[PATCH 2/7] mm/pagewalk: replace mm_walk->skip with more general mm_walk->control
From: Naoya Horiguchi
Date: Fri Jun 06 2014 - 19:00:11 EST
Originally mm_walk->skip is used to determine whether we walk over a vma
or not. But this is not enough because one of the page table walker's caller
subpage_mark_vma_nohuge(), will need another behavior PTWALK_BREAK, which
let us break current loop and continue from the beginning of the next loop.
To implement this behavior and make it extensible for future users, this patch
replaces mm_walk->skip with more flexible mm_walk->control, and changes its
default value to PTWALK_NEXT (which is equivalent to present walk->skip == 1.)
This is because PTWALK_NEXT provides the behavior which is most likely to be
used globally.
Signed-off-by: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx>
---
fs/proc/task_mmu.c | 20 +++++++-------
include/linux/mm.h | 13 ++++++---
mm/memcontrol.c | 5 ++--
mm/mempolicy.c | 3 +--
mm/pagewalk.c | 79 +++++++++++++++++++++++++++++++++---------------------
5 files changed, 71 insertions(+), 49 deletions(-)
diff --git v3.15-rc8-mmots-2014-06-03-16-28.orig/fs/proc/task_mmu.c v3.15-rc8-mmots-2014-06-03-16-28/fs/proc/task_mmu.c
index fa6d6a4e85b3..2864028ae2f8 100644
--- v3.15-rc8-mmots-2014-06-03-16-28.orig/fs/proc/task_mmu.c
+++ v3.15-rc8-mmots-2014-06-03-16-28/fs/proc/task_mmu.c
@@ -502,9 +502,8 @@ static int smaps_pmd(pmd_t *pmd, unsigned long addr, unsigned long end,
smaps_pte((pte_t *)pmd, addr, addr + HPAGE_PMD_SIZE, walk);
spin_unlock(ptl);
mss->anonymous_thp += HPAGE_PMD_SIZE;
- /* don't call smaps_pte() */
- walk->skip = 1;
- }
+ } else
+ walk->control = PTWALK_DOWN;
return 0;
}
@@ -762,13 +761,14 @@ static int clear_refs_test_walk(unsigned long start, unsigned long end,
* Writing 4 to /proc/pid/clear_refs affects all pages.
*/
if (cp->type == CLEAR_REFS_ANON && vma->vm_file)
- walk->skip = 1;
+ return 0;
if (cp->type == CLEAR_REFS_MAPPED && !vma->vm_file)
- walk->skip = 1;
+ return 0;
if (cp->type == CLEAR_REFS_SOFT_DIRTY) {
if (vma->vm_flags & VM_SOFTDIRTY)
vma->vm_flags &= ~VM_SOFTDIRTY;
}
+ walk->control = PTWALK_DOWN;
return 0;
}
@@ -1006,9 +1006,8 @@ static int pagemap_pmd(pmd_t *pmd, unsigned long addr, unsigned long end,
break;
}
spin_unlock(ptl);
- /* don't call pagemap_pte() */
- walk->skip = 1;
- }
+ } else
+ walk->control = PTWALK_DOWN;
return err;
}
@@ -1288,9 +1287,8 @@ static int gather_pmd_stats(pmd_t *pmd, unsigned long addr,
gather_stats(page, md, pte_dirty(huge_pte),
HPAGE_PMD_SIZE/PAGE_SIZE);
spin_unlock(ptl);
- /* don't call gather_pte_stats() */
- walk->skip = 1;
- }
+ } else
+ walk->control = PTWALK_DOWN;
return 0;
}
#ifdef CONFIG_HUGETLB_PAGE
diff --git v3.15-rc8-mmots-2014-06-03-16-28.orig/include/linux/mm.h v3.15-rc8-mmots-2014-06-03-16-28/include/linux/mm.h
index b4aa6579f2b1..43449eba3032 100644
--- v3.15-rc8-mmots-2014-06-03-16-28.orig/include/linux/mm.h
+++ v3.15-rc8-mmots-2014-06-03-16-28/include/linux/mm.h
@@ -1106,8 +1106,7 @@ void unmap_vmas(struct mmu_gather *tlb, struct vm_area_struct *start_vma,
* right now." 0 means "skip the current vma."
* @mm: mm_struct representing the target process of page table walk
* @vma: vma currently walked
- * @skip: internal control flag which is set when we skip the lower
- * level entries.
