In preparation for supporting try_to_unmap_one() to unmap PMD-mapped
folios, start the pagewalk first, then call split_huge_pmd_address()
to split the folio.
Suggested-by: David Hildenbrand <[email protected]>
Signed-off-by: Lance Yang <[email protected]>
---
include/linux/huge_mm.h | 2 ++
mm/huge_memory.c | 42 +++++++++++++++++++++--------------------
mm/rmap.c | 26 +++++++++++++++++++------
3 files changed, 44 insertions(+), 26 deletions(-)
diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h
index c8d3ec116e29..2daadfcc6776 100644
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -36,6 +36,8 @@ bool move_huge_pmd(struct vm_area_struct *vma, unsigned long old_addr,
int change_huge_pmd(struct mmu_gather *tlb, struct vm_area_struct *vma,
pmd_t *pmd, unsigned long addr, pgprot_t newprot,
unsigned long cp_flags);
+void split_huge_pmd_locked(struct vm_area_struct *vma, unsigned long address,
+ pmd_t *pmd, bool freeze, struct folio *folio);
vm_fault_t vmf_insert_pfn_pmd(struct vm_fault *vmf, pfn_t pfn, bool write);
vm_fault_t vmf_insert_pfn_pud(struct vm_fault *vmf, pfn_t pfn, bool write);
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 8261b5669397..145505a1dd05 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -2584,6 +2584,27 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
pmd_populate(mm, pmd, pgtable);
}
+void split_huge_pmd_locked(struct vm_area_struct *vma, unsigned long address,
+ pmd_t *pmd, bool freeze, struct folio *folio)
+{
+ VM_WARN_ON_ONCE(folio && !folio_test_pmd_mappable(folio));
+ VM_WARN_ON_ONCE(!IS_ALIGNED(address, HPAGE_PMD_SIZE));
+ VM_WARN_ON_ONCE(folio && !folio_test_locked(folio));
+ VM_BUG_ON(freeze && !folio);
+
+ /*
+ * When the caller requests to set up a migration entry, we
+ * require a folio to check the PMD against. Otherwise, there
+ * is a risk of replacing the wrong folio.
+ */
+ if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd) ||
+ is_pmd_migration_entry(*pmd)) {
+ if (folio && folio != pmd_folio(*pmd))
+ return;
+ __split_huge_pmd_locked(vma, pmd, address, freeze);
+ }
+}
+
void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
unsigned long address, bool freeze, struct folio *folio)
{
@@ -2595,26 +2616,7 @@ void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
(address & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE);
mmu_notifier_invalidate_range_start(&range);
ptl = pmd_lock(vma->vm_mm, pmd);
-
- /*
- * If caller asks to setup a migration entry, we need a folio to check
- * pmd against. Otherwise we can end up replacing wrong folio.
- */
- VM_BUG_ON(freeze && !folio);
- VM_WARN_ON_ONCE(folio && !folio_test_locked(folio));
-
- if (pmd_trans_huge(*pmd) || pmd_devmap(*pmd) ||
- is_pmd_migration_entry(*pmd)) {
- /*
- * It's safe to call pmd_page when folio is set because it's
- * guaranteed that pmd is present.
- */
- if (folio && folio != pmd_folio(*pmd))
- goto out;
- __split_huge_pmd_locked(vma, pmd, range.start, freeze);
- }
-
-out:
+ split_huge_pmd_locked(vma, range.start, pmd, freeze, folio);
spin_unlock(ptl);
mmu_notifier_invalidate_range_end(&range);
}
diff --git a/mm/rmap.c b/mm/rmap.c
index 7e2575d669a9..e42f436c7ff3 100644
--- a/mm/rmap.c
+++ b/mm/rmap.c
@@ -1636,9 +1636,6 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
if (flags & TTU_SYNC)
pvmw.flags = PVMW_SYNC;
- if (flags & TTU_SPLIT_HUGE_PMD)
- split_huge_pmd_address(vma, address, false, folio);
-
/*
* For THP, we have to assume the worse case ie pmd for invalidation.
