Messages in this thread | | | Subject | Re: Race in new page migration code? | From | Lee Schermerhorn <> | Date | Tue, 17 Jan 2006 13:46:11 -0500 |
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On Tue, 2006-01-17 at 09:29 -0800, Christoph Lameter wrote: > On Mon, 16 Jan 2006, Hugh Dickins wrote: > > > Hmm, that battery of unusual tests at the start of migrate_page_add > > is odd: the tests don't quite match the comment, and it isn't clear > > what reasoning lies behind the comment anyway. > > Here is patch to clarify the test. I'd be glad if someone could make > the tests more accurate. This ultimately comes down to a concept of > ownership of page by a process / mm_struct that we have to approximate. > > === > > Explain the complicated check in migrate_page_add by putting the logic > into a separate function migration_check. This way any enhancements can > be easily added. > > Signed-off-by: Christoph Lameter <clameter@sgi.com> > > Index: linux-2.6.15/mm/mempolicy.c > =================================================================== > --- linux-2.6.15.orig/mm/mempolicy.c 2006-01-14 10:56:28.000000000 -0800 > +++ linux-2.6.15/mm/mempolicy.c 2006-01-17 09:24:20.000000000 -0800 > @@ -551,6 +551,37 @@ out: > return rc; > } > > +static inline int migration_check(struct mm_struct *mm, struct page *page) > +{ > + /* > + * If the page has no mapping then we do not track reverse mappings. > + * Thus the page is not mapped by other mms, so its safe to move. > + */ > + if (page->mapping) should this be "if (!page->mapping)" ??? > + return 1; > +
<snip> > - if ((flags & MPOL_MF_MOVE_ALL) || !page->mapping || PageAnon(page) || like here ......................................^^^^^^^^^^^^^^ > - mapping_writably_mapped(page->mapping) || > - single_mm_mapping(vma->vm_mm, page->mapping)) > + if ((flags & MPOL_MF_MOVE_ALL) || migration_check(vma->vm_mm, page)) > if (isolate_lru_page(page) == 1) > list_add(&page->lru, pagelist); > }
Lee
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