[PATCH 05/19] mm, mpol: Create special PROT_NONE infrastructure
From: Peter Zijlstra
Date: Tue Jul 31 2012 - 15:46:55 EST
In order to facilitate a lazy -- fault driven -- migration of pages,
create a special transient PROT_NONE variant, we can then use the
'spurious' protection faults to drive our migrations from.
Pages that already had an effective PROT_NONE mapping will not
be detected to generate these 'spuriuos' faults for the simple reason
that we cannot distinguish them on their protection bits, see
pte_prot_none.
This isn't a problem since PROT_NONE (and possible PROT_WRITE with
dirty tracking) aren't used or are rare enough for us to not care
about their placement.
Suggested-by: Rik van Riel <riel@xxxxxxxxxx>
Cc: Paul Turner <pjt@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
---
include/linux/huge_mm.h | 3 +
include/linux/mempolicy.h | 4 +-
include/linux/mm.h | 12 ++++++
mm/huge_memory.c | 21 +++++++++++
mm/memory.c | 86 ++++++++++++++++++++++++++++++++++++++++++----
mm/mempolicy.c | 24 ++++++++++++
mm/mprotect.c | 24 +++++++++---
7 files changed, 159 insertions(+), 15 deletions(-)
--- a/include/linux/huge_mm.h
+++ b/include/linux/huge_mm.h
@@ -11,6 +11,9 @@ extern int copy_huge_pmd(struct mm_struc
extern int do_huge_pmd_wp_page(struct mm_struct *mm, struct vm_area_struct *vma,
unsigned long address, pmd_t *pmd,
pmd_t orig_pmd);
+extern void do_huge_pmd_prot_none(struct mm_struct *mm, struct vm_area_struct *vma,
+ unsigned long address, pmd_t *pmd,
+ unsigned int flags, pmd_t orig_pmd);
extern pgtable_t get_pmd_huge_pte(struct mm_struct *mm);
extern struct page *follow_trans_huge_pmd(struct mm_struct *mm,
unsigned long addr,
--- a/include/linux/mempolicy.h
+++ b/include/linux/mempolicy.h
@@ -254,7 +254,9 @@ static inline int vma_migratable(struct
return 1;
}
-#else
+extern void lazy_migrate_process(struct mm_struct *mm);
+
+#else /* CONFIG_NUMA */
struct mempolicy {};
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -1046,6 +1046,9 @@ extern unsigned long move_page_tables(st
extern unsigned long do_mremap(unsigned long addr,
unsigned long old_len, unsigned long new_len,
unsigned long flags, unsigned long new_addr);
+extern void change_protection(struct vm_area_struct *vma, unsigned long start,
+ unsigned long end, pgprot_t newprot,
+ int dirty_accountable);
extern int mprotect_fixup(struct vm_area_struct *vma,
struct vm_area_struct **pprev, unsigned long start,
unsigned long end, unsigned long newflags);
@@ -1495,6 +1498,15 @@ static inline pgprot_t vm_get_page_prot(
}
#endif
+static inline pgprot_t vma_prot_none(struct vm_area_struct *vma)
+{
+ /*
+ * obtain PROT_NONE by removing READ|WRITE|EXEC privs
+ */
+ vm_flags_t vmflags = vma->vm_flags & ~(VM_READ|VM_WRITE|VM_EXEC);
+ return pgprot_modify(vma->vm_page_prot, vm_get_page_prot(vmflags));
+}
+
struct vm_area_struct *find_extend_vma(struct mm_struct *, unsigned long addr);
int remap_pfn_range(struct vm_area_struct *, unsigned long addr,
unsigned long pfn, unsigned long size, pgprot_t);
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -750,6 +750,27 @@ int do_huge_pmd_anonymous_page(struct mm
return handle_pte_fault(mm, vma, address, pte, pmd, flags);
}
+void do_huge_pmd_prot_none(struct mm_struct *mm, struct vm_area_struct *vma,
+ unsigned long address, pmd_t *pmd,
+ unsigned int flags, pmd_t entry)
+{
+ unsigned long haddr = address & HPAGE_PMD_MASK;
+
+ spin_lock(&mm->page_table_lock);
+ if (unlikely(!pmd_same(*pmd, entry)))
+ goto out_unlock;
+
+ /* do fancy stuff */
+
+ /* change back to regular protection */
+ entry = pmd_modify(entry, vma->vm_page_prot);
+ if (pmdp_set_access_flags(vma, haddr, pmd, entry, 1))
+ update_mmu_cache(vma, address, entry);
+
+out_unlock:
+ spin_unlock(&mm->page_table_lock);
+}
+
int copy_huge_pmd(struct mm_struct *dst_mm, struct mm_struct *src_mm,
pmd_t *dst_pmd, pmd_t *src_pmd, unsigned long addr,
struct vm_area_struct *vma)
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -3415,6 +3415,71 @@ static int do_nonlinear_fault(struct mm_
return __do_fault(mm, vma, address, pmd, pgoff, flags, orig_pte);
}
+static bool pte_prot_none(struct vm_area_struct *vma, pte_t pte)
+{
+ /*
+ * If we have the normal vma->vm_page_prot protections we're not a
+ * 'special' PROT_NONE page.
