[PATCH 1/5] Revert "mm/khugepaged: remove definition of struct khugepaged_mm_slot"
From: Lorenzo Stoakes (ARM)
Date: Tue Nov 03 2026 - 03:32:21 EST
This partially reverts commit b4c9ffb54b32 ("mm/khugepaged: remove
definition of struct khugepaged_mm_slot"), as a subsequent commit needs to
resurrect this type to store additional data alongside the mm_slot.
The stated intent of the commit was to address a NULL check in
__khugepaged_exit():
mm_slot = mm_slot_entry(slot, struct khugepaged_mm_slot, slot);
slot can be NULL and mm_slot_entry() is an alias for container_of(), so
this is container_of() a NULL value.
This was benign as there was only 1 field in khugepaged_mm_slot (offsetting
NULL at 0 results in NULL), however it was right to fix this, so retain the
fix.
It also unwrapped KMEM_CACHE() in khugepaged_init(). This was a mistake,
and was itself reverted in commit c14bdcc9f274 ("mm/khugepaged: use
KMEM_CACHE()"). Therefore, retain the KMEM_CACHE() form in this revert.
Signed-off-by: Lorenzo Stoakes (ARM) <ljs@xxxxxxxxxx>
---
mm/khugepaged.c | 57 ++++++++++++++++++++++++++++++++++++++-------------------
1 file changed, 38 insertions(+), 19 deletions(-)
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
index da91762f6358..aad8797f8d5a 100644
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -66,6 +66,14 @@ static DEFINE_READ_MOSTLY_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS);
static struct kmem_cache *mm_slot_cache __ro_after_init;
+/**
+ * struct khugepaged_mm_slot - khugepaged information per mm that is being scanned
+ * @slot: hash lookup from mm to mm_slot
+ */
+struct khugepaged_mm_slot {
+ struct mm_slot slot;
+};
+
/**
* struct khugepaged_scan - cursor for scanning
* @mm_head: the head of the mm list to scan
@@ -76,7 +84,7 @@ static struct kmem_cache *mm_slot_cache __ro_after_init;
*/
struct khugepaged_scan {
struct list_head mm_head;
- struct mm_slot *mm_slot;
+ struct khugepaged_mm_slot *mm_slot;
unsigned long address;
};
@@ -386,7 +394,7 @@ int hugepage_madvise(struct vm_area_struct *vma,
int __init khugepaged_init(void)
{
- mm_slot_cache = KMEM_CACHE(mm_slot, 0);
+ mm_slot_cache = KMEM_CACHE(khugepaged_mm_slot, 0);
if (!mm_slot_cache)
return -ENOMEM;
@@ -446,20 +454,22 @@ static bool hugepage_enabled(void)
void __khugepaged_enter(struct mm_struct *mm)
{
+ struct khugepaged_mm_slot *mm_slot;
struct mm_slot *slot;
int wakeup;
/* __khugepaged_exit() must not run from under us */
VM_BUG_ON_MM(collapse_test_exit(mm), mm);
- slot = mm_slot_alloc(mm_slot_cache);
- if (!slot)
+ mm_slot = mm_slot_alloc(mm_slot_cache);
+ if (!mm_slot)
return;
if (unlikely(mm_flags_test_and_set(MMF_VM_HUGEPAGE, mm))) {
- mm_slot_free(mm_slot_cache, slot);
+ mm_slot_free(mm_slot_cache, mm_slot);
return;
}
+ slot = &mm_slot->slot;
spin_lock(&khugepaged_mm_lock);
mm_slot_insert(mm_slots_hash, mm, slot);
@@ -504,12 +514,15 @@ void khugepaged_enter_vma(struct vm_area_struct *vma,
void __khugepaged_exit(struct mm_struct *mm)
{
+ struct khugepaged_mm_slot *mm_slot;
struct mm_slot *slot;
int free = 0;
spin_lock(&khugepaged_mm_lock);
slot = mm_slot_lookup(mm_slots_hash, mm);
- if (slot && khugepaged_scan.mm_slot != slot) {
+
+ mm_slot = slot ? mm_slot_entry(slot, struct khugepaged_mm_slot, slot) : NULL;
