2021-01-16 09:29:54

by Miaohe Lin

Subject: [PATCH] hugetlbfs: remove meaningless variable avoid_reserve

The variable avoid_reserve is meaningless because we never changed its
value and just passed it to alloc_huge_page(). So remove it to make code
more clear that in hugetlbfs_fallocate, we never avoid reserve when alloc
hugepage yet.

Signed-off-by: Miaohe Lin <[email protected]>
---
fs/hugetlbfs/inode.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
index 88751e35e69d..23ad6ed8b75f 100644
--- a/fs/hugetlbfs/inode.c
+++ b/fs/hugetlbfs/inode.c
@@ -680,7 +680,6 @@ static long hugetlbfs_fallocate(struct file *file, int mode, loff_t offset,
*/
struct page *page;
unsigned long addr;
- int avoid_reserve = 0;

cond_resched();

@@ -717,7 +716,7 @@ static long hugetlbfs_fallocate(struct file *file, int mode, loff_t offset,
}

/* Allocate page and add to page cache */
- page = alloc_huge_page(&pseudo_vma, addr, avoid_reserve);
+ page = alloc_huge_page(&pseudo_vma, addr, 0);
hugetlb_drop_vma_policy(&pseudo_vma);
if (IS_ERR(page)) {
mutex_unlock(&hugetlb_fault_mutex_table[hash]);
--
2.19.1

2021-01-16 09:43:15

by Souptick Joarder

Subject: Re: [PATCH] hugetlbfs: remove meaningless variable avoid_reserve

On Sat, Jan 16, 2021 at 2:57 PM Miaohe Lin <[email protected]> wrote:
>
> The variable avoid_reserve is meaningless because we never changed its
> value and just passed it to alloc_huge_page(). So remove it to make code
> more clear that in hugetlbfs_fallocate, we never avoid reserve when alloc
> hugepage yet.
>
> Signed-off-by: Miaohe Lin <[email protected]>

Acked-by: Souptick Joarder <[email protected]>

> ---
> fs/hugetlbfs/inode.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
> index 88751e35e69d..23ad6ed8b75f 100644
> --- a/fs/hugetlbfs/inode.c
> +++ b/fs/hugetlbfs/inode.c
> @@ -680,7 +680,6 @@ static long hugetlbfs_fallocate(struct file *file, int mode, loff_t offset,
> */
> struct page *page;
> unsigned long addr;
> - int avoid_reserve = 0;
>
> cond_resched();
>
> @@ -717,7 +716,7 @@ static long hugetlbfs_fallocate(struct file *file, int mode, loff_t offset,
> }
>
> /* Allocate page and add to page cache */
> - page = alloc_huge_page(&pseudo_vma, addr, avoid_reserve);
> + page = alloc_huge_page(&pseudo_vma, addr, 0);
> hugetlb_drop_vma_policy(&pseudo_vma);
> if (IS_ERR(page)) {
> mutex_unlock(&hugetlb_fault_mutex_table[hash]);
> --
> 2.19.1
>
>

2021-01-18 21:43:24

by David Hildenbrand

Subject: Re: [PATCH] hugetlbfs: remove meaningless variable avoid_reserve

On 16.01.21 10:26, Miaohe Lin wrote:
> The variable avoid_reserve is meaningless because we never changed its
> value and just passed it to alloc_huge_page(). So remove it to make code
> more clear that in hugetlbfs_fallocate, we never avoid reserve when alloc
> hugepage yet.
>
> Signed-off-by: Miaohe Lin <[email protected]>
> ---
> fs/hugetlbfs/inode.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
> index 88751e35e69d..23ad6ed8b75f 100644
> --- a/fs/hugetlbfs/inode.c
> +++ b/fs/hugetlbfs/inode.c
> @@ -680,7 +680,6 @@ static long hugetlbfs_fallocate(struct file *file, int mode, loff_t offset,
> */
> struct page *page;
> unsigned long addr;
> - int avoid_reserve = 0;
>
> cond_resched();
>
> @@ -717,7 +716,7 @@ static long hugetlbfs_fallocate(struct file *file, int mode, loff_t offset,
> }
>
> /* Allocate page and add to page cache */
> - page = alloc_huge_page(&pseudo_vma, addr, avoid_reserve);
> + page = alloc_huge_page(&pseudo_vma, addr, 0);
> hugetlb_drop_vma_policy(&pseudo_vma);
> if (IS_ERR(page)) {
> mutex_unlock(&hugetlb_fault_mutex_table[hash]);
>

Reviewed-by: David Hildenbrand <[email protected]>

--
Thanks,

David / dhildenb

2021-01-19 19:14:46

by Mike Kravetz

Subject: Re: [PATCH] hugetlbfs: remove meaningless variable avoid_reserve

Please CC Andrew on hugetlb patches as they need to go through his tree.