* For hugetlb, it could be much worse if we need to do pud
@@ -1650,6 +1647,10 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
range.end = vma_address_end(&pvmw);
mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma->vm_mm,
address, range.end);
+ if (flags & TTU_SPLIT_HUGE_PMD) {
+ range.start = address & HPAGE_PMD_MASK;
+ range.end = (address & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE;
+ }
if (folio_test_hugetlb(folio)) {
/*
* If sharing is possible, start and end will be adjusted
@@ -1664,9 +1665,6 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
mmu_notifier_invalidate_range_start(&range);
while (page_vma_mapped_walk(&pvmw)) {
- /* Unexpected PMD-mapped THP? */
- VM_BUG_ON_FOLIO(!pvmw.pte, folio);
-
/*
* If the folio is in an mlock()d vma, we must not swap it out.
*/
@@ -1678,6 +1676,22 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
goto walk_done_err;
}
+ if (!pvmw.pte && (flags & TTU_SPLIT_HUGE_PMD)) {
+ /*
+ * We temporarily have to drop the PTL and start once
+ * again from that now-PTE-mapped page table.
+ */
+ split_huge_pmd_locked(vma, range.start, pvmw.pmd, false,
+ folio);
+ pvmw.pmd = NULL;
+ spin_unlock(pvmw.ptl);
+ flags &= ~TTU_SPLIT_HUGE_PMD;
+ continue;
+ }
+
+ /* Unexpected PMD-mapped THP? */
+ VM_BUG_ON_FOLIO(!pvmw.pte, folio);
+
pfn = pte_pfn(ptep_get(pvmw.pte));
subpage = folio_page(folio, pfn - folio_pfn(folio));
address = pvmw.address;
--
2.33.1
Hi Lance,
On Mon, 29 Apr 2024 21:23:07 +0800 Lance Yang <[email protected]> wrote:
> In preparation for supporting try_to_unmap_one() to unmap PMD-mapped
> folios, start the pagewalk first, then call split_huge_pmd_address()
> to split the folio.
>
> Suggested-by: David Hildenbrand <[email protected]>
> Signed-off-by: Lance Yang <[email protected]>
> ---
> include/linux/huge_mm.h | 2 ++
> mm/huge_memory.c | 42 +++++++++++++++++++++--------------------
> mm/rmap.c | 26 +++++++++++++++++++------
> 3 files changed, 44 insertions(+), 26 deletions(-)
>
[...]
> diff --git a/mm/rmap.c b/mm/rmap.c
> index 7e2575d669a9..e42f436c7ff3 100644
> --- a/mm/rmap.c
> +++ b/mm/rmap.c
> @@ -1636,9 +1636,6 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
> if (flags & TTU_SYNC)
> pvmw.flags = PVMW_SYNC;
>
> - if (flags & TTU_SPLIT_HUGE_PMD)
> - split_huge_pmd_address(vma, address, false, folio);
> -
> /*
> * For THP, we have to assume the worse case ie pmd for invalidation.
> * For hugetlb, it could be much worse if we need to do pud
> @@ -1650,6 +1647,10 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
> range.end = vma_address_end(&pvmw);
> mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma->vm_mm,
> address, range.end);
> + if (flags & TTU_SPLIT_HUGE_PMD) {
> + range.start = address & HPAGE_PMD_MASK;
> + range.end = (address & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE;
> + }
I found the latest mm-unstable fails one[1] of my build configuration
with below error message. And 'git bisect' points this patch.
