>
> From: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
>
> When processing a hugetlb fault for no page present, check the vma to
> determine if faults are to be handled via userfaultfd. If so, drop the
> hugetlb_fault_mutex and call handle_userfault().
>
> Signed-off-by: Mike Kravetz <mike.kravetz@xxxxxxxxxx>
> Signed-off-by: Andrea Arcangeli <aarcange@xxxxxxxxxx>
> ---
Acked-by: Hillf Danton <hillf.zj@xxxxxxxxxxxxxxx>
> mm/hugetlb.c | 33 +++++++++++++++++++++++++++++++++
> 1 file changed, 33 insertions(+)
>
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index baf7fd4..7247f8c 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -32,6 +32,7 @@
> #include <linux/hugetlb.h>
> #include <linux/hugetlb_cgroup.h>
> #include <linux/node.h>
> +#include <linux/userfaultfd_k.h>
> #include "internal.h"
>
> int hugepages_treat_as_movable;
> @@ -3589,6 +3590,38 @@ static int hugetlb_no_page(struct mm_struct *mm, struct vm_area_struct *vma,
> size = i_size_read(mapping->host) >> huge_page_shift(h);
> if (idx >= size)
> goto out;
> +
> + /*
> + * Check for page in userfault range
> + */
> + if (userfaultfd_missing(vma)) {
> + u32 hash;
> + struct fault_env fe = {
> + .vma = vma,
> + .address = address,
> + .flags = flags,
> + /*
> + * Hard to debug if it ends up being
> + * used by a callee that assumes
> + * something about the other
> + * uninitialized fields... same as in
> + * memory.c
> + */
> + };
> +
> + /*
> + * hugetlb_fault_mutex must be dropped before
> + * handling userfault. Reacquire after handling
> + * fault to make calling code simpler.
> + */
> + hash = hugetlb_fault_mutex_hash(h, mm, vma, mapping,
> + idx, address);
> + mutex_unlock(&hugetlb_fault_mutex_table[hash]);
> + ret = handle_userfault(&fe, VM_UFFD_MISSING);
> + mutex_lock(&hugetlb_fault_mutex_table[hash]);
> + goto out;
> + }
> +
> page = alloc_huge_page(vma, address, 0);
> if (IS_ERR(page)) {
> ret = PTR_ERR(page);
>
--
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