On Mon 26-09-16 10:34:13, zhongjiang wrote:
> From: zhong jiang <zhongjiang@xxxxxxxxxx>
>
> when the huge page is added to the page cahce (huge_add_to_page_cache),
> the page private flag will be cleared. since this code
> (remove_inode_hugepages) will only be called for pages in the
> page cahce, PagePrivate(page) will always be false.
>
> The patch remove the code without any functional change.
>
> Signed-off-by: zhong jiang <zhongjiang@xxxxxxxxxx>
> ---
> fs/hugetlbfs/inode.c | 10 ++++------
> include/linux/hugetlb.h | 2 +-
> mm/hugetlb.c | 4 ++--
> 3 files changed, 7 insertions(+), 9 deletions(-)
>
> diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
> index 4ea71eb..81f8bbf4 100644
> --- a/fs/hugetlbfs/inode.c
> +++ b/fs/hugetlbfs/inode.c
> @@ -458,18 +458,16 @@ static void remove_inode_hugepages(struct inode *inode, loff_t lstart,
> * cache (remove_huge_page) BEFORE removing the
> * region/reserve map (hugetlb_unreserve_pages). In
> * rare out of memory conditions, removal of the
> - * region/reserve map could fail. Before free'ing
> - * the page, note PagePrivate which is used in case
> - * of error.
> + * region/reserve map could fail. Correspondingly,
> + * the subpool and global reserve usage count can need
> + * to be adjusted.
> */
> - rsv_on_error = !PagePrivate(page);
This whole code is tricky as hell. I would be calmer if we just stick a
VM_BUG_ON here to make sure that this assumption will not break later
on.
> 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);
> --
> 1.8.3.1
--
Michal Hocko
SUSE Labs
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