From: Zi Yan <ziy@nvidia.com>
Date: Wed, 22 Jan 2025 16:19:27 +0000 (-0500)
Subject: mm/huge_memory: allow split shmem large folio to any lower order
X-Git-Tag: v6.15-rc1~81^2~415
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=9b2f764933eb5e3ac9ebba26e3341529219c4401;p=thirdparty%2Fkernel%2Flinux.git

mm/huge_memory: allow split shmem large folio to any lower order

Commit 4d684b5f92ba ("mm: shmem: add large folio support for tmpfs") has
added large folio support to shmem.  Remove the restriction in
split_huge_page*().

Link: https://lkml.kernel.org/r/20250122161928.1240637-2-ziy@nvidia.com
Signed-off-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Reviewed-by: Yang Shi <yang@os.amperecomputing.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: Miaohe Lin <linmiaohe@huawei.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Yu Zhao <yuzhao@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 118f2127c7856..e33da765c428e 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -3299,7 +3299,7 @@ static void __split_huge_page(struct page *page, struct list_head *list,
 		/* Some pages can be beyond EOF: drop them from page cache */
 		if (tail->index >= end) {
 			if (shmem_mapping(folio->mapping))
-				nr_dropped++;
+				nr_dropped += new_nr;
 			else if (folio_test_clear_dirty(tail))
 				folio_account_cleaned(tail,
 					inode_to_wb(folio->mapping->host));
@@ -3465,12 +3465,6 @@ int split_huge_page_to_list_to_order(struct page *page, struct list_head *list,
 			return -EINVAL;
 		}
 	} else if (new_order) {
-		/* Split shmem folio to non-zero order not supported */
-		if (shmem_mapping(folio->mapping)) {
-			VM_WARN_ONCE(1,
-				"Cannot split shmem folio to non-0 order");
-			return -EINVAL;
-		}
 		/*
 		 * No split if the file system does not support large folio.
 		 * Note that we might still have THPs in such mappings due to