On Sat, Mar 16, 2013 at 09:03:04AM -0400, Konrad Rzeszutek Wilk wrote:
>On Thu, Mar 14, 2013 at 06:08:14PM +0800, Wanpeng Li wrote:
>> Introduce zero-filled pages handler to capture and handle zero pages.
>>
>> Acked-by: Dan Magenheimer <dan.magenheimer@xxxxxxxxxx>
>> Signed-off-by: Wanpeng Li <liwanp@xxxxxxxxxxxxxxxxxx>
>> ---
>> drivers/staging/zcache/zcache-main.c | 26 ++++++++++++++++++++++++++
>> 1 files changed, 26 insertions(+), 0 deletions(-)
>>
>> diff --git a/drivers/staging/zcache/zcache-main.c b/drivers/staging/zcache/zcache-main.c
>> index 328898e..b71e033 100644
>> --- a/drivers/staging/zcache/zcache-main.c
>> +++ b/drivers/staging/zcache/zcache-main.c
>> @@ -460,6 +460,32 @@ static void zcache_obj_free(struct tmem_obj *obj, struct tmem_pool *pool)
>> kmem_cache_free(zcache_obj_cache, obj);
>> }
>>
>> +static bool page_zero_filled(void *ptr)
>
>Shouldn't this be 'struct page *p' ?
>> +{
>> + unsigned int pos;
>> + unsigned long *page;
>> +
>> + page = (unsigned long *)ptr;
>
>That way you can avoid this casting.
Great point! I will also clean it in zram implementation.
>> +
>> + for (pos = 0; pos < PAGE_SIZE / sizeof(*page); pos++) {
>> + if (page[pos])
>> + return false;
>
>Perhaps allocate a static page filled with zeros and just do memcmp?
>> + }
>> +
>> + return true;
>> +}
>> +
>> +static void handle_zero_page(void *page)
>> +{
>> + void *user_mem;
>> +
>> + user_mem = kmap_atomic(page);
>> + memset(user_mem, 0, PAGE_SIZE);
>> + kunmap_atomic(user_mem);
>> +
>> + flush_dcache_page(page);
To make sure kernel store is visiable to user space mappings of that page.
>
>This is new. Could you kindly explain why it is needed? Thanks.
>> +}
>> +
>> static struct tmem_hostops zcache_hostops = {
>> .obj_alloc = zcache_obj_alloc,
>> .obj_free = zcache_obj_free,
>> --
>> 1.7.7.6
>>
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