[PATCH v3 01/17] Revert "mm: pgtable: make ptlock be freed by RCU"

Qi Zheng
2024-12-23T09:43:18Z

This reverts commit 2f3443770437e49abc39af26962d293851cbab6d.

Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
---
include/linux/mm.h | 2 +-
include/linux/mm_types.h | 9 +--------
mm/memory.c | 22 ++++++----------------
3 files changed, 8 insertions(+), 25 deletions(-)

diff --git a/include/linux/mm.h b/include/linux/mm.h
index d61b9c7a3a7b0..c49bc7b764535 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2925,7 +2925,7 @@ void ptlock_free(struct ptdesc *ptdesc);

static inline spinlock_t *ptlock_ptr(struct ptdesc *ptdesc)
{
- return &(ptdesc->ptl->ptl);
+ return ptdesc->ptl;
}
#else /* ALLOC_SPLIT_PTLOCKS */
static inline void ptlock_cache_init(void)
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 90ab8293d714a..6b27db7f94963 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -434,13 +434,6 @@ FOLIO_MATCH(flags, _flags_2a);
FOLIO_MATCH(compound_head, _head_2a);
#undef FOLIO_MATCH

-#if ALLOC_SPLIT_PTLOCKS
-struct pt_lock {
- spinlock_t ptl;
- struct rcu_head rcu;
-};
-#endif
-
/**
* struct ptdesc - Memory descriptor for page tables.
* @__page_flags: Same as page flags. Powerpc only.
@@ -489,7 +482,7 @@ struct ptdesc {
union {
unsigned long _pt_pad_2;
#if ALLOC_SPLIT_PTLOCKS
- struct pt_lock *ptl;
+ spinlock_t *ptl;
#else
spinlock_t ptl;
#endif
diff --git a/mm/memory.c b/mm/memory.c
index b9b05c3f93f11..9423967b24180 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -7034,34 +7034,24 @@ static struct kmem_cache *page_ptl_cachep;

void __init ptlock_cache_init(void)
{
- page_ptl_cachep = kmem_cache_create("page->ptl", sizeof(struct pt_lock), 0,
+ page_ptl_cachep = kmem_cache_create("page->ptl", sizeof(spinlock_t), 0,
SLAB_PANIC, NULL);
}

bool ptlock_alloc(struct ptdesc *ptdesc)
{
- struct pt_lock *pt_lock;
+ spinlock_t *ptl;

- pt_lock = kmem_cache_alloc(page_ptl_cachep, GFP_KERNEL);
- if (!pt_lock)
+ ptl = kmem_cache_alloc(page_ptl_cachep, GFP_KERNEL);
+ if (!ptl)
return false;
- ptdesc->ptl = pt_lock;
+ ptdesc->ptl = ptl;
return true;
}

-static void ptlock_free_rcu(struct rcu_head *head)
-{
- struct pt_lock *pt_lock;
-
- pt_lock = container_of(head, struct pt_lock, rcu);
- kmem_cache_free(page_ptl_cachep, pt_lock);
-}
-
void ptlock_free(struct ptdesc *ptdesc)
{
- struct pt_lock *pt_lock = ptdesc->ptl;
-
- call_rcu(&pt_lock->rcu, ptlock_free_rcu);
+ kmem_cache_free(page_ptl_cachep, ptdesc->ptl);
}
#endif

--
2.20.1