On 4/2/21 2:32 AM, Miaohe Lin wrote:
> The resv_map could be NULL since this routine can be called in the evict
> inode path for all hugetlbfs inodes. So we could have chg = 0 and this
> would result in a negative value when chg - freed. This is unexpected for
> hugepage_subpool_put_pages() and hugetlb_acct_memory().
I am not sure if this is possible.
It is true that resv_map could be NULL. However, I believe resv map
can only be NULL for inodes that are not regular or link inodes. This
is the inode creation code in hugetlbfs_get_inode().
/*
* Reserve maps are only needed for inodes that can have associated
* page allocations.
*/
if (S_ISREG(mode) || S_ISLNK(mode)) {
resv_map = resv_map_alloc();
if (!resv_map)
return NULL;
}
If resv_map is NULL, then no hugetlb pages can be allocated/associated
with the file. As a result, remove_inode_hugepages will never find any
huge pages associated with the inode and the passed value 'freed' will
always be zero.
Does that sound correct?
--
Mike Kravetz
>
> Fixes: b5cec28d36f5 ("hugetlbfs: truncate_hugepages() takes a range of pages")
> Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
> ---
> mm/hugetlb.c | 4 +++-
> 1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index b7864abded3d..bdff8d23803f 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -5413,6 +5413,7 @@ long hugetlb_unreserve_pages(struct inode *inode, long start, long end,
> long chg = 0;
> struct hugepage_subpool *spool = subpool_inode(inode);
> long gbl_reserve;
> + long delta;
>
> /*
> * Since this routine can be called in the evict inode path for all
> @@ -5437,7 +5438,8 @@ long hugetlb_unreserve_pages(struct inode *inode, long start, long end,
> * If the subpool has a minimum size, the number of global
> * reservations to be released may be adjusted.
> */
> - gbl_reserve = hugepage_subpool_put_pages(spool, (chg - freed));
> + delta = chg > 0 ? chg - freed : freed;
> + gbl_reserve = hugepage_subpool_put_pages(spool, delta);
> hugetlb_acct_memory(h, -gbl_reserve);
>
> return 0;
>
