* [Patch] tmpfs: clean up shmem_find_get_pages_and_swap()
@ 2012-01-24 15:48 Cong Wang
2012-01-25 23:25 ` Hugh Dickins
0 siblings, 1 reply; 2+ messages in thread
From: Cong Wang @ 2012-01-24 15:48 UTC (permalink / raw)
To: linux-kernel; +Cc: Andrew Morton, Hugh Dickins, WANG Cong, linux-mm
This patch cleans up shmem_find_get_pages_and_swap() interface:
a) Pass struct pagevec* instead of ->pages
b) Check if nr_pages is greater than PAGEVEC_SIZE inside the function
c) Return the result via ->nr instead of using return value
Compiling test only.
Cc: Hugh Dickins <hughd@google.com>
Signed-off-by: WANG Cong <xiyou.wangcong@gmail.com>
---
diff --git a/mm/shmem.c b/mm/shmem.c
index 269d049..c4e08e2 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -312,15 +312,19 @@ static void shmem_delete_from_page_cache(struct page *page, void *radswap)
/*
* Like find_get_pages, but collecting swap entries as well as pages.
*/
-static unsigned shmem_find_get_pages_and_swap(struct address_space *mapping,
+static void shmem_find_get_pages_and_swap(struct address_space *mapping,
pgoff_t start, unsigned int nr_pages,
- struct page **pages, pgoff_t *indices)
+ struct pagevec *pvec, pgoff_t *indices)
{
unsigned int i;
unsigned int ret;
unsigned int nr_found;
+ struct page **pages = pvec->pages;
rcu_read_lock();
+
+ if (nr_pages > PAGEVEC_SIZE)
+ nr_pages = PAGEVEC_SIZE;
restart:
nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree,
(void ***)pages, indices, start, nr_pages);
@@ -357,7 +361,7 @@ export:
if (unlikely(!ret && nr_found))
goto restart;
rcu_read_unlock();
- return ret;
+ pvec->nr = ret;
}
/*
@@ -409,8 +413,8 @@ void shmem_unlock_mapping(struct address_space *mapping)
* Avoid pagevec_lookup(): find_get_pages() returns 0 as if it
* has finished, if it hits a row of PAGEVEC_SIZE swap entries.
*/
- pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
- PAGEVEC_SIZE, pvec.pages, indices);
+ shmem_find_get_pages_and_swap(mapping, index,
+ PAGEVEC_SIZE, &pvec, indices);
if (!pvec.nr)
break;
index = indices[pvec.nr - 1] + 1;
@@ -442,9 +446,8 @@ void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
pagevec_init(&pvec, 0);
index = start;
while (index <= end) {
- pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
- min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1,
- pvec.pages, indices);
+ shmem_find_get_pages_and_swap(mapping, index,
+ end - index + 1, &pvec, indices);
if (!pvec.nr)
break;
mem_cgroup_uncharge_start();
@@ -490,9 +493,8 @@ void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
index = start;
for ( ; ; ) {
cond_resched();
- pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
- min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1,
- pvec.pages, indices);
+ shmem_find_get_pages_and_swap(mapping, index,
+ end - index + 1, &pvec, indices);
if (!pvec.nr) {
if (index == start)
break;
^ permalink raw reply related [flat|nested] 2+ messages in thread
* Re: [Patch] tmpfs: clean up shmem_find_get_pages_and_swap()
2012-01-24 15:48 [Patch] tmpfs: clean up shmem_find_get_pages_and_swap() Cong Wang
@ 2012-01-25 23:25 ` Hugh Dickins
0 siblings, 0 replies; 2+ messages in thread
From: Hugh Dickins @ 2012-01-25 23:25 UTC (permalink / raw)
To: Cong Wang; +Cc: linux-kernel, Andrew Morton, linux-mm
On Tue, 24 Jan 2012, Cong Wang wrote:
> This patch cleans up shmem_find_get_pages_and_swap() interface:
>
> a) Pass struct pagevec* instead of ->pages
> b) Check if nr_pages is greater than PAGEVEC_SIZE inside the function
> c) Return the result via ->nr instead of using return value
>
> Compiling test only.
