On 3/15/21 7:27 PM, Miaohe Lin wrote:
> The fault_mutex hashing overhead can be avoided in truncate_op case
> because page faults can not race with truncation in this routine. So
> calculate hash for fault_mutex only in !truncate_op case to save some cpu
> cycles.
>
> Reviewed-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
> Signed-off-by: Miaohe Lin <linmiaohe@xxxxxxxxxx>
> Cc: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
> ---
> v1->v2:
> remove unnecessary initialization for variable hash
> collect Reviewed-by tag from Mike Kravetz
My apologies for not replying sooner and any misunderstanding from my
previous comments.
If the compiler is going to produce a warning because the variable is
not initialized, then we will need to keep the initialization.
Otherwise, this will show up as a build regression. Ideally, there
would be a modifier which could be used to tell the compiler the
variable will used. I do not know if such a modifier exists.
The patch can not produce a new warning. So, if you need to initialize
the variable then do it. My Reviewed-by still applies.
--
Mike Kravetz
> ---
> fs/hugetlbfs/inode.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/fs/hugetlbfs/inode.c b/fs/hugetlbfs/inode.c
> index c262566f7c5d..f7ec94bc7337 100644
> --- a/fs/hugetlbfs/inode.c
> +++ b/fs/hugetlbfs/inode.c
> @@ -485,7 +485,6 @@ static void remove_inode_hugepages(struct inode *inode, loff_t lstart,
> u32 hash;
>
> index = page->index;
> - hash = hugetlb_fault_mutex_hash(mapping, index);
> if (!truncate_op) {
> /*
> * Only need to hold the fault mutex in the
> @@ -493,6 +492,7 @@ static void remove_inode_hugepages(struct inode *inode, loff_t lstart,
> * page faults. Races are not possible in the
> * case of truncation.
> */
> + hash = hugetlb_fault_mutex_hash(mapping, index);
> mutex_lock(&hugetlb_fault_mutex_table[hash]);
> }
>
>
