Subject: [RFC PATCH 5/5] mm: Remove the page size change check in tlb_remove_page

From: "Aneesh Kumar K.V" <[email-masked]>
Date: Tue, 11 Oct 2016 23:01:21 +0530

Now that we check for page size change early in the loop, we can
partially revert e9d55e157034a9efd99405c99c1565d64619d82b
("mm: change the interface for __tlb_remove_page").

This simplies the code much, by removing the need to track the last
address with which we adjusted the range. We also go back to the older
way of filling the mmu_gather array, ie, we add an entry and then
check whether the gather batch is full.

Signed-off-by: Aneesh Kumar K.V <[email-masked]>
---
 arch/arm/include/asm/tlb.h  | 13 +++----------
 arch/ia64/include/asm/tlb.h | 16 ++++------------
 arch/s390/include/asm/tlb.h |  6 ------
 arch/sh/include/asm/tlb.h   |  6 ------
 arch/um/include/asm/tlb.h   |  6 ------
 include/asm-generic/tlb.h   | 28 ++--------------------------
 mm/memory.c                 | 21 ++++++---------------
 7 files changed, 15 insertions(+), 81 deletions(-)

diff --git a/arch/arm/include/asm/tlb.h b/arch/arm/include/asm/tlb.h
index a9d6de4746ea..3f2eb76243e3 100644
--- a/arch/arm/include/asm/tlb.h
+++ b/arch/arm/include/asm/tlb.h
@@ -213,18 +213,17 @@ tlb_end_vma(struct mmu_gather *tlb, struct vm_area_struct *vma)
 
 static inline bool __tlb_remove_page(struct mmu_gather *tlb, struct page *page)
 {
+	tlb->pages[tlb->nr++] = page;
+	VM_WARN_ON(tlb->nr > tlb->max);
 	if (tlb->nr == tlb->max)
 		return true;
-	tlb->pages[tlb->nr++] = page;
 	return false;
 }
 
 static inline void tlb_remove_page(struct mmu_gather *tlb, struct page *page)
 {
-	if (__tlb_remove_page(tlb, page)) {
+	if (__tlb_remove_page(tlb, page))
 		tlb_flush_mmu(tlb);
-		__tlb_remove_page(tlb, page);
-	}
 }
 
 static inline bool __tlb_remove_page_size(struct mmu_gather *tlb,
@@ -233,12 +232,6 @@ static inline bool __tlb_remove_page_size(struct mmu_gather *tlb,
 	return __tlb_remove_page(tlb, page);
 }
 
-static inline bool __tlb_remove_pte_page(struct mmu_gather *tlb,
-					 struct page *page)
-{
-	return __tlb_remove_page(tlb, page);
-}
-
 static inline void tlb_remove_page_size(struct mmu_gather *tlb,
 					struct page *page, int page_size)
 {
diff --git a/arch/ia64/include/asm/tlb.h b/arch/ia64/include/asm/tlb.h
index bfe6295aa746..fced197b9626 100644
--- a/arch/ia64/include/asm/tlb.h
+++ b/arch/ia64/include/asm/tlb.h
@@ -207,15 +207,15 @@ tlb_finish_mmu(struct mmu_gather *tlb, unsigned long start, unsigned long end)
  */
 static inline bool __tlb_remove_page(struct mmu_gather *tlb, struct page *page)
 {
-	if (tlb->nr == tlb->max)
-		return true;
-
 	tlb->need_flush = 1;
 
 	if (!tlb->nr && tlb->pages == tlb->local)
 		__tlb_alloc_page(tlb);
 
 	tlb->pages[tlb->nr++] = page;
+	VM_WARN_ON(tlb->nr > tlb->max);
+	if (tlb->nr == tlb->max)
+		return true;
 	return false;
 }
 
