Re: [PATCH 2/4] mm/swap: use SECTORS_PER_PAGE_SHIFT to clean up code

2020-05-06 Thread Leizhen (ThunderTown) 



On 2020/5/6 11:47, Leizhen (ThunderTown) wrote:
> 
> 
> On 2020/5/6 9:33, Leizhen (ThunderTown) wrote:
>>
>>
>> On 2020/5/6 1:25, Matthew Wilcox wrote:
>>> On Tue, May 05, 2020 at 07:55:41PM +0800, Zhen Lei wrote:
 +++ b/mm/swapfile.c
 @@ -177,8 +177,8 @@ static int discard_swap(struct swap_info_struct *si)
  
/* Do not discard the swap header page! */
se = first_se(si);
 -  start_block = (se->start_block + 1) << (PAGE_SHIFT - 9);
 -  nr_blocks = ((sector_t)se->nr_pages - 1) << (PAGE_SHIFT - 9);
 +  start_block = (se->start_block + 1) << SECTORS_PER_PAGE_SHIFT;
 +  nr_blocks = ((sector_t)se->nr_pages - 1) << SECTORS_PER_PAGE_SHIFT;
>>>
>>> Thinking about this some more, wouldn't this look better?
>>>
>>> start_block = page_sectors(se->start_block + 1);
>>> nr_block = page_sectors(se->nr_pages - 1);
>>>
>>
>> OK，That's fine, it's clearer. And in this way, there won't be more than 80 
>> columns.
> 
> Should we rename "page_sectors" to "page_to_sectors"? Because we may need to 
> define
> "sectors_to_page" also.

Change the "sectors_to_page" to "sectors_to_npage", npage means "number of 
pages"
or "page number". To distinguish the use case of "pfn_to_page()" etc. The latter
returns the pointer of "struct page".

> 
>>
>>>
>>> .
>>>

Re: [PATCH 2/4] mm/swap: use SECTORS_PER_PAGE_SHIFT to clean up code

2020-05-05 Thread Leizhen (ThunderTown) 



On 2020/5/6 9:33, Leizhen (ThunderTown) wrote:
> 
> 
> On 2020/5/6 1:25, Matthew Wilcox wrote:
>> On Tue, May 05, 2020 at 07:55:41PM +0800, Zhen Lei wrote:
>>> +++ b/mm/swapfile.c
>>> @@ -177,8 +177,8 @@ static int discard_swap(struct swap_info_struct *si)
>>>  
>>> /* Do not discard the swap header page! */
>>> se = first_se(si);
>>> -   start_block = (se->start_block + 1) << (PAGE_SHIFT - 9);
>>> -   nr_blocks = ((sector_t)se->nr_pages - 1) << (PAGE_SHIFT - 9);
>>> +   start_block = (se->start_block + 1) << SECTORS_PER_PAGE_SHIFT;
>>> +   nr_blocks = ((sector_t)se->nr_pages - 1) << SECTORS_PER_PAGE_SHIFT;
>>
>> Thinking about this some more, wouldn't this look better?
>>
>>  start_block = page_sectors(se->start_block + 1);
>>  nr_block = page_sectors(se->nr_pages - 1);
>>
> 
> OK，That's fine, it's clearer. And in this way, there won't be more than 80 
> columns.

Should we rename "page_sectors" to "page_to_sectors"? Because we may need to 
define
"sectors_to_page" also.

> 
>>
>> .
>>

Re: [PATCH 2/4] mm/swap: use SECTORS_PER_PAGE_SHIFT to clean up code

2020-05-05 Thread Leizhen (ThunderTown) 



On 2020/5/6 1:25, Matthew Wilcox wrote:
> On Tue, May 05, 2020 at 07:55:41PM +0800, Zhen Lei wrote:
>> +++ b/mm/swapfile.c
>> @@ -177,8 +177,8 @@ static int discard_swap(struct swap_info_struct *si)
>>  
>>  /* Do not discard the swap header page! */
>>  se = first_se(si);
>> -start_block = (se->start_block + 1) << (PAGE_SHIFT - 9);
>> -nr_blocks = ((sector_t)se->nr_pages - 1) << (PAGE_SHIFT - 9);
>> +start_block = (se->start_block + 1) << SECTORS_PER_PAGE_SHIFT;
>> +nr_blocks = ((sector_t)se->nr_pages - 1) << SECTORS_PER_PAGE_SHIFT;
> 
> Thinking about this some more, wouldn't this look better?
> 
>   start_block = page_sectors(se->start_block + 1);
>   nr_block = page_sectors(se->nr_pages - 1);
> 

OK，That's fine, it's clearer. And in this way, there won't be more than 80 
columns.

