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Subject[PATCH v5 1/2] mm: make dev_pagemap_mapping_shift() externally visible
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KVM has a use case for determining the size of a dax mapping.

The KVM code has easy access to the address and the mm, and
dev_pagemap_mapping_shift() needs only those parameters. It was
deriving them from page and vma. This commit changes those parameters
from (page, vma) to (address, mm).

Signed-off-by: Barret Rhoden <brho@google.com>
Reviewed-by: David Hildenbrand <david@redhat.com>
Acked-by: Dan Williams <dan.j.williams@intel.com>
---
include/linux/mm.h | 3 +++
mm/memory-failure.c | 38 +++-----------------------------------
mm/util.c | 34 ++++++++++++++++++++++++++++++++++
3 files changed, 40 insertions(+), 35 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index a2adf95b3f9c..bfd1882dd5c6 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1013,6 +1013,9 @@ static inline bool is_pci_p2pdma_page(const struct page *page)
#define page_ref_zero_or_close_to_overflow(page) \
((unsigned int) page_ref_count(page) + 127u <= 127u)

+unsigned long dev_pagemap_mapping_shift(unsigned long address,
+ struct mm_struct *mm);
+
static inline void get_page(struct page *page)
{
page = compound_head(page);
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 3151c87dff73..bafa464c8290 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -261,40 +261,6 @@ void shake_page(struct page *p, int access)
}
EXPORT_SYMBOL_GPL(shake_page);

-static unsigned long dev_pagemap_mapping_shift(struct page *page,
- struct vm_area_struct *vma)
-{
- unsigned long address = vma_address(page, vma);
- pgd_t *pgd;
- p4d_t *p4d;
- pud_t *pud;
- pmd_t *pmd;
- pte_t *pte;
-
- pgd = pgd_offset(vma->vm_mm, address);
- if (!pgd_present(*pgd))
- return 0;
- p4d = p4d_offset(pgd, address);
- if (!p4d_present(*p4d))
- return 0;
- pud = pud_offset(p4d, address);
- if (!pud_present(*pud))
- return 0;
- if (pud_devmap(*pud))
- return PUD_SHIFT;
- pmd = pmd_offset(pud, address);
- if (!pmd_present(*pmd))
- return 0;
- if (pmd_devmap(*pmd))
- return PMD_SHIFT;
- pte = pte_offset_map(pmd, address);
- if (!pte_present(*pte))
- return 0;
- if (pte_devmap(*pte))
- return PAGE_SHIFT;
- return 0;
-}
-
/*
* Failure handling: if we can't find or can't kill a process there's
* not much we can do. We just print a message and ignore otherwise.
@@ -324,7 +290,9 @@ static void add_to_kill(struct task_struct *tsk, struct page *p,
}
tk->addr = page_address_in_vma(p, vma);
if (is_zone_device_page(p))
- tk->size_shift = dev_pagemap_mapping_shift(p, vma);
+ tk->size_shift =
+ dev_pagemap_mapping_shift(vma_address(page, vma),
+ vma->vm_mm);
else
tk->size_shift = compound_order(compound_head(p)) + PAGE_SHIFT;

diff --git a/mm/util.c b/mm/util.c
index 3ad6db9a722e..59984e6b40ab 100644
--- a/mm/util.c
+++ b/mm/util.c
@@ -901,3 +901,37 @@ int memcmp_pages(struct page *page1, struct page *page2)
kunmap_atomic(addr1);
return ret;
}
+
+unsigned long dev_pagemap_mapping_shift(unsigned long address,
+ struct mm_struct *mm)
+{
+ pgd_t *pgd;
+ p4d_t *p4d;
+ pud_t *pud;
+ pmd_t *pmd;
+ pte_t *pte;
+
+ pgd = pgd_offset(mm, address);
+ if (!pgd_present(*pgd))
+ return 0;
+ p4d = p4d_offset(pgd, address);
+ if (!p4d_present(*p4d))
+ return 0;
+ pud = pud_offset(p4d, address);
+ if (!pud_present(*pud))
+ return 0;
+ if (pud_devmap(*pud))
+ return PUD_SHIFT;
+ pmd = pmd_offset(pud, address);
+ if (!pmd_present(*pmd))
+ return 0;
+ if (pmd_devmap(*pmd))
+ return PMD_SHIFT;
+ pte = pte_offset_map(pmd, address);
+ if (!pte_present(*pte))
+ return 0;
+ if (pte_devmap(*pte))
+ return PAGE_SHIFT;
+ return 0;
+}
+EXPORT_SYMBOL_GPL(dev_pagemap_mapping_shift);
--
2.24.0.525.g8f36a354ae-goog
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