[PATCH v4 4/4] mm: use vma_start_write_killable() in process_vma_walk_lock()

Suren Baghdasaryan
2026-03-22T05:43:52Z

Replace vma_start_write() with vma_start_write_killable() when
process_vma_walk_lock() is used with PGWALK_WRLOCK option.
Adjust its direct and indirect users to check for a possible error
and handle it. Ensure users handle EINTR correctly and do not ignore
it.

Signed-off-by: Suren Baghdasaryan <surenb@google.com>
---
fs/proc/task_mmu.c | 5 ++++-
mm/mempolicy.c | 1 +
mm/pagewalk.c | 20 ++++++++++++++------
3 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index e091931d7ca1..2fe3d11aad03 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -1797,6 +1797,7 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf,
struct clear_refs_private cp = {
.type = type,
};
+ int err;

if (mmap_write_lock_killable(mm)) {
count = -EINTR;
@@ -1824,7 +1825,9 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf,
0, mm, 0, -1UL);
mmu_notifier_invalidate_range_start(&range);
}
- walk_page_range(mm, 0, -1, &clear_refs_walk_ops, &cp);
+ err = walk_page_range(mm, 0, -1, &clear_refs_walk_ops, &cp);
+ if (err)
+ count = err;
if (type == CLEAR_REFS_SOFT_DIRTY) {
mmu_notifier_invalidate_range_end(&range);
flush_tlb_mm(mm);
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index 929e843543cf..bb5b0e83ce0f 100644
--- a/mm/mempolicy.c
+++ b/mm/mempolicy.c
@@ -969,6 +969,7 @@ static const struct mm_walk_ops queue_pages_lock_vma_walk_ops = {
* (a hugetlbfs page or a transparent huge page being counted as 1).
* -EIO - a misplaced page found, when MPOL_MF_STRICT specified without MOVEs.
* -EFAULT - a hole in the memory range, when MPOL_MF_DISCONTIG_OK unspecified.
+ * -EINTR - walk got terminated due to pending fatal signal.
*/
static long
queue_pages_range(struct mm_struct *mm, unsigned long start, unsigned long end,
diff --git a/mm/pagewalk.c b/mm/pagewalk.c
index eda74273c8ec..a42cd6a6d812 100644
--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -438,14 +438,13 @@ static inline void process_mm_walk_lock(struct mm_struct *mm,
mmap_assert_write_locked(mm);
}

-static inline void process_vma_walk_lock(struct vm_area_struct *vma,
+static inline int process_vma_walk_lock(struct vm_area_struct *vma,
enum page_walk_lock walk_lock)
{
#ifdef CONFIG_PER_VMA_LOCK
switch (walk_lock) {
case PGWALK_WRLOCK:
- vma_start_write(vma);
- break;
+ return vma_start_write_killable(vma);
case PGWALK_WRLOCK_VERIFY:
vma_assert_write_locked(vma);
break;
@@ -457,6 +456,7 @@ static inline void process_vma_walk_lock(struct vm_area_struct *vma,
break;
}
#endif
+ return 0;
}

/*
@@ -500,7 +500,9 @@ int walk_page_range_mm_unsafe(struct mm_struct *mm, unsigned long start,
if (ops->pte_hole)
err = ops->pte_hole(start, next, -1, &walk);
} else { /* inside vma */
- process_vma_walk_lock(vma, ops->walk_lock);
+ err = process_vma_walk_lock(vma, ops->walk_lock);
+ if (err)
+ break;
walk.vma = vma;
next = min(end, vma->vm_end);
vma = find_vma(mm, vma->vm_end);
@@ -717,6 +719,7 @@ int walk_page_range_vma_unsafe(struct vm_area_struct *vma, unsigned long start,
.vma = vma,
.private = private,
};
+ int err;

if (start >= end || !walk.mm)
return -EINVAL;
@@ -724,7 +727,9 @@ int walk_page_range_vma_unsafe(struct vm_area_struct *vma, unsigned long start,
return -EINVAL;

process_mm_walk_lock(walk.mm, ops->walk_lock);
- process_vma_walk_lock(vma, ops->walk_lock);
+ err = process_vma_walk_lock(vma, ops->walk_lock);
+ if (err)
+ return err;
return __walk_page_range(start, end, &walk);
}

@@ -747,6 +752,7 @@ int walk_page_vma(struct vm_area_struct *vma, const struct mm_walk_ops *ops,
.vma = vma,
.private = private,
};
+ int err;

if (!walk.mm)
return -EINVAL;
@@ -754,7 +760,9 @@ int walk_page_vma(struct vm_area_struct *vma, const struct mm_walk_ops *ops,
return -EINVAL;

process_mm_walk_lock(walk.mm, ops->walk_lock);
- process_vma_walk_lock(vma, ops->walk_lock);
+ err = process_vma_walk_lock(vma, ops->walk_lock);
+ if (err)
+ return err;
return __walk_page_range(vma->vm_start, vma->vm_end, &walk);
}

--
2.53.0.1018.g2bb0e51243-goog