On Thu, 3 Apr 2014 17:35:21 +0300 "Kirill A. Shutemov" <kirill.shutemov@xxxxxxxxxxxxxxx> wrote:
> Nesting level in __get_user_pages() is just insane. Let's try to fix it
> a bit.
>
> --- a/mm/gup.c
> +++ b/mm/gup.c
> @@ -388,69 +443,22 @@ long __get_user_pages(struct task_struct *tsk, struct mm_struct *mm,
> while (!(page = follow_page_mask(vma, start,
> foll_flags, &page_mask))) {
> int ret;
> - unsigned int fault_flags = 0;
> -
> - /* For mlock, just skip the stack guard page. */
> - if (foll_flags & FOLL_MLOCK) {
> - if (stack_guard_page(vma, start))
> - goto next_page;
> - }
> - if (foll_flags & FOLL_WRITE)
> - fault_flags |= FAULT_FLAG_WRITE;
> - if (nonblocking)
> - fault_flags |= FAULT_FLAG_ALLOW_RETRY;
> - if (foll_flags & FOLL_NOWAIT)
> - fault_flags |= (FAULT_FLAG_ALLOW_RETRY | FAULT_FLAG_RETRY_NOWAIT);
> -
> - ret = handle_mm_fault(mm, vma, start,
> - fault_flags);
> -
> - if (ret & VM_FAULT_ERROR) {
> - if (ret & VM_FAULT_OOM)
> - return i ? i : -ENOMEM;
> - if (ret & (VM_FAULT_HWPOISON |
> - VM_FAULT_HWPOISON_LARGE)) {
> - if (i)
> - return i;
> - else if (gup_flags & FOLL_HWPOISON)
> - return -EHWPOISON;
> - else
> - return -EFAULT;
> - }
> - if (ret & VM_FAULT_SIGBUS)
> - return i ? i : -EFAULT;
> - BUG();
> - }
> -
> - if (tsk) {
> - if (ret & VM_FAULT_MAJOR)
> - tsk->maj_flt++;
> - else
> - tsk->min_flt++;
> - }
> -
> - if (ret & VM_FAULT_RETRY) {
> - if (nonblocking)
> - *nonblocking = 0;
> + ret = faultin_page(tsk, vma, start, &foll_flags,
> + nonblocking);
> + switch (ret) {
> + case 0:
> + break;
> + case -EFAULT:
> + case -ENOMEM:
> + case -EHWPOISON:
> + return i ? i : ret;
> + case -EBUSY:
> return i;
> + case -ENOENT:
> + goto next_page;
> + default:
> + BUILD_BUG();
hm, why the BUILD_BUG? It triggers all the time. I'll switch it to
BUG but I worry about how this passed your testing.
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