@ -1375,17 +1367,8 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
> is_device_exclusive_entry(entry)) {
> struct page *page = pfn_swap_entry_to_page(entry);
>
> - if (unlikely(details && details->check_mapping)) {
> - /*
> - * unmap_shared_mapping_pages() wants to
> - * invalidate cache without truncating:
> - * unmap shared but keep private pages.
> - */
> - if (details->check_mapping !=
> - page_rmapping(page))
> - continue;
> - }
> -
> + if (unlikely(zap_skip_check_mapping(details, page)))
> + continue;
> pte_clear_not_present_full(mm, addr, pte, tlb->fullmm);
> rss[mm_counter(page)]--;
>
> @@ -3368,7 +3351,7 @@ void unmap_mapping_page(struct page *page)
> first_index = page->index;
> last_index = page->index + thp_nr_pages(page) - 1;
>
> - details.check_mapping = mapping;
> + details.zap_mapping = mapping;
> details.single_page = page;
>
> i_mmap_lock_write(mapping);
> @@ -3396,7 +3379,7 @@ void unmap_mapping_pages(struct address_space *mapping, pgoff_t start,
> pgoff_t first_index = start, last_index = start + nr - 1;
> struct zap_details details = { };
>
> - details.check_mapping = even_cows ? NULL : mapping;
> + details.zap_mapping = even_cows ? NULL : mapping;
> if (last_index < first_index)
> last_index = ULONG_MAX;
>
>
On Fri, Sep 03, 2021 at 10:58:53AM +1000, Alistair Popple wrote:
> On Friday, 3 September 2021 6:18:19 AM AEST Peter Xu wrote:
> > Use the helper for the checks. Rename "check_mapping" into "zap_mapping"
> > because "check_mapping" looks like a bool but in fact it stores the mapping
> > itself. When it's set, we check the mapping (it must be non-NULL). When it's
> > cleared we skip the check, which works like the old way.
> >
> > Move the duplicated comments to the helper too.
> >
> > Signed-off-by: Peter Xu <[email protected]>
> > ---
> > include/linux/mm.h | 15 ++++++++++++++-
> > mm/memory.c | 29 ++++++-----------------------
> > 2 files changed, 20 insertions(+), 24 deletions(-)
> >
> > diff --git a/include/linux/mm.h b/include/linux/mm.h
> > index 69259229f090..81e402a5fbc9 100644
> > --- a/include/linux/mm.h
> > +++ b/include/linux/mm.h
> > @@ -1720,10 +1720,23 @@ extern void user_shm_unlock(size_t, struct ucounts *);
> > * Parameter block passed down to zap_pte_range in exceptional cases.
> > */
> > struct zap_details {
> > - struct address_space *check_mapping; /* Check page->mapping if set */
> > + struct address_space *zap_mapping; /* Check page->mapping if set */
> > struct page *single_page; /* Locked page to be unmapped */
> > };
> >
> > +/*
> > + * We set details->zap_mappings when we want to unmap shared but keep private
> > + * pages. Return true if skip zapping this page, false otherwise.
> > + */
> > +static inline bool
> > +zap_skip_check_mapping(struct zap_details *details, struct page *page)
> > +{
> > + if (!details || !page)
> > + return false;
> > +
> > + return details->zap_mapping != page_rmapping(page);
>
> Shouldn't this check still be
> details->zap_mapping && details->zap_mapping != page_rmapping(page)?
>
> Previously we wouldn't skip zapping pages if even_cows == true (ie.
> details->check_mapping == NULL). With this change the check when
> even_cows == true becomes NULL != page_rmapping(page). Doesn't this mean we
> will now skip zapping any pages with a mapping when even_cows == true?
Yes I think so. Thanks for pointing that out, Alistair, I'll fix in v3.
But frankly I really think we should simply have that flag I used to introduce.
It'll make everything much clearer.
--
Peter Xu
On Friday, 3 September 2021 11:39:32 AM AEST Peter Xu wrote:
> On Fri, Sep 03, 2021 at 10:58:53AM +1000, Alistair Popple wrote:
> > On Friday, 3 September 2021 6:18:19 AM AEST Peter Xu wrote:
> > > Use the helper for the checks. Rename "check_mapping" into "zap_mapping"
> > > because "check_mapping" looks like a bool but in fact it stores the mapping
> > > itself. When it's set, we check the mapping (it must be non-NULL). When it's
> > > cleared we skip the check, which works like the old way.
> > >
> > > Move the duplicated comments to the helper too.