On 1/16/21 1:26 AM, Miaohe Lin wrote:
> The variable avoid_reserve is meaningless because we never changed its
> value and just passed it to alloc_huge_page(). So remove it to make code
> more clear that in hugetlbfs_fallocate, we never avoid reserve when alloc
> hugepage yet.

One might argue that using a named variable makes the call to alloc_huge_page
more clear. I do not disagree with the change, However, there are some
subtle reasons why alloc_huge_page is called with 'avoid_reserve = 0' from
fallocate. Therefore, I would prefer that a comment be added above the call
in addition to this change. See below.

>
> Signed-off-by: Miaohe Lin <[email protected]>
> ---
> fs/hugetlbfs/inode.c | 3 +--
> 1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
> index 88751e35e69d..23ad6ed8b75f 100644
> --- a/fs/hugetlbfs/inode.c
> +++ b/fs/hugetlbfs/inode.c
> @@ -680,7 +680,6 @@ static long hugetlbfs_fallocate(struct file *file, int mode, loff_t offset,
> */
> struct page *page;
> unsigned long addr;
> - int avoid_reserve = 0;
>
> cond_resched();
>
> @@ -717,7 +716,7 @@ static long hugetlbfs_fallocate(struct file *file, int mode, loff_t offset,
> }
>
> /* Allocate page and add to page cache */

Perhaps, change comment to read:

/*
* Allocate page without setting the avoid_reserve argument.
* There certainly are no reserves associated with the
* pseudo_vma. However, there could be shared mappings with
* reserves for the file at the inode level. If we fallocate
* pages in these areas, we need to consume the reserves
* to keep reservation accounting consistent.
*/

--
Mike Kravetz

> - page = alloc_huge_page(&pseudo_vma, addr, avoid_reserve);
> + page = alloc_huge_page(&pseudo_vma, addr, 0);
> hugetlb_drop_vma_policy(&pseudo_vma);
> if (IS_ERR(page)) {
> mutex_unlock(&hugetlb_fault_mutex_table[hash]);
>

2021-01-20 02:13:30

by Miaohe Lin

Subject: Re: [PATCH] hugetlbfs: remove meaningless variable avoid_reserve

Hi:
On 2021/1/20 2:41, Mike Kravetz wrote:
> Please CC Andrew on hugetlb patches as they need to go through his tree.
>
> On 1/16/21 1:26 AM, Miaohe Lin wrote:
>> The variable avoid_reserve is meaningless because we never changed its
>> value and just passed it to alloc_huge_page(). So remove it to make code
>> more clear that in hugetlbfs_fallocate, we never avoid reserve when alloc
>> hugepage yet.
>
> One might argue that using a named variable makes the call to alloc_huge_page
> more clear. I do not disagree with the change, However, there are some
> subtle reasons why alloc_huge_page is called with 'avoid_reserve = 0' from
> fallocate. Therefore, I would prefer that a comment be added above the call
> in addition to this change. See below.
>
>>
>> Signed-off-by: Miaohe Lin <[email protected]>
>> ---
>> fs/hugetlbfs/inode.c | 3 +--
>> 1 file changed, 1 insertion(+), 2 deletions(-)
>>
>> diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
>> index 88751e35e69d..23ad6ed8b75f 100644
>> --- a/fs/hugetlbfs/inode.c
>> +++ b/fs/hugetlbfs/inode.c
>> @@ -680,7 +680,6 @@ static long hugetlbfs_fallocate(struct file *file, int mode, loff_t offset,
>> */
>> struct page *page;
>> unsigned long addr;
>> - int avoid_reserve = 0;
>>
>> cond_resched();
>>
>> @@ -717,7 +716,7 @@ static long hugetlbfs_fallocate(struct file *file, int mode, loff_t offset,
>> }
>>
>> /* Allocate page and add to page cache */
>
> Perhaps, change comment to read:
>
> /*
> * Allocate page without setting the avoid_reserve argument.
> * There certainly are no reserves associated with the
> * pseudo_vma. However, there could be shared mappings with
> * reserves for the file at the inode level. If we fallocate
> * pages in these areas, we need to consume the reserves
> * to keep reservation accounting consistent.
> */
>

Many thanks for detailed and excellent comment. Will do it in v2.
Thanks again.