[Devel] [PATCH rh7 2/2] net/sock: teach sock_kmalloc() to call kvmalloc() when possible

[Konstantin Khorenko]

On 03/21/2018 03:59 PM, Andrey Ryabinin wrote:
>
>
> On 03/21/2018 02:11 PM, Konstantin Khorenko wrote:
>> sock_setsockopt()
>>  sk_attach_filter()
>>   sock_kmalloc()
>>
>> Memory size to be allocated depends on the number of rules provided by
>> userspace, but not more than net.core.optmem_max (20480 by default),
>> which still allows to allocate 3rd order pages via kmalloc() =>
>> it's better to substitute it with kvmalloc().
>>
>> But sock_kmalloc() can be called with GFP_ATOMIC from some places,
>> so we cannot unconditionally call kvmalloc() instead of kmalloc().
>>
>> Hopefully sk_attach_filter() calls sock_kmalloc() with GFP_KERNEL,
>> so kvmalloc() can be used there.
>>
>> => use kvmalloc_check() which calls kvmalloc() if it's allowed
>> by provided flags.
>>
>
> seems fishy. What we are going to do when we GFP_ATOMIC will ask for 3 order?

In this particular case (from sk_attach_filter()) sock_kmalloc() is called with GFP_KERNEL,
so we cover the problem case we've got.

When we face high-order kmalloc with GFP_ATOMIC, well, we'll find a way.


>> https://jira.sw.ru/browse/PSBM-82593
>>
>> Signed-off-by: Konstantin Khorenko <khorenko at virtuozzo.com>
>> ---
>>  net/core/sock.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/net/core/sock.c b/net/core/sock.c
>> index b4abbbf35797..5d2016807042 100644
>> --- a/net/core/sock.c
>> +++ b/net/core/sock.c
>> @@ -1707,7 +1707,7 @@ void *sock_kmalloc(struct sock *sk, int size, gfp_t priority)
>>  		 * might sleep.
>>  		 */
>>  		atomic_add(size, &sk->sk_omem_alloc);
>> -		mem = kmalloc(size, priority);
>> +		mem = kvmalloc_check(size, priority);
>>  		if (mem)
>>  			return mem;
>>  		atomic_sub(size, &sk->sk_omem_alloc);
>> @@ -1721,7 +1721,7 @@ EXPORT_SYMBOL(sock_kmalloc);
>>   */
>>  void sock_kfree_s(struct sock *sk, void *mem, int size)
>>  {
>> -	kfree(mem);
>> +	kvfree(mem);
>>  	atomic_sub(size, &sk->sk_omem_alloc);
>>  }
>>  EXPORT_SYMBOL(sock_kfree_s);
>>
> .
>