Re: [PATCH] z3fold: limit first_num to the actual range of possible buddy indexes

[Vitaly Wool]

On Tue, Oct 18, 2016 at 3:57 PM, Dan Streetman  wrote:
> On Tue, Oct 18, 2016 at 3:42 AM, zhongjiang  wrote:
>> From: zhong jiang 
>>
>> At present, Tying the first_num size to NCHUNKS_ORDER is confusing.
>> the number of chunks is completely unrelated to the number of buddies.
>>
>> The patch limit the first_num to actual range of possible buddy indexes.
>> and that is more reasonable and obvious without functional change.
>>
>> Suggested-by: Dan Streetman 
>> Signed-off-by: zhong jiang 
>
> Acked-by: Dan Streetman 

Acked-by: Vitaly Wool 

>> --->  mm/z3fold.c | 10 +++---
>>  1 file changed, 7 insertions(+), 3 deletions(-)
>>
>> diff --git a/mm/z3fold.c b/mm/z3fold.c
>> index 8f9e89c..207e5dd 100644
>> --- a/mm/z3fold.c
>> +++ b/mm/z3fold.c
>> @@ -50,7 +50,7 @@
>>  #define ZHDR_SIZE_ALIGNED CHUNK_SIZE
>>  #define NCHUNKS((PAGE_SIZE - ZHDR_SIZE_ALIGNED) >> 
>> CHUNK_SHIFT)
>>
>> -#define BUDDY_MASK ((1 << NCHUNKS_ORDER) - 1)
>> +#define BUDDY_MASK (0x3)
>>
>>  struct z3fold_pool;
>>  struct z3fold_ops {
>> @@ -109,7 +109,7 @@ struct z3fold_header {
>> unsigned short middle_chunks;
>> unsigned short last_chunks;
>> unsigned short start_middle;
>> -   unsigned short first_num:NCHUNKS_ORDER;
>> +   unsigned short first_num:2;
>>  };
>>
>>  /*
>> @@ -179,7 +179,11 @@ static struct z3fold_header 
>> *handle_to_z3fold_header(unsigned long handle)
>> return (struct z3fold_header *)(handle & PAGE_MASK);
>>  }
>>
>> -/* Returns buddy number */
>> +/*
>> + * (handle & BUDDY_MASK) < zhdr->first_num is possible in encode_handle
>> + *  but that doesn't matter. because the masking will result in the
>> + *  correct buddy number.
>> + */
>>  static enum buddy handle_to_buddy(unsigned long handle)
>>  {
>> struct z3fold_header *zhdr = handle_to_z3fold_header(handle);
>> --
>> 1.8.3.1
>>

Re: [PATCH] z3fold: limit first_num to the actual range of possible buddy indexes

[Vitaly Wool]

On Tue, Oct 18, 2016 at 3:57 PM, Dan Streetman  wrote:
> On Tue, Oct 18, 2016 at 3:42 AM, zhongjiang  wrote:
>> From: zhong jiang 
>>
>> At present, Tying the first_num size to NCHUNKS_ORDER is confusing.
>> the number of chunks is completely unrelated to the number of buddies.
>>
>> The patch limit the first_num to actual range of possible buddy indexes.
>> and that is more reasonable and obvious without functional change.
>>
>> Suggested-by: Dan Streetman 
>> Signed-off-by: zhong jiang 
>
> Acked-by: Dan Streetman 

Acked-by: Vitaly Wool 

>> --->  mm/z3fold.c | 10 +++---
>>  1 file changed, 7 insertions(+), 3 deletions(-)
>>
>> diff --git a/mm/z3fold.c b/mm/z3fold.c
>> index 8f9e89c..207e5dd 100644
>> --- a/mm/z3fold.c
>> +++ b/mm/z3fold.c
>> @@ -50,7 +50,7 @@
>>  #define ZHDR_SIZE_ALIGNED CHUNK_SIZE
>>  #define NCHUNKS((PAGE_SIZE - ZHDR_SIZE_ALIGNED) >> 
>> CHUNK_SHIFT)
>>
>> -#define BUDDY_MASK ((1 << NCHUNKS_ORDER) - 1)
>> +#define BUDDY_MASK (0x3)
>>
>>  struct z3fold_pool;
>>  struct z3fold_ops {
>> @@ -109,7 +109,7 @@ struct z3fold_header {
>> unsigned short middle_chunks;
>> unsigned short last_chunks;
>> unsigned short start_middle;
>> -   unsigned short first_num:NCHUNKS_ORDER;
>> +   unsigned short first_num:2;
>>  };
>>
>>  /*
>> @@ -179,7 +179,11 @@ static struct z3fold_header 
>> *handle_to_z3fold_header(unsigned long handle)
>> return (struct z3fold_header *)(handle & PAGE_MASK);
>>  }
>>
>> -/* Returns buddy number */
>> +/*
>> + * (handle & BUDDY_MASK) < zhdr->first_num is possible in encode_handle
>> + *  but that doesn't matter. because the masking will result in the
>> + *  correct buddy number.
>> + */
>>  static enum buddy handle_to_buddy(unsigned long handle)
>>  {
>> struct z3fold_header *zhdr = handle_to_z3fold_header(handle);
>> --
>> 1.8.3.1
>>