+ if (mm_slot && khugepaged_scan.mm_slot != mm_slot) {
mm_slot_remove(slot);
free = 1;
}
@@ -517,9 +530,9 @@ void __khugepaged_exit(struct mm_struct *mm)
if (free) {
mm_flags_clear(MMF_VM_HUGEPAGE, mm);
- mm_slot_free(mm_slot_cache, slot);
+ mm_slot_free(mm_slot_cache, mm_slot);
mmdrop(mm);
- } else if (slot) {
+ } else if (mm_slot) {
/*
* This is required to serialize against
* collapse_test_exit() (which is guaranteed to run
@@ -1773,8 +1786,9 @@ static enum scan_result collapse_scan_anon(struct vm_area_struct *vma,
return result;
}
-static void collect_mm_slot(struct mm_slot *slot)
+static void collect_mm_slot(struct khugepaged_mm_slot *mm_slot)
{
+ struct mm_slot *slot = &mm_slot->slot;
struct mm_struct *mm = slot->mm;
lockdep_assert_held(&khugepaged_mm_lock);
@@ -1790,7 +1804,7 @@ static void collect_mm_slot(struct mm_slot *slot)
*/
/* khugepaged_mm_lock actually not necessary for the below */
- mm_slot_free(mm_slot_cache, slot);
+ mm_slot_free(mm_slot_cache, mm_slot);
mmdrop(mm);
}
}
@@ -2891,6 +2905,7 @@ static void collapse_scan_mm_slot(unsigned int progress_max,
__acquires(&khugepaged_mm_lock)
{
struct vma_iterator vmi;
+ struct khugepaged_mm_slot *mm_slot;
struct mm_slot *slot;
struct mm_struct *mm;
struct vm_area_struct *vma;
@@ -2900,12 +2915,14 @@ static void collapse_scan_mm_slot(unsigned int progress_max,
*result = SCAN_FAIL;
if (khugepaged_scan.mm_slot) {
- slot = khugepaged_scan.mm_slot;
+ mm_slot = khugepaged_scan.mm_slot;
+ slot = &mm_slot->slot;
} else {
slot = list_first_entry(&khugepaged_scan.mm_head,
struct mm_slot, mm_node);
+ mm_slot = mm_slot_entry(slot, struct khugepaged_mm_slot, slot);
khugepaged_scan.address = 0;
- khugepaged_scan.mm_slot = slot;
+ khugepaged_scan.mm_slot = mm_slot;
}
spin_unlock(&khugepaged_mm_lock);
@@ -2981,7 +2998,7 @@ static void collapse_scan_mm_slot(unsigned int progress_max,
breakouterloop_mmap_lock:
spin_lock(&khugepaged_mm_lock);
- VM_BUG_ON(khugepaged_scan.mm_slot != slot);
+ VM_BUG_ON(khugepaged_scan.mm_slot != mm_slot);
/*
* Release the current mm_slot if this mm is about to die, or
* if we scanned all vmas of this mm, or THP got disabled.
@@ -2993,14 +3010,16 @@ static void collapse_scan_mm_slot(unsigned int progress_max,
* mm_slot not pointing to the exiting mm.
*/
if (!list_is_last(&slot->mm_node, &khugepaged_scan.mm_head)) {
- khugepaged_scan.mm_slot = list_next_entry(slot, mm_node);
+ slot = list_next_entry(slot, mm_node);
+ khugepaged_scan.mm_slot =
+ mm_slot_entry(slot, struct khugepaged_mm_slot, slot);
khugepaged_scan.address = 0;
} else {
khugepaged_scan.mm_slot = NULL;
khugepaged_full_scans++;
}
- collect_mm_slot(slot);
+ collect_mm_slot(mm_slot);
}
trace_mm_khugepaged_scan(mm, cc->progress - progress_prev,
@@ -3090,7 +3109,7 @@ static void khugepaged_wait_work(void)
static int khugepaged(void *none)
{
- struct mm_slot *slot;
+ struct khugepaged_mm_slot *mm_slot;
set_freezable();
set_user_nice(current, MAX_NICE);
@@ -3101,10 +3120,10 @@ static int khugepaged(void *none)
}
spin_lock(&khugepaged_mm_lock);
- slot = khugepaged_scan.mm_slot;
+ mm_slot = khugepaged_scan.mm_slot;
khugepaged_scan.mm_slot = NULL;
- if (slot)
- collect_mm_slot(slot);
+ if (mm_slot)
+ collect_mm_slot(mm_slot);
spin_unlock(&khugepaged_mm_lock);
return 0;
}
--
2.56.0