From: Minchan Kim <minchan@xxxxxxxxxx>
By vrange(2) semantic, user should see SIGBUG if he try to access
purged page without vrange(...VRANGE_NOVOLATILE).
This patch implements it.
XXX: I reused PSE bit for quick prototype without enough considering
so need time to see what's empty bit and I am surely missing
many places to handle vrange pte bit. I should investigate all of
pte handling places, especially pte_none case.
Cc: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: Android Kernel Team <kernel-team@xxxxxxxxxxx>
Cc: Robert Love <rlove@xxxxxxxxxx>
Cc: Mel Gorman <mel@xxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Dave Hansen <dave@xxxxxxxxxxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Dmitry Adamushko <dmitry.adamushko@xxxxxxxxx>
Cc: Dave Chinner <david@xxxxxxxxxxxxx>
Cc: Neil Brown <neilb@xxxxxxx>
Cc: Andrea Righi <andrea@xxxxxxxxxxxxxxx>
Cc: Andrea Arcangeli <aarcange@xxxxxxxxxx>
Cc: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxxxxxxx>
Cc: Mike Hommey <mh@xxxxxxxxxxxx>
Cc: Taras Glek <tglek@xxxxxxxxxxx>
Cc: Dhaval Giani <dgiani@xxxxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxx>
Cc: Michel Lespinasse <walken@xxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: linux-mm@xxxxxxxxx <linux-mm@xxxxxxxxx>
Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
[jstultz: Extended to work with file pages]
Signed-off-by: John Stultz <john.stultz@xxxxxxxxxx>
---
arch/x86/include/asm/pgtable_types.h | 2 ++
include/asm-generic/pgtable.h | 11 +++++++++++
include/linux/vrange.h | 2 ++
mm/memory.c | 23 +++++++++++++++++++++--
mm/vrange.c | 35 ++++++++++++++++++++++++++++++++++-
5 files changed, 70 insertions(+), 3 deletions(-)
diff --git a/arch/x86/include/asm/pgtable_types.h b/arch/x86/include/asm/pgtable_types.h
index e642300..d7ea6a0 100644
--- a/arch/x86/include/asm/pgtable_types.h
+++ b/arch/x86/include/asm/pgtable_types.h
@@ -64,6 +64,8 @@
#define _PAGE_FILE (_AT(pteval_t, 1) << _PAGE_BIT_FILE)
#define _PAGE_PROTNONE (_AT(pteval_t, 1) << _PAGE_BIT_PROTNONE)
+#define _PAGE_VRANGE _PAGE_BIT_PSE
+
/*
* _PAGE_NUMA indicates that this page will trigger a numa hinting
* minor page fault to gather numa placement statistics (see
diff --git a/include/asm-generic/pgtable.h b/include/asm-generic/pgtable.h
index a59ff51..91e8f6f 100644
--- a/include/asm-generic/pgtable.h
+++ b/include/asm-generic/pgtable.h
@@ -479,6 +479,17 @@ static inline unsigned long my_zero_pfn(unsigned long addr)
#ifdef CONFIG_MMU
+static inline pte_t pte_mkvrange(pte_t pte)
+{
+ pte = pte_set_flags(pte, _PAGE_VRANGE);
+ return pte_clear_flags(pte, _PAGE_PRESENT);
+}
+
+static inline int pte_vrange(pte_t pte)
+{
+ return ((pte_flags(pte) | _PAGE_PRESENT) == _PAGE_VRANGE);
+}
+
#ifndef CONFIG_TRANSPARENT_HUGEPAGE
static inline int pmd_trans_huge(pmd_t pmd)
{
diff --git a/include/linux/vrange.h b/include/linux/vrange.h
index cbb609a..75754d1 100644
--- a/include/linux/vrange.h
+++ b/include/linux/vrange.h
@@ -41,6 +41,8 @@ int discard_vpage(struct page *page);
bool vrange_address(struct mm_struct *mm, unsigned long start,
unsigned long end);
+extern bool is_purged_vrange(struct mm_struct *mm, unsigned long address);
