netdev - [PATCH 3/6] kernel: remove iterator use outside the loop

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Date:   Tue,  1 Mar 2022 15:58:36 +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 3/6] kernel: remove iterator use outside the loop

Demonstrations for:
 - list_for_each_entry_inside
 - list_for_each_entry_continue_inside
 - list_for_each_entry_safe_continue_inside

Signed-off-by: Xiaomeng Tong <xiam0nd.tong@...il.com>
---
 kernel/power/snapshot.c | 28 ++++++++++++++++------------
 kernel/signal.c         |  6 +++---
 2 files changed, 19 insertions(+), 15 deletions(-)

diff --git a/kernel/power/snapshot.c b/kernel/power/snapshot.c
index 330d49937..75958b5fa 100644
--- a/kernel/power/snapshot.c
+++ b/kernel/power/snapshot.c
@@ -625,16 +625,18 @@ static int create_mem_extents(struct list_head *list, gfp_t gfp_mask)
 
 	for_each_populated_zone(zone) {
 		unsigned long zone_start, zone_end;
-		struct mem_extent *ext, *cur, *aux;
+		struct mem_extent *me = NULL;
 
 		zone_start = zone->zone_start_pfn;
 		zone_end = zone_end_pfn(zone);
 
-		list_for_each_entry(ext, list, hook)
-			if (zone_start <= ext->end)
+		list_for_each_entry_inside(ext, struct mem_extent, list, hook)
+			if (zone_start <= ext->end) {
+				me = ext;
 				break;
+			}
 
-		if (&ext->hook == list || zone_end < ext->start) {
+		if (!me || zone_end < me->start) {
 			/* New extent is necessary */
 			struct mem_extent *new_ext;
 
@@ -645,23 +647,25 @@ static int create_mem_extents(struct list_head *list, gfp_t gfp_mask)
 			}
 			new_ext->start = zone_start;
 			new_ext->end = zone_end;
-			list_add_tail(&new_ext->hook, &ext->hook);
+			if (!me)
+				list_add_tail(&new_ext->hook, list);
+			else
+				list_add_tail(&new_ext->hook, &me->hook);
 			continue;
 		}
 
 		/* Merge this zone's range of PFNs with the existing one */
-		if (zone_start < ext->start)
-			ext->start = zone_start;
-		if (zone_end > ext->end)
-			ext->end = zone_end;
+		if (zone_start < me->start)
+			me->start = zone_start;
+		if (zone_end > me->end)
+			me->end = zone_end;
 
 		/* More merging may be possible */
-		cur = ext;
-		list_for_each_entry_safe_continue(cur, aux, list, hook) {
+		list_for_each_entry_safe_continue_inside(cur, aux, me, list, hook) {
 			if (zone_end < cur->start)
 				break;
 			if (zone_end < cur->end)
-				ext->end = cur->end;
+				me->end = cur->end;
 			list_del(&cur->hook);
 			kfree(cur);
 		}
diff --git a/kernel/signal.c b/kernel/signal.c
index 9b04631ac..da2c20de1 100644
--- a/kernel/signal.c
+++ b/kernel/signal.c
@@ -711,7 +711,7 @@ static int dequeue_synchronous_signal(kernel_siginfo_t *info)
 {
 	struct task_struct *tsk = current;
 	struct sigpending *pending = &tsk->pending;
-	struct sigqueue *q, *sync = NULL;
+	struct sigqueue *sync = NULL;
 
 	/*
 	 * Might a synchronous signal be in the queue?
@@ -722,7 +722,7 @@ static int dequeue_synchronous_signal(kernel_siginfo_t *info)
 	/*
 	 * Return the first synchronous signal in the queue.
 	 */
-	list_for_each_entry(q, &pending->list, list) {
+	list_for_each_entry_inside(q, struct sigqueue, &pending->list, list) {
 		/* Synchronous signals have a positive si_code */
 		if ((q->info.si_code > SI_USER) &&
 		    (sigmask(q->info.si_signo) & SYNCHRONOUS_MASK)) {
@@ -735,7 +735,7 @@ static int dequeue_synchronous_signal(kernel_siginfo_t *info)
 	/*
 	 * Check if there is another siginfo for the same signal.
 	 */
-	list_for_each_entry_continue(q, &pending->list, list) {
+	list_for_each_entry_continue_inside(q, sync, &pending->list, list) {
 		if (q->info.si_signo == sync->info.si_signo)
 			goto still_pending;
 	}
-- 
2.17.1