+ *
+ * This means we cannot get 'special' PROT_NONE faults from genuine
+ * PROT_NONE maps, nor from PROT_WRITE file maps that do dirty
+ * tracking.
+ *
+ * Neither case is really interesting for our current use though so we
+ * don't care.
+ */
+ if (pte_same(pte, pte_modify(pte, vma->vm_page_prot)))
+ return false;
+
+ return pte_same(pte, pte_modify(pte, vma_prot_none(vma)));
+}
+
+static bool pmd_prot_none(struct vm_area_struct *vma, pmd_t pmd)
+{
+ /*
+ * See pte_prot_none().
+ */
+ if (pmd_same(pmd, pmd_modify(pmd, vma->vm_page_prot)))
+ return false;
+
+ return pmd_same(pmd, pmd_modify(pmd, vma_prot_none(vma)));
+}
+
+static int do_prot_none(struct mm_struct *mm, struct vm_area_struct *vma,
+ unsigned long address, pte_t *ptep, pmd_t *pmd,
+ unsigned int flags, pte_t entry)
+{
+ spinlock_t *ptl;
+ int ret = 0;
+
+ if (!pte_unmap_same(mm, pmd, ptep, entry))
+ goto out;
+
+ /*
+ * Do fancy stuff...
+ */
+
+ /*
+ * OK, nothing to do,.. change the protection back to what it
+ * ought to be.
+ */
+ ptep = pte_offset_map_lock(mm, pmd, address, &ptl);
+ if (unlikely(!pte_same(*ptep, entry)))
+ goto unlock;
+
+ flush_cache_page(vma, address, pte_pfn(entry));
+
+ ptep_modify_prot_start(mm, address, ptep);
+ entry = pte_modify(entry, vma->vm_page_prot);
+ ptep_modify_prot_commit(mm, address, ptep, entry);
+
+ update_mmu_cache(vma, address, ptep);
+unlock:
+ pte_unmap_unlock(ptep, ptl);
+out:
+ return ret;
+}
+
/*
* These routines also need to handle stuff like marking pages dirty
* and/or accessed for architectures that don't do it in hardware (most
@@ -3453,6 +3518,9 @@ int handle_pte_fault(struct mm_struct *m
pte, pmd, flags, entry);
}
+ if (pte_prot_none(vma, entry))
+ return do_prot_none(mm, vma, address, pte, pmd, flags, entry);
+
ptl = pte_lockptr(mm, pmd);
spin_lock(ptl);
if (unlikely(!pte_same(*pte, entry)))
@@ -3517,13 +3585,16 @@ int handle_mm_fault(struct mm_struct *mm
pmd, flags);
} else {
pmd_t orig_pmd = *pmd;
- int ret;
+ int ret = 0;
barrier();
- if (pmd_trans_huge(orig_pmd)) {
- if (flags & FAULT_FLAG_WRITE &&
- !pmd_write(orig_pmd) &&
- !pmd_trans_splitting(orig_pmd)) {
+ if (pmd_trans_huge(orig_pmd) && !pmd_trans_splitting(orig_pmd)) {
+ if (pmd_prot_none(vma, orig_pmd)) {
+ do_huge_pmd_prot_none(mm, vma, address, pmd,
+ flags, orig_pmd);
+ }
+
+ if ((flags & FAULT_FLAG_WRITE) && !pmd_write(orig_pmd)) {
ret = do_huge_pmd_wp_page(mm, vma, address, pmd,
orig_pmd);
/*
@@ -3533,12 +3604,13 @@ int handle_mm_fault(struct mm_struct *mm
*/
if (unlikely(ret & VM_FAULT_OOM))
goto retry;
- return ret;
}
- return 0;
+
+ return ret;
}
}
+
/*
* Use __pte_alloc instead of pte_alloc_map, because we can't