@@ -236,10 +236,8 @@ static inline void tlb_flush_mmu(struct mmu_gather *tlb)
 
 static inline void tlb_remove_page(struct mmu_gather *tlb, struct page *page)
 {
-	if (__tlb_remove_page(tlb, page)) {
+	if (__tlb_remove_page(tlb, page))
 		tlb_flush_mmu(tlb);
-		__tlb_remove_page(tlb, page);
-	}
 }
 
 static inline bool __tlb_remove_page_size(struct mmu_gather *tlb,
@@ -248,12 +246,6 @@ static inline bool __tlb_remove_page_size(struct mmu_gather *tlb,
 	return __tlb_remove_page(tlb, page);
 }
 
-static inline bool __tlb_remove_pte_page(struct mmu_gather *tlb,
-					 struct page *page)
-{
-	return __tlb_remove_page(tlb, page);
-}
-
 static inline void tlb_remove_page_size(struct mmu_gather *tlb,
 					struct page *page, int page_size)
 {
diff --git a/arch/s390/include/asm/tlb.h b/arch/s390/include/asm/tlb.h
index 28b159c87c38..853b2a3d8dee 100644
--- a/arch/s390/include/asm/tlb.h
+++ b/arch/s390/include/asm/tlb.h
@@ -104,12 +104,6 @@ static inline bool __tlb_remove_page_size(struct mmu_gather *tlb,
 	return __tlb_remove_page(tlb, page);
 }
 
-static inline bool __tlb_remove_pte_page(struct mmu_gather *tlb,
-					 struct page *page)
-{
-	return __tlb_remove_page(tlb, page);
-}
-
 static inline void tlb_remove_page_size(struct mmu_gather *tlb,
 					struct page *page, int page_size)
 {
diff --git a/arch/sh/include/asm/tlb.h b/arch/sh/include/asm/tlb.h
index 0f988b3e484b..46e0d635e36f 100644
--- a/arch/sh/include/asm/tlb.h
+++ b/arch/sh/include/asm/tlb.h
@@ -118,12 +118,6 @@ static inline bool __tlb_remove_page_size(struct mmu_gather *tlb,
 	return __tlb_remove_page(tlb, page);
 }
 
-static inline bool __tlb_remove_pte_page(struct mmu_gather *tlb,
-					 struct page *page)
-{
-	return __tlb_remove_page(tlb, page);
-}
-
 static inline void tlb_remove_page_size(struct mmu_gather *tlb,
 					struct page *page, int page_size)
 {
diff --git a/arch/um/include/asm/tlb.h b/arch/um/include/asm/tlb.h
index 8258dd4bb13c..600a2e9bfee2 100644
--- a/arch/um/include/asm/tlb.h
+++ b/arch/um/include/asm/tlb.h
@@ -116,12 +116,6 @@ static inline bool __tlb_remove_page_size(struct mmu_gather *tlb,
 	return __tlb_remove_page(tlb, page);
 }
 
-static inline bool __tlb_remove_pte_page(struct mmu_gather *tlb,
-					 struct page *page)
-{
-	return __tlb_remove_page(tlb, page);
-}
-
 static inline void tlb_remove_page_size(struct mmu_gather *tlb,
 					struct page *page, int page_size)
 {
diff --git a/include/asm-generic/tlb.h b/include/asm-generic/tlb.h
index 256c9de71fdb..7eed8cf3130a 100644
--- a/include/asm-generic/tlb.h
+++ b/include/asm-generic/tlb.h
@@ -107,11 +107,6 @@ struct mmu_gather {
 	struct mmu_gather_batch	local;
 	struct page		*__pages[MMU_GATHER_BUNDLE];
 	unsigned int		batch_count;
-	/*
-	 * __tlb_adjust_range  will track the new addr here,
-	 * that that we can adjust the range after the flush
-	 */
-	unsigned long addr;
 	int page_size;
 };
 
