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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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