On Fri, 16 Nov 2012, Kirill A. Shutemov wrote: > > > > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > > > > > index d767a7c..05490b3 100644 > > > > > --- a/mm/huge_memory.c > > > > > +++ b/mm/huge_memory.c > > > > > @@ -1259,6 +1259,8 @@ int change_huge_pmd(struct vm_area_struct *vma, pmd_t *pmd, > > > > > pmd_t entry; > > > > > entry = pmdp_get_and_clear(mm, addr, pmd); > > > > > entry = pmd_modify(entry, newprot); > > > > > + if (is_huge_zero_pmd(entry)) > > > > > + entry = pmd_wrprotect(entry); > > > > > set_pmd_at(mm, addr, pmd, entry); > > > > > spin_unlock(&vma->vm_mm->page_table_lock); > > > > > ret = 1; > > > > > > > > Nack, this should be handled in pmd_modify(). > > > > > > I disagree. It means we will have to enable hzp per arch. Bad idea. > > > > > > > pmd_modify() only exists for those architectures with thp support already, > > so you've already implicitly enabled for all the necessary architectures > > with your patchset. > > Now we have huge zero page fully implemented inside mm/huge_memory.c. Push > this logic to pmd_modify() means we expose hzp implementation details to > arch code. Looks ugly for me. > So you are suggesting that anybody who ever does pmd_modify() in the future is responsible for knowing about the zero page and to protect against giving it write permission in the calling code?? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>