[PATCH v4 11/17] mm/huge_memory: move filemap management into the file split helper
From: Kairui Song via B4 Relay
Date: Mon Sep 07 2026 - 14:14:48 EST
From: Kairui Song <kasong@xxxxxxxxxxx>
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.
Signed-off-by: Kairui Song <kasong@xxxxxxxxxxx>
---
mm/huge_memory.c | 102 ++++++++++++++++++++++++-------------------------------
1 file changed, 44 insertions(+), 58 deletions(-)
diff --git a/mm/huge_memory.c b/mm/huge_memory.c
index 17bd2c053210..c4910c0b6018 100644
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -4087,16 +4087,42 @@ static int __folio_freeze_split_anon(struct folio *folio,
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);
@@ -4114,15 +4140,15 @@ static int __folio_freeze_split_file(struct folio *folio,
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;
}
@@ -4149,7 +4175,7 @@ static int __folio_freeze_split_file(struct folio *folio,
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);
/*
@@ -4205,9 +4231,19 @@ static int __folio_freeze_split_file(struct folio *folio,
* If we want to use try_to_migrate() on file in unmap_folio,
* remember to add remap_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;
}
@@ -4236,11 +4272,9 @@ static int __folio_split(struct folio *folio, unsigned int new_order,
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;
@@ -4287,60 +4321,15 @@ static int __folio_split(struct folio *folio, unsigned int new_order,
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.
@@ -4364,14 +4353,11 @@ static int __folio_split(struct folio *folio, unsigned int new_order,
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);
--
2.55.0