+ mm-huge_memory-move-filemap-management-into-the-file-split-helper.patch added to mm-new branch

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

The patch titled
     Subject: mm/huge_memory: move filemap management into the file split helper
has been added to the -mm mm-new branch.  Its filename is
     mm-huge_memory-move-filemap-management-into-the-file-split-helper.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-move-filemap-management-into-the-file-split-helper.patch

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

Note, mm-new is a provisional staging ground for work-in-progress
patches, and acceptance into mm-new is a notification for others take
notice and to finish up reviews.  Please do not hesitate to respond to
review feedback and post updated versions to replace or incrementally
fixup patches in mm-new.

The mm-new branch of mm.git is not included in linux-next

If a few days of testing in mm-new is successful, the patch will me moved
into mm.git's mm-unstable branch, which is included in linux-next

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------------------------------------------------------
From: Kairui Song <kasong@tencent.com>
Subject: mm/huge_memory: move filemap management into the file split helper
Date: Tue, 15 Sep 2026 01:14:52 +0800

Only file split needs the filemap and xarray handling and related
variables.  Move them out of __folio_split() into the file helper so the
helper is self-contained, and simplify the parameters.

No functional change.

Link: https://lore.kernel.org/20260915-swap-thp-cleanup-v5-11-39878b37dfb0@tencent.com
Signed-off-by: Kairui Song <kasong@tencent.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Zi Yan <ziy@nvidia.com>
Reviewed-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
Reviewed-by: Yeoreum Yun <yeoreum.yun@arm.com>
Cc: Baolin Wang <baolin.wang@linux.alibaba.com>
Cc: Baoquan He <baoquan.he@linux.dev>
Cc: Barry Song <baohua@kernel.org>
Cc: Chris Li <chrisl@kernel.org>
Cc: David Hildenbrand (Arm) <david@kernel.org>
Cc: Dev Jain <dev.jain@arm.com>
Cc: Kemeng Shi <shikemeng@huaweicloud.com>
Cc: Lance Yang <lance.yang@linux.dev>
Cc: Liam R. Howlett <liam@infradead.org>
Cc: Lorenzo Stoakes <ljs@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Nhat Pham <nphamcs@gmail.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Suren Baghdasaryan <surenb@google.com>
Cc: Vlastimil Babka <vbabka@kernel.org>
---

 mm/huge_memory.c |  102 +++++++++++++++++++--------------------------
 1 file changed, 44 insertions(+), 58 deletions(-)

--- a/mm/huge_memory.c~mm-huge_memory-move-filemap-management-into-the-file-split-helper
+++ a/mm/huge_memory.c
@@ -4107,16 +4107,42 @@ out_no_split:
 
 static int __folio_freeze_split_file(struct folio *folio,
 		unsigned int new_order, struct page *split_at,
-		struct xa_state *xas, struct address_space *mapping,
 		bool do_lru, struct list_head *list,
 		enum split_type split_type)
 {
+	struct address_space *mapping = folio->mapping;
+	XA_STATE(xas, &mapping->i_pages, folio->index);
 	struct folio *end_folio = folio_next(folio);
 	struct folio *new_folio, *next;
 	int nr_shmem_dropped = 0;
+	unsigned int min_order;
 	struct lruvec *lruvec;
 	pgoff_t end;
-	int ret;
+	gfp_t gfp;
+	int ret = 0;
+
+	min_order = mapping_min_folio_order(mapping);
+	if (new_order < min_order)
+		return -EINVAL;
+
+	gfp = current_gfp_context(mapping_gfp_mask(mapping) & GFP_RECLAIM_MASK);
+	if (!filemap_release_folio(folio, gfp))
+		return -EBUSY;
+
+	mapping_set_update(&xas, mapping);
+
+	if (split_type == SPLIT_TYPE_UNIFORM) {
+		int old_order = folio_order(folio);
+
+		xas_set_order(&xas, folio->index, new_order);
+		xas_split_alloc(&xas, folio, old_order, gfp);
+		if (xas_error(&xas)) {
+			ret = xas_error(&xas);
+			goto fail_free;
+		}
+	}
+
+	i_mmap_lock_read(mapping);
 
