* [PATCH] mm/swap_slots.c: Remove unnecessary NULL pointer check
@ 2021-01-09 8:09 Miaohe Lin
2021-01-09 17:40 ` Matthew Wilcox
0 siblings, 1 reply; 3+ messages in thread
From: Miaohe Lin @ 2021-01-09 8:09 UTC (permalink / raw)
To: akpm; +Cc: linux-mm, linux-kernel, linmiaohe
The cache->slots and cache->slots_ret is already checked before we try to
drain it. And kvfree can handle the NULL pointer itself. So remove the
NULL pointer check here.
Signed-off-by: Miaohe Lin <linmiaohe@huawei.com>
---
mm/swap_slots.c | 7 +++----
1 file changed, 3 insertions(+), 4 deletions(-)
diff --git a/mm/swap_slots.c b/mm/swap_slots.c
index 0357fbe70645..4cf99ce033d0 100644
--- a/mm/swap_slots.c
+++ b/mm/swap_slots.c
@@ -178,7 +178,7 @@ static void drain_slots_cache_cpu(unsigned int cpu, unsigned int type,
swapcache_free_entries(cache->slots + cache->cur, cache->nr);
cache->cur = 0;
cache->nr = 0;
- if (free_slots && cache->slots) {
+ if (free_slots) {
kvfree(cache->slots);
cache->slots = NULL;
}
@@ -188,13 +188,12 @@ static void drain_slots_cache_cpu(unsigned int cpu, unsigned int type,
spin_lock_irq(&cache->free_lock);
swapcache_free_entries(cache->slots_ret, cache->n_ret);
cache->n_ret = 0;
- if (free_slots && cache->slots_ret) {
+ if (free_slots) {
slots = cache->slots_ret;
cache->slots_ret = NULL;
}
spin_unlock_irq(&cache->free_lock);
- if (slots)
- kvfree(slots);
+ kvfree(slots);
}
}
--
2.19.1
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] mm/swap_slots.c: Remove unnecessary NULL pointer check
2021-01-09 8:09 [PATCH] mm/swap_slots.c: Remove unnecessary NULL pointer check Miaohe Lin
@ 2021-01-09 17:40 ` Matthew Wilcox
2021-01-14 2:34 ` Miaohe Lin
0 siblings, 1 reply; 3+ messages in thread
From: Matthew Wilcox @ 2021-01-09 17:40 UTC (permalink / raw)
To: Miaohe Lin; +Cc: akpm, linux-mm, linux-kernel
On Sat, Jan 09, 2021 at 03:09:43AM -0500, Miaohe Lin wrote:
> The cache->slots and cache->slots_ret is already checked before we try to
> drain it. And kvfree can handle the NULL pointer itself. So remove the
> NULL pointer check here.
> @@ -178,7 +178,7 @@ static void drain_slots_cache_cpu(unsigned int cpu, unsigned int type,
> swapcache_free_entries(cache->slots + cache->cur, cache->nr);
> cache->cur = 0;
> cache->nr = 0;
> - if (free_slots && cache->slots) {
> + if (free_slots) {
Prove that swapcache_free_entries() doesn't change cache->slots.
> @@ -188,13 +188,12 @@ static void drain_slots_cache_cpu(unsigned int cpu, unsigned int type,
> spin_lock_irq(&cache->free_lock);
> swapcache_free_entries(cache->slots_ret, cache->n_ret);
> cache->n_ret = 0;
> - if (free_slots && cache->slots_ret) {
> + if (free_slots) {
... or ->slots_ret
> - if (slots)
> - kvfree(slots);
> + kvfree(slots);
This is fine.
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] mm/swap_slots.c: Remove unnecessary NULL pointer check
2021-01-09 17:40 ` Matthew Wilcox
@ 2021-01-14 2:34 ` Miaohe Lin
0 siblings, 0 replies; 3+ messages in thread
From: Miaohe Lin @ 2021-01-14 2:34 UTC (permalink / raw)
To: Matthew Wilcox; +Cc: akpm, linux-mm, linux-kernel
Hi:
On 2021/1/10 1:40, Matthew Wilcox wrote:
> On Sat, Jan 09, 2021 at 03:09:43AM -0500, Miaohe Lin wrote:
>> The cache->slots and cache->slots_ret is already checked before we try to
>> drain it. And kvfree can handle the NULL pointer itself. So remove the
>> NULL pointer check here.
>
>> @@ -178,7 +178,7 @@ static void drain_slots_cache_cpu(unsigned int cpu, unsigned int type,
>> swapcache_free_entries(cache->slots + cache->cur, cache->nr);
>> cache->cur = 0;
>> cache->nr = 0;
>> - if (free_slots && cache->slots) {
>> + if (free_slots) {
>
> Prove that swapcache_free_entries() doesn't change cache->slots.
>
Yeh... I see. I thought swap_slots_cache_mutex could totally guard against this.
>> @@ -188,13 +188,12 @@ static void drain_slots_cache_cpu(unsigned int cpu, unsigned int type,
>> spin_lock_irq(&cache->free_lock);
>> swapcache_free_entries(cache->slots_ret, cache->n_ret);
>> cache->n_ret = 0;
>> - if (free_slots && cache->slots_ret) {
>> + if (free_slots) {
>
> ... or ->slots_ret
>
>> - if (slots)
>> - kvfree(slots);
>> + kvfree(slots);
>
> This is fine.
> .
>
Many thanks for your review and reply!
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2021-01-14 2:35 UTC | newest]
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2021-01-09 8:09 [PATCH] mm/swap_slots.c: Remove unnecessary NULL pointer check Miaohe Lin
2021-01-09 17:40 ` Matthew Wilcox
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