> 
> .
>

Re: [PATCH 2/4] mm/swap: use SECTORS_PER_PAGE_SHIFT to clean up code

2020-05-05 Thread Matthew Wilcox 
On Tue, May 05, 2020 at 07:55:41PM +0800, Zhen Lei wrote:
> +++ b/mm/swapfile.c
> @@ -177,8 +177,8 @@ static int discard_swap(struct swap_info_struct *si)
>  
>   /* Do not discard the swap header page! */
>   se = first_se(si);
> - start_block = (se->start_block + 1) << (PAGE_SHIFT - 9);
> - nr_blocks = ((sector_t)se->nr_pages - 1) << (PAGE_SHIFT - 9);
> + start_block = (se->start_block + 1) << SECTORS_PER_PAGE_SHIFT;
> + nr_blocks = ((sector_t)se->nr_pages - 1) << SECTORS_PER_PAGE_SHIFT;

Thinking about this some more, wouldn't this look better?

start_block = page_sectors(se->start_block + 1);
nr_block = page_sectors(se->nr_pages - 1);

[PATCH 2/4] mm/swap: use SECTORS_PER_PAGE_SHIFT to clean up code

2020-05-05 Thread Zhen Lei 
1. Replace "PAGE_SHIFT - 9" with SECTORS_PER_PAGE_SHIFT

Signed-off-by: Zhen Lei 
---
 mm/page_io.c  |  4 ++--
 mm/swapfile.c | 12 ++--
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/mm/page_io.c b/mm/page_io.c
index b1d4f4558e6b..51f25238fd9a 100644
--- a/mm/page_io.c
+++ b/mm/page_io.c
@@ -38,7 +38,7 @@ static struct bio *get_swap_bio(gfp_t gfp_flags,
 
bio->bi_iter.bi_sector = map_swap_page(page, &bdev);
bio_set_dev(bio, bdev);
-   bio->bi_iter.bi_sector <<= PAGE_SHIFT - 9;
+   bio->bi_iter.bi_sector <<= SECTORS_PER_PAGE_SHIFT;
bio->bi_end_io = end_io;
 
bio_add_page(bio, page, PAGE_SIZE * hpage_nr_pages(page), 0);
@@ -266,7 +266,7 @@ int swap_writepage(struct page *page, struct 
writeback_control *wbc)
 
 static sector_t swap_page_sector(struct page *page)
 {
-   return (sector_t)__page_file_index(page) << (PAGE_SHIFT - 9);
+   return (sector_t)__page_file_index(page) << SECTORS_PER_PAGE_SHIFT;
 }
 
 static inline void count_swpout_vm_event(struct page *page)
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 5871a2aa86a5..0871023c0166 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -177,8 +177,8 @@ static int discard_swap(struct swap_info_struct *si)
 
/* Do not discard the swap header page! */
se = first_se(si);
-   start_block = (se->start_block + 1) << (PAGE_SHIFT - 9);
-   nr_blocks = ((sector_t)se->nr_pages - 1) << (PAGE_SHIFT - 9);
+   start_block = (se->start_block + 1) << SECTORS_PER_PAGE_SHIFT;
+   nr_blocks = ((sector_t)se->nr_pages - 1) << SECTORS_PER_PAGE_SHIFT;
if (nr_blocks) {
err = blkdev_issue_discard(si->bdev, start_block,
nr_blocks, GFP_KERNEL, 0);
@@ -188,8 +188,8 @@ static int discard_swap(struct swap_info_struct *si)
}
 
for (se = next_se(se); se; se = next_se(se)) {
-   start_block = se->start_block << (PAGE_SHIFT - 9);
-   nr_blocks = (sector_t)se->nr_pages << (PAGE_SHIFT - 9);
+   start_block = se->start_block << SECTORS_PER_PAGE_SHIFT;
+   nr_blocks = (sector_t)se->nr_pages << SECTORS_PER_PAGE_SHIFT;
 
err = blkdev_issue_discard(si->bdev, start_block,
nr_blocks, GFP_KERNEL, 0);
@@ -240,8 +240,8 @@ static void discard_swap_cluster(struct swap_info_struct 
*si,
start_page += nr_blocks;
nr_pages -= nr_blocks;
 
-   start_block <<= PAGE_SHIFT - 9;
-   nr_blocks <<= PAGE_SHIFT - 9;
+   start_block <<= SECTORS_PER_PAGE_SHIFT;
+   nr_blocks <<= SECTORS_PER_PAGE_SHIFT;
if (blkdev_issue_discard(si->bdev, start_block,
nr_blocks, GFP_NOIO, 0))
break;
-- 
2.26.0.106.g9fadedd