* [PATCH] z3fold: limit first_num to the actual range of possible buddy indexes
@ 2016-10-18 7:42 zhongjiang
2016-10-18 13:57 ` Dan Streetman
0 siblings, 1 reply; 3+ messages in thread
From: zhongjiang @ 2016-10-18 7:42 UTC (permalink / raw)
To: ddstreet, akpm, david; +Cc: vitalywool, linux-kernel, linux-mm
From: zhong jiang <zhongjiang@huawei.com>
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 <ddstreet@ieee.org>
Signed-off-by: zhong jiang <zhongjiang@huawei.com>
---
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
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
^ permalink raw reply related [flat|nested] 3+ messages in thread* Re: [PATCH] z3fold: limit first_num to the actual range of possible buddy indexes
2016-10-18 7:42 [PATCH] z3fold: limit first_num to the actual range of possible buddy indexes zhongjiang
@ 2016-10-18 13:57 ` Dan Streetman
2016-10-18 14:54 ` Vitaly Wool
0 siblings, 1 reply; 3+ messages in thread
From: Dan Streetman @ 2016-10-18 13:57 UTC (permalink / raw)
To: zhongjiang
Cc: Andrew Morton, Dave Chinner, Vitaly Wool, linux-kernel, Linux-MM
On Tue, Oct 18, 2016 at 3:42 AM, zhongjiang <zhongjiang@huawei.com> wrote:
> From: zhong jiang <zhongjiang@huawei.com>
>
> 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 <ddstreet@ieee.org>
> Signed-off-by: zhong jiang <zhongjiang@huawei.com>
Acked-by: Dan Streetman <ddstreet@ieee.org>
> ---> 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
>
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
^ permalink raw reply [flat|nested] 3+ messages in thread* Re: [PATCH] z3fold: limit first_num to the actual range of possible buddy indexes
2016-10-18 13:57 ` Dan Streetman
@ 2016-10-18 14:54 ` Vitaly Wool
0 siblings, 0 replies; 3+ messages in thread
From: Vitaly Wool @ 2016-10-18 14:54 UTC (permalink / raw)
To: Dan Streetman
Cc: zhongjiang, Andrew Morton, Dave Chinner, linux-kernel, Linux-MM
On Tue, Oct 18, 2016 at 3:57 PM, Dan Streetman <ddstreet@ieee.org> wrote:
> On Tue, Oct 18, 2016 at 3:42 AM, zhongjiang <zhongjiang@huawei.com> wrote:
>> From: zhong jiang <zhongjiang@huawei.com>
>>
>> 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 <ddstreet@ieee.org>
>> Signed-off-by: zhong jiang <zhongjiang@huawei.com>
>
> Acked-by: Dan Streetman <ddstreet@ieee.org>
Acked-by: Vitaly Wool <vitalywool@gmail.com>
>> ---> 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
>>
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2016-10-18 14:54 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2016-10-18 7:42 [PATCH] z3fold: limit first_num to the actual range of possible buddy indexes zhongjiang
2016-10-18 13:57 ` Dan Streetman
2016-10-18 14:54 ` Vitaly Wool
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).