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From:   Qi Zheng <zhengqi.arch@bytedance.com>
To:     akpm@linux-foundation.org, willy@infradead.org, vbabka@suse.cz,
        hannes@cmpxchg.org, minchan@kernel.org, rppt@kernel.org
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Qi Zheng <zhengqi.arch@bytedance.com>
Subject: [PATCH 7/7] ksm: convert to use common struct mm_slot
Date:   Mon, 29 Aug 2022 22:30:55 +0800
Message-Id: <20220829143055.41201-8-zhengqi.arch@bytedance.com>
In-Reply-To: <20220829143055.41201-1-zhengqi.arch@bytedance.com>
References: <20220829143055.41201-1-zhengqi.arch@bytedance.com>
MIME-Version: 1.0
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Convert to use common struct mm_slot, no functional change.

Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
---
 mm/ksm.c | 132 +++++++++++++++++++++++--------------------------------
 1 file changed, 56 insertions(+), 76 deletions(-)

diff --git a/mm/ksm.c b/mm/ksm.c
index 667efca75b0d..051a09d24d54 100644
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -42,6 +42,7 @@
 
 #include <asm/tlbflush.h>
 #include "internal.h"
+#include "mm_slot.h"
 
 #ifdef CONFIG_NUMA
 #define NUMA(x)		(x)
@@ -113,16 +114,12 @@
 
 /**
  * struct ksm_mm_slot - ksm information per mm that is being scanned
- * @hash: link to the mm_slots hash list
- * @mm_node: link into the mm_slots list, rooted in ksm_mm_head
+ * @slot: hash lookup from mm to mm_slot
  * @rmap_list: head for this mm_slot's singly-linked list of rmap_items
- * @mm: the mm that this information is valid for
  */
 struct ksm_mm_slot {
-	struct hlist_node hash;
-	struct list_head mm_node;
+	struct mm_slot slot;
 	struct ksm_rmap_item *rmap_list;
-	struct mm_struct *mm;
 };
 
 /**
@@ -231,7 +228,7 @@ static LIST_HEAD(migrate_nodes);
 static DEFINE_HASHTABLE(mm_slots_hash, MM_SLOTS_HASH_BITS);
 
 static struct ksm_mm_slot ksm_mm_head = {
-	.mm_node = LIST_HEAD_INIT(ksm_mm_head.mm_node),
+	.slot.mm_node = LIST_HEAD_INIT(ksm_mm_head.slot.mm_node),
 };
 static struct ksm_scan ksm_scan = {
 	.mm_slot = &ksm_mm_head,
@@ -408,36 +405,6 @@ static inline void free_stable_node(struct ksm_stable_node *stable_node)
 	kmem_cache_free(stable_node_cache, stable_node);
 }
 
-static inline struct ksm_mm_slot *alloc_mm_slot(void)
-{
-	if (!mm_slot_cache)	/* initialization failed */
-		return NULL;
-	return kmem_cache_zalloc(mm_slot_cache, GFP_KERNEL);
-}
-
-static inline void free_mm_slot(struct ksm_mm_slot *mm_slot)
-{
-	kmem_cache_free(mm_slot_cache, mm_slot);
-}
-
-static struct ksm_mm_slot *get_mm_slot(struct mm_struct *mm)
-{
-	struct ksm_mm_slot *slot;
-
-	hash_for_each_possible(mm_slots_hash, slot, hash, (unsigned long)mm)
-		if (slot->mm == mm)
-			return slot;
-
-	return NULL;
-}
-
-static void insert_to_mm_slots_hash(struct mm_struct *mm,
-				    struct ksm_mm_slot *mm_slot)
-{
-	mm_slot->mm = mm;
-	hash_add(mm_slots_hash, &mm_slot->hash, (unsigned long)mm);
-}
-
 /*
  * ksmd, and unmerge_and_remove_all_rmap_items(), must not touch an mm's
  * page tables after it has passed through ksm_exit() - which, if necessary,
@@ -975,20 +942,22 @@ static int remove_all_stable_nodes(void)
 static int unmerge_and_remove_all_rmap_items(void)
 {
 	struct ksm_mm_slot *mm_slot;
+	struct mm_slot *slot;
 	struct mm_struct *mm;
 	struct vm_area_struct *vma;
 	int err = 0;
 
