Re: [RFC] remove unnecessary condition in remove_inode_hugepages

From: Michal Hocko
Date: Fri Sep 23 2016 - 04:18:32 EST


[CC Naoya]

On Fri 23-09-16 09:53:52, zhong jiang wrote:
>
> At present, we need to call hugetlb_fix_reserve_count when hugetlb_unrserve_pages fails,
> and PagePrivate will decide hugetlb reserves counts.
>
> we obtain the page from page cache. and use page both lock_page and mutex_lock.
> alloc_huge_page add page to page chace always hold lock page, then bail out clearpageprivate
> before unlock page.
>
> but I' m not sure it is right or I miss the points.
>
>
> diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
> index 4ea71eb..010723b 100644
> --- a/fs/hugetlbfs/inode.c
> +++ b/fs/hugetlbfs/inode.c
> @@ -462,14 +462,12 @@ static void remove_inode_hugepages(struct inode *inode, loff_t lstart,
> * the page, note PagePrivate which is used in case
> * of error.
> */
> - rsv_on_error = !PagePrivate(page);
> remove_huge_page(page);
> freed++;
> if (!truncate_op) {
> if (unlikely(hugetlb_unreserve_pages(inode,
> next, next + 1, 1)))
> - hugetlb_fix_reserve_counts(inode,
> - rsv_on_error);
> + hugetlb_fix_reserve_counts(inode)
> }
>
> unlock_page(page);
> diff --git a/include/linux/hugetlb.h b/include/linux/hugetlb.h
> index c26d463..d2e0fc5 100644
> --- a/include/linux/hugetlb.h
> +++ b/include/linux/hugetlb.h
> @@ -90,7 +90,7 @@ int dequeue_hwpoisoned_huge_page(struct page *page);
> bool isolate_huge_page(struct page *page, struct list_head *list);
> void putback_active_hugepage(struct page *page);
> void free_huge_page(struct page *page);
> -void hugetlb_fix_reserve_counts(struct inode *inode, bool restore_reserve);
> +void hugetlb_fix_reserve_counts(struct inode *inode);
> extern struct mutex *hugetlb_fault_mutex_table;
> u32 hugetlb_fault_mutex_hash(struct hstate *h, struct mm_struct *mm,
> struct vm_area_struct *vma,
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 87e11d8..28a079a 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -567,13 +567,13 @@ retry:
> * appear as a "reserved" entry instead of simply dangling with incorrect
> * counts.
> */
> -void hugetlb_fix_reserve_counts(struct inode *inode, bool restore_reserve)
> +void hugetlb_fix_reserve_counts(struct inode *inode)
> {
> struct hugepage_subpool *spool = subpool_inode(inode);
> long rsv_adjust;
>
> rsv_adjust = hugepage_subpool_get_pages(spool, 1);
> - if (restore_reserve && rsv_adjust) {
> + if (rsv_adjust) {
> struct hstate *h = hstate_inode(inode);
>
> hugetlb_acct_memory(h, 1);
>
>
> --
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--
Michal Hocko
SUSE Labs