+ mm-huge_memory-add-folio_split-to-debugfs-testing-interface.patch added to mm-unstable branch

[Andrew Morton <akpm@linux-foundation.org>]

The patch titled
     Subject: mm/huge_memory: add folio_split() to debugfs testing interface
has been added to the -mm mm-unstable branch.  Its filename is
     mm-huge_memory-add-folio_split-to-debugfs-testing-interface.patch

This patch will shortly appear at
     https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-huge_memory-add-folio_split-to-debugfs-testing-interface.patch

This patch will later appear in the mm-unstable branch at
    git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm

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------------------------------------------------------
From: Zi Yan <ziy@nvidia.com>
Subject: mm/huge_memory: add folio_split() to debugfs testing interface
Date: Fri, 7 Mar 2025 12:39:59 -0500

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

Link: https://lkml.kernel.org/r/20250307174001.242794-7-ziy@nvidia.com
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>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 mm/huge_memory.c |   47 ++++++++++++++++++++++++++++++++-------------
 1 file changed, 34 insertions(+), 13 deletions(-)

--- a/mm/huge_memory.c~mm-huge_memory-add-folio_split-to-debugfs-testing-interface
+++ a/mm/huge_memory.c
@@ -4325,7 +4325,8 @@ static inline bool vma_not_suitable_for_
 }
 
 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;
@@ -4409,8 +4410,16 @@ static int split_huge_pages_pid(int pid,
 		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:
 
@@ -4433,7 +4442,8 @@ out:
 }
 
 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;
@@ -4482,8 +4492,15 @@ static int split_huge_pages_in_file(cons
 		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);
@@ -4516,6 +4533,7 @@ static ssize_t split_huge_pages_write(st
 	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)
@@ -4544,30 +4562,33 @@ static ssize_t split_huge_pages_write(st
 			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:
_

Patches currently in -mm which might be from ziy@nvidia.com are

mm-migrate-fix-shmem-xarray-update-during-migration.patch
selftests-mm-make-file-backed-thp-split-work-by-writing-pmd-size-data.patch
mm-huge_memory-allow-split-shmem-large-folio-to-any-lower-order.patch
selftests-mm-test-splitting-file-backed-thp-to-any-lower-order.patch
xarray-add-xas_try_split-to-split-a-multi-index-entry.patch
mm-huge_memory-add-two-new-not-yet-used-functions-for-folio_split.patch
mm-huge_memory-move-folio-split-common-code-to-__folio_split.patch
mm-huge_memory-add-buddy-allocator-like-non-uniform-folio_split.patch
mm-huge_memory-remove-the-old-unused-__split_huge_page.patch
mm-huge_memory-add-folio_split-to-debugfs-testing-interface.patch
mm-truncate-use-folio_split-in-truncate-operation.patch
selftests-mm-add-tests-for-folio_split-buddy-allocator-like-split.patch