 	spin_lock(&ksm_mmlist_lock);
-	ksm_scan.mm_slot = list_entry(ksm_mm_head.mm_node.next,
-						struct ksm_mm_slot, mm_node);
+	slot = list_entry(ksm_mm_head.slot.mm_node.next,
+			  struct mm_slot, mm_node);
+	ksm_scan.mm_slot = mm_slot_entry(slot, struct ksm_mm_slot, slot);
 	spin_unlock(&ksm_mmlist_lock);
 
 	for (mm_slot = ksm_scan.mm_slot; mm_slot != &ksm_mm_head;
 	     mm_slot = ksm_scan.mm_slot) {
-		VMA_ITERATOR(vmi, mm_slot->mm, 0);
+		VMA_ITERATOR(vmi, mm_slot->slot.mm, 0);
 
-		mm = mm_slot->mm;
+		mm = mm_slot->slot.mm;
 		mmap_read_lock(mm);
 		for_each_vma(vmi, vma) {
 			if (ksm_test_exit(mm))
@@ -1005,14 +974,15 @@ static int unmerge_and_remove_all_rmap_items(void)
 		mmap_read_unlock(mm);
 
 		spin_lock(&ksm_mmlist_lock);
-		ksm_scan.mm_slot = list_entry(mm_slot->mm_node.next,
-						struct ksm_mm_slot, mm_node);
+		slot = list_entry(mm_slot->slot.mm_node.next,
+				  struct mm_slot, mm_node);
+		ksm_scan.mm_slot = mm_slot_entry(slot, struct ksm_mm_slot, slot);
 		if (ksm_test_exit(mm)) {
-			hash_del(&mm_slot->hash);
-			list_del(&mm_slot->mm_node);
+			hash_del(&mm_slot->slot.hash);
+			list_del(&mm_slot->slot.mm_node);
 			spin_unlock(&ksm_mmlist_lock);
 
-			free_mm_slot(mm_slot);
+			free_mm_slot(mm_slot_cache, mm_slot);
 			clear_bit(MMF_VM_MERGEABLE, &mm->flags);
 			mmdrop(mm);
 		} else
@@ -2233,7 +2203,7 @@ static struct ksm_rmap_item *get_next_rmap_item(struct ksm_mm_slot *mm_slot,
 	rmap_item = alloc_rmap_item();
 	if (rmap_item) {
 		/* It has already been zeroed */
-		rmap_item->mm = mm_slot->mm;
+		rmap_item->mm = mm_slot->slot.mm;
 		rmap_item->address = addr;
 		rmap_item->rmap_list = *rmap_list;
 		*rmap_list = rmap_item;
@@ -2244,17 +2214,18 @@ static struct ksm_rmap_item *get_next_rmap_item(struct ksm_mm_slot *mm_slot,
 static struct ksm_rmap_item *scan_get_next_rmap_item(struct page **page)
 {
 	struct mm_struct *mm;
-	struct ksm_mm_slot *slot;
+	struct ksm_mm_slot *mm_slot;
+	struct mm_slot *slot;
 	struct vm_area_struct *vma;
 	struct ksm_rmap_item *rmap_item;
 	struct vma_iterator vmi;
 	int nid;
 
-	if (list_empty(&ksm_mm_head.mm_node))
+	if (list_empty(&ksm_mm_head.slot.mm_node))
 		return NULL;
 
