With the recent update on page table walker, we can use common code for
the walking more. Unlike many other users, this swapin_walk expects to
handle swap entries. As a result we should be careful about ptl locking.
Swapin operation, read_swap_cache_async(), could cause page reclaim, so
we can't keep holding ptl throughout this pte loop.
In order to properly handle ptl in pte_entry(), this patch adds two new
members on struct mm_walk.
This cleanup is necessary to get to the final form of page table walker,
where we should do all caller's specific work on leaf entries (IOW, all
pmd_entry() should be used for trans_pmd.)
Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
---
include/linux/mm.h | 4 ++++
mm/madvise.c | 54 +++++++++++++++++++++++-------------------------------
mm/pagewalk.c | 11 +++++------
3 files changed, 32 insertions(+), 37 deletions(-)
diff --git mmotm-2014-05-21-16-57.orig/include/linux/mm.h mmotm-2014-05-21-16-57/include/linux/mm.h
index b4aa6579f2b1..aa832161a1ff 100644
--- mmotm-2014-05-21-16-57.orig/include/linux/mm.h
+++ mmotm-2014-05-21-16-57/include/linux/mm.h
@@ -1108,6 +1108,8 @@ void unmap_vmas(struct mmu_gather *tlb, struct vm_area_struct *start_vma,
* @vma: vma currently walked
* @skip: internal control flag which is set when we skip the lower
* level entries.
+ * @pmd: current pmd entry
+ * @ptl: page table lock associated with current entry
* @private: private data for callbacks' use
*
* (see the comment on walk_page_range() for more details)
@@ -1126,6 +1128,8 @@ struct mm_walk {
struct mm_struct *mm;
struct vm_area_struct *vma;
int skip;
+ pmd_t *pmd;
+ spinlock_t *ptl;
void *private;
};
diff --git mmotm-2014-05-21-16-57.orig/mm/madvise.c mmotm-2014-05-21-16-57/mm/madvise.c
index a402f8fdc68e..06b390a6fbbd 100644
--- mmotm-2014-05-21-16-57.orig/mm/madvise.c
+++ mmotm-2014-05-21-16-57/mm/madvise.c
@@ -135,38 +135,31 @@ static long madvise_behavior(struct vm_area_struct *vma,
}
#ifdef CONFIG_SWAP
-static int swapin_walk_pmd_entry(pmd_t *pmd, unsigned long start,
+/*
+ * Assuming that page table walker holds page table lock.
+ */
+static int swapin_walk_pte_entry(pte_t *pte, unsigned long start,
unsigned long end, struct mm_walk *walk)
{
- pte_t *orig_pte;
- struct vm_area_struct *vma = walk->private;
- unsigned long index;
-
- if (pmd_none_or_trans_huge_or_clear_bad(pmd))
- return 0;
-
- for (index = start; index != end; index += PAGE_SIZE) {
- pte_t pte;
- swp_entry_t entry;
- struct page *page;
- spinlock_t *ptl;
-
- orig_pte = pte_offset_map_lock(vma->vm_mm, pmd, start, &ptl);
- pte = *(orig_pte + ((index - start) / PAGE_SIZE));
- pte_unmap_unlock(orig_pte, ptl);
-
- if (pte_present(pte) || pte_none(pte) || pte_file(pte))
- continue;
- entry = pte_to_swp_entry(pte);
- if (unlikely(non_swap_entry(entry)))
- continue;
-
- page = read_swap_cache_async(entry, GFP_HIGHUSER_MOVABLE,
- vma, index);
- if (page)
- page_cache_release(page);
- }
+ pte_t ptent;
+ pte_t *orig_pte = pte - ((start & (PMD_SIZE - 1)) >> PAGE_SHIFT);
+ swp_entry_t entry;
+ struct page *page;
+ ptent = *pte;
+ pte_unmap_unlock(orig_pte, walk->ptl);
+ if (pte_present(ptent) || pte_none(ptent) || pte_file(ptent))
+ goto lock;
+ entry = pte_to_swp_entry(ptent);
+ if (unlikely(non_swap_entry(entry)))
+ goto lock;
+ page = read_swap_cache_async(entry, GFP_HIGHUSER_MOVABLE,
+ walk->vma, start);
+ if (page)
+ page_cache_release(page);
+lock:
+ pte_offset_map(walk->pmd, start & PMD_MASK);
+ spin_lock(walk->ptl);
return 0;
}
@@ -175,8 +168,7 @@ static void force_swapin_readahead(struct vm_area_struct *vma,
{
struct mm_walk walk = {
.mm = vma->vm_mm,
- .pmd_entry = swapin_walk_pmd_entry,
- .private = vma,
+ .pte_entry = swapin_walk_pte_entry,
};
walk_page_range(start, end, &walk);
diff --git mmotm-2014-05-21-16-57.orig/mm/pagewalk.c mmotm-2014-05-21-16-57/mm/pagewalk.c
index e734f63276c2..24311d6f5c20 100644
--- mmotm-2014-05-21-16-57.orig/mm/pagewalk.c
+++ mmotm-2014-05-21-16-57/mm/pagewalk.c
@@ -27,10 +27,10 @@ static int walk_pte_range(pmd_t *pmd, unsigned long addr,
struct mm_struct *mm = walk->mm;
pte_t *pte;
pte_t *orig_pte;
- spinlock_t *ptl;
int err = 0;
- orig_pte = pte = pte_offset_map_lock(mm, pmd, addr, &ptl);
+ walk->pmd = pmd;
+ orig_pte = pte = pte_offset_map_lock(mm, pmd, addr, &walk->ptl);
do {
if (pte_none(*pte)) {
if (walk->pte_hole)
@@ -48,7 +48,7 @@ static int walk_pte_range(pmd_t *pmd, unsigned long addr,
if (err)
break;
} while (pte++, addr += PAGE_SIZE, addr < end);
- pte_unmap_unlock(orig_pte, ptl);
+ pte_unmap_unlock(orig_pte, walk->ptl);
cond_resched();
return addr == end ? 0 : err;
}
@@ -172,7 +172,6 @@ static int walk_hugetlb_range(unsigned long addr, unsigned long end,
unsigned long hmask = huge_page_mask(h);
pte_t *pte;
int err = 0;
- spinlock_t *ptl;
do {
next = hugetlb_entry_end(h, addr, end);
@@ -186,14 +185,14 @@ static int walk_hugetlb_range(unsigned long addr, unsigned long end,
break;
continue;
}
- ptl = huge_pte_lock(h, mm, pte);
+ walk->ptl = huge_pte_lock(h, mm, pte);
/*
* Callers should have their own way to handle swap entries
* in walk->hugetlb_entry().
*/
if (walk->hugetlb_entry)
err = walk->hugetlb_entry(pte, addr, next, walk);
- spin_unlock(ptl);
+ spin_unlock(walk->ptl);
if (err)
break;
} while (addr = next, addr != end);
--
1.9.3
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