| From | "Kirill A. Shutemov" <> | Subject | Re: [PATCHv4 33/39] thp, mm: implement do_huge_linear_fault() | Date | Wed, 22 May 2013 18:26:15 +0300 (EEST) |
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Hillf Danton wrote: > On Sun, May 12, 2013 at 9:23 AM, Kirill A. Shutemov > <kirill.shutemov@linux.intel.com> wrote: > > page = vmf.page; > > + > > + /* > > + * If we asked for huge page we expect to get it or VM_FAULT_FALLBACK. > > + * If we don't ask for huge page it must be splitted in ->fault(). > > + */ > > + BUG_ON(PageTransHuge(page) != thp); > > + > Based on the log message in 34/39( > If the area of page cache required to create huge is empty, we create a > new huge page and return it.), the above trap looks bogus.
The statement in 34/39 is true for (flags & FAULT_FLAG_TRANSHUGE). For !(flags & FAULT_FLAG_TRANSHUGE) huge page must be split in ->fault.
The BUG_ON() above is shortcut for two checks:
if (thp) BUG_ON(!PageTransHuge(page)); if (!thp) BUG_ON(PageTransHuge(page));
-- Kirill A. Shutemov
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