[PATCH v2 1/4] fs/proc/task_mmu: update functions to clear the soft-dirty bit

Muhammad Usama Anjum
2022-08-25T07:09:55Z

Update the clear_soft_dirty() and clear_soft_dirty_pmd() to optionally
clear and return the status if page is dirty.

Signed-off-by: Muhammad Usama Anjum <usama.anjum@collabora.com>
---
Changes in v2:
- Move back the functions back to their original file
---
fs/proc/task_mmu.c | 82 ++++++++++++++++++++++++++++------------------
1 file changed, 51 insertions(+), 31 deletions(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index 8b4f3073f8f5..f66674033207 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -1095,8 +1095,8 @@ static inline bool pte_is_pinned(struct vm_area_struct *vma, unsigned long addr,
return page_maybe_dma_pinned(page);
}

-static inline void clear_soft_dirty(struct vm_area_struct *vma,
- unsigned long addr, pte_t *pte)
+static inline bool check_soft_dirty(struct vm_area_struct *vma,
+ unsigned long addr, pte_t *pte, bool clear)
{
/*
* The soft-dirty tracker uses #PF-s to catch writes
@@ -1105,55 +1105,75 @@ static inline void clear_soft_dirty(struct vm_area_struct *vma,
* of how soft-dirty works.
*/
pte_t ptent = *pte;
+ int dirty = 0;

if (pte_present(ptent)) {
pte_t old_pte;

- if (pte_is_pinned(vma, addr, ptent))
- return;
- old_pte = ptep_modify_prot_start(vma, addr, pte);
- ptent = pte_wrprotect(old_pte);
- ptent = pte_clear_soft_dirty(ptent);
- ptep_modify_prot_commit(vma, addr, pte, old_pte, ptent);
+ dirty = pte_soft_dirty(ptent);
+
+ if (dirty && clear && !pte_is_pinned(vma, addr, ptent)) {
+ old_pte = ptep_modify_prot_start(vma, addr, pte);
+ ptent = pte_wrprotect(old_pte);
+ ptent = pte_clear_soft_dirty(ptent);
+ ptep_modify_prot_commit(vma, addr, pte, old_pte, ptent);
+ }
} else if (is_swap_pte(ptent)) {
- ptent = pte_swp_clear_soft_dirty(ptent);
- set_pte_at(vma->vm_mm, addr, pte, ptent);
+ dirty = pte_swp_soft_dirty(ptent);
+
+ if (dirty && clear) {
+ ptent = pte_swp_clear_soft_dirty(ptent);
+ set_pte_at(vma->vm_mm, addr, pte, ptent);
+ }
}
+
+ return !!dirty;
}
#else
-static inline void clear_soft_dirty(struct vm_area_struct *vma,
- unsigned long addr, pte_t *pte)
+static inline bool check_soft_dirty(struct vm_area_struct *vma,
+ unsigned long addr, pte_t *pte, bool clear)
{
+ return false;
}
#endif

#if defined(CONFIG_MEM_SOFT_DIRTY) && defined(CONFIG_TRANSPARENT_HUGEPAGE)
-static inline void clear_soft_dirty_pmd(struct vm_area_struct *vma,
- unsigned long addr, pmd_t *pmdp)
+static inline bool check_soft_dirty_pmd(struct vm_area_struct *vma,
+ unsigned long addr, pmd_t *pmdp, bool clear)
{
pmd_t old, pmd = *pmdp;
+ int dirty = 0;

if (pmd_present(pmd)) {
- /* See comment in change_huge_pmd() */
- old = pmdp_invalidate(vma, addr, pmdp);
- if (pmd_dirty(old))
- pmd = pmd_mkdirty(pmd);
- if (pmd_young(old))
- pmd = pmd_mkyoung(pmd);
-
- pmd = pmd_wrprotect(pmd);
- pmd = pmd_clear_soft_dirty(pmd);
-
- set_pmd_at(vma->vm_mm, addr, pmdp, pmd);
+ dirty = pmd_soft_dirty(pmd);
+ if (dirty && clear) {
+ /* See comment in change_huge_pmd() */
+ old = pmdp_invalidate(vma, addr, pmdp);
+ if (pmd_dirty(old))
+ pmd = pmd_mkdirty(pmd);
+ if (pmd_young(old))
+ pmd = pmd_mkyoung(pmd);
+
+ pmd = pmd_wrprotect(pmd);
+ pmd = pmd_clear_soft_dirty(pmd);
+
+ set_pmd_at(vma->vm_mm, addr, pmdp, pmd);
+ }
} else if (is_migration_entry(pmd_to_swp_entry(pmd))) {
- pmd = pmd_swp_clear_soft_dirty(pmd);
- set_pmd_at(vma->vm_mm, addr, pmdp, pmd);
+ dirty = pmd_swp_soft_dirty(pmd);
+
+ if (dirty && clear) {
+ pmd = pmd_swp_clear_soft_dirty(pmd);
+ set_pmd_at(vma->vm_mm, addr, pmdp, pmd);
+ }
}
+ return !!dirty;
}
#else
-static inline void clear_soft_dirty_pmd(struct vm_area_struct *vma,
- unsigned long addr, pmd_t *pmdp)
+static inline bool check_soft_dirty_pmd(struct vm_area_struct *vma,
+ unsigned long addr, pmd_t *pmdp, bool clear)
{
+ return false;
}
#endif

@@ -1169,7 +1189,7 @@ static int clear_refs_pte_range(pmd_t *pmd, unsigned long addr,
ptl = pmd_trans_huge_lock(pmd, vma);
if (ptl) {
if (cp->type == CLEAR_REFS_SOFT_DIRTY) {
- clear_soft_dirty_pmd(vma, addr, pmd);
+ check_soft_dirty_pmd(vma, addr, pmd, true);
goto out;
}

@@ -1195,7 +1215,7 @@ static int clear_refs_pte_range(pmd_t *pmd, unsigned long addr,
ptent = *pte;

if (cp->type == CLEAR_REFS_SOFT_DIRTY) {
- clear_soft_dirty(vma, addr, pte);
+ check_soft_dirty(vma, addr, pte, true);
continue;
}

--
2.30.2