@@ -130,12 +125,6 @@ static inline void __tlb_adjust_range(struct mmu_gather *tlb,
 {
 	tlb->start = min(tlb->start, address);
 	tlb->end = max(tlb->end, address + range_size);
-	/*
-	 * Track the last address with which we adjusted the range. This
-	 * will be used later to adjust again after a mmu_flush due to
-	 * failed __tlb_remove_page
-	 */
-	tlb->addr = address;
 }
 
 static inline void __tlb_reset_range(struct mmu_gather *tlb)
@@ -151,15 +140,11 @@ static inline void __tlb_reset_range(struct mmu_gather *tlb)
 static inline void tlb_remove_page_size(struct mmu_gather *tlb,
 					struct page *page, int page_size)
 {
-	if (__tlb_remove_page_size(tlb, page, page_size)) {
+	if (__tlb_remove_page_size(tlb, page, page_size))
 		tlb_flush_mmu(tlb);
-		tlb->page_size = page_size;
-		__tlb_adjust_range(tlb, tlb->addr, page_size);
-		__tlb_remove_page_size(tlb, page, page_size);
-	}
 }
 
-static bool __tlb_remove_page(struct mmu_gather *tlb, struct page *page)
+static inline bool __tlb_remove_page(struct mmu_gather *tlb, struct page *page)
 {
 	return __tlb_remove_page_size(tlb, page, PAGE_SIZE);
 }
@@ -173,15 +158,6 @@ static inline void tlb_remove_page(struct mmu_gather *tlb, struct page *page)
 	return tlb_remove_page_size(tlb, page, PAGE_SIZE);
 }
 
-static inline bool __tlb_remove_pte_page(struct mmu_gather *tlb, struct page *page)
-{
-	/* active->nr should be zero when we call this */
-	VM_BUG_ON_PAGE(tlb->active->nr, page);
-	tlb->page_size = PAGE_SIZE;
-	__tlb_adjust_range(tlb, tlb->addr, PAGE_SIZE);
-	return __tlb_remove_page(tlb, page);
-}
-
 #ifndef tlb_remove_check_page_size_change
 #define tlb_remove_check_page_size_change tlb_remove_check_page_size_change
 static inline void tlb_remove_check_page_size_change(struct mmu_gather *tlb,
diff --git a/mm/memory.c b/mm/memory.c
index 0ab75fd2514e..26d1ba8c87e6 100644
--- a/mm/memory.c
+++ b/mm/memory.c
@@ -300,15 +300,14 @@ bool __tlb_remove_page_size(struct mmu_gather *tlb, struct page *page, int page_
 	struct mmu_gather_batch *batch;
 
 	VM_BUG_ON(!tlb->end);
-
-	if (!tlb->page_size)
-		tlb->page_size = page_size;
-	else {
-		if (page_size != tlb->page_size)
-			return true;
-	}
+	VM_WARN_ON(tlb->page_size != page_size);
 
 	batch = tlb->active;
+	/*
+	 * Add the page and check if we are full. If so
+	 * force a flush.
+	 */
+	batch->pages[batch->nr++] = page;
 	if (batch->nr == batch->max) {
 		if (!tlb_next_batch(tlb))
 			return true;
@@ -316,7 +315,6 @@ bool __tlb_remove_page_size(struct mmu_gather *tlb, struct page *page, int page_
 	}
 	VM_BUG_ON_PAGE(batch->nr > batch->max, page);
 
-	batch->pages[batch->nr++] = page;
 	return false;
 }
 
@@ -1118,7 +1116,6 @@ static unsigned long zap_pte_range(struct mmu_gather *tlb,
 	pte_t *start_pte;
 	pte_t *pte;
 	swp_entry_t entry;
-	struct page *pending_page = NULL;
 
 	tlb_remove_check_page_size_change(tlb, PAGE_SIZE);
 again:
@@ -1173,7 +1170,6 @@ again:
 				print_bad_pte(vma, addr, ptent, page);
 			if (unlikely(__tlb_remove_page(tlb, page))) {
 				force_flush = 1;
-				pending_page = page;
 				addr += PAGE_SIZE;
 				break;
 			}
@@ -1214,11 +1210,6 @@ again:
 	if (force_flush) {
 		force_flush = 0;
 		tlb_flush_mmu_free(tlb);
-		if (pending_page) {
-			/* remove the page with new size */
-			__tlb_remove_pte_page(tlb, pending_page);
-			pending_page = NULL;
-		}
 		if (addr != end)
 			goto again;
 	}
-- 
2.10.1