Messages in this thread Patch in this message | | | Date | Tue, 17 Jan 2006 12:15:29 -0800 (PST) | From | Christoph Lameter <> | Subject | Re: Race in new page migration code? |
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On Tue, 17 Jan 2006, Hugh Dickins wrote:
> Of course, page_mapcount may go up an instant later; but equally, > another vma may get added to the prio_tree an instant later.
Right. The check does not have to be race free.
> It may be that, after much argument to and fro, the whole function will > just reduce to checking "page_mapcount(page) == 1": if so, then I think > you can go back to inlining it literally.
Oh. I love simplicity.... Sadly, one sometimes has these complicated notions in ones brain. Thanks.
Simplify migrate_page_add after feedback from Hugh.
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 12:12:42.000000000 -0800 @@ -527,42 +527,13 @@ long do_get_mempolicy(int *policy, nodem * page migration */ -/* Check if we are the only process mapping the page in question */ -static inline int single_mm_mapping(struct mm_struct *mm, - struct address_space *mapping) -{ - struct vm_area_struct *vma; - struct prio_tree_iter iter; - int rc = 1; - - spin_lock(&mapping->i_mmap_lock); - vma_prio_tree_foreach(vma, &iter, &mapping->i_mmap, 0, ULONG_MAX) - if (mm != vma->vm_mm) { - rc = 0; - goto out; - } - list_for_each_entry(vma, &mapping->i_mmap_nonlinear, shared.vm_set.list) - if (mm != vma->vm_mm) { - rc = 0; - goto out; - } -out: - spin_unlock(&mapping->i_mmap_lock); - return rc; -} - -/* - * Add a page to be migrated to the pagelist - */ static void migrate_page_add(struct vm_area_struct *vma, struct page *page, struct list_head *pagelist, unsigned long flags) { /* - * Avoid migrating a page that is shared by others and not writable. + * Avoid migrating a page that is shared with others. */ - if ((flags & MPOL_MF_MOVE_ALL) || !page->mapping || PageAnon(page) || - mapping_writably_mapped(page->mapping) || - single_mm_mapping(vma->vm_mm, page->mapping)) + if ((flags & MPOL_MF_MOVE_ALL) || page_mapcount(page) ==1) if (isolate_lru_page(page) == 1) list_add(&page->lru, pagelist); } - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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