 	/* Currently device private folios can only back anonymous memory. */
 	VM_WARN_ON_ONCE_FOLIO(folio_is_device_private(folio), folio);
@@ -4134,15 +4160,15 @@ static int __folio_freeze_split_file(str
 
 	ret = unmap_folio(folio);
 	if (ret)
-		return ret;
+		goto fail_mmap_unlock;
 
-	xas_lock_irq(xas);
+	xas_lock_irq(&xas);
 
 	/*
 	 * Check if the folio is present in page cache.
 	 * We assume all tail are present too, if folio is there.
 	 */
-	if (xas_load(xas) != folio) {
+	if (xas_load(&xas) != folio) {
 		ret = -EAGAIN;
 		goto fail;
 	}
@@ -4169,7 +4195,7 @@ static int __folio_freeze_split_file(str
 	if (do_lru)
 		lruvec = folio_lruvec_lock(folio);
 
-	ret = __split_frozen_folio(folio, new_order, split_at, xas,
+	ret = __split_frozen_folio(folio, new_order, split_at, &xas,
 				   mapping, split_type);
 
 	/*
@@ -4225,9 +4251,19 @@ fail:
 	 * If we want to use try_to_migrate() on file in unmap_folio,
 	 * remember to add remap_anon_folio() and adapt it.
 	 */
-	xas_unlock_irq(xas);
+	xas_unlock_irq(&xas);
+fail_mmap_unlock:
 	if (nr_shmem_dropped)
 		shmem_uncharge(mapping->host, nr_shmem_dropped);
+	/*
+	 * Drop the mapping while the inode is still pinned. @folio stays
+	 * locked and present in the page cache, so eviction cannot free
+	 * the inode yet, nothing past this point may touch the inode or
+	 * the mapping.
+	 */
+	i_mmap_unlock_read(mapping);
+fail_free:
+	xas_destroy(&xas);
 	return ret;
 }
 
@@ -4256,11 +4292,9 @@ static int __folio_split(struct folio *f
 		struct page *split_at, struct page *lock_at,
 		struct list_head *list, enum split_type split_type)
 {
-	XA_STATE(xas, &folio->mapping->i_pages, folio->index);
 	struct folio *end_folio = folio_next(folio);
 	bool is_anon = folio_test_anon(folio);
 	struct mem_cgroup *memcg, *old_memcg;
-	struct address_space *mapping = NULL;
 	struct anon_vma *anon_vma = NULL;
 	int old_order = folio_order(folio);
 	struct folio *new_folio, *next;
@@ -4307,61 +4341,16 @@ static int __folio_split(struct folio *f
 			goto out;
 		}
 		anon_vma_lock_write(anon_vma);
-		mapping = NULL;
-	} else {
-		unsigned int min_order;
-		gfp_t gfp;
-
-		mapping = folio->mapping;
-		min_order = mapping_min_folio_order(mapping);
-		if (new_order < min_order) {
-			ret = -EINVAL;
-			goto out;
-		}
-
-		gfp = current_gfp_context(mapping_gfp_mask(mapping) &
-							GFP_RECLAIM_MASK);
-
-		if (!filemap_release_folio(folio, gfp)) {
-			ret = -EBUSY;
-			goto out;
-		}
-
-		mapping_set_update(&xas, mapping);
-
-		if (split_type == SPLIT_TYPE_UNIFORM) {
-			xas_set_order(&xas, folio->index, new_order);
-			xas_split_alloc(&xas, folio, old_order, gfp);
-			if (xas_error(&xas)) {
-				ret = xas_error(&xas);
-				goto out;
-			}
-		}
-
-		anon_vma = NULL;
-		i_mmap_lock_read(mapping);
 	}
 
 	if (is_anon)
 		ret = __folio_freeze_split_anon(folio, new_order, split_at,
 						true, list, split_type);
 	else
-		ret = __folio_freeze_split_file(folio, new_order, split_at, &xas, mapping,
+		ret = __folio_freeze_split_file(folio, new_order, split_at,
 						true, list, split_type);
 
