linux-kernel - [PATCH 01/12] Revert "mm: pgtable: make ptlock be freed by RCU"

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Message-Id: <1fdb3ee32e6958ad82229941b2213ef76b7c4705.1734164094.git.zhengqi.arch@bytedance.com>
Date: Sat, 14 Dec 2024 17:02:47 +0800
From: Qi Zheng <zhengqi.arch@...edance.com>
To: peterz@...radead.org,
	tglx@...utronix.de,
	david@...hat.com,
	jannh@...gle.com,
	hughd@...gle.com,
	yuzhao@...gle.com,
	willy@...radead.org,
	muchun.song@...ux.dev,
	vbabka@...nel.org,
	lorenzo.stoakes@...cle.com,
	akpm@...ux-foundation.org,
	rientjes@...gle.com
Cc: linux-mm@...ck.org,
	linux-kernel@...r.kernel.org,
	Qi Zheng <zhengqi.arch@...edance.com>
Subject: [PATCH 01/12] Revert "mm: pgtable: make ptlock be freed by RCU"

This reverts commit 2f3443770437e49abc39af26962d293851cbab6d.

Signed-off-by: Qi Zheng <zhengqi.arch@...edance.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 e7902980439cc..5e73e53c34e9e 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2988,7 +2988,7 @@ 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 df8f5152644ec..5d8779997266e 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.
@@ -485,7 +478,7 @@ 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 d9af83dd86bbf..83765632e20b0 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -7041,34 +7041,24 @@ 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