>
> Cc: Hugh Dickins <hughd@google.com>
> Signed-off-by: WANG Cong <xiyou.wangcong@gmail.com>
I don't see any cleanup: just a difference in taste, I suppose.
shmem_find_get_pages_and_swap() is modelled on find_get_pages():
I'd prefer to keep it that way unless there's good reason to diverge.
I do see a slight change in behaviour, where you've undone the range
limitation (coming from invalidate_inode_pages2_range() originally, but
now in several functions in mm/truncate.c). I think you misunderstood
> - min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1,
When doing a range, that's trying to stop the radix_tree gang lookup
looking further than could ever be necessary. Not a big deal, it is
imperfect anyway - makes more sense when the range is 1 than larger;
but shouldn't be undone without justification.
Hugh
>
> ---
> diff --git a/mm/shmem.c b/mm/shmem.c
> index 269d049..c4e08e2 100644
> --- a/mm/shmem.c
> +++ b/mm/shmem.c
> @@ -312,15 +312,19 @@ static void shmem_delete_from_page_cache(struct page *page, void *radswap)
> /*
> * Like find_get_pages, but collecting swap entries as well as pages.
> */
> -static unsigned shmem_find_get_pages_and_swap(struct address_space *mapping,
> +static void shmem_find_get_pages_and_swap(struct address_space *mapping,
> pgoff_t start, unsigned int nr_pages,
> - struct page **pages, pgoff_t *indices)
> + struct pagevec *pvec, pgoff_t *indices)
> {
> unsigned int i;
> unsigned int ret;
> unsigned int nr_found;
> + struct page **pages = pvec->pages;
>
> rcu_read_lock();
> +
> + if (nr_pages > PAGEVEC_SIZE)
> + nr_pages = PAGEVEC_SIZE;
> restart:
> nr_found = radix_tree_gang_lookup_slot(&mapping->page_tree,
> (void ***)pages, indices, start, nr_pages);
> @@ -357,7 +361,7 @@ export:
> if (unlikely(!ret && nr_found))
> goto restart;
> rcu_read_unlock();
> - return ret;
> + pvec->nr = ret;
> }
>
> /*
> @@ -409,8 +413,8 @@ void shmem_unlock_mapping(struct address_space *mapping)
> * Avoid pagevec_lookup(): find_get_pages() returns 0 as if it
> * has finished, if it hits a row of PAGEVEC_SIZE swap entries.
> */
> - pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
> - PAGEVEC_SIZE, pvec.pages, indices);
> + shmem_find_get_pages_and_swap(mapping, index,
> + PAGEVEC_SIZE, &pvec, indices);
> if (!pvec.nr)
> break;
> index = indices[pvec.nr - 1] + 1;
> @@ -442,9 +446,8 @@ void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
> pagevec_init(&pvec, 0);
> index = start;
> while (index <= end) {
> - pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
> - min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1,
> - pvec.pages, indices);
> + shmem_find_get_pages_and_swap(mapping, index,
> + end - index + 1, &pvec, indices);
> if (!pvec.nr)
> break;
> mem_cgroup_uncharge_start();
> @@ -490,9 +493,8 @@ void shmem_truncate_range(struct inode *inode, loff_t lstart, loff_t lend)
> index = start;
> for ( ; ; ) {
> cond_resched();
> - pvec.nr = shmem_find_get_pages_and_swap(mapping, index,
> - min(end - index, (pgoff_t)PAGEVEC_SIZE - 1) + 1,
> - pvec.pages, indices);
> + shmem_find_get_pages_and_swap(mapping, index,
> + end - index + 1, &pvec, indices);
> if (!pvec.nr) {
> if (index == start)
> break;
^ permalink raw reply [flat|nested] 2+ messages in thread
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2012-01-24 15:48 [Patch] tmpfs: clean up shmem_find_get_pages_and_swap() Cong Wang
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