From: Pengfei Li <lpf.vector@gmail.com>
To: akpm@linux-foundation.org
Cc: urezki@gmail.com, rpenyaev@suse.de, peterz@infradead.org,
guro@fb.com, rick.p.edgecombe@intel.com, rppt@linux.ibm.com,
aryabinin@virtuozzo.com, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, Pengfei Li <lpf.vector@gmail.com>
Subject: [PATCH] mm/vmalloc.c: Remove always-true conditional in vmap_init_free_space
Date: Tue, 9 Jul 2019 01:06:31 +0800 [thread overview]
Message-ID: <20190708170631.2130-1-lpf.vector@gmail.com> (raw)
When unsigned long variables are subtracted from one another,
the result is always non-negative.
The vmap_area_list is sorted by address.
So the following two conditions are always true.
1) if (busy->va_start - vmap_start > 0)
2) if (vmap_end - vmap_start > 0)
Just remove them.
Signed-off-by: Pengfei Li <lpf.vector@gmail.com>
---
mm/vmalloc.c | 32 +++++++++++++-------------------
1 file changed, 13 insertions(+), 19 deletions(-)
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index 0f76cca32a1c..c7bdbdc18472 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -1810,31 +1810,25 @@ static void vmap_init_free_space(void)
* |<--------------------------------->|
*/
list_for_each_entry(busy, &vmap_area_list, list) {
- if (busy->va_start - vmap_start > 0) {
- free = kmem_cache_zalloc(vmap_area_cachep, GFP_NOWAIT);
- if (!WARN_ON_ONCE(!free)) {
- free->va_start = vmap_start;
- free->va_end = busy->va_start;
-
- insert_vmap_area_augment(free, NULL,
- &free_vmap_area_root,
- &free_vmap_area_list);
- }
- }
-
- vmap_start = busy->va_end;
- }
-
- if (vmap_end - vmap_start > 0) {
free = kmem_cache_zalloc(vmap_area_cachep, GFP_NOWAIT);
if (!WARN_ON_ONCE(!free)) {
free->va_start = vmap_start;
- free->va_end = vmap_end;
+ free->va_end = busy->va_start;
insert_vmap_area_augment(free, NULL,
- &free_vmap_area_root,
- &free_vmap_area_list);
+ &free_vmap_area_root, &free_vmap_area_list);
}
+
+ vmap_start = busy->va_end;
+ }
+
+ free = kmem_cache_zalloc(vmap_area_cachep, GFP_NOWAIT);
+ if (!WARN_ON_ONCE(!free)) {
+ free->va_start = vmap_start;
+ free->va_end = vmap_end;
+
+ insert_vmap_area_augment(free, NULL,
+ &free_vmap_area_root, &free_vmap_area_list);
}
}
--
2.21.0
next reply other threads:[~2019-07-08 17:06 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-08 17:06 Pengfei Li [this message]
2019-07-08 17:35 ` Matthew Wilcox
2019-07-08 17:57 ` Pengfei Li
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