CC mm/rmap.o
In file included from <command-line>:
.../linux/mm/rmap.c: In function 'try_to_unmap_one':
.../linux/include/linux/compiler_types.h:460:38: error: call to '__compiletime_assert_455' declared with attribute error: BUILD_BUG failed
460 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
| ^
.../linux/include/linux/compiler_types.h:441:4: note: in definition of macro '__compiletime_assert'
441 | prefix ## suffix(); \
| ^~~~~~
.../linux/include/linux/compiler_types.h:460:2: note: in expansion of macro '_compiletime_assert'
460 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
| ^~~~~~~~~~~~~~~~~~~
.../linux/include/linux/build_bug.h:39:37: note: in expansion of macro 'compiletime_assert'
39 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
| ^~~~~~~~~~~~~~~~~~
.../linux/include/linux/build_bug.h:59:21: note: in expansion of macro 'BUILD_BUG_ON_MSG'
59 | #define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed")
| ^~~~~~~~~~~~~~~~
.../linux/include/linux/huge_mm.h:97:28: note: in expansion of macro 'BUILD_BUG'
97 | #define HPAGE_PMD_SHIFT ({ BUILD_BUG(); 0; })
| ^~~~~~~~~
.../linux/include/linux/huge_mm.h:104:34: note: in expansion of macro 'HPAGE_PMD_SHIFT'
104 | #define HPAGE_PMD_SIZE ((1UL) << HPAGE_PMD_SHIFT)
| ^~~~~~~~~~~~~~~
.../linux/include/linux/huge_mm.h:103:27: note: in expansion of macro 'HPAGE_PMD_SIZE'
103 | #define HPAGE_PMD_MASK (~(HPAGE_PMD_SIZE - 1))
| ^~~~~~~~~~~~~~
.../linux/mm/rmap.c:1651:27: note: in expansion of macro 'HPAGE_PMD_MASK'
1651 | range.start = address & HPAGE_PMD_MASK;
| ^~~~~~~~~~~~~~
I haven't looked into the code yet, but seems this code need to handle
CONFIG_PGTABLE_HAS_HUGE_LEAVES undefined case? May I ask your opinion?
[1] https://github.com/awslabs/damon-tests/blob/next/corr/tests/build_arm64.sh
Thanks,
SJ
[...]
Hey SJ,
Thanks a lot for reporting!
On Tue, Apr 30, 2024 at 4:20 AM SeongJae Park <[email protected]> wrote:
>
> Hi Lance,
>
> On Mon, 29 Apr 2024 21:23:07 +0800 Lance Yang <[email protected]> wrote:
>
> > In preparation for supporting try_to_unmap_one() to unmap PMD-mapped
> > folios, start the pagewalk first, then call split_huge_pmd_address()
> > to split the folio.
> >
> > Suggested-by: David Hildenbrand <[email protected]>
> > Signed-off-by: Lance Yang <[email protected]>
> > ---
> > include/linux/huge_mm.h | 2 ++
> > mm/huge_memory.c | 42 +++++++++++++++++++++--------------------
> > mm/rmap.c | 26 +++++++++++++++++++------
> > 3 files changed, 44 insertions(+), 26 deletions(-)
> >
> [...]
> > diff --git a/mm/rmap.c b/mm/rmap.c
> > index 7e2575d669a9..e42f436c7ff3 100644
> > --- a/mm/rmap.c
> > +++ b/mm/rmap.c
> > @@ -1636,9 +1636,6 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
> > if (flags & TTU_SYNC)
> > pvmw.flags = PVMW_SYNC;
> >
> > - if (flags & TTU_SPLIT_HUGE_PMD)
> > - split_huge_pmd_address(vma, address, false, folio);
> > -
> > /*
> > * For THP, we have to assume the worse case ie pmd for invalidation.
> > * For hugetlb, it could be much worse if we need to do pud
> > @@ -1650,6 +1647,10 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
> > range.end = vma_address_end(&pvmw);
> > mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma->vm_mm,
> > address, range.end);
> > + if (flags & TTU_SPLIT_HUGE_PMD) {
> > + range.start = address & HPAGE_PMD_MASK;
> > + range.end = (address & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE;
> > + }
>
> I found the latest mm-unstable fails one[1] of my build configuration
> with below error message. And 'git bisect' points this patch.
Thanks for taking time to 'git bisect' and identify this bug!
