Messages in this thread | | | From | "Chen, Kenneth W" <> | Subject | RE: hugetlb demand paging patch part [2/3] | Date | Thu, 15 Apr 2004 10:27:58 -0700 |
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>>>> David Gibson wrote on Thursday, April 15, 2004 12:17 AM > > diff -Nurp linux-2.6.5/mm/memory.c linux-2.6.5.htlb/mm/memory.c > > +++ linux-2.6.5.htlb/mm/memory.c 2004-04-13 12:02:31.000000000 -0700 > > @@ -769,11 +769,6 @@ int get_user_pages(struct task_struct *t > > if ((pages && vm_io) || !(flags & vma->vm_flags)) > > return i ? : -EFAULT; > > > > - if (is_vm_hugetlb_page(vma)) { > > - i = follow_hugetlb_page(mm, vma, pages, vmas, > > - &start, &len, i); > > - continue; > > - } > > spin_lock(&mm->page_table_lock); > > do { > > struct page *map = NULL; > > Ok, I notice that you've removed the follow_hugtlb_page() function > (and from the arch specific stuff, as well). As far as I can tell, > this isn't actually related to demand-paging, in fact as far as I can > tell this function is unnecessary
That was the reason I removed the function because it is no longer used with demand paging.
> should already work for huge pages. In particular the path in > get_user_pages() which can call handle_mm_fault() (which won't work on > hugepages without your patch) should never get triggered, since > hugepages are all prefaulted.
> Does that sound right? In other words, do you think the patch below, > which just kills off follow_hugetlb_page() is safe, or have I missed > something? > > Index: working-2.6/mm/memory.c > =================================================================== > --- working-2.6.orig/mm/memory.c 2004-04-13 11:42:42.000000000 +1000 > +++ working-2.6/mm/memory.c 2004-04-15 17:03:01.421905400 +1000 > @@ -766,16 +766,13 @@ > [snip] > spin_lock(&mm->page_table_lock); > do { > struct page *map; > int lookup_write = write; > while (!(map = follow_page(mm, start, lookup_write))) { > + /* hugepages should always be prefaulted */ > + BUG_ON(is_vm_hugetlb_page(vma)); > /* > * Shortcut for anonymous pages. We don't want > * to force the creation of pages tables for
This portion is incorrect, because it will trigger BUG_ON all the time for faulting hugetlb page.
Yes, killing follow_hugetlb_page() is safe because follow_page() takes care of hugetlb page. See 2nd patch posted earlier in hugetlb_demanding_generic.patch
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