-	slot = ksm_scan.mm_slot;
-	if (slot == &ksm_mm_head) {
+	mm_slot = ksm_scan.mm_slot;
+	if (mm_slot == &ksm_mm_head) {
 		/*
 		 * A number of pages can hang around indefinitely on per-cpu
 		 * pagevecs, raised page count preventing write_protect_page
@@ -2291,20 +2262,23 @@ static struct ksm_rmap_item *scan_get_next_rmap_item(struct page **page)
 			root_unstable_tree[nid] = RB_ROOT;
 
 		spin_lock(&ksm_mmlist_lock);
-		slot = list_entry(slot->mm_node.next, struct ksm_mm_slot, mm_node);
-		ksm_scan.mm_slot = slot;
+		slot = list_entry(mm_slot->slot.mm_node.next,
+				  struct mm_slot, mm_node);
+		mm_slot = mm_slot_entry(slot, struct ksm_mm_slot, slot);
+		ksm_scan.mm_slot = mm_slot;
 		spin_unlock(&ksm_mmlist_lock);
 		/*
 		 * Although we tested list_empty() above, a racing __ksm_exit
 		 * of the last mm on the list may have removed it since then.
 		 */
-		if (slot == &ksm_mm_head)
+		if (mm_slot == &ksm_mm_head)
 			return NULL;
 next_mm:
 		ksm_scan.address = 0;
-		ksm_scan.rmap_list = &slot->rmap_list;
+		ksm_scan.rmap_list = &mm_slot->rmap_list;
 	}
 
+	slot = &mm_slot->slot;
 	mm = slot->mm;
 	vma_iter_init(&vmi, mm, ksm_scan.address);
 
@@ -2334,7 +2308,7 @@ static struct ksm_rmap_item *scan_get_next_rmap_item(struct page **page)
 			if (PageAnon(*page)) {
 				flush_anon_page(vma, *page, ksm_scan.address);
 				flush_dcache_page(*page);
-				rmap_item = get_next_rmap_item(slot,
+				rmap_item = get_next_rmap_item(mm_slot,
 					ksm_scan.rmap_list, ksm_scan.address);
 				if (rmap_item) {
 					ksm_scan.rmap_list =
@@ -2355,7 +2329,7 @@ static struct ksm_rmap_item *scan_get_next_rmap_item(struct page **page)
 	if (ksm_test_exit(mm)) {
 no_vmas:
 		ksm_scan.address = 0;
-		ksm_scan.rmap_list = &slot->rmap_list;
+		ksm_scan.rmap_list = &mm_slot->rmap_list;
 	}
 	/*
 	 * Nuke all the rmap_items that are above this current rmap:
@@ -2364,8 +2338,9 @@ static struct ksm_rmap_item *scan_get_next_rmap_item(struct page **page)
 	remove_trailing_rmap_items(ksm_scan.rmap_list);
 
 	spin_lock(&ksm_mmlist_lock);
-	ksm_scan.mm_slot = list_entry(slot->mm_node.next,
-						struct ksm_mm_slot, mm_node);
+	slot = list_entry(mm_slot->slot.mm_node.next,
+			  struct mm_slot, mm_node);
+	ksm_scan.mm_slot = mm_slot_entry(slot, struct ksm_mm_slot, slot);
 	if (ksm_scan.address == 0) {
 		/*
 		 * We've completed a full scan of all vmas, holding mmap_lock
@@ -2376,11 +2351,11 @@ static struct ksm_rmap_item *scan_get_next_rmap_item(struct page **page)
 		 * or when all VM_MERGEABLE areas have been unmapped (and
 		 * mmap_lock then protects against race with MADV_MERGEABLE).
 		 */
-		hash_del(&slot->hash);
-		list_del(&slot->mm_node);
+		hash_del(&mm_slot->slot.hash);
+		list_del(&mm_slot->slot.mm_node);
 		spin_unlock(&ksm_mmlist_lock);
 
-		free_mm_slot(slot);
+		free_mm_slot(mm_slot_cache, mm_slot);
 		clear_bit(MMF_VM_MERGEABLE, &mm->flags);
 		mmap_read_unlock(mm);
 		mmdrop(mm);
@@ -2397,8 +2372,8 @@ static struct ksm_rmap_item *scan_get_next_rmap_item(struct page **page)
 	}
 
