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SubjectRe: [PATCH -V4 02/10] hugetlbfs: don't use ERR_PTR with VM_FAULT* values
On Fri 16-03-12 23:09:22, Aneesh Kumar K.V wrote:
> From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
>
> Using VM_FAULT_* codes with ERR_PTR will require us to make sure
> VM_FAULT_* values will not exceed MAX_ERRNO value.
>
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
> ---
> mm/hugetlb.c | 18 +++++++++++++-----
> 1 files changed, 13 insertions(+), 5 deletions(-)
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index d623e71..3782da8 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
[...]
> @@ -1047,7 +1047,7 @@ static struct page *alloc_huge_page(struct vm_area_struct *vma,
> page = alloc_buddy_huge_page(h, NUMA_NO_NODE);
> if (!page) {
> hugetlb_put_quota(inode->i_mapping, chg);
> - return ERR_PTR(-VM_FAULT_SIGBUS);
> + return ERR_PTR(-ENOSPC);

Hmm, so one error code abuse replaced by another?
I know that ENOMEM would revert 4a6018f7 which would be unfortunate but
ENOSPC doesn't feel right as well.

> }
> }
>
> @@ -2395,6 +2395,7 @@ retry_avoidcopy:
> new_page = alloc_huge_page(vma, address, outside_reserve);
>
> if (IS_ERR(new_page)) {
> + int err = PTR_ERR(new_page);
> page_cache_release(old_page);
>
> /*
> @@ -2424,7 +2425,10 @@ retry_avoidcopy:
>
> /* Caller expects lock to be held */
> spin_lock(&mm->page_table_lock);
> - return -PTR_ERR(new_page);
> + if (err == -ENOMEM)
> + return VM_FAULT_OOM;
> + else
> + return VM_FAULT_SIGBUS;
> }
>
> /*
> @@ -2542,7 +2546,11 @@ retry:
> goto out;
> page = alloc_huge_page(vma, address, 0);
> if (IS_ERR(page)) {
> - ret = -PTR_ERR(page);
> + ret = PTR_ERR(page);
> + if (ret == -ENOMEM)
> + ret = VM_FAULT_OOM;
> + else
> + ret = VM_FAULT_SIGBUS;
> goto out;
> }
> clear_huge_page(page, address, pages_per_huge_page(h));
> --
> 1.7.9
>

--
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9
Czech Republic


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