+
#else
static inline void vrange_init(void) {};
diff --git a/mm/memory.c b/mm/memory.c
index 61a262b..cc5c70b 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -59,6 +59,7 @@
#include <linux/gfp.h>
#include <linux/migrate.h>
#include <linux/string.h>
+#include <linux/vrange.h>
#include <asm/io.h>
#include <asm/pgalloc.h>
@@ -832,7 +833,7 @@ copy_one_pte(struct mm_struct *dst_mm, struct mm_struct *src_mm,
/* pte contains position in swap or file, so copy. */
if (unlikely(!pte_present(pte))) {
- if (!pte_file(pte)) {
+ if (!pte_file(pte) && !pte_vrange(pte)) {
swp_entry_t entry = pte_to_swp_entry(pte);
if (swap_duplicate(entry) < 0)
@@ -1172,7 +1173,7 @@ again:
if (pte_file(ptent)) {
if (unlikely(!(vma->vm_flags & VM_NONLINEAR)))
print_bad_pte(vma, addr, ptent, NULL);
- } else {
+ } else if (!pte_vrange(ptent)) {
swp_entry_t entry = pte_to_swp_entry(ptent);
if (!non_swap_entry(entry))
@@ -3707,9 +3708,27 @@ int handle_pte_fault(struct mm_struct *mm,
return do_linear_fault(mm, vma, address,
pte, pmd, flags, entry);
}
+anon:
return do_anonymous_page(mm, vma, address,
pte, pmd, flags);
}
+
+ if (unlikely(pte_vrange(entry))) {
+ if (!is_purged_vrange(mm, address)) {
+ /* zap pte */
+ ptl = pte_lockptr(mm, pmd);
+ spin_lock(ptl);
+ if (unlikely(!pte_same(*pte, entry)))
+ goto unlock;
+ flush_cache_page(vma, address, pte_pfn(*pte));
+ ptep_clear_flush(vma, address, pte);
+ pte_unmap_unlock(pte, ptl);
+ goto anon;
+ }
+
+ return VM_FAULT_SIGBUS;
+ }
+
if (pte_file(entry))
return do_nonlinear_fault(mm, vma, address,
pte, pmd, flags, entry);
diff --git a/mm/vrange.c b/mm/vrange.c
index 1c8c447..fa965fb 100644
--- a/mm/vrange.c
+++ b/mm/vrange.c
@@ -504,7 +504,9 @@ int try_to_discard_one(struct vrange_root *vroot, struct page *page,
present = pte_present(*pte);
flush_cache_page(vma, address, page_to_pfn(page));
- pteval = ptep_clear_flush(vma, address, pte);
+
+ ptep_clear_flush(vma, address, pte);
+ pteval = pte_mkvrange(*pte);
update_hiwater_rss(mm);
if (PageAnon(page))
@@ -521,6 +523,7 @@ int try_to_discard_one(struct vrange_root *vroot, struct page *page,
BUG_ON(1);
}
+ set_pte_at(mm, address, pte, pteval);
pte_unmap_unlock(pte, ptl);
mmu_notifier_invalidate_page(mm, address);
ret = 1;
@@ -696,3 +699,33 @@ int discard_vpage(struct page *page)
return 0;
}
+bool is_purged_vrange(struct mm_struct *mm, unsigned long address)
+{
+ struct vrange_root *vroot;
+ struct interval_tree_node *node;
+ struct vrange *range;
+ unsigned long vstart_idx;
+ struct vm_area_struct *vma;
+ bool ret = false;
+
+ vma = find_vma(mm, address);
+ if (vma->vm_file && (vma->vm_flags & VM_SHARED)) {
+ vroot = &vma->vm_file->f_mapping->vroot;
+ vstart_idx = vma->vm_pgoff + address - vma->vm_start;
+ } else {
+ vroot = &mm->vroot;
+ vstart_idx = address;
+ }
+
+ vrange_lock(vroot);
+ node = interval_tree_iter_first(&vroot->v_rb, vstart_idx,
+ vstart_idx + PAGE_SIZE - 1);
+ if (node) {
+ range = container_of(node, struct vrange, node);
+ if (range->purged)
+ ret = true;
+ }
+ vrange_unlock(vroot);
+ return ret;
+}
+
--
1.8.1.2
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