patchsets/0001-Revert-mm-pgtable-allow-pte_offset_map-_lock-to-fail.patch

From 7d1a899f667cf3ced1089821d74ea9e456428103 Mon Sep 17 00:00:00 2001
From: Yongqin Liu <yongqin.liu@linaro.org>
Date: Fri, 28 Jul 2023 15:52:11 +0800
Subject: [PATCH 1/7] Revert "mm/pgtable: allow pte_offset_map[_lock]() to
 fail"

This reverts commit 0d940a9b270b9220dcff74d8e9123c9788365751.
---
 Documentation/mm/split_page_table_lock.rst | 17 +++----
 include/linux/mm.h                         | 27 ++++-------
 include/linux/pgtable.h                    | 22 +++------
 mm/pgtable-generic.c                       | 56 ----------------------
 4 files changed, 21 insertions(+), 101 deletions(-)

diff --git a/Documentation/mm/split_page_table_lock.rst b/Documentation/mm/split_page_table_lock.rst
index a834fad9de12..50ee0dfc95be 100644
--- a/Documentation/mm/split_page_table_lock.rst
+++ b/Documentation/mm/split_page_table_lock.rst
@@ -14,20 +14,15 @@ tables. Access to higher level tables protected by mm->page_table_lock.
 There are helpers to lock/unlock a table and other accessor functions:
 
  - pte_offset_map_lock()
-	maps PTE and takes PTE table lock, returns pointer to PTE with
-	pointer to its PTE table lock, or returns NULL if no PTE table;
- - pte_offset_map_nolock()
-	maps PTE, returns pointer to PTE with pointer to its PTE table
-	lock (not taken), or returns NULL if no PTE table;
- - pte_offset_map()
-	maps PTE, returns pointer to PTE, or returns NULL if no PTE table;
- - pte_unmap()
-	unmaps PTE table;
+	maps pte and takes PTE table lock, returns pointer to the taken
+	lock;
  - pte_unmap_unlock()
 	unlocks and unmaps PTE table;
  - pte_alloc_map_lock()
-	allocates PTE table if needed and takes its lock, returns pointer to
-	PTE with pointer to its lock, or returns NULL if allocation failed;
+	allocates PTE table if needed and take the lock, returns pointer
+	to taken lock or NULL if allocation failed;
+ - pte_lockptr()
+	returns pointer to PTE table lock;
  - pmd_lock()
 	takes PMD table lock, returns pointer to taken lock;
  - pmd_lockptr()
diff --git a/include/linux/mm.h b/include/linux/mm.h
index ae866bc9bad6..09bd0eaf1253 100644
--- a/include/linux/mm.h
+++ b/include/linux/mm.h
@@ -2824,25 +2824,14 @@ static inline void pgtable_pte_page_dtor(struct page *page)
 	dec_lruvec_page_state(page, NR_PAGETABLE);
 }
 
-pte_t *__pte_offset_map(pmd_t *pmd, unsigned long addr, pmd_t *pmdvalp);
-static inline pte_t *pte_offset_map(pmd_t *pmd, unsigned long addr)
-{
-	return __pte_offset_map(pmd, addr, NULL);
-}
-
-pte_t *__pte_offset_map_lock(struct mm_struct *mm, pmd_t *pmd,
-			unsigned long addr, spinlock_t **ptlp);
-static inline pte_t *pte_offset_map_lock(struct mm_struct *mm, pmd_t *pmd,
-			unsigned long addr, spinlock_t **ptlp)
-{
-	pte_t *pte;
-
-	__cond_lock(*ptlp, pte = __pte_offset_map_lock(mm, pmd, addr, ptlp));
-	return pte;
-}
-
-pte_t *pte_offset_map_nolock(struct mm_struct *mm, pmd_t *pmd,
-			unsigned long addr, spinlock_t **ptlp);
+#define pte_offset_map_lock(mm, pmd, address, ptlp)	\
+({							\
+	spinlock_t *__ptl = pte_lockptr(mm, pmd);	\
+	pte_t *__pte = pte_offset_map(pmd, address);	\
+	*(ptlp) = __ptl;				\
+	spin_lock(__ptl);				\
+	__pte;						\
+})
 
