[PATCH v6 5/6] mm: use vma_start_write_killable() in process_vma_walk_lock()

Suren Baghdasaryan
2026-03-27T20:55:47Z

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. When queue_pages_range() fails, check whether it failed due to
a fatal signal or some other reason and return appropriate error.

Suggested-by: Matthew Wilcox <willy@infradead.org>
Signed-off-by: Suren Baghdasaryan <surenb@google.com>
---
fs/proc/task_mmu.c | 12 ++++++------
mm/mempolicy.c | 10 +++++++++-
mm/pagewalk.c | 22 +++++++++++++++-------
3 files changed, 30 insertions(+), 14 deletions(-)

diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
index e091931d7ca1..33e5094a7842 100644
--- a/fs/proc/task_mmu.c
+++ b/fs/proc/task_mmu.c
@@ -1774,15 +1774,15 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf,
struct vm_area_struct *vma;
enum clear_refs_types type;
int itype;
- int rv;
+ int err;

if (count > sizeof(buffer) - 1)
count = sizeof(buffer) - 1;
if (copy_from_user(buffer, buf, count))
return -EFAULT;
- rv = kstrtoint(strstrip(buffer), 10, &itype);
- if (rv < 0)
- return rv;
+ err = kstrtoint(strstrip(buffer), 10, &itype);
+ if (err)
+ return err;
type = (enum clear_refs_types)itype;
if (type < CLEAR_REFS_ALL || type >= CLEAR_REFS_LAST)
return -EINVAL;
@@ -1824,7 +1824,7 @@ 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 (type == CLEAR_REFS_SOFT_DIRTY) {
mmu_notifier_invalidate_range_end(&range);
flush_tlb_mm(mm);
@@ -1837,7 +1837,7 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf,
}
put_task_struct(task);

- return count;
+ return err ? : count;
}

const struct file_operations proc_clear_refs_operations = {
diff --git a/mm/mempolicy.c b/mm/mempolicy.c
index c38a90487531..51f298cfc33b 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,
@@ -1545,7 +1546,14 @@ static long do_mbind(unsigned long start, unsigned long len,
flags | MPOL_MF_INVERT | MPOL_MF_WRLOCK, &pagelist);

if (nr_failed < 0) {
- err = nr_failed;
+ /*
+ * queue_pages_range() might override the original error with -EFAULT.
+ * Confirm that fatal signals are still treated correctly.
+ */
+ if (fatal_signal_pending(current))
+ err = -EINTR;
+ else
+ err = nr_failed;
nr_failed = 0;
} else {
vma_iter_init(&vmi, mm, start);
diff --git a/mm/pagewalk.c b/mm/pagewalk.c
index 3ae2586ff45b..eca7bc711617 100644
--- a/mm/pagewalk.c
+++ b/mm/pagewalk.c
@@ -443,14 +443,13 @@ 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,
- enum page_walk_lock walk_lock)
+static 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;
@@ -462,6 +461,7 @@ static inline void process_vma_walk_lock(struct vm_area_struct *vma,
break;
}
#endif
+ return 0;
}

/*
@@ -505,7 +505,9 @@ 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);
@@ -722,6 +724,7 @@ 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;
@@ -729,7 +732,9 @@ 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);
}

@@ -752,6 +757,7 @@ 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;
@@ -759,7 +765,9 @@ 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