[PATCH v9 6/8] mm/huge_memory: add folio_split() to debugfs testing interface

Zi Yan
2025-02-26T21:01:01Z

This allows to test folio_split() by specifying an additional in folio
page offset parameter to split_huge_page debugfs interface.

Signed-off-by: Zi Yan <ziy@nvidia.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: Kefeng Wang <wangkefeng.wang@huawei.com>
Cc: Kirill A. Shuemov <kirill.shutemov@linux.intel.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Miaohe Lin <linmiaohe@huawei.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Yang Shi <yang@os.amperecomputing.com>
Cc: Yu Zhao <yuzhao@google.com>
Cc: Kairui Song <kasong@tencent.com>
---
mm/huge_memory.c | 47 ++++++++++++++++++++++++++++++++++-------------
1 file changed, 34 insertions(+), 13 deletions(-)

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index e7e50b2b23f6..6298be12e843 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -4312,7 +4312,8 @@ static inline bool vma_not_suitable_for_thp_split(struct vm_area_struct *vma)
}

static int split_huge_pages_pid(int pid, unsigned long vaddr_start,
- unsigned long vaddr_end, unsigned int new_order)
+ unsigned long vaddr_end, unsigned int new_order,
+ long in_folio_offset)
{
int ret = 0;
struct task_struct *task;
@@ -4396,8 +4397,16 @@ static int split_huge_pages_pid(int pid, unsigned long vaddr_start,
if (!folio_test_anon(folio) && folio->mapping != mapping)
goto unlock;

- if (!split_folio_to_order(folio, target_order))
- split++;
+ if (in_folio_offset < 0 ||
+ in_folio_offset >= folio_nr_pages(folio)) {
+ if (!split_folio_to_order(folio, target_order))
+ split++;
+ } else {
+ struct page *split_at = folio_page(folio,
+ in_folio_offset);
+ if (!folio_split(folio, target_order, split_at, NULL))
+ split++;
+ }

unlock:

@@ -4420,7 +4429,8 @@ static int split_huge_pages_pid(int pid, unsigned long vaddr_start,
}

static int split_huge_pages_in_file(const char *file_path, pgoff_t off_start,
- pgoff_t off_end, unsigned int new_order)
+ pgoff_t off_end, unsigned int new_order,
+ long in_folio_offset)
{
struct filename *file;
struct file *candidate;
@@ -4469,8 +4479,15 @@ static int split_huge_pages_in_file(const char *file_path, pgoff_t off_start,
if (folio->mapping != mapping)
goto unlock;

- if (!split_folio_to_order(folio, target_order))
- split++;
+ if (in_folio_offset < 0 || in_folio_offset >= nr_pages) {
+ if (!split_folio_to_order(folio, target_order))
+ split++;
+ } else {
+ struct page *split_at = folio_page(folio,
+ in_folio_offset);
+ if (!folio_split(folio, target_order, split_at, NULL))
+ split++;
+ }

unlock:
folio_unlock(folio);
@@ -4503,6 +4520,7 @@ static ssize_t split_huge_pages_write(struct file *file, const char __user *buf,
int pid;
unsigned long vaddr_start, vaddr_end;
unsigned int new_order = 0;
+ long in_folio_offset = -1;

ret = mutex_lock_interruptible(&split_debug_mutex);
if (ret)
@@ -4531,30 +4549,33 @@ static ssize_t split_huge_pages_write(struct file *file, const char __user *buf,
goto out;
}

- ret = sscanf(tok_buf, "0x%lx,0x%lx,%d", &off_start,
- &off_end, &new_order);
- if (ret != 2 && ret != 3) {
+ ret = sscanf(tok_buf, "0x%lx,0x%lx,%d,%ld", &off_start, &off_end,
+ &new_order, &in_folio_offset);
+ if (ret != 2 && ret != 3 && ret != 4) {
ret = -EINVAL;
goto out;
}
- ret = split_huge_pages_in_file(file_path, off_start, off_end, new_order);
+ ret = split_huge_pages_in_file(file_path, off_start, off_end,
+ new_order, in_folio_offset);
if (!ret)
ret = input_len;

goto out;
}

- ret = sscanf(input_buf, "%d,0x%lx,0x%lx,%d", &pid, &vaddr_start, &vaddr_end, &new_order);
+ ret = sscanf(input_buf, "%d,0x%lx,0x%lx,%d,%ld", &pid, &vaddr_start,
+ &vaddr_end, &new_order, &in_folio_offset);
if (ret == 1 && pid == 1) {
split_huge_pages_all();
ret = strlen(input_buf);
goto out;
- } else if (ret != 3 && ret != 4) {
+ } else if (ret != 3 && ret != 4 && ret != 5) {
ret = -EINVAL;
goto out;
}

- ret = split_huge_pages_pid(pid, vaddr_start, vaddr_end, new_order);
+ ret = split_huge_pages_pid(pid, vaddr_start, vaddr_end, new_order,
+ in_folio_offset);
if (!ret)
ret = strlen(input_buf);
out:
--
2.47.2