 #define pte_unmap_unlock(pte, ptl)	do {		\
 	spin_unlock(ptl);				\
diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h
index 5063b482e34f..e4e9734ac395 100644
--- a/include/linux/pgtable.h
+++ b/include/linux/pgtable.h
@@ -94,22 +94,14 @@ static inline pte_t *pte_offset_kernel(pmd_t *pmd, unsigned long address)
 #define pte_offset_kernel pte_offset_kernel
 #endif
 
-#ifdef CONFIG_HIGHPTE
-#define __pte_map(pmd, address) \
-	((pte_t *)kmap_local_page(pmd_page(*(pmd))) + pte_index((address)))
-#define pte_unmap(pte)	do {	\
-	kunmap_local((pte));	\
-	/* rcu_read_unlock() to be added later */	\
-} while (0)
+#if defined(CONFIG_HIGHPTE)
+#define pte_offset_map(dir, address)				\
+	((pte_t *)kmap_local_page(pmd_page(*(dir))) +		\
+	 pte_index((address)))
+#define pte_unmap(pte) kunmap_local((pte))
 #else
-static inline pte_t *__pte_map(pmd_t *pmd, unsigned long address)
-{
-	return pte_offset_kernel(pmd, address);
-}
-static inline void pte_unmap(pte_t *pte)
-{
-	/* rcu_read_unlock() to be added later */
-}
+#define pte_offset_map(dir, address)	pte_offset_kernel((dir), (address))
+#define pte_unmap(pte) ((void)(pte))	/* NOP */
 #endif
 
 /* Find an entry in the second-level page table.. */
diff --git a/mm/pgtable-generic.c b/mm/pgtable-generic.c
index 4d454953046f..e6c582e659c9 100644
--- a/mm/pgtable-generic.c
+++ b/mm/pgtable-generic.c
@@ -10,8 +10,6 @@
 #include <linux/pagemap.h>
 #include <linux/hugetlb.h>
 #include <linux/pgtable.h>
-#include <linux/swap.h>
-#include <linux/swapops.h>
 #include <linux/mm_inline.h>
 #include <asm/tlb.h>
 
@@ -231,57 +229,3 @@ pmd_t pmdp_collapse_flush(struct vm_area_struct *vma, unsigned long address,
 }
 #endif
 #endif /* CONFIG_TRANSPARENT_HUGEPAGE */
-
-pte_t *__pte_offset_map(pmd_t *pmd, unsigned long addr, pmd_t *pmdvalp)
-{
-	pmd_t pmdval;
-
-	/* rcu_read_lock() to be added later */
-	pmdval = pmdp_get_lockless(pmd);
-	if (pmdvalp)
-		*pmdvalp = pmdval;
-	if (unlikely(pmd_none(pmdval) || is_pmd_migration_entry(pmdval)))
-		goto nomap;
-	if (unlikely(pmd_trans_huge(pmdval) || pmd_devmap(pmdval)))
-		goto nomap;
-	if (unlikely(pmd_bad(pmdval))) {
-		pmd_clear_bad(pmd);
-		goto nomap;
-	}
-	return __pte_map(&pmdval, addr);
-nomap:
-	/* rcu_read_unlock() to be added later */
-	return NULL;
-}
-
-pte_t *pte_offset_map_nolock(struct mm_struct *mm, pmd_t *pmd,
-			     unsigned long addr, spinlock_t **ptlp)
-{
-	pmd_t pmdval;
-	pte_t *pte;
-
-	pte = __pte_offset_map(pmd, addr, &pmdval);
-	if (likely(pte))
-		*ptlp = pte_lockptr(mm, &pmdval);
-	return pte;
-}
-
-pte_t *__pte_offset_map_lock(struct mm_struct *mm, pmd_t *pmd,
-			     unsigned long addr, spinlock_t **ptlp)
-{
-	spinlock_t *ptl;
-	pmd_t pmdval;
-	pte_t *pte;
-again:
-	pte = __pte_offset_map(pmd, addr, &pmdval);
-	if (unlikely(!pte))
-		return pte;
-	ptl = pte_lockptr(mm, &pmdval);
-	spin_lock(ptl);
-	if (likely(pmd_same(pmdval, pmdp_get_lockless(pmd)))) {
-		*ptlp = ptl;
-		return pte;
-	}
-	pte_unmap_unlock(pte, ptl);
-	goto again;
-}
-- 
2.25.1