+ * @control: walk control flag
* @private: private data for callbacks' use
*
* (see the comment on walk_page_range() for more details)
@@ -1125,10 +1124,18 @@ struct mm_walk {
struct mm_walk *walk);
struct mm_struct *mm;
struct vm_area_struct *vma;
- int skip;
+ int control;
void *private;
};
+enum mm_walk_control {
+ PTWALK_NEXT = 0, /* Go to the next entry in the same level or
+ * the next vma. This is default behavior. */
+ PTWALK_DOWN, /* Go down to lower level */
+ PTWALK_BREAK, /* Break current loop and continue from the
+ * next loop */
+};
+
int walk_page_range(unsigned long addr, unsigned long end,
struct mm_walk *walk);
int walk_page_vma(struct vm_area_struct *vma, struct mm_walk *walk);
diff --git v3.15-rc8-mmots-2014-06-03-16-28.orig/mm/memcontrol.c v3.15-rc8-mmots-2014-06-03-16-28/mm/memcontrol.c
index 6970857ba0c8..aeab82bce739 100644
--- v3.15-rc8-mmots-2014-06-03-16-28.orig/mm/memcontrol.c
+++ v3.15-rc8-mmots-2014-06-03-16-28/mm/memcontrol.c
@@ -6729,9 +6729,8 @@ static int mem_cgroup_count_precharge_pmd(pmd_t *pmd,
if (get_mctgt_type_thp(vma, addr, *pmd, NULL) == MC_TARGET_PAGE)
mc.precharge += HPAGE_PMD_NR;
spin_unlock(ptl);
- /* don't call mem_cgroup_count_precharge_pte() */
- walk->skip = 1;
- }
+ } else
+ skip->control = PTWALK_DOWN;
return 0;
}
diff --git v3.15-rc8-mmots-2014-06-03-16-28.orig/mm/mempolicy.c v3.15-rc8-mmots-2014-06-03-16-28/mm/mempolicy.c
index cf3b995b21d0..cc9dc8c06bcb 100644
--- v3.15-rc8-mmots-2014-06-03-16-28.orig/mm/mempolicy.c
+++ v3.15-rc8-mmots-2014-06-03-16-28/mm/mempolicy.c
@@ -596,7 +596,6 @@ static int queue_pages_test_walk(unsigned long start, unsigned long end,
}
qp->prev = vma;
- walk->skip = 1;
if (vma->vm_flags & VM_PFNMAP)
return 0;
@@ -610,7 +609,7 @@ static int queue_pages_test_walk(unsigned long start, unsigned long end,
((flags & (MPOL_MF_MOVE | MPOL_MF_MOVE_ALL)) &&
vma_migratable(vma)))
/* queue pages from current vma */
- walk->skip = 0;
+ walk->control = PTWALK_DOWN;
return 0;
}
diff --git v3.15-rc8-mmots-2014-06-03-16-28.orig/mm/pagewalk.c v3.15-rc8-mmots-2014-06-03-16-28/mm/pagewalk.c
index 15c7585e8684..385efd59178f 100644
--- v3.15-rc8-mmots-2014-06-03-16-28.orig/mm/pagewalk.c
+++ v3.15-rc8-mmots-2014-06-03-16-28/mm/pagewalk.c
@@ -3,22 +3,12 @@
#include <linux/sched.h>
#include <linux/hugetlb.h>
-/*
- * Check the current skip status of page table walker.
- *
- * Here what I mean by skip is to skip lower level walking, and that was
- * determined for each entry independently. For example, when walk_pmd_range
- * handles a pmd_trans_huge we don't have to walk over ptes under that pmd,
- * and the skipping does not affect the walking over ptes under other pmds.
- * That's why we reset @walk->skip after tested.
