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    SubjectRe: [PATCH -V8 02/16] hugetlb: don't use ERR_PTR with VM_FAULT* values
    On Sat, Jun 09, 2012 at 02:29:47PM +0530, Aneesh Kumar K.V wrote:
    > From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
    >
    > The current use of VM_FAULT_* codes with ERR_PTR requires us to ensure
    > VM_FAULT_* values will not exceed MAX_ERRNO value. Decouple the
    > VM_FAULT_* values from MAX_ERRNO.

    I see you using the -ENOMEM|-ENOSPC, but I don't see any reference in the
    code to MAX_ERRNO? Can you provide a comment explaining in a tad little
    bit about the interaction of MAX_ERRNO and VM_FAULT?

    >
    > Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
    > Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
    > ---
    > mm/hugetlb.c | 18 +++++++++++++-----
    > 1 file changed, 13 insertions(+), 5 deletions(-)
    >
    > diff --git a/mm/hugetlb.c b/mm/hugetlb.c
    > index c868309..34a7e23 100644
    > --- a/mm/hugetlb.c
    > +++ b/mm/hugetlb.c
    > @@ -1123,10 +1123,10 @@ static struct page *alloc_huge_page(struct vm_area_struct *vma,
    > */
    > chg = vma_needs_reservation(h, vma, addr);
    > if (chg < 0)
    > - return ERR_PTR(-VM_FAULT_OOM);
    > + return ERR_PTR(-ENOMEM);
    > if (chg)
    > if (hugepage_subpool_get_pages(spool, chg))
    > - return ERR_PTR(-VM_FAULT_SIGBUS);
    > + return ERR_PTR(-ENOSPC);
    >
    > spin_lock(&hugetlb_lock);
    > page = dequeue_huge_page_vma(h, vma, addr, avoid_reserve);
    > @@ -1136,7 +1136,7 @@ static struct page *alloc_huge_page(struct vm_area_struct *vma,
    > page = alloc_buddy_huge_page(h, NUMA_NO_NODE);
    > if (!page) {
    > hugepage_subpool_put_pages(spool, chg);
    > - return ERR_PTR(-VM_FAULT_SIGBUS);
    > + return ERR_PTR(-ENOSPC);
    > }
    > }
    >
    > @@ -2496,6 +2496,7 @@ retry_avoidcopy:
    > new_page = alloc_huge_page(vma, address, outside_reserve);
    >
    > if (IS_ERR(new_page)) {
    > + long err = PTR_ERR(new_page);
    > page_cache_release(old_page);
    >
    > /*
    > @@ -2524,7 +2525,10 @@ 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;
    > }
    >
    > /*
    > @@ -2642,7 +2646,11 @@ 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));
    > --
    > 1.7.10
    >
    > --
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    >


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