linux-kernel - [RFC PATCH v2 1/1] mm/vmalloc.c: simplify /proc/vmallocinfo implementation

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Date:   Tue, 27 Sep 2016 22:08:19 +0800
From:   zijun_hu <zijun_hu@...o.com>
To:     Andrew Morton <akpm@...ux-foundation.org>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org, zijun_hu@....com,
        tj@...nel.org, mingo@...nel.org, rientjes@...gle.com,
        iamjoonsoo.kim@....com, mgorman@...hsingularity.net,
        npiggin@...il.com, mhocko@...nel.org
Subject: [RFC PATCH v2 1/1] mm/vmalloc.c: simplify /proc/vmallocinfo
 implementation

From: zijun_hu <zijun_hu@....com>

simplify /proc/vmallocinfo implementation via existing seq_file
helpers for list_head

Signed-off-by: zijun_hu <zijun_hu@....com>
---
 Changes in v2:
  - more detailed commit message is provided
  - the redundant type cast for list_entry() is removed as advised
    by rientjes@...gle.com

 mm/vmalloc.c | 27 +++++----------------------
 1 file changed, 5 insertions(+), 22 deletions(-)

diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index cc6ecd60cc0e..8b80931654b7 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -2576,32 +2576,13 @@ void pcpu_free_vm_areas(struct vm_struct **vms, int nr_vms)
 static void *s_start(struct seq_file *m, loff_t *pos)
 	__acquires(&vmap_area_lock)
 {
-	loff_t n = *pos;
-	struct vmap_area *va;
-
 	spin_lock(&vmap_area_lock);
-	va = list_first_entry(&vmap_area_list, typeof(*va), list);
-	while (n > 0 && &va->list != &vmap_area_list) {
-		n--;
-		va = list_next_entry(va, list);
-	}
-	if (!n && &va->list != &vmap_area_list)
-		return va;
-
-	return NULL;
-
+	return seq_list_start(&vmap_area_list, *pos);
 }
 
 static void *s_next(struct seq_file *m, void *p, loff_t *pos)
 {
-	struct vmap_area *va = p, *next;
-
-	++*pos;
-	next = list_next_entry(va, list);
-	if (&next->list != &vmap_area_list)
-		return next;
-
-	return NULL;
+	return seq_list_next(p, &vmap_area_list, pos);
 }
 
 static void s_stop(struct seq_file *m, void *p)
@@ -2636,9 +2617,11 @@ static void show_numa_info(struct seq_file *m, struct vm_struct *v)
 
 static int s_show(struct seq_file *m, void *p)
 {
-	struct vmap_area *va = p;
+	struct vmap_area *va;
 	struct vm_struct *v;
 
+	va = list_entry(p, struct vmap_area, list);
+
 	/*
 	 * s_show can encounter race with remove_vm_area, !VM_VM_AREA on
 	 * behalf of vmap area is being tear down or vm_map_ram allocation.
-- 
1.9.1