- */
-static bool skip_lower_level_walking(struct mm_walk *walk)
+static int get_reset_walk_control(struct mm_walk *walk)
{
- if (walk->skip) {
- walk->skip = 0;
- return true;
- }
- return false;
+ int ret = walk->control;
+ /* Reset to default value */
+ walk->control = PTWALK_NEXT;
+ return ret;
}
static int walk_pte_range(pmd_t *pmd, unsigned long addr,
@@ -47,7 +37,18 @@ static int walk_pte_range(pmd_t *pmd, unsigned long addr,
err = walk->pte_entry(pte, addr, addr + PAGE_SIZE, walk);
if (err)
break;
+ switch (get_reset_walk_control(walk)) {
+ case PTWALK_NEXT:
+ continue;
+ case PTWALK_DOWN:
+ break;
+ case PTWALK_BREAK:
+ goto out_unlock;
+ default:
+ BUG();
+ }
} while (pte++, addr += PAGE_SIZE, addr < end);
+out_unlock:
pte_unmap_unlock(orig_pte, ptl);
cond_resched();
return addr == end ? 0 : err;
@@ -75,10 +76,16 @@ static int walk_pmd_range(pud_t *pud, unsigned long addr,
if (walk->pmd_entry) {
err = walk->pmd_entry(pmd, addr, next, walk);
- if (skip_lower_level_walking(walk))
- continue;
if (err)
break;
+ switch (get_reset_walk_control(walk)) {
+ case PTWALK_NEXT:
+ continue;
+ case PTWALK_DOWN:
+ break;
+ default:
+ BUG();
+ }
}
if (walk->pte_entry) {
@@ -204,13 +211,13 @@ static inline int walk_hugetlb_range(unsigned long addr, unsigned long end,
#endif /* CONFIG_HUGETLB_PAGE */
/*
- * Decide whether we really walk over the current vma on [@start, @end)
- * or skip it. When we skip it, we set @walk->skip to 1.
- * The return value is used to control the page table walking to
- * continue (for zero) or not (for non-zero).
+ * Decide whether we really walk over the current vma on [@start, @end) or
+ * skip it. If we walk over it, we should set @walk->control to PTWALK_DOWN.
+ * Otherwise, we skip it. The return value is used to control the current
+ * walking to continue (for zero) or terminate (for non-zero).
*
- * Default check (only VM_PFNMAP check for now) is used when the caller
- * doesn't define test_walk() callback.
+ * We fall through to the default check if the caller doesn't define its own
+ * test_walk() callback.
*/
static int walk_page_test(unsigned long start, unsigned long end,
struct mm_walk *walk)
@@ -224,8 +231,8 @@ static int walk_page_test(unsigned long start, unsigned long end,
* Do not walk over vma(VM_PFNMAP), because we have no valid struct
* page backing a VM_PFNMAP range. See also commit a9ff785e4437.
*/
- if (vma->vm_flags & VM_PFNMAP)
- walk->skip = 1;
+ if (!(vma->vm_flags & VM_PFNMAP))
+ walk->control = PTWALK_DOWN;
return 0;
}
@@ -266,7 +273,7 @@ static int __walk_page_range(unsigned long start, unsigned long end,
* defines test_walk(), pmd_entry(), and pte_entry(), then callbacks are
* called in the order of test_walk(), pmd_entry(), and pte_entry().
* If you don't want to go down to lower level at some point and move to
- * the next entry in the same level, you set @walk->skip to 1.
+ * the next entry in the same level, you set @walk->control to PTWALK_DOWN.
* For example if you succeed to handle some pmd entry as trans_huge entry,
* you need not call walk_pte_range() any more, so set it to avoid that.
* We can't determine whether to go down to lower level with the return
@@ -310,10 +317,16 @@ int walk_page_range(unsigned long start, unsigned long end,
next = min(end, vma->vm_end);
err = walk_page_test(start, next, walk);
- if (skip_lower_level_walking(walk))
- continue;
if (err)
break;
+ switch (get_reset_walk_control(walk)) {
+ case PTWALK_NEXT:
+ continue;
+ case PTWALK_DOWN:
+ break;
+ default:
+ BUG();
+ }
}
err = __walk_page_range(start, next, walk);
if (err)
@@ -333,9 +346,15 @@ int walk_page_vma(struct vm_area_struct *vma, struct mm_walk *walk)
VM_BUG_ON(!vma);
walk->vma = vma;
err = walk_page_test(vma->vm_start, vma->vm_end, walk);
- if (skip_lower_level_walking(walk))
- return 0;
if (err)
return err;
+ switch (get_reset_walk_control(walk)) {
+ case PTWALK_NEXT:
+ return 0;
+ case PTWALK_DOWN:
+ break;
+ default:
+ BUG();
+ }
return __walk_page_range(vma->vm_start, vma->vm_end, walk);
}
--
1.9.3
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