>
> CC mm/rmap.o
> In file included from <command-line>:
> .../linux/mm/rmap.c: In function 'try_to_unmap_one':
> .../linux/include/linux/compiler_types.h:460:38: error: call to '__compiletime_assert_455' declared with attribute error: BUILD_BUG failed
> 460 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
> | ^
> .../linux/include/linux/compiler_types.h:441:4: note: in definition of macro '__compiletime_assert'
> 441 | prefix ## suffix(); \
> | ^~~~~~
> .../linux/include/linux/compiler_types.h:460:2: note: in expansion of macro '_compiletime_assert'
> 460 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
> | ^~~~~~~~~~~~~~~~~~~
> .../linux/include/linux/build_bug.h:39:37: note: in expansion of macro 'compiletime_assert'
> 39 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
> | ^~~~~~~~~~~~~~~~~~
> .../linux/include/linux/build_bug.h:59:21: note: in expansion of macro 'BUILD_BUG_ON_MSG'
> 59 | #define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed")
> | ^~~~~~~~~~~~~~~~
> .../linux/include/linux/huge_mm.h:97:28: note: in expansion of macro 'BUILD_BUG'
> 97 | #define HPAGE_PMD_SHIFT ({ BUILD_BUG(); 0; })
> | ^~~~~~~~~
> .../linux/include/linux/huge_mm.h:104:34: note: in expansion of macro 'HPAGE_PMD_SHIFT'
> 104 | #define HPAGE_PMD_SIZE ((1UL) << HPAGE_PMD_SHIFT)
> | ^~~~~~~~~~~~~~~
> .../linux/include/linux/huge_mm.h:103:27: note: in expansion of macro 'HPAGE_PMD_SIZE'
> 103 | #define HPAGE_PMD_MASK (~(HPAGE_PMD_SIZE - 1))
> | ^~~~~~~~~~~~~~
> .../linux/mm/rmap.c:1651:27: note: in expansion of macro 'HPAGE_PMD_MASK'
> 1651 | range.start = address & HPAGE_PMD_MASK;
> | ^~~~~~~~~~~~~~
>
> I haven't looked into the code yet, but seems this code need to handle
> CONFIG_PGTABLE_HAS_HUGE_LEAVES undefined case? May I ask your opinion?
>
> [1] https://github.com/awslabs/damon-tests/blob/next/corr/tests/build_arm64.sh
I'll fix this bug and rebuild using the config you've provided above.
Thanks again for reporting!
Lance
>
>
> Thanks,
> SJ
> [...]
On Tue, Apr 30, 2024 at 10:03 AM Lance Yang <[email protected]> wrote:
>
> Hey SJ,
>
> Thanks a lot for reporting!
>
> On Tue, Apr 30, 2024 at 4:20 AM SeongJae Park <[email protected]> wrote:
> >
> > Hi Lance,
> >
> > On Mon, 29 Apr 2024 21:23:07 +0800 Lance Yang <[email protected]> wrote:
> >
> > > In preparation for supporting try_to_unmap_one() to unmap PMD-mapped
> > > folios, start the pagewalk first, then call split_huge_pmd_address()
> > > to split the folio.
> > >
> > > Suggested-by: David Hildenbrand <[email protected]>
> > > Signed-off-by: Lance Yang <[email protected]>
> > > ---
> > > include/linux/huge_mm.h | 2 ++
> > > mm/huge_memory.c | 42 +++++++++++++++++++++--------------------
> > > mm/rmap.c | 26 +++++++++++++++++++------
> > > 3 files changed, 44 insertions(+), 26 deletions(-)
> > >
> > [...]
> > > diff --git a/mm/rmap.c b/mm/rmap.c
> > > index 7e2575d669a9..e42f436c7ff3 100644
> > > --- a/mm/rmap.c
> > > +++ b/mm/rmap.c
> > > @@ -1636,9 +1636,6 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
> > > if (flags & TTU_SYNC)
> > > pvmw.flags = PVMW_SYNC;
> > >
> > > - if (flags & TTU_SPLIT_HUGE_PMD)
> > > - split_huge_pmd_address(vma, address, false, folio);
> > > -
> > > /*
> > > * For THP, we have to assume the worse case ie pmd for invalidation.