Re: [PATCH] z3fold: limit first_num to the actual range of possible buddy indexes

[Dan Streetman]

On Tue, Oct 18, 2016 at 3:42 AM, zhongjiang  wrote:
> From: zhong jiang 
>
> At present, Tying the first_num size to NCHUNKS_ORDER is confusing.
> the number of chunks is completely unrelated to the number of buddies.
>
> The patch limit the first_num to actual range of possible buddy indexes.
> and that is more reasonable and obvious without functional change.
>
> Suggested-by: Dan Streetman 
> Signed-off-by: zhong jiang 

Acked-by: Dan Streetman 

> --->  mm/z3fold.c | 10 +++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/mm/z3fold.c b/mm/z3fold.c
> index 8f9e89c..207e5dd 100644
> --- a/mm/z3fold.c
> +++ b/mm/z3fold.c
> @@ -50,7 +50,7 @@
>  #define ZHDR_SIZE_ALIGNED CHUNK_SIZE
>  #define NCHUNKS((PAGE_SIZE - ZHDR_SIZE_ALIGNED) >> 
> CHUNK_SHIFT)
>
> -#define BUDDY_MASK ((1 << NCHUNKS_ORDER) - 1)
> +#define BUDDY_MASK (0x3)
>
>  struct z3fold_pool;
>  struct z3fold_ops {
> @@ -109,7 +109,7 @@ struct z3fold_header {
> unsigned short middle_chunks;
> unsigned short last_chunks;
> unsigned short start_middle;
> -   unsigned short first_num:NCHUNKS_ORDER;
> +   unsigned short first_num:2;
>  };
>
>  /*
> @@ -179,7 +179,11 @@ static struct z3fold_header 
> *handle_to_z3fold_header(unsigned long handle)
> return (struct z3fold_header *)(handle & PAGE_MASK);
>  }
>
> -/* Returns buddy number */
> +/*
> + * (handle & BUDDY_MASK) < zhdr->first_num is possible in encode_handle
> + *  but that doesn't matter. because the masking will result in the
> + *  correct buddy number.
> + */
>  static enum buddy handle_to_buddy(unsigned long handle)
>  {
> struct z3fold_header *zhdr = handle_to_z3fold_header(handle);
> --
> 1.8.3.1
>

Re: [PATCH] z3fold: limit first_num to the actual range of possible buddy indexes

[Dan Streetman]

On Tue, Oct 18, 2016 at 3:42 AM, zhongjiang  wrote:
> From: zhong jiang 
>
> At present, Tying the first_num size to NCHUNKS_ORDER is confusing.
> the number of chunks is completely unrelated to the number of buddies.
>
> The patch limit the first_num to actual range of possible buddy indexes.
> and that is more reasonable and obvious without functional change.
>
> Suggested-by: Dan Streetman 
> Signed-off-by: zhong jiang 

Acked-by: Dan Streetman 

> --->  mm/z3fold.c | 10 +++---
>  1 file changed, 7 insertions(+), 3 deletions(-)
>
> diff --git a/mm/z3fold.c b/mm/z3fold.c
> index 8f9e89c..207e5dd 100644
> --- a/mm/z3fold.c
> +++ b/mm/z3fold.c
> @@ -50,7 +50,7 @@
>  #define ZHDR_SIZE_ALIGNED CHUNK_SIZE
>  #define NCHUNKS((PAGE_SIZE - ZHDR_SIZE_ALIGNED) >> 
> CHUNK_SHIFT)
>
> -#define BUDDY_MASK ((1 << NCHUNKS_ORDER) - 1)
> +#define BUDDY_MASK (0x3)
>
>  struct z3fold_pool;
>  struct z3fold_ops {
> @@ -109,7 +109,7 @@ struct z3fold_header {
> unsigned short middle_chunks;
> unsigned short last_chunks;
> unsigned short start_middle;
> -   unsigned short first_num:NCHUNKS_ORDER;
> +   unsigned short first_num:2;
>  };
>
>  /*
> @@ -179,7 +179,11 @@ static struct z3fold_header 
> *handle_to_z3fold_header(unsigned long handle)
> return (struct z3fold_header *)(handle & PAGE_MASK);
>  }
>
> -/* Returns buddy number */
> +/*
> + * (handle & BUDDY_MASK) < zhdr->first_num is possible in encode_handle
> + *  but that doesn't matter. because the masking will result in the
> + *  correct buddy number.
> + */
>  static enum buddy handle_to_buddy(unsigned long handle)
>  {
> struct z3fold_header *zhdr = handle_to_z3fold_header(handle);
> --
> 1.8.3.1
>