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authorDan Williams <dan.j.williams@intel.com>2016-01-15 16:56:52 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2016-01-15 17:56:32 -0800
commit5c7fb56e5e3f7035dd798a8e1adee639f87043e5 (patch)
treee3419de32c4b42c918267a50120549cbec2ed63f /mm/huge_memory.c
parent5c2c2587b13235bf8b5c9027589f22eff68bdf49 (diff)
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mm, dax: dax-pmd vs thp-pmd vs hugetlbfs-pmd
A dax-huge-page mapping while it uses some thp helpers is ultimately not a transparent huge page. The distinction is especially important in the get_user_pages() path. pmd_devmap() is used to distinguish dax-pmds from pmd_huge() and pmd_trans_huge() which have slightly different semantics. Explicitly mark the pmd_trans_huge() helpers that dax needs by adding pmd_devmap() checks. [kirill.shutemov@linux.intel.com: fix regression in handling mlocked pages in __split_huge_pmd()] Signed-off-by: Dan Williams <dan.j.williams@intel.com> Cc: Dave Hansen <dave@sr71.net> Cc: Mel Gorman <mgorman@suse.de> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Matthew Wilcox <willy@linux.intel.com> Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/huge_memory.c')
-rw-r--r--mm/huge_memory.c38
1 files changed, 21 insertions, 17 deletions
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index d93706013a55..82bed2bec3ed 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -995,7 +995,7 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
ret = -EAGAIN;
pmd = *src_pmd;
- if (unlikely(!pmd_trans_huge(pmd))) {
+ if (unlikely(!pmd_trans_huge(pmd) && !pmd_devmap(pmd))) {
pte_free(dst_mm, pgtable);
goto out_unlock;
}
@@ -1018,17 +1018,20 @@ int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
goto out_unlock;
}
- src_page = pmd_page(pmd);
- VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
- get_page(src_page);
- page_dup_rmap(src_page, true);
- add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
+ if (pmd_trans_huge(pmd)) {
+ /* thp accounting separate from pmd_devmap accounting */
+ src_page = pmd_page(pmd);
+ VM_BUG_ON_PAGE(!PageHead(src_page), src_page);
+ get_page(src_page);
+ page_dup_rmap(src_page, true);
+ add_mm_counter(dst_mm, MM_ANONPAGES, HPAGE_PMD_NR);
+ atomic_long_inc(&dst_mm->nr_ptes);
+ pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
+ }
pmdp_set_wrprotect(src_mm, addr, src_pmd);
pmd = pmd_mkold(pmd_wrprotect(pmd));
- pgtable_trans_huge_deposit(dst_mm, dst_pmd, pgtable);
set_pmd_at(dst_mm, addr, dst_pmd, pmd);
- atomic_long_inc(&dst_mm->nr_ptes);
ret = 0;
out_unlock:
@@ -1716,7 +1719,7 @@ bool __pmd_trans_huge_lock(pmd_t *pmd, struct vm_area_struct *vma,
spinlock_t **ptl)
{
*ptl = pmd_lock(vma->vm_mm, pmd);
- if (likely(pmd_trans_huge(*pmd)))
+ if (likely(pmd_trans_huge(*pmd) || pmd_devmap(*pmd)))
return true;
spin_unlock(*ptl);
return false;
@@ -2788,7 +2791,7 @@ static void __split_huge_pmd_locked(struct vm_area_struct *vma, pmd_t *pmd,
VM_BUG_ON(haddr & ~HPAGE_PMD_MASK);
VM_BUG_ON_VMA(vma->vm_start > haddr, vma);
VM_BUG_ON_VMA(vma->vm_end < haddr + HPAGE_PMD_SIZE, vma);
- VM_BUG_ON(!pmd_trans_huge(*pmd));
+ VM_BUG_ON(!pmd_trans_huge(*pmd) && !pmd_devmap(*pmd));
count_vm_event(THP_SPLIT_PMD);
@@ -2901,14 +2904,15 @@ void __split_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd,
mmu_notifier_invalidate_range_start(mm, haddr, haddr + HPAGE_PMD_SIZE);
ptl = pmd_lock(mm, pmd);
- if (unlikely(!pmd_trans_huge(*pmd)))
+ if (pmd_trans_huge(*pmd)) {
+ page = pmd_page(*pmd);
+ if (PageMlocked(page))
+ get_page(page);
+ else
+ page = NULL;
+ } else if (!pmd_devmap(*pmd))
goto out;
- page = pmd_page(*pmd);
__split_huge_pmd_locked(vma, pmd, haddr, false);
- if (PageMlocked(page))
- get_page(page);
- else
- page = NULL;
out:
spin_unlock(ptl);
mmu_notifier_invalidate_range_end(mm, haddr, haddr + HPAGE_PMD_SIZE);
@@ -2938,7 +2942,7 @@ static void split_huge_pmd_address(struct vm_area_struct *vma,
return;
pmd = pmd_offset(pud, address);
- if (!pmd_present(*pmd) || !pmd_trans_huge(*pmd))
+ if (!pmd_present(*pmd) || (!pmd_trans_huge(*pmd) && !pmd_devmap(*pmd)))
return;
/*
* Caller holds the mmap_sem write mode, so a huge pmd cannot