> > >
> > > Signed-off-by: Peter Xu <[email protected]>
> > > ---
> > > include/linux/mm.h | 15 ++++++++++++++-
> > > mm/memory.c | 29 ++++++-----------------------
> > > 2 files changed, 20 insertions(+), 24 deletions(-)
> > >
> > > diff --git a/include/linux/mm.h b/include/linux/mm.h
> > > index 69259229f090..81e402a5fbc9 100644
> > > --- a/include/linux/mm.h
> > > +++ b/include/linux/mm.h
> > > @@ -1720,10 +1720,23 @@ extern void user_shm_unlock(size_t, struct ucounts *);
> > > * Parameter block passed down to zap_pte_range in exceptional cases.
> > > */
> > > struct zap_details {
> > > - struct address_space *check_mapping; /* Check page->mapping if set */
> > > + struct address_space *zap_mapping; /* Check page->mapping if set */
> > > struct page *single_page; /* Locked page to be unmapped */
> > > };
> > >
> > > +/*
> > > + * We set details->zap_mappings when we want to unmap shared but keep private
> > > + * pages. Return true if skip zapping this page, false otherwise.
> > > + */
> > > +static inline bool
> > > +zap_skip_check_mapping(struct zap_details *details, struct page *page)
> > > +{
> > > + if (!details || !page)
> > > + return false;
> > > +
> > > + return details->zap_mapping != page_rmapping(page);
> >
> > Shouldn't this check still be
> > details->zap_mapping && details->zap_mapping != page_rmapping(page)?
> >
> > Previously we wouldn't skip zapping pages if even_cows == true (ie.
> > details->check_mapping == NULL). With this change the check when
> > even_cows == true becomes NULL != page_rmapping(page). Doesn't this mean we
> > will now skip zapping any pages with a mapping when even_cows == true?
>
> Yes I think so. Thanks for pointing that out, Alistair, I'll fix in v3.
>
> But frankly I really think we should simply have that flag I used to introduce.
> It'll make everything much clearer.
Yeah, I think a flag would also be fine.
- Alistair
On 03.09.21 03:50, Alistair Popple wrote:
> On Friday, 3 September 2021 11:39:32 AM AEST Peter Xu wrote:
>> On Fri, Sep 03, 2021 at 10:58:53AM +1000, Alistair Popple wrote:
>>> On Friday, 3 September 2021 6:18:19 AM AEST Peter Xu wrote:
>>>> Use the helper for the checks. Rename "check_mapping" into "zap_mapping"
>>>> because "check_mapping" looks like a bool but in fact it stores the mapping
>>>> itself. When it's set, we check the mapping (it must be non-NULL). When it's
>>>> cleared we skip the check, which works like the old way.
>>>>
>>>> Move the duplicated comments to the helper too.
>>>>
>>>> Signed-off-by: Peter Xu <[email protected]>
>>>> ---
>>>> include/linux/mm.h | 15 ++++++++++++++-
>>>> mm/memory.c | 29 ++++++-----------------------
>>>> 2 files changed, 20 insertions(+), 24 deletions(-)
>>>>
>>>> diff --git a/include/linux/mm.h b/include/linux/mm.h
>>>> index 69259229f090..81e402a5fbc9 100644
>>>> --- a/include/linux/mm.h
>>>> +++ b/include/linux/mm.h
>>>> @@ -1720,10 +1720,23 @@ extern void user_shm_unlock(size_t, struct ucounts *);
>>>> * Parameter block passed down to zap_pte_range in exceptional cases.
>>>> */
>>>> struct zap_details {
>>>> - struct address_space *check_mapping; /* Check page->mapping if set */
>>>> + struct address_space *zap_mapping; /* Check page->mapping if set */
>>>> struct page *single_page; /* Locked page to be unmapped */
>>>> };
>>>>
>>>> +/*
>>>> + * We set details->zap_mappings when we want to unmap shared but keep private
>>>> + * pages. Return true if skip zapping this page, false otherwise.
>>>> + */
>>>> +static inline bool
>>>> +zap_skip_check_mapping(struct zap_details *details, struct page *page)
>>>> +{
>>>> + if (!details || !page)
>>>> + return false;
>>>> +
>>>> + return details->zap_mapping != page_rmapping(page);
>>>
>>> Shouldn't this check still be
>>> details->zap_mapping && details->zap_mapping != page_rmapping(page)?
>>>
>>> Previously we wouldn't skip zapping pages if even_cows == true (ie.
>>> details->check_mapping == NULL). With this change the check when
>>> even_cows == true becomes NULL != page_rmapping(page). Doesn't this mean we
>>> will now skip zapping any pages with a mapping when even_cows == true?
>>
>> Yes I think so. Thanks for pointing that out, Alistair, I'll fix in v3.
>>
>> But frankly I really think we should simply have that flag I used to introduce.
>> It'll make everything much clearer.
>
> Yeah, I think a flag would also be fine.
I still don't see the need for a flag quite frankly. Just factor out the
checks we already have ... no change in behavior.
--
Thanks,
David / dhildenb