* run pte_offset_map on the pmd, if an huge pmd could
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -565,6 +565,12 @@ static inline int check_pgd_range(struct
return 0;
}
+static void
+change_prot_none(struct vm_area_struct *vma, unsigned long start, unsigned long end)
+{
+ change_protection(vma, start, end, vma_prot_none(vma), 0);
+}
+
/*
* Check if all pages in a range are on a set of nodes.
* If pagelist != NULL then isolate pages from the LRU and
@@ -1197,6 +1203,24 @@ static long do_mbind(unsigned long start
return err;
}
+static void lazy_migrate_vma(struct vm_area_struct *vma)
+{
+ if (!vma_migratable(vma))
+ return;
+
+ change_prot_none(vma, vma->vm_start, vma->vm_end);
+}
+
+void lazy_migrate_process(struct mm_struct *mm)
+{
+ struct vm_area_struct *vma;
+
+ down_read(&mm->mmap_sem);
+ for (vma = mm->mmap; vma; vma = vma->vm_next)
+ lazy_migrate_vma(vma);
+ up_read(&mm->mmap_sem);
+}
+
/*
* User space interface with variable sized bitmaps for nodelists.
*/
--- a/mm/mprotect.c
+++ b/mm/mprotect.c
@@ -119,7 +119,7 @@ static inline void change_pud_range(stru
} while (pud++, addr = next, addr != end);
}
-static void change_protection(struct vm_area_struct *vma,
+static void change_protection_range(struct vm_area_struct *vma,
unsigned long addr, unsigned long end, pgprot_t newprot,
int dirty_accountable)
{
@@ -141,6 +141,20 @@ static void change_protection(struct vm_
flush_tlb_range(vma, start, end);
}
+void change_protection(struct vm_area_struct *vma, unsigned long start,
+ unsigned long end, pgprot_t newprot,
+ int dirty_accountable)
+{
+ struct mm_struct *mm = vma->vm_mm;
+
+ mmu_notifier_invalidate_range_start(mm, start, end);
+ if (is_vm_hugetlb_page(vma))
+ hugetlb_change_protection(vma, start, end, newprot);
+ else
+ change_protection_range(vma, start, end, newprot, dirty_accountable);
+ mmu_notifier_invalidate_range_end(mm, start, end);
+}
+
int
mprotect_fixup(struct vm_area_struct *vma, struct vm_area_struct **pprev,
unsigned long start, unsigned long end, unsigned long newflags)
@@ -213,12 +227,8 @@ mprotect_fixup(struct vm_area_struct *vm
dirty_accountable = 1;
}
- mmu_notifier_invalidate_range_start(mm, start, end);
- if (is_vm_hugetlb_page(vma))
- hugetlb_change_protection(vma, start, end, vma->vm_page_prot);
- else
- change_protection(vma, start, end, vma->vm_page_prot, dirty_accountable);
- mmu_notifier_invalidate_range_end(mm, start, end);
+ change_protection(vma, start, end, vma->vm_page_prot, dirty_accountable);
+
vm_stat_account(mm, oldflags, vma->vm_file, -nrpages);
vm_stat_account(mm, newflags, vma->vm_file, nrpages);
perf_event_mmap(vma);
--
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