Messages in this thread | | | Date | Sat, 11 Mar 2006 15:54:42 +1100 | From | Nick Piggin <> | Subject | Re: [patch][rfc] nommu: reverse mappings for nommu to solve get_user_pages problem |
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Nick Piggin wrote:
> int get_user_pages(struct task_struct *tsk, struct mm_struct *mm, > unsigned long start, int len, int write, int force, > struct page **pages, struct vm_area_struct **vmas) > { > int i; > - static struct vm_area_struct dummy_vma; > + struct page *__page; > + static struct vm_area_struct *__vma; > + unsigned long addr = start; > > for (i = 0; i < len; i++) { > + __vma = find_vma(mm, addr); > + if (!__vma) > + goto out_failed; > + > + __page = virt_to_page(addr); > + if (!__page) > + goto out_failed; > + > + BUG_ON(page_vma(__page) != __vma); > +
Actually this check is leftover from a previous version. I think it needs to be removed.
> if (pages) { > - pages[i] = virt_to_page(start); > - if (pages[i]) > - page_cache_get(pages[i]); > + if (!__page->mapping) { > + printk(KERN_INFO "get_user_pages on unaligned" > + "anonymous page unsupported\n"); dump_stack(); > + goto out_failed; > + } > +
And this could trigger for file-backed pages that have been truncated meanwhile I think. It wouldn't be a problem for a simple test-run, but does need to be reworked slightly in order to be correct. Sub-page anonymous mappings cause a lot of headaches :)
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