> > > * For hugetlb, it could be much worse if we need to do pud
> > > @@ -1650,6 +1647,10 @@ static bool try_to_unmap_one(struct folio *folio, struct vm_area_struct *vma,
> > > range.end = vma_address_end(&pvmw);
> > > mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, vma->vm_mm,
> > > address, range.end);
> > > + if (flags & TTU_SPLIT_HUGE_PMD) {
> > > + range.start = address & HPAGE_PMD_MASK;
> > > + range.end = (address & HPAGE_PMD_MASK) + HPAGE_PMD_SIZE;
> > > + }
> >
> > I found the latest mm-unstable fails one[1] of my build configuration
> > with below error message. And 'git bisect' points this patch.
>
> Thanks for taking time to 'git bisect' and identify this bug!
>
> >
> > CC mm/rmap.o
> > In file included from <command-line>:
> > .../linux/mm/rmap.c: In function 'try_to_unmap_one':
> > .../linux/include/linux/compiler_types.h:460:38: error: call to '__compiletime_assert_455' declared with attribute error: BUILD_BUG failed
> > 460 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
> > | ^
> > .../linux/include/linux/compiler_types.h:441:4: note: in definition of macro '__compiletime_assert'
> > 441 | prefix ## suffix(); \
> > | ^~~~~~
> > .../linux/include/linux/compiler_types.h:460:2: note: in expansion of macro '_compiletime_assert'
> > 460 | _compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
> > | ^~~~~~~~~~~~~~~~~~~
> > .../linux/include/linux/build_bug.h:39:37: note: in expansion of macro 'compiletime_assert'
> > 39 | #define BUILD_BUG_ON_MSG(cond, msg) compiletime_assert(!(cond), msg)
> > | ^~~~~~~~~~~~~~~~~~
> > .../linux/include/linux/build_bug.h:59:21: note: in expansion of macro 'BUILD_BUG_ON_MSG'
> > 59 | #define BUILD_BUG() BUILD_BUG_ON_MSG(1, "BUILD_BUG failed")
> > | ^~~~~~~~~~~~~~~~
> > .../linux/include/linux/huge_mm.h:97:28: note: in expansion of macro 'BUILD_BUG'
> > 97 | #define HPAGE_PMD_SHIFT ({ BUILD_BUG(); 0; })
> > | ^~~~~~~~~
> > .../linux/include/linux/huge_mm.h:104:34: note: in expansion of macro 'HPAGE_PMD_SHIFT'
> > 104 | #define HPAGE_PMD_SIZE ((1UL) << HPAGE_PMD_SHIFT)
> > | ^~~~~~~~~~~~~~~
> > .../linux/include/linux/huge_mm.h:103:27: note: in expansion of macro 'HPAGE_PMD_SIZE'
> > 103 | #define HPAGE_PMD_MASK (~(HPAGE_PMD_SIZE - 1))
> > | ^~~~~~~~~~~~~~
> > .../linux/mm/rmap.c:1651:27: note: in expansion of macro 'HPAGE_PMD_MASK'
> > 1651 | range.start = address & HPAGE_PMD_MASK;
> > | ^~~~~~~~~~~~~~
> >
> > I haven't looked into the code yet, but seems this code need to handle
> > CONFIG_PGTABLE_HAS_HUGE_LEAVES undefined case? May I ask your opinion?
> >
> > [1] https://github.com/awslabs/damon-tests/blob/next/corr/tests/build_arm64.sh
>
> I'll fix this bug and rebuild using the config you've provided above.
Hey Andrew,
Could you please temporarily drop this series from the mm tree?
I'll fix this bug in the next version.
Thanks,
Lance
>
> Thanks again for reporting!
> Lance
>
> >
> >
> > Thanks,
> > SJ
> > [...]