 	/* Repeat until we've completed scanning the whole list */
-	slot = ksm_scan.mm_slot;
-	if (slot != &ksm_mm_head)
+	mm_slot = ksm_scan.mm_slot;
+	if (mm_slot != &ksm_mm_head)
 		goto next_mm;
 
 	ksm_scan.seqnr++;
@@ -2426,7 +2401,7 @@ static void ksm_do_scan(unsigned int scan_npages)
 
 static int ksmd_should_run(void)
 {
-	return (ksm_run & KSM_RUN_MERGE) && !list_empty(&ksm_mm_head.mm_node);
+	return (ksm_run & KSM_RUN_MERGE) && !list_empty(&ksm_mm_head.slot.mm_node);
 }
 
 static int ksm_scan_thread(void *nothing)
@@ -2516,17 +2491,20 @@ EXPORT_SYMBOL_GPL(ksm_madvise);
 int __ksm_enter(struct mm_struct *mm)
 {
 	struct ksm_mm_slot *mm_slot;
+	struct mm_slot *slot;
 	int needs_wakeup;
 
-	mm_slot = alloc_mm_slot();
+	mm_slot = alloc_mm_slot(mm_slot_cache);
 	if (!mm_slot)
 		return -ENOMEM;
 
+	slot = &mm_slot->slot;
+
 	/* Check ksm_run too?  Would need tighter locking */
-	needs_wakeup = list_empty(&ksm_mm_head.mm_node);
+	needs_wakeup = list_empty(&ksm_mm_head.slot.mm_node);
 
 	spin_lock(&ksm_mmlist_lock);
-	insert_to_mm_slots_hash(mm, mm_slot);
+	insert_to_mm_slots_hash(mm_slots_hash, mm, slot);
 	/*
 	 * When KSM_RUN_MERGE (or KSM_RUN_STOP),
 	 * insert just behind the scanning cursor, to let the area settle
@@ -2538,9 +2516,9 @@ int __ksm_enter(struct mm_struct *mm)
 	 * missed: then we might as well insert at the end of the list.
 	 */
 	if (ksm_run & KSM_RUN_UNMERGE)
-		list_add_tail(&mm_slot->mm_node, &ksm_mm_head.mm_node);
+		list_add_tail(&slot->mm_node, &ksm_mm_head.slot.mm_node);
 	else
-		list_add_tail(&mm_slot->mm_node, &ksm_scan.mm_slot->mm_node);
+		list_add_tail(&slot->mm_node, &ksm_scan.mm_slot->slot.mm_node);
 	spin_unlock(&ksm_mmlist_lock);
 
 	set_bit(MMF_VM_MERGEABLE, &mm->flags);
@@ -2555,6 +2533,7 @@ int __ksm_enter(struct mm_struct *mm)
 void __ksm_exit(struct mm_struct *mm)
 {
 	struct ksm_mm_slot *mm_slot;
+	struct mm_slot *slot;
 	int easy_to_free = 0;
 
 	/*
@@ -2567,21 +2546,22 @@ void __ksm_exit(struct mm_struct *mm)
 	 */
 
 	spin_lock(&ksm_mmlist_lock);
-	mm_slot = get_mm_slot(mm);
+	slot = get_mm_slot(mm_slots_hash, mm);
+	mm_slot = mm_slot_entry(slot, struct ksm_mm_slot, slot);
 	if (mm_slot && ksm_scan.mm_slot != mm_slot) {
 		if (!mm_slot->rmap_list) {
-			hash_del(&mm_slot->hash);
-			list_del(&mm_slot->mm_node);
+			hash_del(&slot->hash);
+			list_del(&slot->mm_node);
 			easy_to_free = 1;
 		} else {
-			list_move(&mm_slot->mm_node,
-				  &ksm_scan.mm_slot->mm_node);
+			list_move(&slot->mm_node,
+				  &ksm_scan.mm_slot->slot.mm_node);
 		}
 	}
 	spin_unlock(&ksm_mmlist_lock);
 
 	if (easy_to_free) {
-		free_mm_slot(mm_slot);
+		free_mm_slot(mm_slot_cache, mm_slot);
 		clear_bit(MMF_VM_MERGEABLE, &mm->flags);
 		mmdrop(mm);
 	} else if (mm_slot) {
-- 
2.20.1