 	/*
-	 * Drop the mapping while the inode is still pinned. @folio stays
-	 * locked and present in the page cache until the loop below, so
-	 * eviction cannot free the inode yet; @lock_at is not enough, it may
-	 * be a tail beyond EOF that the split already dropped from the page
-	 * cache. Nothing past this point may touch the inode or the mapping.
-	 */
-	if (mapping) {
-		i_mmap_unlock_read(mapping);
-		mapping = NULL;
-	}
-
-	/*
 	 * Unlock all after-split folios except the one containing
 	 * @lock_at page. If @folio is not split, it will be kept locked.
 	 */
@@ -4384,14 +4373,11 @@ static int __folio_split(struct folio *f
 		anon_vma_unlock_write(anon_vma);
 		put_anon_vma(anon_vma);
 	}
-	if (mapping)
-		i_mmap_unlock_read(mapping);
 out:
 	/* restore to caller's old_memcg */
 	set_active_memcg(old_memcg);
 	mem_cgroup_put(memcg);
 out_no_memcg:
-	xas_destroy(&xas);
 	if (is_pmd_order(old_order))
 		count_vm_event(!ret ? THP_SPLIT_PAGE : THP_SPLIT_PAGE_FAILED);
 	count_mthp_stat(old_order, !ret ? MTHP_STAT_SPLIT : MTHP_STAT_SPLIT_FAILED);
_

Patches currently in -mm which might be from kasong@tencent.com are

mm-memcontrol-move-the-lru_zone_size-sanity-check-to-the-reader-side.patch
mm-mglru-introduce-helpers-for-manipulating-gen-and-refs-flags.patch
mm-migrate-copy-all-referenced-state-via-folio_migrate_lru_refs.patch
mm-mglru-move-max_seq-read-into-walk_update_folio.patch
mm-mglru-use-explicit-tier-range-in-read_ctrl_pos.patch
mm-mglru-fix-potential-generation-folio-number-leak.patch
mm-swap-fix-off-by-one-in-swap-cache-replace-sanity-check.patch
mm-huge_memory-fix-rejection-of-swap-cache-folios-with-a-mapping.patch
mm-huge_memory-invert-folio_ref_freeze-check-to-reduce-indentation.patch
mm-huge_memory-split-the-routine-for-splitting-anon-and-file-folio.patch
mm-huge_memory-rename-__split_unmapped_folio-to-__split_frozen_folio.patch
mm-huge_memory-consolidate-irq-and-locking-for-folio-split.patch
mm-huge_memory-move-eof-trimming-into-the-file-split-helper.patch
mm-huge_memory-move-unmap-and-remap-into-the-split-helpers.patch
mm-huge_memory-rename-remap_page-to-remap_anon_folio.patch
mm-huge_memory-move-the-racy-refcount-check-into-unmap_folio.patch
mm-huge_memory-move-filemap-management-into-the-file-split-helper.patch
mm-huge_memory-move-anon_vma-handling-into-the-anon-split-helper.patch
mm-huge_memory-move-memcg-switch-into-the-file-split-helper.patch
mm-huge_memory-drop-the-unused-do_lru-argument-of-the-file-split-helper.patch
mm-huge_memory-clean-up-after-split-folio-freeing-in-__folio_split.patch
mm-huge_memory-count-only-swap-cache-refs-in-anon-folio-split.patch
mm-huge_memory-drop-the-redundant-mapping-argument-of-__split_frozen_folio.patch