linux-kernel - [PATCH 4/6] mm: remove iterator use outside the loop

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Message-Id: <20220301075839.4156-5-xiam0nd.tong@gmail.com>
Date:   Tue,  1 Mar 2022 15:58:37 +0800
From:   Xiaomeng Tong <xiam0nd.tong@...il.com>
To:     torvalds@...ux-foundation.org
Cc:     arnd@...db.de, jakobkoschel@...il.com,
        linux-kernel@...r.kernel.org, gregkh@...uxfoundation.org,
        keescook@...omium.org, jannh@...gle.com,
        linux-kbuild@...r.kernel.org, linux-mm@...ck.org,
        netdev@...r.kernel.org, Xiaomeng Tong <xiam0nd.tong@...il.com>
Subject: [PATCH 4/6] mm: remove iterator use outside the loop

Demonstrations for:
 - list_for_each_entry_inside
 - list_for_each_entry_reverse_inside
 - list_for_each_entry_safe_inside
 - list_for_each_entry_from_inside
 - list_for_each_entry_continue_reverse_inside

Signed-off-by: Xiaomeng Tong <xiam0nd.tong@...il.com>
---
 mm/list_lru.c    | 10 ++++++----
 mm/slab_common.c |  7 ++-----
 mm/vmalloc.c     |  6 +++---
 3 files changed, 11 insertions(+), 12 deletions(-)

diff --git a/mm/list_lru.c b/mm/list_lru.c
index 0cd5e89ca..d8aab53a7 100644
--- a/mm/list_lru.c
+++ b/mm/list_lru.c
@@ -493,20 +493,22 @@ static void memcg_cancel_update_list_lru(struct list_lru *lru,
 int memcg_update_all_list_lrus(int new_size)
 {
 	int ret = 0;
-	struct list_lru *lru;
+	struct list_lru *ll = NULL;
 	int old_size = memcg_nr_cache_ids;
 
 	mutex_lock(&list_lrus_mutex);
-	list_for_each_entry(lru, &memcg_list_lrus, list) {
+	list_for_each_entry_inside(lru, struct list_lru, &memcg_list_lrus, list) {
 		ret = memcg_update_list_lru(lru, old_size, new_size);
-		if (ret)
+		if (ret) {
+			ll = lru;
 			goto fail;
+		}
 	}
 out:
 	mutex_unlock(&list_lrus_mutex);
 	return ret;
 fail:
-	list_for_each_entry_continue_reverse(lru, &memcg_list_lrus, list)
+	list_for_each_entry_continue_reverse_inside(lru, ll, &memcg_list_lrus, list)
 		memcg_cancel_update_list_lru(lru, old_size, new_size);
 	goto out;
 }
diff --git a/mm/slab_common.c b/mm/slab_common.c
index 23f2ab071..68a25d385 100644
--- a/mm/slab_common.c
+++ b/mm/slab_common.c
@@ -186,8 +186,6 @@ int slab_unmergeable(struct kmem_cache *s)
 struct kmem_cache *find_mergeable(unsigned int size, unsigned int align,
 		slab_flags_t flags, const char *name, void (*ctor)(void *))
 {
-	struct kmem_cache *s;
-
 	if (slab_nomerge)
 		return NULL;
 
@@ -202,7 +200,7 @@ struct kmem_cache *find_mergeable(unsigned int size, unsigned int align,
 	if (flags & SLAB_NEVER_MERGE)
 		return NULL;
 
-	list_for_each_entry_reverse(s, &slab_caches, list) {
+	list_for_each_entry_reverse_inside(s, struct kmem_cache, &slab_caches, list) {
 		if (slab_unmergeable(s))
 			continue;
 
@@ -419,7 +417,6 @@ EXPORT_SYMBOL(kmem_cache_create);
 static void slab_caches_to_rcu_destroy_workfn(struct work_struct *work)
 {
 	LIST_HEAD(to_destroy);
-	struct kmem_cache *s, *s2;
 
 	/*
 	 * On destruction, SLAB_TYPESAFE_BY_RCU kmem_caches are put on the
@@ -439,7 +436,7 @@ static void slab_caches_to_rcu_destroy_workfn(struct work_struct *work)
 
 	rcu_barrier();
 
-	list_for_each_entry_safe(s, s2, &to_destroy, list) {
+	list_for_each_entry_safe_inside(s, s2, struct kmem_cache, &to_destroy, list) {
 		debugfs_slab_release(s);
 		kfence_shutdown_cache(s);
 #ifdef SLAB_SUPPORTS_SYSFS
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 4165304d3..65a9f1db7 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -3417,14 +3417,14 @@ long vread(char *buf, char *addr, unsigned long count)
 	if ((unsigned long)addr + count <= va->va_start)
 		goto finished;
 
-	list_for_each_entry_from(va, &vmap_area_list, list) {
+	list_for_each_entry_from_inside(iter, va, &vmap_area_list, list) {
 		if (!count)
 			break;
 
-		if (!va->vm)
+		if (!iter->vm)
 			continue;
 
-		vm = va->vm;
+		vm = iter->vm;
 		vaddr = (char *) vm->addr;
 		if (addr >= vaddr + get_vm_area_size(vm))
 			continue;
-- 
2.17.1